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| author | Mauro Carvalho Chehab | 2019-06-27 20:39:22 +0200 |
|---|---|---|
| committer | Mauro Carvalho Chehab | 2019-07-15 16:03:02 +0200 |
| commit | baa293e9544bea71361950d071579f0e4d5713ed (patch) | |
| tree | 29e0400c806016783a3fd7a380be40a201956653 /Documentation/driver-api | |
| parent | docs: admin-guide: add a series of orphaned documents (diff) | |
| download | kernel-qcow2-linux-baa293e9544bea71361950d071579f0e4d5713ed.tar.gz kernel-qcow2-linux-baa293e9544bea71361950d071579f0e4d5713ed.tar.xz kernel-qcow2-linux-baa293e9544bea71361950d071579f0e4d5713ed.zip | |
docs: driver-api: add a series of orphaned documents
There are lots of documents under Documentation/*.txt and a few other
orphan documents elsehwere that belong to the driver-API book.
Move them to their right place.
Reviewed-by: Cornelia Huck <cohuck@redhat.com> # vfio-related parts
Acked-by: Logan Gunthorpe <logang@deltatee.com> # switchtec
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Diffstat (limited to 'Documentation/driver-api')
27 files changed, 5692 insertions, 0 deletions
diff --git a/Documentation/driver-api/bt8xxgpio.rst b/Documentation/driver-api/bt8xxgpio.rst new file mode 100644 index 000000000000..a845feb074de --- /dev/null +++ b/Documentation/driver-api/bt8xxgpio.rst @@ -0,0 +1,62 @@ +=================================================================== +A driver for a selfmade cheap BT8xx based PCI GPIO-card (bt8xxgpio) +=================================================================== + +For advanced documentation, see http://www.bu3sch.de/btgpio.php + +A generic digital 24-port PCI GPIO card can be built out of an ordinary +Brooktree bt848, bt849, bt878 or bt879 based analog TV tuner card. The +Brooktree chip is used in old analog Hauppauge WinTV PCI cards. You can easily +find them used for low prices on the net. + +The bt8xx chip does have 24 digital GPIO ports. +These ports are accessible via 24 pins on the SMD chip package. + + +How to physically access the GPIO pins +====================================== + +The are several ways to access these pins. One might unsolder the whole chip +and put it on a custom PCI board, or one might only unsolder each individual +GPIO pin and solder that to some tiny wire. As the chip package really is tiny +there are some advanced soldering skills needed in any case. + +The physical pinouts are drawn in the following ASCII art. +The GPIO pins are marked with G00-G23:: + + G G G G G G G G G G G G G G G G G G + 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 + 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 + | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | + --------------------------------------------------------------------------- + --| ^ ^ |-- + --| pin 86 pin 67 |-- + --| |-- + --| pin 61 > |-- G18 + --| |-- G19 + --| |-- G20 + --| |-- G21 + --| |-- G22 + --| pin 56 > |-- G23 + --| |-- + --| Brooktree 878/879 |-- + --| |-- + --| |-- + --| |-- + --| |-- + --| |-- + --| |-- + --| |-- + --| |-- + --| |-- + --| |-- + --| |-- + --| |-- + --| |-- + --| O |-- + --| |-- + --------------------------------------------------------------------------- + | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | + ^ + This is pin 1 + diff --git a/Documentation/driver-api/connector.rst b/Documentation/driver-api/connector.rst new file mode 100644 index 000000000000..c100c7482289 --- /dev/null +++ b/Documentation/driver-api/connector.rst @@ -0,0 +1,156 @@ +.. SPDX-License-Identifier: GPL-2.0 + +================ +Kernel Connector +================ + +Kernel connector - new netlink based userspace <-> kernel space easy +to use communication module. + +The Connector driver makes it easy to connect various agents using a +netlink based network. One must register a callback and an identifier. +When the driver receives a special netlink message with the appropriate +identifier, the appropriate callback will be called. + +From the userspace point of view it's quite straightforward: + + - socket(); + - bind(); + - send(); + - recv(); + +But if kernelspace wants to use the full power of such connections, the +driver writer must create special sockets, must know about struct sk_buff +handling, etc... The Connector driver allows any kernelspace agents to use +netlink based networking for inter-process communication in a significantly +easier way:: + + int cn_add_callback(struct cb_id *id, char *name, void (*callback) (struct cn_msg *, struct netlink_skb_parms *)); + void cn_netlink_send_multi(struct cn_msg *msg, u16 len, u32 portid, u32 __group, int gfp_mask); + void cn_netlink_send(struct cn_msg *msg, u32 portid, u32 __group, int gfp_mask); + + struct cb_id + { + __u32 idx; + __u32 val; + }; + +idx and val are unique identifiers which must be registered in the +connector.h header for in-kernel usage. `void (*callback) (void *)` is a +callback function which will be called when a message with above idx.val +is received by the connector core. The argument for that function must +be dereferenced to `struct cn_msg *`:: + + struct cn_msg + { + struct cb_id id; + + __u32 seq; + __u32 ack; + + __u32 len; /* Length of the following data */ + __u8 data[0]; + }; + +Connector interfaces +==================== + + .. kernel-doc:: include/linux/connector.h + + Note: + When registering new callback user, connector core assigns + netlink group to the user which is equal to its id.idx. + +Protocol description +==================== + +The current framework offers a transport layer with fixed headers. The +recommended protocol which uses such a header is as following: + +msg->seq and msg->ack are used to determine message genealogy. When +someone sends a message, they use a locally unique sequence and random +acknowledge number. The sequence number may be copied into +nlmsghdr->nlmsg_seq too. + +The sequence number is incremented with each message sent. + +If you expect a reply to the message, then the sequence number in the +received message MUST be the same as in the original message, and the +acknowledge number MUST be the same + 1. + +If we receive a message and its sequence number is not equal to one we +are expecting, then it is a new message. If we receive a message and +its sequence number is the same as one we are expecting, but its +acknowledge is not equal to the sequence number in the original +message + 1, then it is a new message. + +Obviously, the protocol header contains the above id. + +The connector allows event notification in the following form: kernel +driver or userspace process can ask connector to notify it when +selected ids will be turned on or off (registered or unregistered its +callback). It is done by sending a special command to the connector +driver (it also registers itself with id={-1, -1}). + +As example of this usage can be found in the cn_test.c module which +uses the connector to request notification and to send messages. + +Reliability +=========== + +Netlink itself is not a reliable protocol. That means that messages can +be lost due to memory pressure or process' receiving queue overflowed, +so caller is warned that it must be prepared. That is why the struct +cn_msg [main connector's message header] contains u32 seq and u32 ack +fields. + +Userspace usage +=============== + +2.6.14 has a new netlink socket implementation, which by default does not +allow people to send data to netlink groups other than 1. +So, if you wish to use a netlink socket (for example using connector) +with a different group number, the userspace application must subscribe to +that group first. It can be achieved by the following pseudocode:: + + s = socket(PF_NETLINK, SOCK_DGRAM, NETLINK_CONNECTOR); + + l_local.nl_family = AF_NETLINK; + l_local.nl_groups = 12345; + l_local.nl_pid = 0; + + if (bind(s, (struct sockaddr *)&l_local, sizeof(struct sockaddr_nl)) == -1) { + perror("bind"); + close(s); + return -1; + } + + { + int on = l_local.nl_groups; + setsockopt(s, 270, 1, &on, sizeof(on)); + } + +Where 270 above is SOL_NETLINK, and 1 is a NETLINK_ADD_MEMBERSHIP socket +option. To drop a multicast subscription, one should call the above socket +option with the NETLINK_DROP_MEMBERSHIP parameter which is defined as 0. + +2.6.14 netlink code only allows to select a group which is less or equal to +the maximum group number, which is used at netlink_kernel_create() time. +In case of connector it is CN_NETLINK_USERS + 0xf, so if you want to use +group number 12345, you must increment CN_NETLINK_USERS to that number. +Additional 0xf numbers are allocated to be used by non-in-kernel users. + +Due to this limitation, group 0xffffffff does not work now, so one can +not use add/remove connector's group notifications, but as far as I know, +only cn_test.c test module used it. + +Some work in netlink area is still being done, so things can be changed in +2.6.15 timeframe, if it will happen, documentation will be updated for that +kernel. + +Code samples +============ + +Sample code for a connector test module and user space can be found +in samples/connector/. To build this code, enable CONFIG_CONNECTOR +and CONFIG_SAMPLES. diff --git a/Documentation/driver-api/console.rst b/Documentation/driver-api/console.rst new file mode 100644 index 000000000000..8394ad7747ac --- /dev/null +++ b/Documentation/driver-api/console.rst @@ -0,0 +1,152 @@ +.. SPDX-License-Identifier: GPL-2.0 + +=============== +Console Drivers +=============== + +The Linux kernel has 2 general types of console drivers. The first type is +assigned by the kernel to all the virtual consoles during the boot process. +This type will be called 'system driver', and only one system driver is allowed +to exist. The system driver is persistent and it can never be unloaded, though +it may become inactive. + +The second type has to be explicitly loaded and unloaded. This will be called +'modular driver' by this document. Multiple modular drivers can coexist at +any time with each driver sharing the console with other drivers including +the system driver. However, modular drivers cannot take over the console +that is currently occupied by another modular driver. (Exception: Drivers that +call do_take_over_console() will succeed in the takeover regardless of the type +of driver occupying the consoles.) They can only take over the console that is +occupied by the system driver. In the same token, if the modular driver is +released by the console, the system driver will take over. + +Modular drivers, from the programmer's point of view, have to call:: + + do_take_over_console() - load and bind driver to console layer + give_up_console() - unload driver; it will only work if driver + is fully unbound + +In newer kernels, the following are also available:: + + do_register_con_driver() + do_unregister_con_driver() + +If sysfs is enabled, the contents of /sys/class/vtconsole can be +examined. This shows the console backends currently registered by the +system which are named vtcon<n> where <n> is an integer from 0 to 15. +Thus:: + + ls /sys/class/vtconsole + . .. vtcon0 vtcon1 + +Each directory in /sys/class/vtconsole has 3 files:: + + ls /sys/class/vtconsole/vtcon0 + . .. bind name uevent + +What do these files signify? + + 1. bind - this is a read/write file. It shows the status of the driver if + read, or acts to bind or unbind the driver to the virtual consoles + when written to. The possible values are: + + 0 + - means the driver is not bound and if echo'ed, commands the driver + to unbind + + 1 + - means the driver is bound and if echo'ed, commands the driver to + bind + + 2. name - read-only file. Shows the name of the driver in this format:: + + cat /sys/class/vtconsole/vtcon0/name + (S) VGA+ + + '(S)' stands for a (S)ystem driver, i.e., it cannot be directly + commanded to bind or unbind + + 'VGA+' is the name of the driver + + cat /sys/class/vtconsole/vtcon1/name + (M) frame buffer device + + In this case, '(M)' stands for a (M)odular driver, one that can be + directly commanded to bind or unbind. + + 3. uevent - ignore this file + +When unbinding, the modular driver is detached first, and then the system +driver takes over the consoles vacated by the driver. Binding, on the other +hand, will bind the driver to the consoles that are currently occupied by a +system driver. + +NOTE1: + Binding and unbinding must be selected in Kconfig. It's under:: + + Device Drivers -> + Character devices -> + Support for binding and unbinding console drivers + +NOTE2: + If any of the virtual consoles are in KD_GRAPHICS mode, then binding or + unbinding will not succeed. An example of an application that sets the + console to KD_GRAPHICS is X. + +How useful is this feature? This is very useful for console driver +developers. By unbinding the driver from the console layer, one can unload the +driver, make changes, recompile, reload and rebind the driver without any need +for rebooting the kernel. For regular users who may want to switch from +framebuffer console to VGA console and vice versa, this feature also makes +this possible. (NOTE NOTE NOTE: Please read fbcon.txt under Documentation/fb +for more details.) + +Notes for developers +==================== + +do_take_over_console() is now broken up into:: + + do_register_con_driver() + do_bind_con_driver() - private function + +give_up_console() is a wrapper to do_unregister_con_driver(), and a driver must +be fully unbound for this call to succeed. con_is_bound() will check if the +driver is bound or not. + +Guidelines for console driver writers +===================================== + +In order for binding to and unbinding from the console to properly work, +console drivers must follow these guidelines: + +1. All drivers, except system drivers, must call either do_register_con_driver() + or do_take_over_console(). do_register_con_driver() will just add the driver + to the console's internal list. It won't take over the + console. do_take_over_console(), as it name implies, will also take over (or + bind to) the console. + +2. All resources allocated during con->con_init() must be released in + con->con_deinit(). + +3. All resources allocated in con->con_startup() must be released when the + driver, which was previously bound, becomes unbound. The console layer + does not have a complementary call to con->con_startup() so it's up to the + driver to check when it's legal to release these resources. Calling + con_is_bound() in con->con_deinit() will help. If the call returned + false(), then it's safe to release the resources. This balance has to be + ensured because con->con_startup() can be called again when a request to + rebind the driver to the console arrives. + +4. Upon exit of the driver, ensure that the driver is totally unbound. If the + condition is satisfied, then the driver must call do_unregister_con_driver() + or give_up_console(). + +5. do_unregister_con_driver() can also be called on conditions which make it + impossible for the driver to service console requests. This can happen + with the framebuffer console that suddenly lost all of its drivers. + +The current crop of console drivers should still work correctly, but binding +and unbinding them may cause problems. With minimal fixes, these drivers can +be made to work correctly. + +Antonino Daplas <adaplas@pol.net> diff --git a/Documentation/driver-api/dcdbas.rst b/Documentation/driver-api/dcdbas.rst new file mode 100644 index 000000000000..309cc57a7c1c --- /dev/null +++ b/Documentation/driver-api/dcdbas.rst @@ -0,0 +1,99 @@ +=================================== +Dell Systems Management Base Driver +=================================== + +Overview +======== + +The Dell Systems Management Base Driver provides a sysfs interface for +systems management software such as Dell OpenManage to perform system +management interrupts and host control actions (system power cycle or +power off after OS shutdown) on certain Dell systems. + +Dell OpenManage requires this driver on the following Dell PowerEdge systems: +300, 1300, 1400, 400SC, 500SC, 1500SC, 1550, 600SC, 1600SC, 650, 1655MC, +700, and 750. Other Dell software such as the open source libsmbios project +is expected to make use of this driver, and it may include the use of this +driver on other Dell systems. + +The Dell libsmbios project aims towards providing access to as much BIOS +information as possible. See http://linux.dell.com/libsmbios/main/ for +more information about the libsmbios project. + + +System Management Interrupt +=========================== + +On some Dell systems, systems management software must access certain +management information via a system management interrupt (SMI). The SMI data +buffer must reside in 32-bit address space, and the physical address of the +buffer is required for the SMI. The driver maintains the memory required for +the SMI and provides a way for the application to generate the SMI. +The driver creates the following sysfs entries for systems management +software to perform these system management interrupts:: + + /sys/devices/platform/dcdbas/smi_data + /sys/devices/platform/dcdbas/smi_data_buf_phys_addr + /sys/devices/platform/dcdbas/smi_data_buf_size + /sys/devices/platform/dcdbas/smi_request + +Systems management software must perform the following steps to execute +a SMI using this driver: + +1) Lock smi_data. +2) Write system management command to smi_data. +3) Write "1" to smi_request to generate a calling interface SMI or + "2" to generate a raw SMI. +4) Read system management command response from smi_data. +5) Unlock smi_data. + + +Host Control Action +=================== + +Dell OpenManage supports a host control feature that allows the administrator +to perform a power cycle or power off of the system after the OS has finished +shutting down. On some Dell systems, this host control feature requires that +a driver perform a SMI after the OS has finished shutting down. + +The driver creates the following sysfs entries for systems management software +to schedule the driver to perform a power cycle or power off host control +action after the system has finished shutting down: + +/sys/devices/platform/dcdbas/host_control_action +/sys/devices/platform/dcdbas/host_control_smi_type +/sys/devices/platform/dcdbas/host_control_on_shutdown + +Dell OpenManage performs the following steps to execute a power cycle or +power off host control action using this driver: + +1) Write host control action to be performed to host_control_action. +2) Write type of SMI that driver needs to perform to host_control_smi_type. +3) Write "1" to host_control_on_shutdown to enable host control action. +4) Initiate OS shutdown. + (Driver will perform host control SMI when it is notified that the OS + has finished shutting down.) + + +Host Control SMI Type +===================== + +The following table shows the value to write to host_control_smi_type to +perform a power cycle or power off host control action: + +=================== ===================== +PowerEdge System Host Control SMI Type +=================== ===================== + 300 HC_SMITYPE_TYPE1 + 1300 HC_SMITYPE_TYPE1 + 1400 HC_SMITYPE_TYPE2 + 500SC HC_SMITYPE_TYPE2 + 1500SC HC_SMITYPE_TYPE2 + 1550 HC_SMITYPE_TYPE2 + 600SC HC_SMITYPE_TYPE2 + 1600SC HC_SMITYPE_TYPE2 + 650 HC_SMITYPE_TYPE2 + 1655MC HC_SMITYPE_TYPE2 + 700 HC_SMITYPE_TYPE3 + 750 HC_SMITYPE_TYPE3 +=================== ===================== diff --git a/Documentation/driver-api/dell_rbu.rst b/Documentation/driver-api/dell_rbu.rst new file mode 100644 index 000000000000..5d1ce7bcd04d --- /dev/null +++ b/Documentation/driver-api/dell_rbu.rst @@ -0,0 +1,128 @@ +============================================================= +Usage of the new open sourced rbu (Remote BIOS Update) driver +============================================================= + +Purpose +======= + +Document demonstrating the use of the Dell Remote BIOS Update driver. +for updating BIOS images on Dell servers and desktops. + +Scope +===== + +This document discusses the functionality of the rbu driver only. +It does not cover the support needed from applications to enable the BIOS to +update itself with the image downloaded in to the memory. + +Overview +======== + +This driver works with Dell OpenManage or Dell Update Packages for updating +the BIOS on Dell servers (starting from servers sold since 1999), desktops +and notebooks (starting from those sold in 2005). + +Please go to http://support.dell.com register and you can find info on +OpenManage and Dell Update packages (DUP). + +Libsmbios can also be used to update BIOS on Dell systems go to +http://linux.dell.com/libsmbios/ for details. + +Dell_RBU driver supports BIOS update using the monolithic image and packetized +image methods. In case of monolithic the driver allocates a contiguous chunk +of physical pages having the BIOS image. In case of packetized the app +using the driver breaks the image in to packets of fixed sizes and the driver +would place each packet in contiguous physical memory. The driver also +maintains a link list of packets for reading them back. + +If the dell_rbu driver is unloaded all the allocated memory is freed. + +The rbu driver needs to have an application (as mentioned above)which will +inform the BIOS to enable the update in the next system reboot. + +The user should not unload the rbu driver after downloading the BIOS image +or updating. + +The driver load creates the following directories under the /sys file system:: + + /sys/class/firmware/dell_rbu/loading + /sys/class/firmware/dell_rbu/data + /sys/devices/platform/dell_rbu/image_type + /sys/devices/platform/dell_rbu/data + /sys/devices/platform/dell_rbu/packet_size + +The driver supports two types of update mechanism; monolithic and packetized. +These update mechanism depends upon the BIOS currently running on the system. +Most of the Dell systems support a monolithic update where the BIOS image is +copied to a single contiguous block of physical memory. + +In case of packet mechanism the single memory can be broken in smaller chunks +of contiguous memory and the BIOS image is scattered in these packets. + +By default the driver uses monolithic memory for the update type. This can be +changed to packets during the driver load time by specifying the load +parameter image_type=packet. This can also be changed later as below:: + + echo packet > /sys/devices/platform/dell_rbu/image_type + +In packet update mode the packet size has to be given before any packets can +be downloaded. It is done as below:: + + echo XXXX > /sys/devices/platform/dell_rbu/packet_size + +In the packet update mechanism, the user needs to create a new file having +packets of data arranged back to back. It can be done as follows +The user creates packets header, gets the chunk of the BIOS image and +places it next to the packetheader; now, the packetheader + BIOS image chunk +added together should match the specified packet_size. This makes one +packet, the user needs to create more such packets out of the entire BIOS +image file and then arrange all these packets back to back in to one single +file. + +This file is then copied to /sys/class/firmware/dell_rbu/data. +Once this file gets to the driver, the driver extracts packet_size data from +the file and spreads it across the physical memory in contiguous packet_sized +space. + +This method makes sure that all the packets get to the driver in a single operation. + +In monolithic update the user simply get the BIOS image (.hdr file) and copies +to the data file as is without any change to the BIOS image itself. + +Do the steps below to download the BIOS image. + +1) echo 1 > /sys/class/firmware/dell_rbu/loading +2) cp bios_image.hdr /sys/class/firmware/dell_rbu/data +3) echo 0 > /sys/class/firmware/dell_rbu/loading + +The /sys/class/firmware/dell_rbu/ entries will remain till the following is +done. + +:: + + echo -1 > /sys/class/firmware/dell_rbu/loading + +Until this step is completed the driver cannot be unloaded. + +Also echoing either mono, packet or init in to image_type will free up the +memory allocated by the driver. + +If a user by accident executes steps 1 and 3 above without executing step 2; +it will make the /sys/class/firmware/dell_rbu/ entries disappear. + +The entries can be recreated by doing the following:: + + echo init > /sys/devices/platform/dell_rbu/image_type + +.. note:: echoing init in image_type does not change it original value. + +Also the driver provides /sys/devices/platform/dell_rbu/data readonly file to +read back the image downloaded. + +.. note:: + + After updating the BIOS image a user mode application needs to execute + code which sends the BIOS update request to the BIOS. So on the next reboot + the BIOS knows about the new image downloaded and it updates itself. + Also don't unload the rbu driver if the image has to be updated. + diff --git a/Documentation/driver-api/edid.rst b/Documentation/driver-api/edid.rst new file mode 100644 index 000000000000..b1b5acd501ed --- /dev/null +++ b/Documentation/driver-api/edid.rst @@ -0,0 +1,58 @@ +.. SPDX-License-Identifier: GPL-2.0 + +==== +EDID +==== + +In the good old days when graphics parameters were configured explicitly +in a file called xorg.conf, even broken hardware could be managed. + +Today, with the advent of Kernel Mode Setting, a graphics board is +either correctly working because all components follow the standards - +or the computer is unusable, because the screen remains dark after +booting or it displays the wrong area. Cases when this happens are: +- The graphics board does not recognize the monitor. +- The graphics board is unable to detect any EDID data. +- The graphics board incorrectly forwards EDID data to the driver. +- The monitor sends no or bogus EDID data. +- A KVM sends its own EDID data instead of querying the connected monitor. +Adding the kernel parameter "nomodeset" helps in most cases, but causes +restrictions later on. + +As a remedy for such situations, the kernel configuration item +CONFIG_DRM_LOAD_EDID_FIRMWARE was introduced. It allows to provide an +individually prepared or corrected EDID data set in the /lib/firmware +directory from where it is loaded via the firmware interface. The code +(see drivers/gpu/drm/drm_edid_load.c) contains built-in data sets for +commonly used screen resolutions (800x600, 1024x768, 1280x1024, 1600x1200, +1680x1050, 1920x1080) as binary blobs, but the kernel source tree does +not contain code to create these data. In order to elucidate the origin +of the built-in binary EDID blobs and to facilitate the creation of +individual data for a specific misbehaving monitor, commented sources +and a Makefile environment are given here. + +To create binary EDID and C source code files from the existing data +material, simply type "make". + +If you want to create your own EDID file, copy the file 1024x768.S, +replace the settings with your own data and add a new target to the +Makefile. Please note that the EDID data structure expects the timing +values in a different way as compared to the standard X11 format. + +X11: + HTimings: + hdisp hsyncstart hsyncend htotal + VTimings: + vdisp vsyncstart vsyncend vtotal + +EDID:: + + #define XPIX hdisp + #define XBLANK htotal-hdisp + #define XOFFSET hsyncstart-hdisp + #define XPULSE hsyncend-hsyncstart + + #define YPIX vdisp + #define YBLANK vtotal-vdisp + #define YOFFSET vsyncstart-vdisp + #define YPULSE vsyncend-vsyncstart diff --git a/Documentation/driver-api/eisa.rst b/Documentation/driver-api/eisa.rst new file mode 100644 index 000000000000..c07565ba57da --- /dev/null +++ b/Documentation/driver-api/eisa.rst @@ -0,0 +1,230 @@ +================ +EISA bus support +================ + +:Author: Marc Zyngier <maz@wild-wind.fr.eu.org> + +This document groups random notes about porting EISA drivers to the +new EISA/sysfs API. + +Starting from version 2.5.59, the EISA bus is almost given the same +status as other much more mainstream busses such as PCI or USB. This +has been possible through sysfs, which defines a nice enough set of +abstractions to manage busses, devices and drivers. + +Although the new API is quite simple to use, converting existing +drivers to the new infrastructure is not an easy task (mostly because +detection code is generally also used to probe ISA cards). Moreover, +most EISA drivers are among the oldest Linux drivers so, as you can +imagine, some dust has settled here over the years. + +The EISA infrastructure is made up of three parts: + + - The bus code implements most of the generic code. It is shared + among all the architectures that the EISA code runs on. It + implements bus probing (detecting EISA cards available on the bus), + allocates I/O resources, allows fancy naming through sysfs, and + offers interfaces for driver to register. + + - The bus root driver implements the glue between the bus hardware + and the generic bus code. It is responsible for discovering the + device implementing the bus, and setting it up to be latter probed + by the bus code. This can go from something as simple as reserving + an I/O region on x86, to the rather more complex, like the hppa + EISA code. This is the part to implement in order to have EISA + running on an "new" platform. + + - The driver offers the bus a list of devices that it manages, and + implements the necessary callbacks to probe and release devices + whenever told to. + +Every function/structure below lives in <linux/eisa.h>, which depends +heavily on <linux/device.h>. + +Bus root driver +=============== + +:: + + int eisa_root_register (struct eisa_root_device *root); + +The eisa_root_register function is used to declare a device as the +root of an EISA bus. The eisa_root_device structure holds a reference +to this device, as well as some parameters for probing purposes:: + + struct eisa_root_device { + struct device *dev; /* Pointer to bridge device */ + struct resource *res; + unsigned long bus_base_addr; + int slots; /* Max slot number */ + int force_probe; /* Probe even when no slot 0 */ + u64 dma_mask; /* from bridge device */ + int bus_nr; /* Set by eisa_root_register */ + struct resource eisa_root_res; /* ditto */ + }; + +============= ====================================================== +node used for eisa_root_register internal purpose +dev pointer to the root device +res root device I/O resource +bus_base_addr slot 0 address on this bus +slots max slot number to probe +force_probe Probe even when slot 0 is empty (no EISA mainboard) +dma_mask Default DMA mask. Usually the bridge device dma_mask. +bus_nr unique bus id, set by eisa_root_register +============= ====================================================== + +Driver +====== + +:: + + int eisa_driver_register (struct eisa_driver *edrv); + void eisa_driver_unregister (struct eisa_driver *edrv); + +Clear enough ? + +:: + + struct eisa_device_id { + char sig[EISA_SIG_LEN]; + unsigned long driver_data; + }; + + struct eisa_driver { + const struct eisa_device_id *id_table; + struct device_driver driver; + }; + +=============== ==================================================== +id_table an array of NULL terminated EISA id strings, + followed by an empty string. Each string can + optionally be paired with a driver-dependent value + (driver_data). + +driver a generic driver, such as described in + Documentation/driver-api/driver-model/driver.rst. Only .name, + .probe and .remove members are mandatory. +=============== ==================================================== + +An example is the 3c59x driver:: + + static struct eisa_device_id vortex_eisa_ids[] = { + { "TCM5920", EISA_3C592_OFFSET }, + { "TCM5970", EISA_3C597_OFFSET }, + { "" } + }; + + static struct eisa_driver vortex_eisa_driver = { + .id_table = vortex_eisa_ids, + .driver = { + .name = "3c59x", + .probe = vortex_eisa_probe, + .remove = vortex_eisa_remove + } + }; + +Device +====== + +The sysfs framework calls .probe and .remove functions upon device +discovery and removal (note that the .remove function is only called +when driver is built as a module). + +Both functions are passed a pointer to a 'struct device', which is +encapsulated in a 'struct eisa_device' described as follows:: + + struct eisa_device { + struct eisa_device_id id; + int slot; + int state; + unsigned long base_addr; + struct resource res[EISA_MAX_RESOURCES]; + u64 dma_mask; + struct device dev; /* generic device */ + }; + +======== ============================================================ +id EISA id, as read from device. id.driver_data is set from the + matching driver EISA id. +slot slot number which the device was detected on +state set of flags indicating the state of the device. Current + flags are EISA_CONFIG_ENABLED and EISA_CONFIG_FORCED. +res set of four 256 bytes I/O regions allocated to this device +dma_mask DMA mask set from the parent device. +dev generic device (see Documentation/driver-api/driver-model/device.rst) +======== ============================================================ + +You can get the 'struct eisa_device' from 'struct device' using the +'to_eisa_device' macro. + +Misc stuff +========== + +:: + + void eisa_set_drvdata (struct eisa_device *edev, void *data); + +Stores data into the device's driver_data area. + +:: + + void *eisa_get_drvdata (struct eisa_device *edev): + +Gets the pointer previously stored into the device's driver_data area. + +:: + + int eisa_get_region_index (void *addr); + +Returns the region number (0 <= x < EISA_MAX_RESOURCES) of a given +address. + +Kernel parameters +================= + +eisa_bus.enable_dev + A comma-separated list of slots to be enabled, even if the firmware + set the card as disabled. The driver must be able to properly + initialize the device in such conditions. + +eisa_bus.disable_dev + A comma-separated list of slots to be enabled, even if the firmware + set the card as enabled. The driver won't be called to handle this + device. + +virtual_root.force_probe + Force the probing code to probe EISA slots even when it cannot find an + EISA compliant mainboard (nothing appears on slot 0). Defaults to 0 + (don't force), and set to 1 (force probing) when either + CONFIG_ALPHA_JENSEN or CONFIG_EISA_VLB_PRIMING are set. + +Random notes +============ + +Converting an EISA driver to the new API mostly involves *deleting* +code (since probing is now in the core EISA code). Unfortunately, most +drivers share their probing routine between ISA, and EISA. Special +care must be taken when ripping out the EISA code, so other busses +won't suffer from these surgical strikes... + +You *must not* expect any EISA device to be detected when returning +from eisa_driver_register, since the chances are that the bus has not +yet been probed. In fact, that's what happens most of the time (the +bus root driver usually kicks in rather late in the boot process). +Unfortunately, most drivers are doing the probing by themselves, and +expect to have explored the whole machine when they exit their probe +routine. + +For example, switching your favorite EISA SCSI card to the "hotplug" +model is "the right thing"(tm). + +Thanks +====== + +I'd like to thank the following people for their help: + +- Xavier Benigni for lending me a wonderful Alpha Jensen, +- James Bottomley, Jeff Garzik for getting this stuff into the kernel, +- Andries Brouwer for contributing numerous EISA ids, +- Catrin Jones for coping with far too many machines at home. diff --git a/Documentation/driver-api/index.rst b/Documentation/driver-api/index.rst index 9fb03b7bdeb1..d1c6513dd20d 100644 --- a/Documentation/driver-api/index.rst +++ b/Documentation/driver-api/index.rst @@ -68,7 +68,33 @@ available subsections can be seen below. fpga/index acpi/index backlight/lp855x-driver.rst + bt8xxgpio + connector + console + dcdbas + dell_rbu + edid + eisa + isa + isapnp generic-counter + lightnvm-pblk + men-chameleon-bus + ntb + nvmem + parport-lowlevel + pti_intel_mid + pwm + rfkill + sgi-ioc4 + sm501 + smsc_ece1099 + switchtec + sync_file + vfio-mediated-device + vfio + xillybus + zorro .. only:: subproject and html diff --git a/Documentation/driver-api/isa.rst b/Documentation/driver-api/isa.rst new file mode 100644 index 000000000000..def4a7b690b5 --- /dev/null +++ b/Documentation/driver-api/isa.rst @@ -0,0 +1,122 @@ +=========== +ISA Drivers +=========== + +The following text is adapted from the commit message of the initial +commit of the ISA bus driver authored by Rene Herman. + +During the recent "isa drivers using platform devices" discussion it was +pointed out that (ALSA) ISA drivers ran into the problem of not having +the option to fail driver load (device registration rather) upon not +finding their hardware due to a probe() error not being passed up +through the driver model. In the course of that, I suggested a separate +ISA bus might be best; Russell King agreed and suggested this bus could +use the .match() method for the actual device discovery. + +The attached does this. For this old non (generically) discoverable ISA +hardware only the driver itself can do discovery so as a difference with +the platform_bus, this isa_bus also distributes match() up to the +driver. + +As another difference: these devices only exist in the driver model due +to the driver creating them because it might want to drive them, meaning +that all device creation has been made internal as well. + +The usage model this provides is nice, and has been acked from the ALSA +side by Takashi Iwai and Jaroslav Kysela. The ALSA driver module_init's +now (for oldisa-only drivers) become:: + + static int __init alsa_card_foo_init(void) + { + return isa_register_driver(&snd_foo_isa_driver, SNDRV_CARDS); + } + + static void __exit alsa_card_foo_exit(void) + { + isa_unregister_driver(&snd_foo_isa_driver); + } + +Quite like the other bus models therefore. This removes a lot of +duplicated init code from the ALSA ISA drivers. + +The passed in isa_driver struct is the regular driver struct embedding a +struct device_driver, the normal probe/remove/shutdown/suspend/resume +callbacks, and as indicated that .match callback. + +The "SNDRV_CARDS" you see being passed in is a "unsigned int ndev" +parameter, indicating how many devices to create and call our methods +with. + +The platform_driver callbacks are called with a platform_device param; +the isa_driver callbacks are being called with a ``struct device *dev, +unsigned int id`` pair directly -- with the device creation completely +internal to the bus it's much cleaner to not leak isa_dev's by passing +them in at all. The id is the only thing we ever want other then the +struct device anyways, and it makes for nicer code in the callbacks as +well. + +With this additional .match() callback ISA drivers have all options. If +ALSA would want to keep the old non-load behaviour, it could stick all +of the old .probe in .match, which would only keep them registered after +everything was found to be present and accounted for. If it wanted the +behaviour of always loading as it inadvertently did for a bit after the +changeover to platform devices, it could just not provide a .match() and +do everything in .probe() as before. + +If it, as Takashi Iwai already suggested earlier as a way of following +the model from saner buses more closely, wants to load when a later bind +could conceivably succeed, it could use .match() for the prerequisites +(such as checking the user wants the card enabled and that port/irq/dma +values have been passed in) and .probe() for everything else. This is +the nicest model. + +To the code... + +This exports only two functions; isa_{,un}register_driver(). + +isa_register_driver() register's the struct device_driver, and then +loops over the passed in ndev creating devices and registering them. +This causes the bus match method to be called for them, which is:: + + int isa_bus_match(struct device *dev, struct device_driver *driver) + { + struct isa_driver *isa_driver = to_isa_driver(driver); + + if (dev->platform_data == isa_driver) { + if (!isa_driver->match || + isa_driver->match(dev, to_isa_dev(dev)->id)) + return 1; + dev->platform_data = NULL; + } + return 0; + } + +The first thing this does is check if this device is in fact one of this +driver's devices by seeing if the device's platform_data pointer is set +to this driver. Platform devices compare strings, but we don't need to +do that with everything being internal, so isa_register_driver() abuses +dev->platform_data as a isa_driver pointer which we can then check here. +I believe platform_data is available for this, but if rather not, moving +the isa_driver pointer to the private struct isa_dev is ofcourse fine as +well. + +Then, if the the driver did not provide a .match, it matches. If it did, +the driver match() method is called to determine a match. + +If it did **not** match, dev->platform_data is reset to indicate this to +isa_register_driver which can then unregister the device again. + +If during all this, there's any error, or no devices matched at all +everything is backed out again and the error, or -ENODEV, is returned. + +isa_unregister_driver() just unregisters the matched devices and the +driver itself. + +module_isa_driver is a helper macro for ISA drivers which do not do +anything special in module init/exit. This eliminates a lot of +boilerplate code. Each module may only use this macro once, and calling +it replaces module_init and module_exit. + +max_num_isa_dev is a macro to determine the maximum possible number of +ISA devices which may be registered in the I/O port address space given +the address extent of the ISA devices. diff --git a/Documentation/driver-api/isapnp.rst b/Documentation/driver-api/isapnp.rst new file mode 100644 index 000000000000..8d0840ac847b --- /dev/null +++ b/Documentation/driver-api/isapnp.rst @@ -0,0 +1,15 @@ +========================================================== +ISA Plug & Play support by Jaroslav Kysela <perex@suse.cz> +========================================================== + +Interface /proc/isapnp +====================== + +The interface has been removed. See pnp.txt for more details. + +Interface /proc/bus/isapnp +========================== + +This directory allows access to ISA PnP cards and logical devices. +The regular files contain the contents of ISA PnP registers for +a logical device. diff --git a/Documentation/driver-api/lightnvm-pblk.rst b/Documentation/driver-api/lightnvm-pblk.rst new file mode 100644 index 000000000000..1040ed1cec81 --- /dev/null +++ b/Documentation/driver-api/lightnvm-pblk.rst @@ -0,0 +1,21 @@ +pblk: Physical Block Device Target +================================== + +pblk implements a fully associative, host-based FTL that exposes a traditional +block I/O interface. Its primary responsibilities are: + + - Map logical addresses onto physical addresses (4KB granularity) in a + logical-to-physical (L2P) table. + - Maintain the integrity and consistency of the L2P table as well as its + recovery from normal tear down and power outage. + - Deal with controller- and media-specific constrains. + - Handle I/O errors. + - Implement garbage collection. + - Maintain consistency across the I/O stack during synchronization points. + +For more information please refer to: + + http://lightnvm.io + +which maintains updated FAQs, manual pages, technical documentation, tools, +contacts, etc. diff --git a/Documentation/driver-api/men-chameleon-bus.rst b/Documentation/driver-api/men-chameleon-bus.rst new file mode 100644 index 000000000000..1b1f048aa748 --- /dev/null +++ b/Documentation/driver-api/men-chameleon-bus.rst @@ -0,0 +1,175 @@ +================= +MEN Chameleon Bus +================= + +.. Table of Contents + ================= + 1 Introduction + 1.1 Scope of this Document + 1.2 Limitations of the current implementation + 2 Architecture + 2.1 MEN Chameleon Bus + 2.2 Carrier Devices + 2.3 Parser + 3 Resource handling + 3.1 Memory Resources + 3.2 IRQs + 4 Writing an MCB driver + 4.1 The driver structure + 4.2 Probing and attaching + 4.3 Initializing the driver + + +Introduction +============ + +This document describes the architecture and implementation of the MEN +Chameleon Bus (called MCB throughout this document). + +Scope of this Document +---------------------- + +This document is intended to be a short overview of the current +implementation and does by no means describe the complete possibilities of MCB +based devices. + +Limitations of the current implementation +----------------------------------------- + +The current implementation is limited to PCI and PCIe based carrier devices +that only use a single memory resource and share the PCI legacy IRQ. Not +implemented are: + +- Multi-resource MCB devices like the VME Controller or M-Module carrier. +- MCB devices that need another MCB device, like SRAM for a DMA Controller's + buffer descriptors or a video controller's video memory. +- A per-carrier IRQ domain for carrier devices that have one (or more) IRQs + per MCB device like PCIe based carriers with MSI or MSI-X support. + +Architecture +============ + +MCB is divided into 3 functional blocks: + +- The MEN Chameleon Bus itself, +- drivers for MCB Carrier Devices and +- the parser for the Chameleon table. + +MEN Chameleon Bus +----------------- + +The MEN Chameleon Bus is an artificial bus system that attaches to a so +called Chameleon FPGA device found on some hardware produced my MEN Mikro +Elektronik GmbH. These devices are multi-function devices implemented in a +single FPGA and usually attached via some sort of PCI or PCIe link. Each +FPGA contains a header section describing the content of the FPGA. The +header lists the device id, PCI BAR, offset from the beginning of the PCI +BAR, size in the FPGA, interrupt number and some other properties currently +not handled by the MCB implementation. + +Carrier Devices +--------------- + +A carrier device is just an abstraction for the real world physical bus the +Chameleon FPGA is attached to. Some IP Core drivers may need to interact with +properties of the carrier device (like querying the IRQ number of a PCI +device). To provide abstraction from the real hardware bus, an MCB carrier +device provides callback methods to translate the driver's MCB function calls +to hardware related function calls. For example a carrier device may +implement the get_irq() method which can be translated into a hardware bus +query for the IRQ number the device should use. + +Parser +------ + +The parser reads the first 512 bytes of a Chameleon device and parses the +Chameleon table. Currently the parser only supports the Chameleon v2 variant +of the Chameleon table but can easily be adopted to support an older or +possible future variant. While parsing the table's entries new MCB devices +are allocated and their resources are assigned according to the resource +assignment in the Chameleon table. After resource assignment is finished, the +MCB devices are registered at the MCB and thus at the driver core of the +Linux kernel. + +Resource handling +================= + +The current implementation assigns exactly one memory and one IRQ resource +per MCB device. But this is likely going to change in the future. + +Memory Resources +---------------- + +Each MCB device has exactly one memory resource, which can be requested from +the MCB bus. This memory resource is the physical address of the MCB device +inside the carrier and is intended to be passed to ioremap() and friends. It +is already requested from the kernel by calling request_mem_region(). + +IRQs +---- + +Each MCB device has exactly one IRQ resource, which can be requested from the +MCB bus. If a carrier device driver implements the ->get_irq() callback +method, the IRQ number assigned by the carrier device will be returned, +otherwise the IRQ number inside the Chameleon table will be returned. This +number is suitable to be passed to request_irq(). + +Writing an MCB driver +===================== + +The driver structure +-------------------- + +Each MCB driver has a structure to identify the device driver as well as +device ids which identify the IP Core inside the FPGA. The driver structure +also contains callback methods which get executed on driver probe and +removal from the system:: + + static const struct mcb_device_id foo_ids[] = { + { .device = 0x123 }, + { } + }; + MODULE_DEVICE_TABLE(mcb, foo_ids); + + static struct mcb_driver foo_driver = { + driver = { + .name = "foo-bar", + .owner = THIS_MODULE, + }, + .probe = foo_probe, + .remove = foo_remove, + .id_table = foo_ids, + }; + +Probing and attaching +--------------------- + +When a driver is loaded and the MCB devices it services are found, the MCB +core will call the driver's probe callback method. When the driver is removed +from the system, the MCB core will call the driver's remove callback method:: + + static init foo_probe(struct mcb_device *mdev, const struct mcb_device_id *id); + static void foo_remove(struct mcb_device *mdev); + +Initializing the driver +----------------------- + +When the kernel is booted or your foo driver module is inserted, you have to +perform driver initialization. Usually it is enough to register your driver +module at the MCB core:: + + static int __init foo_init(void) + { + return mcb_register_driver(&foo_driver); + } + module_init(foo_init); + + static void __exit foo_exit(void) + { + mcb_unregister_driver(&foo_driver); + } + module_exit(foo_exit); + +The module_mcb_driver() macro can be used to reduce the above code:: + + module_mcb_driver(foo_driver); diff --git a/Documentation/driver-api/ntb.rst b/Documentation/driver-api/ntb.rst new file mode 100644 index 000000000000..074a423c853c --- /dev/null +++ b/Documentation/driver-api/ntb.rst @@ -0,0 +1,236 @@ +=========== +NTB Drivers +=========== + +NTB (Non-Transparent Bridge) is a type of PCI-Express bridge chip that connects +the separate memory systems of two or more computers to the same PCI-Express +fabric. Existing NTB hardware supports a common feature set: doorbell +registers and memory translation windows, as well as non common features like +scratchpad and message registers. Scratchpad registers are read-and-writable +registers that are accessible from either side of the device, so that peers can +exchange a small amount of information at a fixed address. Message registers can +be utilized for the same purpose. Additionally they are provided with with +special status bits to make sure the information isn't rewritten by another +peer. Doorbell registers provide a way for peers to send interrupt events. +Memory windows allow translated read and write access to the peer memory. + +NTB Core Driver (ntb) +===================== + +The NTB core driver defines an api wrapping the common feature set, and allows +clients interested in NTB features to discover NTB the devices supported by +hardware drivers. The term "client" is used here to mean an upper layer +component making use of the NTB api. The term "driver," or "hardware driver," +is used here to mean a driver for a specific vendor and model of NTB hardware. + +NTB Client Drivers +================== + +NTB client drivers should register with the NTB core driver. After +registering, the client probe and remove functions will be called appropriately +as ntb hardware, or hardware drivers, are inserted and removed. The +registration uses the Linux Device framework, so it should feel familiar to +anyone who has written a pci driver. + +NTB Typical client driver implementation +---------------------------------------- + +Primary purpose of NTB is to share some peace of memory between at least two +systems. So the NTB device features like Scratchpad/Message registers are +mainly used to perform the proper memory window initialization. Typically +there are two types of memory window interfaces supported by the NTB API: +inbound translation configured on the local ntb port and outbound translation +configured by the peer, on the peer ntb port. The first type is +depicted on the next figure:: + + Inbound translation: + + Memory: Local NTB Port: Peer NTB Port: Peer MMIO: + ____________ + | dma-mapped |-ntb_mw_set_trans(addr) | + | memory | _v____________ | ______________ + | (addr) |<======| MW xlat addr |<====| MW base addr |<== memory-mapped IO + |------------| |--------------| | |--------------| + +So typical scenario of the first type memory window initialization looks: +1) allocate a memory region, 2) put translated address to NTB config, +3) somehow notify a peer device of performed initialization, 4) peer device +maps corresponding outbound memory window so to have access to the shared +memory region. + +The second type of interface, that implies the shared windows being +initialized by a peer device, is depicted on the figure:: + + Outbound translation: + + Memory: Local NTB Port: Peer NTB Port: Peer MMIO: + ____________ ______________ + | dma-mapped | | | MW base addr |<== memory-mapped IO + | memory | | |--------------| + | (addr) |<===================| MW xlat addr |<-ntb_peer_mw_set_trans(addr) + |------------| | |--------------| + +Typical scenario of the second type interface initialization would be: +1) allocate a memory region, 2) somehow deliver a translated address to a peer +device, 3) peer puts the translated address to NTB config, 4) peer device maps +outbound memory window so to have access to the shared memory region. + +As one can see the described scenarios can be combined in one portable +algorithm. + + Local device: + 1) Allocate memory for a shared window + 2) Initialize memory window by translated address of the allocated region + (it may fail if local memory window initialization is unsupported) + 3) Send the translated address and memory window index to a peer device + + Peer device: + 1) Initialize memory window with retrieved address of the allocated + by another device memory region (it may fail if peer memory window + initialization is unsupported) + 2) Map outbound memory window + +In accordance with this scenario, the NTB Memory Window API can be used as +follows: + + Local device: + 1) ntb_mw_count(pidx) - retrieve number of memory ranges, which can + be allocated for memory windows between local device and peer device + of port with specified index. + 2) ntb_get_align(pidx, midx) - retrieve parameters restricting the + shared memory region alignment and size. Then memory can be properly + allocated. + 3) Allocate physically contiguous memory region in compliance with + restrictions retrieved in 2). + 4) ntb_mw_set_trans(pidx, midx) - try to set translation address of + the memory window with specified index for the defined peer device + (it may fail if local translated address setting is not supported) + 5) Send translated base address (usually together with memory window + number) to the peer device using, for instance, scratchpad or message + registers. + + Peer device: + 1) ntb_peer_mw_set_trans(pidx, midx) - try to set received from other + device (related to pidx) translated address for specified memory + window. It may fail if retrieved address, for instance, exceeds + maximum possible address or isn't properly aligned. + 2) ntb_peer_mw_get_addr(widx) - retrieve MMIO address to map the memory + window so to have an access to the shared memory. + +Also it is worth to note, that method ntb_mw_count(pidx) should return the +same value as ntb_peer_mw_count() on the peer with port index - pidx. + +NTB Transport Client (ntb\_transport) and NTB Netdev (ntb\_netdev) +------------------------------------------------------------------ + +The primary client for NTB is the Transport client, used in tandem with NTB +Netdev. These drivers function together to create a logical link to the peer, +across the ntb, to exchange packets of network data. The Transport client +establishes a logical link to the peer, and creates queue pairs to exchange +messages and data. The NTB Netdev then creates an ethernet device using a +Transport queue pair. Network data is copied between socket buffers and the +Transport queue pair buffer. The Transport client may be used for other things +besides Netdev, however no other applications have yet been written. + +NTB Ping Pong Test Client (ntb\_pingpong) +----------------------------------------- + +The Ping Pong test client serves as a demonstration to exercise the doorbell +and scratchpad registers of NTB hardware, and as an example simple NTB client. +Ping Pong enables the link when started, waits for the NTB link to come up, and +then proceeds to read and write the doorbell scratchpad registers of the NTB. +The peers interrupt each other using a bit mask of doorbell bits, which is +shifted by one in each round, to test the behavior of multiple doorbell bits +and interrupt vectors. The Ping Pong driver also reads the first local +scratchpad, and writes the value plus one to the first peer scratchpad, each +round before writing the peer doorbell register. + +Module Parameters: + +* unsafe - Some hardware has known issues with scratchpad and doorbell + registers. By default, Ping Pong will not attempt to exercise such + hardware. You may override this behavior at your own risk by setting + unsafe=1. +* delay\_ms - Specify the delay between receiving a doorbell + interrupt event and setting the peer doorbell register for the next + round. +* init\_db - Specify the doorbell bits to start new series of rounds. A new + series begins once all the doorbell bits have been shifted out of + range. +* dyndbg - It is suggested to specify dyndbg=+p when loading this module, and + then to observe debugging output on the console. + +NTB Tool Test Client (ntb\_tool) +-------------------------------- + +The Tool test client serves for debugging, primarily, ntb hardware and drivers. +The Tool provides access through debugfs for reading, setting, and clearing the +NTB doorbell, and reading and writing scratchpads. + +The Tool does not currently have any module parameters. + +Debugfs Files: + +* *debugfs*/ntb\_tool/*hw*/ + A directory in debugfs will be created for each + NTB device probed by the tool. This directory is shortened to *hw* + below. +* *hw*/db + This file is used to read, set, and clear the local doorbell. Not + all operations may be supported by all hardware. To read the doorbell, + read the file. To set the doorbell, write `s` followed by the bits to + set (eg: `echo 's 0x0101' > db`). To clear the doorbell, write `c` + followed by the bits to clear. +* *hw*/mask + This file is used to read, set, and clear the local doorbell mask. + See *db* for details. +* *hw*/peer\_db + This file is used to read, set, and clear the peer doorbell. + See *db* for details. +* *hw*/peer\_mask + This file is used to read, set, and clear the peer doorbell + mask. See *db* for details. +* *hw*/spad + This file is used to read and write local scratchpads. To read + the values of all scratchpads, read the file. To write values, write a + series of pairs of scratchpad number and value + (eg: `echo '4 0x123 7 0xabc' > spad` + # to set scratchpads `4` and `7` to `0x123` and `0xabc`, respectively). +* *hw*/peer\_spad + This file is used to read and write peer scratchpads. See + *spad* for details. + +NTB Hardware Drivers +==================== + +NTB hardware drivers should register devices with the NTB core driver. After +registering, clients probe and remove functions will be called. + +NTB Intel Hardware Driver (ntb\_hw\_intel) +------------------------------------------ + +The Intel hardware driver supports NTB on Xeon and Atom CPUs. + +Module Parameters: + +* b2b\_mw\_idx + If the peer ntb is to be accessed via a memory window, then use + this memory window to access the peer ntb. A value of zero or positive + starts from the first mw idx, and a negative value starts from the last + mw idx. Both sides MUST set the same value here! The default value is + `-1`. +* b2b\_mw\_share + If the peer ntb is to be accessed via a memory window, and if + the memory window is large enough, still allow the client to use the + second half of the memory window for address translation to the peer. +* xeon\_b2b\_usd\_bar2\_addr64 + If using B2B topology on Xeon hardware, use + this 64 bit address on the bus between the NTB devices for the window + at BAR2, on the upstream side of the link. +* xeon\_b2b\_usd\_bar4\_addr64 - See *xeon\_b2b\_bar2\_addr64*. +* xeon\_b2b\_usd\_bar4\_addr32 - See *xeon\_b2b\_bar2\_addr64*. +* xeon\_b2b\_usd\_bar5\_addr32 - See *xeon\_b2b\_bar2\_addr64*. +* xeon\_b2b\_dsd\_bar2\_addr64 - See *xeon\_b2b\_bar2\_addr64*. +* xeon\_b2b\_dsd\_bar4\_addr64 - See *xeon\_b2b\_bar2\_addr64*. +* xeon\_b2b\_dsd\_bar4\_addr32 - See *xeon\_b2b\_bar2\_addr64*. +* xeon\_b2b\_dsd\_bar5\_addr32 - See *xeon\_b2b\_bar2\_addr64*. diff --git a/Documentation/driver-api/nvmem.rst b/Documentation/driver-api/nvmem.rst new file mode 100644 index 000000000000..d9d958d5c824 --- /dev/null +++ b/Documentation/driver-api/nvmem.rst @@ -0,0 +1,189 @@ +.. SPDX-License-Identifier: GPL-2.0 + +=============== +NVMEM Subsystem +=============== + + Srinivas Kandagatla <srinivas.kandagatla@linaro.org> + +This document explains the NVMEM Framework along with the APIs provided, +and how to use it. + +1. Introduction +=============== +*NVMEM* is the abbreviation for Non Volatile Memory layer. It is used to +retrieve configuration of SOC or Device specific data from non volatile +memories like eeprom, efuses and so on. + +Before this framework existed, NVMEM drivers like eeprom were stored in +drivers/misc, where they all had to duplicate pretty much the same code to +register a sysfs file, allow in-kernel users to access the content of the +devices they were driving, etc. + +This was also a problem as far as other in-kernel users were involved, since +the solutions used were pretty much different from one driver to another, there +was a rather big abstraction leak. + +This framework aims at solve these problems. It also introduces DT +representation for consumer devices to go get the data they require (MAC +Addresses, SoC/Revision ID, part numbers, and so on) from the NVMEMs. This +framework is based on regmap, so that most of the abstraction available in +regmap can be reused, across multiple types of buses. + +NVMEM Providers ++++++++++++++++ + +NVMEM provider refers to an entity that implements methods to initialize, read +and write the non-volatile memory. + +2. Registering/Unregistering the NVMEM provider +=============================================== + +A NVMEM provider can register with NVMEM core by supplying relevant +nvmem configuration to nvmem_register(), on success core would return a valid +nvmem_device pointer. + +nvmem_unregister(nvmem) is used to unregister a previously registered provider. + +For example, a simple qfprom case:: + + static struct nvmem_config econfig = { + .name = "qfprom", + .owner = THIS_MODULE, + }; + + static int qfprom_probe(struct platform_device *pdev) + { + ... + econfig.dev = &pdev->dev; + nvmem = nvmem_register(&econfig); + ... + } + +It is mandatory that the NVMEM provider has a regmap associated with its +struct device. Failure to do would return error code from nvmem_register(). + +Users of board files can define and register nvmem cells using the +nvmem_cell_table struct:: + + static struct nvmem_cell_info foo_nvmem_cells[] = { + { + .name = "macaddr", + .offset = 0x7f00, + .bytes = ETH_ALEN, + } + }; + + static struct nvmem_cell_table foo_nvmem_cell_table = { + .nvmem_name = "i2c-eeprom", + .cells = foo_nvmem_cells, + .ncells = ARRAY_SIZE(foo_nvmem_cells), + }; + + nvmem_add_cell_table(&foo_nvmem_cell_table); + +Additionally it is possible to create nvmem cell lookup entries and register +them with the nvmem framework from machine code as shown in the example below:: + + static struct nvmem_cell_lookup foo_nvmem_lookup = { + .nvmem_name = "i2c-eeprom", + .cell_name = "macaddr", + .dev_id = "foo_mac.0", + .con_id = "mac-address", + }; + + nvmem_add_cell_lookups(&foo_nvmem_lookup, 1); + +NVMEM Consumers ++++++++++++++++ + +NVMEM consumers are the entities which make use of the NVMEM provider to +read from and to NVMEM. + +3. NVMEM cell based consumer APIs +================================= + +NVMEM cells are the data entries/fields in the NVMEM. +The NVMEM framework provides 3 APIs to read/write NVMEM cells:: + + struct nvmem_cell *nvmem_cell_get(struct device *dev, const char *name); + struct nvmem_cell *devm_nvmem_cell_get(struct device *dev, const char *name); + + void nvmem_cell_put(struct nvmem_cell *cell); + void devm_nvmem_cell_put(struct device *dev, struct nvmem_cell *cell); + + void *nvmem_cell_read(struct nvmem_cell *cell, ssize_t *len); + int nvmem_cell_write(struct nvmem_cell *cell, void *buf, ssize_t len); + +`*nvmem_cell_get()` apis will get a reference to nvmem cell for a given id, +and nvmem_cell_read/write() can then read or write to the cell. +Once the usage of the cell is finished the consumer should call +`*nvmem_cell_put()` to free all the allocation memory for the cell. + +4. Direct NVMEM device based consumer APIs +========================================== + +In some instances it is necessary to directly read/write the NVMEM. +To facilitate such consumers NVMEM framework provides below apis:: + + struct nvmem_device *nvmem_device_get(struct device *dev, const char *name); + struct nvmem_device *devm_nvmem_device_get(struct device *dev, + const char *name); + void nvmem_device_put(struct nvmem_device *nvmem); + int nvmem_device_read(struct nvmem_device *nvmem, unsigned int offset, + size_t bytes, void *buf); + int nvmem_device_write(struct nvmem_device *nvmem, unsigned int offset, + size_t bytes, void *buf); + int nvmem_device_cell_read(struct nvmem_device *nvmem, + struct nvmem_cell_info *info, void *buf); + int nvmem_device_cell_write(struct nvmem_device *nvmem, + struct nvmem_cell_info *info, void *buf); + +Before the consumers can read/write NVMEM directly, it should get hold +of nvmem_controller from one of the `*nvmem_device_get()` api. + +The difference between these apis and cell based apis is that these apis always +take nvmem_device as parameter. + +5. Releasing a reference to the NVMEM +===================================== + +When a consumer no longer needs the NVMEM, it has to release the reference +to the NVMEM it has obtained using the APIs mentioned in the above section. +The NVMEM framework provides 2 APIs to release a reference to the NVMEM:: + + void nvmem_cell_put(struct nvmem_cell *cell); + void devm_nvmem_cell_put(struct device *dev, struct nvmem_cell *cell); + void nvmem_device_put(struct nvmem_device *nvmem); + void devm_nvmem_device_put(struct device *dev, struct nvmem_device *nvmem); + +Both these APIs are used to release a reference to the NVMEM and +devm_nvmem_cell_put and devm_nvmem_device_put destroys the devres associated +with this NVMEM. + +Userspace ++++++++++ + +6. Userspace binary interface +============================== + +Userspace can read/write the raw NVMEM file located at:: + + /sys/bus/nvmem/devices/*/nvmem + +ex:: + + hexdump /sys/bus/nvmem/devices/qfprom0/nvmem + + 0000000 0000 0000 0000 0000 0000 0000 0000 0000 + * + 00000a0 db10 2240 0000 e000 0c00 0c00 0000 0c00 + 0000000 0000 0000 0000 0000 0000 0000 0000 0000 + ... + * + 0001000 + +7. DeviceTree Binding +===================== + +See Documentation/devicetree/bindings/nvmem/nvmem.txt diff --git a/Documentation/driver-api/parport-lowlevel.rst b/Documentation/driver-api/parport-lowlevel.rst new file mode 100644 index 000000000000..0633d70ffda7 --- /dev/null +++ b/Documentation/driver-api/parport-lowlevel.rst @@ -0,0 +1,1832 @@ +=============================== +PARPORT interface documentation +=============================== + +:Time-stamp: <2000-02-24 13:30:20 twaugh> + +Described here are the following functions: + +Global functions:: + parport_register_driver + parport_unregister_driver + parport_enumerate + parport_register_device + parport_unregister_device + parport_claim + parport_claim_or_block + parport_release + parport_yield + parport_yield_blocking + parport_wait_peripheral + parport_poll_peripheral + parport_wait_event + parport_negotiate + parport_read + parport_write + parport_open + parport_close + parport_device_id + parport_device_coords + parport_find_class + parport_find_device + parport_set_timeout + +Port functions (can be overridden by low-level drivers): + + SPP:: + port->ops->read_data + port->ops->write_data + port->ops->read_status + port->ops->read_control + port->ops->write_control + port->ops->frob_control + port->ops->enable_irq + port->ops->disable_irq + port->ops->data_forward + port->ops->data_reverse + + EPP:: + port->ops->epp_write_data + port->ops->epp_read_data + port->ops->epp_write_addr + port->ops->epp_read_addr + + ECP:: + port->ops->ecp_write_data + port->ops->ecp_read_data + port->ops->ecp_write_addr + + Other:: + port->ops->nibble_read_data + port->ops->byte_read_data + port->ops->compat_write_data + +The parport subsystem comprises ``parport`` (the core port-sharing +code), and a variety of low-level drivers that actually do the port +accesses. Each low-level driver handles a particular style of port +(PC, Amiga, and so on). + +The parport interface to the device driver author can be broken down +into global functions and port functions. + +The global functions are mostly for communicating between the device +driver and the parport subsystem: acquiring a list of available ports, +claiming a port for exclusive use, and so on. They also include +``generic`` functions for doing standard things that will work on any +IEEE 1284-capable architecture. + +The port functions are provided by the low-level drivers, although the +core parport module provides generic ``defaults`` for some routines. +The port functions can be split into three groups: SPP, EPP, and ECP. + +SPP (Standard Parallel Port) functions modify so-called ``SPP`` +registers: data, status, and control. The hardware may not actually +have registers exactly like that, but the PC does and this interface is +modelled after common PC implementations. Other low-level drivers may +be able to emulate most of the functionality. + +EPP (Enhanced Parallel Port) functions are provided for reading and +writing in IEEE 1284 EPP mode, and ECP (Extended Capabilities Port) +functions are used for IEEE 1284 ECP mode. (What about BECP? Does +anyone care?) + +Hardware assistance for EPP and/or ECP transfers may or may not be +available, and if it is available it may or may not be used. If +hardware is not used, the transfer will be software-driven. In order +to cope with peripherals that only tenuously support IEEE 1284, a +low-level driver specific function is provided, for altering 'fudge +factors'. + +Global functions +================ + +parport_register_driver - register a device driver with parport +--------------------------------------------------------------- + +SYNOPSIS +^^^^^^^^ + +:: + + #include <linux/parport.h> + + struct parport_driver { + const char *name; + void (*attach) (struct parport *); + void (*detach) (struct parport *); + struct parport_driver *next; + }; + int parport_register_driver (struct parport_driver *driver); + +DESCRIPTION +^^^^^^^^^^^ + +In order to be notified about parallel ports when they are detected, +parport_register_driver should be called. Your driver will +immediately be notified of all ports that have already been detected, +and of each new port as low-level drivers are loaded. + +A ``struct parport_driver`` contains the textual name of your driver, +a pointer to a function to handle new ports, and a pointer to a +function to handle ports going away due to a low-level driver +unloading. Ports will only be detached if they are not being used +(i.e. there are no devices registered on them). + +The visible parts of the ``struct parport *`` argument given to +attach/detach are:: + + struct parport + { + struct parport *next; /* next parport in list */ + const char *name; /* port's name */ + unsigned int modes; /* bitfield of hardware modes */ + struct parport_device_info probe_info; + /* IEEE1284 info */ + int number; /* parport index */ + struct parport_operations *ops; + ... + }; + +There are other members of the structure, but they should not be +touched. + +The ``modes`` member summarises the capabilities of the underlying +hardware. It consists of flags which may be bitwise-ored together: + + ============================= =============================================== + PARPORT_MODE_PCSPP IBM PC registers are available, + i.e. functions that act on data, + control and status registers are + probably writing directly to the + hardware. + PARPORT_MODE_TRISTATE The data drivers may be turned off. + This allows the data lines to be used + for reverse (peripheral to host) + transfers. + PARPORT_MODE_COMPAT The hardware can assist with + compatibility-mode (printer) + transfers, i.e. compat_write_block. + PARPORT_MODE_EPP The hardware can assist with EPP + transfers. + PARPORT_MODE_ECP The hardware can assist with ECP + transfers. + PARPORT_MODE_DMA The hardware can use DMA, so you might + want to pass ISA DMA-able memory + (i.e. memory allocated using the + GFP_DMA flag with kmalloc) to the + low-level driver in order to take + advantage of it. + ============================= =============================================== + +There may be other flags in ``modes`` as well. + +The contents of ``modes`` is advisory only. For example, if the +hardware is capable of DMA, and PARPORT_MODE_DMA is in ``modes``, it +doesn't necessarily mean that DMA will always be used when possible. +Similarly, hardware that is capable of assisting ECP transfers won't +necessarily be used. + +RETURN VALUE +^^^^^^^^^^^^ + +Zero on success, otherwise an error code. + +ERRORS +^^^^^^ + +None. (Can it fail? Why return int?) + +EXAMPLE +^^^^^^^ + +:: + + static void lp_attach (struct parport *port) + { + ... + private = kmalloc (...); + dev[count++] = parport_register_device (...); + ... + } + + static void lp_detach (struct parport *port) + { + ... + } + + static struct parport_driver lp_driver = { + "lp", + lp_attach, + lp_detach, + NULL /* always put NULL here */ + }; + + int lp_init (void) + { + ... + if (parport_register_driver (&lp_driver)) { + /* Failed; nothing we can do. */ + return -EIO; + } + ... + } + + +SEE ALSO +^^^^^^^^ + +parport_unregister_driver, parport_register_device, parport_enumerate + + + +parport_unregister_driver - tell parport to forget about this driver +-------------------------------------------------------------------- + +SYNOPSIS +^^^^^^^^ + +:: + + #include <linux/parport.h> + + struct parport_driver { + const char *name; + void (*attach) (struct parport *); + void (*detach) (struct parport *); + struct parport_driver *next; + }; + void parport_unregister_driver (struct parport_driver *driver); + +DESCRIPTION +^^^^^^^^^^^ + +This tells parport not to notify the device driver of new ports or of +ports going away. Registered devices belonging to that driver are NOT +unregistered: parport_unregister_device must be used for each one. + +EXAMPLE +^^^^^^^ + +:: + + void cleanup_module (void) + { + ... + /* Stop notifications. */ + parport_unregister_driver (&lp_driver); + + /* Unregister devices. */ + for (i = 0; i < NUM_DEVS; i++) + parport_unregister_device (dev[i]); + ... + } + +SEE ALSO +^^^^^^^^ + +parport_register_driver, parport_enumerate + + + +parport_enumerate - retrieve a list of parallel ports (DEPRECATED) +------------------------------------------------------------------ + +SYNOPSIS +^^^^^^^^ + +:: + + #include <linux/parport.h> + + struct parport *parport_enumerate (void); + +DESCRIPTION +^^^^^^^^^^^ + +Retrieve the first of a list of valid parallel ports for this machine. +Successive parallel ports can be found using the ``struct parport +*next`` element of the ``struct parport *`` that is returned. If ``next`` +is NULL, there are no more parallel ports in the list. The number of +ports in the list will not exceed PARPORT_MAX. + +RETURN VALUE +^^^^^^^^^^^^ + +A ``struct parport *`` describing a valid parallel port for the machine, +or NULL if there are none. + +ERRORS +^^^^^^ + +This function can return NULL to indicate that there are no parallel +ports to use. + +EXAMPLE +^^^^^^^ + +:: + + int detect_device (void) + { + struct parport *port; + + for (port = parport_enumerate (); + port != NULL; + port = port->next) { + /* Try to detect a device on the port... */ + ... + } + } + + ... + } + +NOTES +^^^^^ + +parport_enumerate is deprecated; parport_register_driver should be +used instead. + +SEE ALSO +^^^^^^^^ + +parport_register_driver, parport_unregister_driver + + + +parport_register_device - register to use a port +------------------------------------------------ + +SYNOPSIS +^^^^^^^^ + +:: + + #include <linux/parport.h> + + typedef int (*preempt_func) (void *handle); + typedef void (*wakeup_func) (void *handle); + typedef int (*irq_func) (int irq, void *handle, struct pt_regs *); + + struct pardevice *parport_register_device(struct parport *port, + const char *name, + preempt_func preempt, + wakeup_func wakeup, + irq_func irq, + int flags, + void *handle); + +DESCRIPTION +^^^^^^^^^^^ + +Use this function to register your device driver on a parallel port +(``port``). Once you have done that, you will be able to use +parport_claim and parport_release in order to use the port. + +The (``name``) argument is the name of the device that appears in /proc +filesystem. The string must be valid for the whole lifetime of the +device (until parport_unregister_device is called). + +This function will register three callbacks into your driver: +``preempt``, ``wakeup`` and ``irq``. Each of these may be NULL in order to +indicate that you do not want a callback. + +When the ``preempt`` function is called, it is because another driver +wishes to use the parallel port. The ``preempt`` function should return +non-zero if the parallel port cannot be released yet -- if zero is +returned, the port is lost to another driver and the port must be +re-claimed before use. + +The ``wakeup`` function is called once another driver has released the +port and no other driver has yet claimed it. You can claim the +parallel port from within the ``wakeup`` function (in which case the +claim is guaranteed to succeed), or choose not to if you don't need it +now. + +If an interrupt occurs on the parallel port your driver has claimed, +the ``irq`` function will be called. (Write something about shared +interrupts here.) + +The ``handle`` is a pointer to driver-specific data, and is passed to +the callback functions. + +``flags`` may be a bitwise combination of the following flags: + + ===================== ================================================= + Flag Meaning + ===================== ================================================= + PARPORT_DEV_EXCL The device cannot share the parallel port at all. + Use this only when absolutely necessary. + ===================== ================================================= + +The typedefs are not actually defined -- they are only shown in order +to make the function prototype more readable. + +The visible parts of the returned ``struct pardevice`` are:: + + struct pardevice { + struct parport *port; /* Associated port */ + void *private; /* Device driver's 'handle' */ + ... + }; + +RETURN VALUE +^^^^^^^^^^^^ + +A ``struct pardevice *``: a handle to the registered parallel port +device that can be used for parport_claim, parport_release, etc. + +ERRORS +^^^^^^ + +A return value of NULL indicates that there was a problem registering +a device on that port. + +EXAMPLE +^^^^^^^ + +:: + + static int preempt (void *handle) + { + if (busy_right_now) + return 1; + + must_reclaim_port = 1; + return 0; + } + + static void wakeup (void *handle) + { + struct toaster *private = handle; + struct pardevice *dev = private->dev; + if (!dev) return; /* avoid races */ + + if (want_port) + parport_claim (dev); + } + + static int toaster_detect (struct toaster *private, struct parport *port) + { + private->dev = parport_register_device (port, "toaster", preempt, + wakeup, NULL, 0, + private); + if (!private->dev) + /* Couldn't register with parport. */ + return -EIO; + + must_reclaim_port = 0; + busy_right_now = 1; + parport_claim_or_block (private->dev); + ... + /* Don't need the port while the toaster warms up. */ + busy_right_now = 0; + ... + busy_right_now = 1; + if (must_reclaim_port) { + parport_claim_or_block (private->dev); + must_reclaim_port = 0; + } + ... + } + +SEE ALSO +^^^^^^^^ + +parport_unregister_device, parport_claim + + + +parport_unregister_device - finish using a port +----------------------------------------------- + +SYNPOPSIS + +:: + + #include <linux/parport.h> + + void parport_unregister_device (struct pardevice *dev); + +DESCRIPTION +^^^^^^^^^^^ + +This function is the opposite of parport_register_device. After using +parport_unregister_device, ``dev`` is no longer a valid device handle. + +You should not unregister a device that is currently claimed, although +if you do it will be released automatically. + +EXAMPLE +^^^^^^^ + +:: + + ... + kfree (dev->private); /* before we lose the pointer */ + parport_unregister_device (dev); + ... + +SEE ALSO +^^^^^^^^ + + +parport_unregister_driver + +parport_claim, parport_claim_or_block - claim the parallel port for a device +---------------------------------------------------------------------------- + +SYNOPSIS +^^^^^^^^ + +:: + + #include <linux/parport.h> + + int parport_claim (struct pardevice *dev); + int parport_claim_or_block (struct pardevice *dev); + +DESCRIPTION +^^^^^^^^^^^ + +These functions attempt to gain control of the parallel port on which +``dev`` is registered. ``parport_claim`` does not block, but +``parport_claim_or_block`` may do. (Put something here about blocking +interruptibly or non-interruptibly.) + +You should not try to claim a port that you have already claimed. + +RETURN VALUE +^^^^^^^^^^^^ + +A return value of zero indicates that the port was successfully +claimed, and the caller now has possession of the parallel port. + +If ``parport_claim_or_block`` blocks before returning successfully, the +return value is positive. + +ERRORS +^^^^^^ + +========== ========================================================== + -EAGAIN The port is unavailable at the moment, but another attempt + to claim it may succeed. +========== ========================================================== + +SEE ALSO +^^^^^^^^ + + +parport_release + +parport_release - release the parallel port +------------------------------------------- + +SYNOPSIS +^^^^^^^^ + +:: + + #include <linux/parport.h> + + void parport_release (struct pardevice *dev); + +DESCRIPTION +^^^^^^^^^^^ + +Once a parallel port device has been claimed, it can be released using +``parport_release``. It cannot fail, but you should not release a +device that you do not have possession of. + +EXAMPLE +^^^^^^^ + +:: + + static size_t write (struct pardevice *dev, const void *buf, + size_t len) + { + ... + written = dev->port->ops->write_ecp_data (dev->port, buf, + len); + parport_release (dev); + ... + } + + +SEE ALSO +^^^^^^^^ + +change_mode, parport_claim, parport_claim_or_block, parport_yield + + + +parport_yield, parport_yield_blocking - temporarily release a parallel port +--------------------------------------------------------------------------- + +SYNOPSIS +^^^^^^^^ + +:: + + #include <linux/parport.h> + + int parport_yield (struct pardevice *dev) + int parport_yield_blocking (struct pardevice *dev); + +DESCRIPTION +^^^^^^^^^^^ + +When a driver has control of a parallel port, it may allow another +driver to temporarily ``borrow`` it. ``parport_yield`` does not block; +``parport_yield_blocking`` may do. + +RETURN VALUE +^^^^^^^^^^^^ + +A return value of zero indicates that the caller still owns the port +and the call did not block. + +A positive return value from ``parport_yield_blocking`` indicates that +the caller still owns the port and the call blocked. + +A return value of -EAGAIN indicates that the caller no longer owns the +port, and it must be re-claimed before use. + +ERRORS +^^^^^^ + +========= ========================================================== + -EAGAIN Ownership of the parallel port was given away. +========= ========================================================== + +SEE ALSO +^^^^^^^^ + +parport_release + + + +parport_wait_peripheral - wait for status lines, up to 35ms +----------------------------------------------------------- + +SYNOPSIS +^^^^^^^^ + +:: + + #include <linux/parport.h> + + int parport_wait_peripheral (struct parport *port, + unsigned char mask, + unsigned char val); + +DESCRIPTION +^^^^^^^^^^^ + +Wait for the status lines in mask to match the values in val. + +RETURN VALUE +^^^^^^^^^^^^ + +======== ========================================================== + -EINTR a signal is pending + 0 the status lines in mask have values in val + 1 timed out while waiting (35ms elapsed) +======== ========================================================== + +SEE ALSO +^^^^^^^^ + +parport_poll_peripheral + + + +parport_poll_peripheral - wait for status lines, in usec +-------------------------------------------------------- + +SYNOPSIS +^^^^^^^^ + +:: + + #include <linux/parport.h> + + int parport_poll_peripheral (struct parport *port, + unsigned char mask, + unsigned char val, + int usec); + +DESCRIPTION +^^^^^^^^^^^ + +Wait for the status lines in mask to match the values in val. + +RETURN VALUE +^^^^^^^^^^^^ + +======== ========================================================== + -EINTR a signal is pending + 0 the status lines in mask have values in val + 1 timed out while waiting (usec microseconds have elapsed) +======== ========================================================== + +SEE ALSO +^^^^^^^^ + +parport_wait_peripheral + + + +parport_wait_event - wait for an event on a port +------------------------------------------------ + +SYNOPSIS +^^^^^^^^ + +:: + + #include <linux/parport.h> + + int parport_wait_event (struct parport *port, signed long timeout) + +DESCRIPTION +^^^^^^^^^^^ + +Wait for an event (e.g. interrupt) on a port. The timeout is in +jiffies. + +RETURN VALUE +^^^^^^^^^^^^ + +======= ========================================================== + 0 success + <0 error (exit as soon as possible) + >0 timed out +======= ========================================================== + +parport_negotiate - perform IEEE 1284 negotiation +------------------------------------------------- + +SYNOPSIS +^^^^^^^^ + +:: + + #include <linux/parport.h> + + int parport_negotiate (struct parport *, int mode); + +DESCRIPTION +^^^^^^^^^^^ + +Perform IEEE 1284 negotiation. + +RETURN VALUE +^^^^^^^^^^^^ + +======= ========================================================== + 0 handshake OK; IEEE 1284 peripheral and mode available + -1 handshake failed; peripheral not compliant (or none present) + 1 handshake OK; IEEE 1284 peripheral present but mode not + available +======= ========================================================== + +SEE ALSO +^^^^^^^^ + +parport_read, parport_write + + + +parport_read - read data from device +------------------------------------ + +SYNOPSIS +^^^^^^^^ + +:: + + #include <linux/parport.h> + + ssize_t parport_read (struct parport *, void *buf, size_t len); + +DESCRIPTION +^^^^^^^^^^^ + +Read data from device in current IEEE 1284 transfer mode. This only +works for modes that support reverse data transfer. + +RETURN VALUE +^^^^^^^^^^^^ + +If negative, an error code; otherwise the number of bytes transferred. + +SEE ALSO +^^^^^^^^ + +parport_write, parport_negotiate + + + +parport_write - write data to device +------------------------------------ + +SYNOPSIS +^^^^^^^^ + +:: + + #include <linux/parport.h> + + ssize_t parport_write (struct parport *, const void *buf, size_t len); + +DESCRIPTION +^^^^^^^^^^^ + +Write data to device in current IEEE 1284 transfer mode. This only +works for modes that support forward data transfer. + +RETURN VALUE +^^^^^^^^^^^^ + +If negative, an error code; otherwise the number of bytes transferred. + +SEE ALSO +^^^^^^^^ + +parport_read, parport_negotiate + + + +parport_open - register device for particular device number +----------------------------------------------------------- + +SYNOPSIS +^^^^^^^^ + +:: + + #include <linux/parport.h> + + struct pardevice *parport_open (int devnum, const char *name, + int (*pf) (void *), + void (*kf) (void *), + void (*irqf) (int, void *, + struct pt_regs *), + int flags, void *handle); + +DESCRIPTION +^^^^^^^^^^^ + +This is like parport_register_device but takes a device number instead +of a pointer to a struct parport. + +RETURN VALUE +^^^^^^^^^^^^ + +See parport_register_device. If no device is associated with devnum, +NULL is returned. + +SEE ALSO +^^^^^^^^ + +parport_register_device + + + +parport_close - unregister device for particular device number +-------------------------------------------------------------- + +SYNOPSIS +^^^^^^^^ + +:: + + #include <linux/parport.h> + + void parport_close (struct pardevice *dev); + +DESCRIPTION +^^^^^^^^^^^ + +This is the equivalent of parport_unregister_device for parport_open. + +SEE ALSO +^^^^^^^^ + +parport_unregister_device, parport_open + + + +parport_device_id - obtain IEEE 1284 Device ID +---------------------------------------------- + +SYNOPSIS +^^^^^^^^ + +:: + + #include <linux/parport.h> + + ssize_t parport_device_id (int devnum, char *buffer, size_t len); + +DESCRIPTION +^^^^^^^^^^^ + +Obtains the IEEE 1284 Device ID associated with a given device. + +RETURN VALUE +^^^^^^^^^^^^ + +If negative, an error code; otherwise, the number of bytes of buffer +that contain the device ID. The format of the device ID is as +follows:: + + [length][ID] + +The first two bytes indicate the inclusive length of the entire Device +ID, and are in big-endian order. The ID is a sequence of pairs of the +form:: + + key:value; + +NOTES +^^^^^ + +Many devices have ill-formed IEEE 1284 Device IDs. + +SEE ALSO +^^^^^^^^ + +parport_find_class, parport_find_device + + + +parport_device_coords - convert device number to device coordinates +------------------------------------------------------------------- + +SYNOPSIS +^^^^^^^^ + +:: + + #include <linux/parport.h> + + int parport_device_coords (int devnum, int *parport, int *mux, + int *daisy); + +DESCRIPTION +^^^^^^^^^^^ + +Convert between device number (zero-based) and device coordinates +(port, multiplexor, daisy chain address). + +RETURN VALUE +^^^^^^^^^^^^ + +Zero on success, in which case the coordinates are (``*parport``, ``*mux``, +``*daisy``). + +SEE ALSO +^^^^^^^^ + +parport_open, parport_device_id + + + +parport_find_class - find a device by its class +----------------------------------------------- + +SYNOPSIS +^^^^^^^^ + +:: + + #include <linux/parport.h> + + typedef enum { + PARPORT_CLASS_LEGACY = 0, /* Non-IEEE1284 device */ + PARPORT_CLASS_PRINTER, + PARPORT_CLASS_MODEM, + PARPORT_CLASS_NET, + PARPORT_CLASS_HDC, /* Hard disk controller */ + PARPORT_CLASS_PCMCIA, + PARPORT_CLASS_MEDIA, /* Multimedia device */ + PARPORT_CLASS_FDC, /* Floppy disk controller */ + PARPORT_CLASS_PORTS, + PARPORT_CLASS_SCANNER, + PARPORT_CLASS_DIGCAM, + PARPORT_CLASS_OTHER, /* Anything else */ + PARPORT_CLASS_UNSPEC, /* No CLS field in ID */ + PARPORT_CLASS_SCSIADAPTER + } parport_device_class; + + int parport_find_class (parport_device_class cls, int from); + +DESCRIPTION +^^^^^^^^^^^ + +Find a device by class. The search starts from device number from+1. + +RETURN VALUE +^^^^^^^^^^^^ + +The device number of the next device in that class, or -1 if no such +device exists. + +NOTES +^^^^^ + +Example usage:: + + int devnum = -1; + while ((devnum = parport_find_class (PARPORT_CLASS_DIGCAM, devnum)) != -1) { + struct pardevice *dev = parport_open (devnum, ...); + ... + } + +SEE ALSO +^^^^^^^^ + +parport_find_device, parport_open, parport_device_id + + + +parport_find_device - find a device by its class +------------------------------------------------ + +SYNOPSIS +^^^^^^^^ + +:: + + #include <linux/parport.h> + + int parport_find_device (const char *mfg, const char *mdl, int from); + +DESCRIPTION +^^^^^^^^^^^ + +Find a device by vendor and model. The search starts from device +number from+1. + +RETURN VALUE +^^^^^^^^^^^^ + +The device number of the next device matching the specifications, or +-1 if no such device exists. + +NOTES +^^^^^ + +Example usage:: + + int devnum = -1; + while ((devnum = parport_find_device ("IOMEGA", "ZIP+", devnum)) != -1) { + struct pardevice *dev = parport_open (devnum, ...); + ... + } + +SEE ALSO +^^^^^^^^ + +parport_find_class, parport_open, parport_device_id + + + +parport_set_timeout - set the inactivity timeout +------------------------------------------------ + +SYNOPSIS +^^^^^^^^ + +:: + + #include <linux/parport.h> + + long parport_set_timeout (struct pardevice *dev, long inactivity); + +DESCRIPTION +^^^^^^^^^^^ + +Set the inactivity timeout, in jiffies, for a registered device. The +previous timeout is returned. + +RETURN VALUE +^^^^^^^^^^^^ + +The previous timeout, in jiffies. + +NOTES +^^^^^ + +Some of the port->ops functions for a parport may take time, owing to +delays at the peripheral. After the peripheral has not responded for +``inactivity`` jiffies, a timeout will occur and the blocking function +will return. + +A timeout of 0 jiffies is a special case: the function must do as much +as it can without blocking or leaving the hardware in an unknown +state. If port operations are performed from within an interrupt +handler, for instance, a timeout of 0 jiffies should be used. + +Once set for a registered device, the timeout will remain at the set +value until set again. + +SEE ALSO +^^^^^^^^ + +port->ops->xxx_read/write_yyy + + + + +PORT FUNCTIONS +============== + +The functions in the port->ops structure (struct parport_operations) +are provided by the low-level driver responsible for that port. + +port->ops->read_data - read the data register +--------------------------------------------- + +SYNOPSIS +^^^^^^^^ + +:: + + #include <linux/parport.h> + + struct parport_operations { + ... + unsigned char (*read_data) (struct parport *port); + ... + }; + +DESCRIPTION +^^^^^^^^^^^ + +If port->modes contains the PARPORT_MODE_TRISTATE flag and the +PARPORT_CONTROL_DIRECTION bit in the control register is set, this +returns the value on the data pins. If port->modes contains the +PARPORT_MODE_TRISTATE flag and the PARPORT_CONTROL_DIRECTION bit is +not set, the return value _may_ be the last value written to the data +register. Otherwise the return value is undefined. + +SEE ALSO +^^^^^^^^ + +write_data, read_status, write_control + + + +port->ops->write_data - write the data register +----------------------------------------------- + +SYNOPSIS +^^^^^^^^ + +:: + + #include <linux/parport.h> + + struct parport_operations { + ... + void (*write_data) (struct parport *port, unsigned char d); + ... + }; + +DESCRIPTION +^^^^^^^^^^^ + +Writes to the data register. May have side-effects (a STROBE pulse, +for instance). + +SEE ALSO +^^^^^^^^ + +read_data, read_status, write_control + + + +port->ops->read_status - read the status register +------------------------------------------------- + +SYNOPSIS +^^^^^^^^ + +:: + + #include <linux/parport.h> + + struct parport_operations { + ... + unsigned char (*read_status) (struct parport *port); + ... + }; + +DESCRIPTION +^^^^^^^^^^^ + +Reads from the status register. This is a bitmask: + +- PARPORT_STATUS_ERROR (printer fault, "nFault") +- PARPORT_STATUS_SELECT (on-line, "Select") +- PARPORT_STATUS_PAPEROUT (no paper, "PError") +- PARPORT_STATUS_ACK (handshake, "nAck") +- PARPORT_STATUS_BUSY (busy, "Busy") + +There may be other bits set. + +SEE ALSO +^^^^^^^^ + +read_data, write_data, write_control + + + +port->ops->read_control - read the control register +--------------------------------------------------- + +SYNOPSIS +^^^^^^^^ + +:: + + #include <linux/parport.h> + + struct parport_operations { + ... + unsigned char (*read_control) (struct parport *port); + ... + }; + +DESCRIPTION +^^^^^^^^^^^ + +Returns the last value written to the control register (either from +write_control or frob_control). No port access is performed. + +SEE ALSO +^^^^^^^^ + +read_data, write_data, read_status, write_control + + + +port->ops->write_control - write the control register +----------------------------------------------------- + +SYNOPSIS +^^^^^^^^ + +:: + + #include <linux/parport.h> + + struct parport_operations { + ... + void (*write_control) (struct parport *port, unsigned char s); + ... + }; + +DESCRIPTION +^^^^^^^^^^^ + +Writes to the control register. This is a bitmask:: + + _______ + - PARPORT_CONTROL_STROBE (nStrobe) + _______ + - PARPORT_CONTROL_AUTOFD (nAutoFd) + _____ + - PARPORT_CONTROL_INIT (nInit) + _________ + - PARPORT_CONTROL_SELECT (nSelectIn) + +SEE ALSO +^^^^^^^^ + +read_data, write_data, read_status, frob_control + + + +port->ops->frob_control - write control register bits +----------------------------------------------------- + +SYNOPSIS +^^^^^^^^ + +:: + + #include <linux/parport.h> + + struct parport_operations { + ... + unsigned char (*frob_control) (struct parport *port, + unsigned char mask, + unsigned char val); + ... + }; + +DESCRIPTION +^^^^^^^^^^^ + +This is equivalent to reading from the control register, masking out +the bits in mask, exclusive-or'ing with the bits in val, and writing +the result to the control register. + +As some ports don't allow reads from the control port, a software copy +of its contents is maintained, so frob_control is in fact only one +port access. + +SEE ALSO +^^^^^^^^ + +read_data, write_data, read_status, write_control + + + +port->ops->enable_irq - enable interrupt generation +--------------------------------------------------- + +SYNOPSIS +^^^^^^^^ + +:: + + #include <linux/parport.h> + + struct parport_operations { + ... + void (*enable_irq) (struct parport *port); + ... + }; + +DESCRIPTION +^^^^^^^^^^^ + +The parallel port hardware is instructed to generate interrupts at +appropriate moments, although those moments are +architecture-specific. For the PC architecture, interrupts are +commonly generated on the rising edge of nAck. + +SEE ALSO +^^^^^^^^ + +disable_irq + + + +port->ops->disable_irq - disable interrupt generation +----------------------------------------------------- + +SYNOPSIS +^^^^^^^^ + +:: + + #include <linux/parport.h> + + struct parport_operations { + ... + void (*disable_irq) (struct parport *port); + ... + }; + +DESCRIPTION +^^^^^^^^^^^ + +The parallel port hardware is instructed not to generate interrupts. +The interrupt itself is not masked. + +SEE ALSO +^^^^^^^^ + +enable_irq + + + +port->ops->data_forward - enable data drivers +--------------------------------------------- + +SYNOPSIS +^^^^^^^^ + +:: + + #include <linux/parport.h> + + struct parport_operations { + ... + void (*data_forward) (struct parport *port); + ... + }; + +DESCRIPTION +^^^^^^^^^^^ + +Enables the data line drivers, for 8-bit host-to-peripheral +communications. + +SEE ALSO +^^^^^^^^ + +data_reverse + + + +port->ops->data_reverse - tristate the buffer +--------------------------------------------- + +SYNOPSIS +^^^^^^^^ + +:: + + #include <linux/parport.h> + + struct parport_operations { + ... + void (*data_reverse) (struct parport *port); + ... + }; + +DESCRIPTION +^^^^^^^^^^^ + +Places the data bus in a high impedance state, if port->modes has the +PARPORT_MODE_TRISTATE bit set. + +SEE ALSO +^^^^^^^^ + +data_forward + + + +port->ops->epp_write_data - write EPP data +------------------------------------------ + +SYNOPSIS +^^^^^^^^ + +:: + + #include <linux/parport.h> + + struct parport_operations { + ... + size_t (*epp_write_data) (struct parport *port, const void *buf, + size_t len, int flags); + ... + }; + +DESCRIPTION +^^^^^^^^^^^ + +Writes data in EPP mode, and returns the number of bytes written. + +The ``flags`` parameter may be one or more of the following, +bitwise-or'ed together: + +======================= ================================================= +PARPORT_EPP_FAST Use fast transfers. Some chips provide 16-bit and + 32-bit registers. However, if a transfer + times out, the return value may be unreliable. +======================= ================================================= + +SEE ALSO +^^^^^^^^ + +epp_read_data, epp_write_addr, epp_read_addr + + + +port->ops->epp_read_data - read EPP data +---------------------------------------- + +SYNOPSIS +^^^^^^^^ + +:: + + #include <linux/parport.h> + + struct parport_operations { + ... + size_t (*epp_read_data) (struct parport *port, void *buf, + size_t len, int flags); + ... + }; + +DESCRIPTION +^^^^^^^^^^^ + +Reads data in EPP mode, and returns the number of bytes read. + +The ``flags`` parameter may be one or more of the following, +bitwise-or'ed together: + +======================= ================================================= +PARPORT_EPP_FAST Use fast transfers. Some chips provide 16-bit and + 32-bit registers. However, if a transfer + times out, the return value may be unreliable. +======================= ================================================= + +SEE ALSO +^^^^^^^^ + +epp_write_data, epp_write_addr, epp_read_addr + + + +port->ops->epp_write_addr - write EPP address +--------------------------------------------- + +SYNOPSIS +^^^^^^^^ + +:: + + #include <linux/parport.h> + + struct parport_operations { + ... + size_t (*epp_write_addr) (struct parport *port, + const void *buf, size_t len, int flags); + ... + }; + +DESCRIPTION +^^^^^^^^^^^ + +Writes EPP addresses (8 bits each), and returns the number written. + +The ``flags`` parameter may be one or more of the following, +bitwise-or'ed together: + +======================= ================================================= +PARPORT_EPP_FAST Use fast transfers. Some chips provide 16-bit and + 32-bit registers. However, if a transfer + times out, the return value may be unreliable. +======================= ================================================= + +(Does PARPORT_EPP_FAST make sense for this function?) + +SEE ALSO +^^^^^^^^ + +epp_write_data, epp_read_data, epp_read_addr + + + +port->ops->epp_read_addr - read EPP address +------------------------------------------- + +SYNOPSIS +^^^^^^^^ + +:: + + #include <linux/parport.h> + + struct parport_operations { + ... + size_t (*epp_read_addr) (struct parport *port, void *buf, + size_t len, int flags); + ... + }; + +DESCRIPTION +^^^^^^^^^^^ + +Reads EPP addresses (8 bits each), and returns the number read. + +The ``flags`` parameter may be one or more of the following, +bitwise-or'ed together: + +======================= ================================================= +PARPORT_EPP_FAST Use fast transfers. Some chips provide 16-bit and + 32-bit registers. However, if a transfer + times out, the return value may be unreliable. +======================= ================================================= + +(Does PARPORT_EPP_FAST make sense for this function?) + +SEE ALSO +^^^^^^^^ + +epp_write_data, epp_read_data, epp_write_addr + + + +port->ops->ecp_write_data - write a block of ECP data +----------------------------------------------------- + +SYNOPSIS +^^^^^^^^ + +:: + + #include <linux/parport.h> + + struct parport_operations { + ... + size_t (*ecp_write_data) (struct parport *port, + const void *buf, size_t len, int flags); + ... + }; + +DESCRIPTION +^^^^^^^^^^^ + +Writes a block of ECP data. The ``flags`` parameter is ignored. + +RETURN VALUE +^^^^^^^^^^^^ + +The number of bytes written. + +SEE ALSO +^^^^^^^^ + +ecp_read_data, ecp_write_addr + + + +port->ops->ecp_read_data - read a block of ECP data +--------------------------------------------------- + +SYNOPSIS +^^^^^^^^ + +:: + + #include <linux/parport.h> + + struct parport_operations { + ... + size_t (*ecp_read_data) (struct parport *port, + void *buf, size_t len, int flags); + ... + }; + +DESCRIPTION +^^^^^^^^^^^ + +Reads a block of ECP data. The ``flags`` parameter is ignored. + +RETURN VALUE +^^^^^^^^^^^^ + +The number of bytes read. NB. There may be more unread data in a +FIFO. Is there a way of stunning the FIFO to prevent this? + +SEE ALSO +^^^^^^^^ + +ecp_write_block, ecp_write_addr + + + +port->ops->ecp_write_addr - write a block of ECP addresses +---------------------------------------------------------- + +SYNOPSIS +^^^^^^^^ + +:: + + #include <linux/parport.h> + + struct parport_operations { + ... + size_t (*ecp_write_addr) (struct parport *port, + const void *buf, size_t len, int flags); + ... + }; + +DESCRIPTION +^^^^^^^^^^^ + +Writes a block of ECP addresses. The ``flags`` parameter is ignored. + +RETURN VALUE +^^^^^^^^^^^^ + +The number of bytes written. + +NOTES +^^^^^ + +This may use a FIFO, and if so shall not return until the FIFO is empty. + +SEE ALSO +^^^^^^^^ + +ecp_read_data, ecp_write_data + + + +port->ops->nibble_read_data - read a block of data in nibble mode +----------------------------------------------------------------- + +SYNOPSIS +^^^^^^^^ + +:: + + #include <linux/parport.h> + + struct parport_operations { + ... + size_t (*nibble_read_data) (struct parport *port, + void *buf, size_t len, int flags); + ... + }; + +DESCRIPTION +^^^^^^^^^^^ + +Reads a block of data in nibble mode. The ``flags`` parameter is ignored. + +RETURN VALUE +^^^^^^^^^^^^ + +The number of whole bytes read. + +SEE ALSO +^^^^^^^^ + +byte_read_data, compat_write_data + + + +port->ops->byte_read_data - read a block of data in byte mode +------------------------------------------------------------- + +SYNOPSIS +^^^^^^^^ + +:: + + #include <linux/parport.h> + + struct parport_operations { + ... + size_t (*byte_read_data) (struct parport *port, + void *buf, size_t len, int flags); + ... + }; + +DESCRIPTION +^^^^^^^^^^^ + +Reads a block of data in byte mode. The ``flags`` parameter is ignored. + +RETURN VALUE +^^^^^^^^^^^^ + +The number of bytes read. + +SEE ALSO +^^^^^^^^ + +nibble_read_data, compat_write_data + + + +port->ops->compat_write_data - write a block of data in compatibility mode +-------------------------------------------------------------------------- + +SYNOPSIS +^^^^^^^^ + +:: + + #include <linux/parport.h> + + struct parport_operations { + ... + size_t (*compat_write_data) (struct parport *port, + const void *buf, size_t len, int flags); + ... + }; + +DESCRIPTION +^^^^^^^^^^^ + +Writes a block of data in compatibility mode. The ``flags`` parameter +is ignored. + +RETURN VALUE +^^^^^^^^^^^^ + +The number of bytes written. + +SEE ALSO +^^^^^^^^ + +nibble_read_data, byte_read_data diff --git a/Documentation/driver-api/pti_intel_mid.rst b/Documentation/driver-api/pti_intel_mid.rst new file mode 100644 index 000000000000..20f1cff42d5f --- /dev/null +++ b/Documentation/driver-api/pti_intel_mid.rst @@ -0,0 +1,106 @@ +.. SPDX-License-Identifier: GPL-2.0 + +============= +Intel MID PTI +============= + +The Intel MID PTI project is HW implemented in Intel Atom +system-on-a-chip designs based on the Parallel Trace +Interface for MIPI P1149.7 cJTAG standard. The kernel solution +for this platform involves the following files:: + + ./include/linux/pti.h + ./drivers/.../n_tracesink.h + ./drivers/.../n_tracerouter.c + ./drivers/.../n_tracesink.c + ./drivers/.../pti.c + +pti.c is the driver that enables various debugging features +popular on platforms from certain mobile manufacturers. +n_tracerouter.c and n_tracesink.c allow extra system information to +be collected and routed to the pti driver, such as trace +debugging data from a modem. Although n_tracerouter +and n_tracesink are a part of the complete PTI solution, +these two line disciplines can work separately from +pti.c and route any data stream from one /dev/tty node +to another /dev/tty node via kernel-space. This provides +a stable, reliable connection that will not break unless +the user-space application shuts down (plus avoids +kernel->user->kernel context switch overheads of routing +data). + +An example debugging usage for this driver system: + + * Hook /dev/ttyPTI0 to syslogd. Opening this port will also start + a console device to further capture debugging messages to PTI. + * Hook /dev/ttyPTI1 to modem debugging data to write to PTI HW. + This is where n_tracerouter and n_tracesink are used. + * Hook /dev/pti to a user-level debugging application for writing + to PTI HW. + * `Use mipi_` Kernel Driver API in other device drivers for + debugging to PTI by first requesting a PTI write address via + mipi_request_masterchannel(1). + +Below is example pseudo-code on how a 'privileged' application +can hook up n_tracerouter and n_tracesink to any tty on +a system. 'Privileged' means the application has enough +privileges to successfully manipulate the ldisc drivers +but is not just blindly executing as 'root'. Keep in mind +the use of ioctl(,TIOCSETD,) is not specific to the n_tracerouter +and n_tracesink line discpline drivers but is a generic +operation for a program to use a line discpline driver +on a tty port other than the default n_tty:: + + /////////// To hook up n_tracerouter and n_tracesink ///////// + + // Note that n_tracerouter depends on n_tracesink. + #include <errno.h> + #define ONE_TTY "/dev/ttyOne" + #define TWO_TTY "/dev/ttyTwo" + + // needed global to hand onto ldisc connection + static int g_fd_source = -1; + static int g_fd_sink = -1; + + // these two vars used to grab LDISC values from loaded ldisc drivers + // in OS. Look at /proc/tty/ldiscs to get the right numbers from + // the ldiscs loaded in the system. + int source_ldisc_num, sink_ldisc_num = -1; + int retval; + + g_fd_source = open(ONE_TTY, O_RDWR); // must be R/W + g_fd_sink = open(TWO_TTY, O_RDWR); // must be R/W + + if (g_fd_source <= 0) || (g_fd_sink <= 0) { + // doubt you'll want to use these exact error lines of code + printf("Error on open(). errno: %d\n",errno); + return errno; + } + + retval = ioctl(g_fd_sink, TIOCSETD, &sink_ldisc_num); + if (retval < 0) { + printf("Error on ioctl(). errno: %d\n", errno); + return errno; + } + + retval = ioctl(g_fd_source, TIOCSETD, &source_ldisc_num); + if (retval < 0) { + printf("Error on ioctl(). errno: %d\n", errno); + return errno; + } + + /////////// To disconnect n_tracerouter and n_tracesink //////// + + // First make sure data through the ldiscs has stopped. + + // Second, disconnect ldiscs. This provides a + // little cleaner shutdown on tty stack. + sink_ldisc_num = 0; + source_ldisc_num = 0; + ioctl(g_fd_uart, TIOCSETD, &sink_ldisc_num); + ioctl(g_fd_gadget, TIOCSETD, &source_ldisc_num); + + // Three, program closes connection, and cleanup: + close(g_fd_uart); + close(g_fd_gadget); + g_fd_uart = g_fd_gadget = NULL; diff --git a/Documentation/driver-api/pwm.rst b/Documentation/driver-api/pwm.rst new file mode 100644 index 000000000000..ab62f1bb0366 --- /dev/null +++ b/Documentation/driver-api/pwm.rst @@ -0,0 +1,165 @@ +====================================== +Pulse Width Modulation (PWM) interface +====================================== + +This provides an overview about the Linux PWM interface + +PWMs are commonly used for controlling LEDs, fans or vibrators in +cell phones. PWMs with a fixed purpose have no need implementing +the Linux PWM API (although they could). However, PWMs are often +found as discrete devices on SoCs which have no fixed purpose. It's +up to the board designer to connect them to LEDs or fans. To provide +this kind of flexibility the generic PWM API exists. + +Identifying PWMs +---------------- + +Users of the legacy PWM API use unique IDs to refer to PWM devices. + +Instead of referring to a PWM device via its unique ID, board setup code +should instead register a static mapping that can be used to match PWM +consumers to providers, as given in the following example:: + + static struct pwm_lookup board_pwm_lookup[] = { + PWM_LOOKUP("tegra-pwm", 0, "pwm-backlight", NULL, + 50000, PWM_POLARITY_NORMAL), + }; + + static void __init board_init(void) + { + ... + pwm_add_table(board_pwm_lookup, ARRAY_SIZE(board_pwm_lookup)); + ... + } + +Using PWMs +---------- + +Legacy users can request a PWM device using pwm_request() and free it +after usage with pwm_free(). + +New users should use the pwm_get() function and pass to it the consumer +device or a consumer name. pwm_put() is used to free the PWM device. Managed +variants of these functions, devm_pwm_get() and devm_pwm_put(), also exist. + +After being requested, a PWM has to be configured using:: + + int pwm_apply_state(struct pwm_device *pwm, struct pwm_state *state); + +This API controls both the PWM period/duty_cycle config and the +enable/disable state. + +The pwm_config(), pwm_enable() and pwm_disable() functions are just wrappers +around pwm_apply_state() and should not be used if the user wants to change +several parameter at once. For example, if you see pwm_config() and +pwm_{enable,disable}() calls in the same function, this probably means you +should switch to pwm_apply_state(). + +The PWM user API also allows one to query the PWM state with pwm_get_state(). + +In addition to the PWM state, the PWM API also exposes PWM arguments, which +are the reference PWM config one should use on this PWM. +PWM arguments are usually platform-specific and allows the PWM user to only +care about dutycycle relatively to the full period (like, duty = 50% of the +period). struct pwm_args contains 2 fields (period and polarity) and should +be used to set the initial PWM config (usually done in the probe function +of the PWM user). PWM arguments are retrieved with pwm_get_args(). + +All consumers should really be reconfiguring the PWM upon resume as +appropriate. This is the only way to ensure that everything is resumed in +the proper order. + +Using PWMs with the sysfs interface +----------------------------------- + +If CONFIG_SYSFS is enabled in your kernel configuration a simple sysfs +interface is provided to use the PWMs from userspace. It is exposed at +/sys/class/pwm/. Each probed PWM controller/chip will be exported as +pwmchipN, where N is the base of the PWM chip. Inside the directory you +will find: + + npwm + The number of PWM channels this chip supports (read-only). + + export + Exports a PWM channel for use with sysfs (write-only). + + unexport + Unexports a PWM channel from sysfs (write-only). + +The PWM channels are numbered using a per-chip index from 0 to npwm-1. + +When a PWM channel is exported a pwmX directory will be created in the +pwmchipN directory it is associated with, where X is the number of the +channel that was exported. The following properties will then be available: + + period + The total period of the PWM signal (read/write). + Value is in nanoseconds and is the sum of the active and inactive + time of the PWM. + + duty_cycle + The active time of the PWM signal (read/write). + Value is in nanoseconds and must be less than the period. + + polarity + Changes the polarity of the PWM signal (read/write). + Writes to this property only work if the PWM chip supports changing + the polarity. The polarity can only be changed if the PWM is not + enabled. Value is the string "normal" or "inversed". + + enable + Enable/disable the PWM signal (read/write). + + - 0 - disabled + - 1 - enabled + +Implementing a PWM driver +------------------------- + +Currently there are two ways to implement pwm drivers. Traditionally +there only has been the barebone API meaning that each driver has +to implement the pwm_*() functions itself. This means that it's impossible +to have multiple PWM drivers in the system. For this reason it's mandatory +for new drivers to use the generic PWM framework. + +A new PWM controller/chip can be added using pwmchip_add() and removed +again with pwmchip_remove(). pwmchip_add() takes a filled in struct +pwm_chip as argument which provides a description of the PWM chip, the +number of PWM devices provided by the chip and the chip-specific +implementation of the supported PWM operations to the framework. + +When implementing polarity support in a PWM driver, make sure to respect the +signal conventions in the PWM framework. By definition, normal polarity +characterizes a signal starts high for the duration of the duty cycle and +goes low for the remainder of the period. Conversely, a signal with inversed +polarity starts low for the duration of the duty cycle and goes high for the +remainder of the period. + +Drivers are encouraged to implement ->apply() instead of the legacy +->enable(), ->disable() and ->config() methods. Doing that should provide +atomicity in the PWM config workflow, which is required when the PWM controls +a critical device (like a regulator). + +The implementation of ->get_state() (a method used to retrieve initial PWM +state) is also encouraged for the same reason: letting the PWM user know +about the current PWM state would allow him to avoid glitches. + +Drivers should not implement any power management. In other words, +consumers should implement it as described in the "Using PWMs" section. + +Locking +------- + +The PWM core list manipulations are protected by a mutex, so pwm_request() +and pwm_free() may not be called from an atomic context. Currently the +PWM core does not enforce any locking to pwm_enable(), pwm_disable() and +pwm_config(), so the calling context is currently driver specific. This +is an issue derived from the former barebone API and should be fixed soon. + +Helpers +------- + +Currently a PWM can only be configured with period_ns and duty_ns. For several +use cases freq_hz and duty_percent might be better. Instead of calculating +this in your driver please consider adding appropriate helpers to the framework. diff --git a/Documentation/driver-api/rfkill.rst b/Documentation/driver-api/rfkill.rst new file mode 100644 index 000000000000..7d3684e81df6 --- /dev/null +++ b/Documentation/driver-api/rfkill.rst @@ -0,0 +1,132 @@ +=============================== +rfkill - RF kill switch support +=============================== + + +.. contents:: + :depth: 2 + +Introduction +============ + +The rfkill subsystem provides a generic interface for disabling any radio +transmitter in the system. When a transmitter is blocked, it shall not +radiate any power. + +The subsystem also provides the ability to react on button presses and +disable all transmitters of a certain type (or all). This is intended for +situations where transmitters need to be turned off, for example on +aircraft. + +The rfkill subsystem has a concept of "hard" and "soft" block, which +differ little in their meaning (block == transmitters off) but rather in +whether they can be changed or not: + + - hard block + read-only radio block that cannot be overridden by software + + - soft block + writable radio block (need not be readable) that is set by + the system software. + +The rfkill subsystem has two parameters, rfkill.default_state and +rfkill.master_switch_mode, which are documented in +admin-guide/kernel-parameters.rst. + + +Implementation details +====================== + +The rfkill subsystem is composed of three main components: + + * the rfkill core, + * the deprecated rfkill-input module (an input layer handler, being + replaced by userspace policy code) and + * the rfkill drivers. + +The rfkill core provides API for kernel drivers to register their radio +transmitter with the kernel, methods for turning it on and off, and letting +the system know about hardware-disabled states that may be implemented on +the device. + +The rfkill core code also notifies userspace of state changes, and provides +ways for userspace to query the current states. See the "Userspace support" +section below. + +When the device is hard-blocked (either by a call to rfkill_set_hw_state() +or from query_hw_block), set_block() will be invoked for additional software +block, but drivers can ignore the method call since they can use the return +value of the function rfkill_set_hw_state() to sync the software state +instead of keeping track of calls to set_block(). In fact, drivers should +use the return value of rfkill_set_hw_state() unless the hardware actually +keeps track of soft and hard block separately. + + +Kernel API +========== + +Drivers for radio transmitters normally implement an rfkill driver. + +Platform drivers might implement input devices if the rfkill button is just +that, a button. If that button influences the hardware then you need to +implement an rfkill driver instead. This also applies if the platform provides +a way to turn on/off the transmitter(s). + +For some platforms, it is possible that the hardware state changes during +suspend/hibernation, in which case it will be necessary to update the rfkill +core with the current state at resume time. + +To create an rfkill driver, driver's Kconfig needs to have:: + + depends on RFKILL || !RFKILL + +to ensure the driver cannot be built-in when rfkill is modular. The !RFKILL +case allows the driver to be built when rfkill is not configured, in which +case all rfkill API can still be used but will be provided by static inlines +which compile to almost nothing. + +Calling rfkill_set_hw_state() when a state change happens is required from +rfkill drivers that control devices that can be hard-blocked unless they also +assign the poll_hw_block() callback (then the rfkill core will poll the +device). Don't do this unless you cannot get the event in any other way. + +rfkill provides per-switch LED triggers, which can be used to drive LEDs +according to the switch state (LED_FULL when blocked, LED_OFF otherwise). + + +Userspace support +================= + +The recommended userspace interface to use is /dev/rfkill, which is a misc +character device that allows userspace to obtain and set the state of rfkill +devices and sets of devices. It also notifies userspace about device addition +and removal. The API is a simple read/write API that is defined in +linux/rfkill.h, with one ioctl that allows turning off the deprecated input +handler in the kernel for the transition period. + +Except for the one ioctl, communication with the kernel is done via read() +and write() of instances of 'struct rfkill_event'. In this structure, the +soft and hard block are properly separated (unlike sysfs, see below) and +userspace is able to get a consistent snapshot of all rfkill devices in the +system. Also, it is possible to switch all rfkill drivers (or all drivers of +a specified type) into a state which also updates the default state for +hotplugged devices. + +After an application opens /dev/rfkill, it can read the current state of all +devices. Changes can be obtained by either polling the descriptor for +hotplug or state change events or by listening for uevents emitted by the +rfkill core framework. + +Additionally, each rfkill device is registered in sysfs and emits uevents. + +rfkill devices issue uevents (with an action of "change"), with the following +environment variables set:: + + RFKILL_NAME + RFKILL_STATE + RFKILL_TYPE + +The content of these variables corresponds to the "name", "state" and +"type" sysfs files explained above. + +For further details consult Documentation/ABI/stable/sysfs-class-rfkill. diff --git a/Documentation/driver-api/sgi-ioc4.rst b/Documentation/driver-api/sgi-ioc4.rst new file mode 100644 index 000000000000..72709222d3c0 --- /dev/null +++ b/Documentation/driver-api/sgi-ioc4.rst @@ -0,0 +1,49 @@ +==================================== +SGI IOC4 PCI (multi function) device +==================================== + +The SGI IOC4 PCI device is a bit of a strange beast, so some notes on +it are in order. + +First, even though the IOC4 performs multiple functions, such as an +IDE controller, a serial controller, a PS/2 keyboard/mouse controller, +and an external interrupt mechanism, it's not implemented as a +multifunction device. The consequence of this from a software +standpoint is that all these functions share a single IRQ, and +they can't all register to own the same PCI device ID. To make +matters a bit worse, some of the register blocks (and even registers +themselves) present in IOC4 are mixed-purpose between these several +functions, meaning that there's no clear "owning" device driver. + +The solution is to organize the IOC4 driver into several independent +drivers, "ioc4", "sgiioc4", and "ioc4_serial". Note that there is no +PS/2 controller driver as this functionality has never been wired up +on a shipping IO card. + +ioc4 +==== +This is the core (or shim) driver for IOC4. It is responsible for +initializing the basic functionality of the chip, and allocating +the PCI resources that are shared between the IOC4 functions. + +This driver also provides registration functions that the other +IOC4 drivers can call to make their presence known. Each driver +needs to provide a probe and remove function, which are invoked +by the core driver at appropriate times. The interface of these +IOC4 function probe and remove operations isn't precisely the same +as PCI device probe and remove operations, but is logically the +same operation. + +sgiioc4 +======= +This is the IDE driver for IOC4. Its name isn't very descriptive +simply for historical reasons (it used to be the only IOC4 driver +component). There's not much to say about it other than it hooks +up to the ioc4 driver via the appropriate registration, probe, and +remove functions. + +ioc4_serial +=========== +This is the serial driver for IOC4. There's not much to say about it +other than it hooks up to the ioc4 driver via the appropriate registration, +probe, and remove functions. diff --git a/Documentation/driver-api/sm501.rst b/Documentation/driver-api/sm501.rst new file mode 100644 index 000000000000..882507453ba4 --- /dev/null +++ b/Documentation/driver-api/sm501.rst @@ -0,0 +1,74 @@ +.. include:: <isonum.txt> + +============ +SM501 Driver +============ + +:Copyright: |copy| 2006, 2007 Simtec Electronics + +The Silicon Motion SM501 multimedia companion chip is a multifunction device +which may provide numerous interfaces including USB host controller USB gadget, +asynchronous serial ports, audio functions, and a dual display video interface. +The device may be connected by PCI or local bus with varying functions enabled. + +Core +---- + +The core driver in drivers/mfd provides common services for the +drivers which manage the specific hardware blocks. These services +include locking for common registers, clock control and resource +management. + +The core registers drivers for both PCI and generic bus based +chips via the platform device and driver system. + +On detection of a device, the core initialises the chip (which may +be specified by the platform data) and then exports the selected +peripheral set as platform devices for the specific drivers. + +The core re-uses the platform device system as the platform device +system provides enough features to support the drivers without the +need to create a new bus-type and the associated code to go with it. + + +Resources +--------- + +Each peripheral has a view of the device which is implicitly narrowed to +the specific set of resources that peripheral requires in order to +function correctly. + +The centralised memory allocation allows the driver to ensure that the +maximum possible resource allocation can be made to the video subsystem +as this is by-far the most resource-sensitive of the on-chip functions. + +The primary issue with memory allocation is that of moving the video +buffers once a display mode is chosen. Indeed when a video mode change +occurs the memory footprint of the video subsystem changes. + +Since video memory is difficult to move without changing the display +(unless sufficient contiguous memory can be provided for the old and new +modes simultaneously) the video driver fully utilises the memory area +given to it by aligning fb0 to the start of the area and fb1 to the end +of it. Any memory left over in the middle is used for the acceleration +functions, which are transient and thus their location is less critical +as it can be moved. + + +Configuration +------------- + +The platform device driver uses a set of platform data to pass +configurations through to the core and the subsidiary drivers +so that there can be support for more than one system carrying +an SM501 built into a single kernel image. + +The PCI driver assumes that the PCI card behaves as per the Silicon +Motion reference design. + +There is an errata (AB-5) affecting the selection of the +of the M1XCLK and M1CLK frequencies. These two clocks +must be sourced from the same PLL, although they can then +be divided down individually. If this is not set, then SM501 may +lock and hang the whole system. The driver will refuse to +attach if the PLL selection is different. diff --git a/Documentation/driver-api/smsc_ece1099.rst b/Documentation/driver-api/smsc_ece1099.rst new file mode 100644 index 000000000000..079277421eaf --- /dev/null +++ b/Documentation/driver-api/smsc_ece1099.rst @@ -0,0 +1,60 @@ +================================================= +Msc Keyboard Scan Expansion/GPIO Expansion device +================================================= + +What is smsc-ece1099? +---------------------- + +The ECE1099 is a 40-Pin 3.3V Keyboard Scan Expansion +or GPIO Expansion device. The device supports a keyboard +scan matrix of 23x8. The device is connected to a Master +via the SMSC BC-Link interface or via the SMBus. +Keypad scan Input(KSI) and Keypad Scan Output(KSO) signals +are multiplexed with GPIOs. + +Interrupt generation +-------------------- + +Interrupts can be generated by an edge detection on a GPIO +pin or an edge detection on one of the bus interface pins. +Interrupts can also be detected on the keyboard scan interface. +The bus interrupt pin (BC_INT# or SMBUS_INT#) is asserted if +any bit in one of the Interrupt Status registers is 1 and +the corresponding Interrupt Mask bit is also 1. + +In order for software to determine which device is the source +of an interrupt, it should first read the Group Interrupt Status Register +to determine which Status register group is a source for the interrupt. +Software should read both the Status register and the associated Mask register, +then AND the two values together. Bits that are 1 in the result of the AND +are active interrupts. Software clears an interrupt by writing a 1 to the +corresponding bit in the Status register. + +Communication Protocol +---------------------- + +- SMbus slave Interface + The host processor communicates with the ECE1099 device + through a series of read/write registers via the SMBus + interface. SMBus is a serial communication protocol between + a computer host and its peripheral devices. The SMBus data + rate is 10KHz minimum to 400 KHz maximum + +- Slave Bus Interface + The ECE1099 device SMBus implementation is a subset of the + SMBus interface to the host. The device is a slave-only SMBus device. + The implementation in the device is a subset of SMBus since it + only supports four protocols. + + The Write Byte, Read Byte, Send Byte, and Receive Byte protocols are the + only valid SMBus protocols for the device. + +- BC-LinkTM Interface + The BC-Link is a proprietary bus that allows communication + between a Master device and a Companion device. The Master + device uses this serial bus to read and write registers + located on the Companion device. The bus comprises three signals, + BC_CLK, BC_DAT and BC_INT#. The Master device always provides the + clock, BC_CLK, and the Companion device is the source for an + independent asynchronous interrupt signal, BC_INT#. The ECE1099 + supports BC-Link speeds up to 24MHz. diff --git a/Documentation/driver-api/switchtec.rst b/Documentation/driver-api/switchtec.rst new file mode 100644 index 000000000000..7611fdc53e19 --- /dev/null +++ b/Documentation/driver-api/switchtec.rst @@ -0,0 +1,102 @@ +======================== +Linux Switchtec Support +======================== + +Microsemi's "Switchtec" line of PCI switch devices is already +supported by the kernel with standard PCI switch drivers. However, the +Switchtec device advertises a special management endpoint which +enables some additional functionality. This includes: + +* Packet and Byte Counters +* Firmware Upgrades +* Event and Error logs +* Querying port link status +* Custom user firmware commands + +The switchtec kernel module implements this functionality. + + +Interface +========= + +The primary means of communicating with the Switchtec management firmware is +through the Memory-mapped Remote Procedure Call (MRPC) interface. +Commands are submitted to the interface with a 4-byte command +identifier and up to 1KB of command specific data. The firmware will +respond with a 4-byte return code and up to 1KB of command-specific +data. The interface only processes a single command at a time. + + +Userspace Interface +=================== + +The MRPC interface will be exposed to userspace through a simple char +device: /dev/switchtec#, one for each management endpoint in the system. + +The char device has the following semantics: + +* A write must consist of at least 4 bytes and no more than 1028 bytes. + The first 4 bytes will be interpreted as the Command ID and the + remainder will be used as the input data. A write will send the + command to the firmware to begin processing. + +* Each write must be followed by exactly one read. Any double write will + produce an error and any read that doesn't follow a write will + produce an error. + +* A read will block until the firmware completes the command and return + the 4-byte Command Return Value plus up to 1024 bytes of output + data. (The length will be specified by the size parameter of the read + call -- reading less than 4 bytes will produce an error.) + +* The poll call will also be supported for userspace applications that + need to do other things while waiting for the command to complete. + +The following IOCTLs are also supported by the device: + +* SWITCHTEC_IOCTL_FLASH_INFO - Retrieve firmware length and number + of partitions in the device. + +* SWITCHTEC_IOCTL_FLASH_PART_INFO - Retrieve address and lengeth for + any specified partition in flash. + +* SWITCHTEC_IOCTL_EVENT_SUMMARY - Read a structure of bitmaps + indicating all uncleared events. + +* SWITCHTEC_IOCTL_EVENT_CTL - Get the current count, clear and set flags + for any event. This ioctl takes in a switchtec_ioctl_event_ctl struct + with the event_id, index and flags set (index being the partition or PFF + number for non-global events). It returns whether the event has + occurred, the number of times and any event specific data. The flags + can be used to clear the count or enable and disable actions to + happen when the event occurs. + By using the SWITCHTEC_IOCTL_EVENT_FLAG_EN_POLL flag, + you can set an event to trigger a poll command to return with + POLLPRI. In this way, userspace can wait for events to occur. + +* SWITCHTEC_IOCTL_PFF_TO_PORT and SWITCHTEC_IOCTL_PORT_TO_PFF convert + between PCI Function Framework number (used by the event system) + and Switchtec Logic Port ID and Partition number (which is more + user friendly). + + +Non-Transparent Bridge (NTB) Driver +=================================== + +An NTB hardware driver is provided for the Switchtec hardware in +ntb_hw_switchtec. Currently, it only supports switches configured with +exactly 2 NT partitions and zero or more non-NT partitions. It also requires +the following configuration settings: + +* Both NT partitions must be able to access each other's GAS spaces. + Thus, the bits in the GAS Access Vector under Management Settings + must be set to support this. +* Kernel configuration MUST include support for NTB (CONFIG_NTB needs + to be set) + +NT EP BAR 2 will be dynamically configured as a Direct Window, and +the configuration file does not need to configure it explicitly. + +Please refer to Documentation/driver-api/ntb.rst in Linux source tree for an overall +understanding of the Linux NTB stack. ntb_hw_switchtec works as an NTB +Hardware Driver in this stack. diff --git a/Documentation/driver-api/sync_file.rst b/Documentation/driver-api/sync_file.rst new file mode 100644 index 000000000000..496fb2c3b3e6 --- /dev/null +++ b/Documentation/driver-api/sync_file.rst @@ -0,0 +1,86 @@ +=================== +Sync File API Guide +=================== + +:Author: Gustavo Padovan <gustavo at padovan dot org> + +This document serves as a guide for device drivers writers on what the +sync_file API is, and how drivers can support it. Sync file is the carrier of +the fences(struct dma_fence) that are needed to synchronize between drivers or +across process boundaries. + +The sync_file API is meant to be used to send and receive fence information +to/from userspace. It enables userspace to do explicit fencing, where instead +of attaching a fence to the buffer a producer driver (such as a GPU or V4L +driver) sends the fence related to the buffer to userspace via a sync_file. + +The sync_file then can be sent to the consumer (DRM driver for example), that +will not use the buffer for anything before the fence(s) signals, i.e., the +driver that issued the fence is not using/processing the buffer anymore, so it +signals that the buffer is ready to use. And vice-versa for the consumer -> +producer part of the cycle. + +Sync files allows userspace awareness on buffer sharing synchronization between +drivers. + +Sync file was originally added in the Android kernel but current Linux Desktop +can benefit a lot from it. + +in-fences and out-fences +------------------------ + +Sync files can go either to or from userspace. When a sync_file is sent from +the driver to userspace we call the fences it contains 'out-fences'. They are +related to a buffer that the driver is processing or is going to process, so +the driver creates an out-fence to be able to notify, through +dma_fence_signal(), when it has finished using (or processing) that buffer. +Out-fences are fences that the driver creates. + +On the other hand if the driver receives fence(s) through a sync_file from +userspace we call these fence(s) 'in-fences'. Receiving in-fences means that +we need to wait for the fence(s) to signal before using any buffer related to +the in-fences. + +Creating Sync Files +------------------- + +When a driver needs to send an out-fence userspace it creates a sync_file. + +Interface:: + + struct sync_file *sync_file_create(struct dma_fence *fence); + +The caller pass the out-fence and gets back the sync_file. That is just the +first step, next it needs to install an fd on sync_file->file. So it gets an +fd:: + + fd = get_unused_fd_flags(O_CLOEXEC); + +and installs it on sync_file->file:: + + fd_install(fd, sync_file->file); + +The sync_file fd now can be sent to userspace. + +If the creation process fail, or the sync_file needs to be released by any +other reason fput(sync_file->file) should be used. + +Receiving Sync Files from Userspace +----------------------------------- + +When userspace needs to send an in-fence to the driver it passes file descriptor +of the Sync File to the kernel. The kernel can then retrieve the fences +from it. + +Interface:: + + struct dma_fence *sync_file_get_fence(int fd); + + +The returned reference is owned by the caller and must be disposed of +afterwards using dma_fence_put(). In case of error, a NULL is returned instead. + +References: + +1. struct sync_file in include/linux/sync_file.h +2. All interfaces mentioned above defined in include/linux/sync_file.h diff --git a/Documentation/driver-api/vfio-mediated-device.rst b/Documentation/driver-api/vfio-mediated-device.rst new file mode 100644 index 000000000000..25eb7d5b834b --- /dev/null +++ b/Documentation/driver-api/vfio-mediated-device.rst @@ -0,0 +1,414 @@ +.. include:: <isonum.txt> + +===================== +VFIO Mediated devices +===================== + +:Copyright: |copy| 2016, NVIDIA CORPORATION. All rights reserved. +:Author: Neo Jia <cjia@nvidia.com> +:Author: Kirti Wankhede <kwankhede@nvidia.com> + +This program is free software; you can redistribute it and/or modify +it under the terms of the GNU General Public License version 2 as +published by the Free Software Foundation. + + +Virtual Function I/O (VFIO) Mediated devices[1] +=============================================== + +The number of use cases for virtualizing DMA devices that do not have built-in +SR_IOV capability is increasing. Previously, to virtualize such devices, +developers had to create their own management interfaces and APIs, and then +integrate them with user space software. To simplify integration with user space +software, we have identified common requirements and a unified management +interface for such devices. + +The VFIO driver framework provides unified APIs for direct device access. It is +an IOMMU/device-agnostic framework for exposing direct device access to user +space in a secure, IOMMU-protected environment. This framework is used for +multiple devices, such as GPUs, network adapters, and compute accelerators. With +direct device access, virtual machines or user space applications have direct +access to the physical device. This framework is reused for mediated devices. + +The mediated core driver provides a common interface for mediated device +management that can be used by drivers of different devices. This module +provides a generic interface to perform these operations: + +* Create and destroy a mediated device +* Add a mediated device to and remove it from a mediated bus driver +* Add a mediated device to and remove it from an IOMMU group + +The mediated core driver also provides an interface to register a bus driver. +For example, the mediated VFIO mdev driver is designed for mediated devices and +supports VFIO APIs. The mediated bus driver adds a mediated device to and +removes it from a VFIO group. + +The following high-level block diagram shows the main components and interfaces +in the VFIO mediated driver framework. The diagram shows NVIDIA, Intel, and IBM +devices as examples, as these devices are the first devices to use this module:: + + +---------------+ + | | + | +-----------+ | mdev_register_driver() +--------------+ + | | | +<------------------------+ | + | | mdev | | | | + | | bus | +------------------------>+ vfio_mdev.ko |<-> VFIO user + | | driver | | probe()/remove() | | APIs + | | | | +--------------+ + | +-----------+ | + | | + | MDEV CORE | + | MODULE | + | mdev.ko | + | +-----------+ | mdev_register_device() +--------------+ + | | | +<------------------------+ | + | | | | | nvidia.ko |<-> physical + | | | +------------------------>+ | device + | | | | callbacks +--------------+ + | | Physical | | + | | device | | mdev_register_device() +--------------+ + | | interface | |<------------------------+ | + | | | | | i915.ko |<-> physical + | | | +------------------------>+ | device + | | | | callbacks +--------------+ + | | | | + | | | | mdev_register_device() +--------------+ + | | | +<------------------------+ | + | | | | | ccw_device.ko|<-> physical + | | | +------------------------>+ | device + | | | | callbacks +--------------+ + | +-----------+ | + +---------------+ + + +Registration Interfaces +======================= + +The mediated core driver provides the following types of registration +interfaces: + +* Registration interface for a mediated bus driver +* Physical device driver interface + +Registration Interface for a Mediated Bus Driver +------------------------------------------------ + +The registration interface for a mediated bus driver provides the following +structure to represent a mediated device's driver:: + + /* + * struct mdev_driver [2] - Mediated device's driver + * @name: driver name + * @probe: called when new device created + * @remove: called when device removed + * @driver: device driver structure + */ + struct mdev_driver { + const char *name; + int (*probe) (struct device *dev); + void (*remove) (struct device *dev); + struct device_driver driver; + }; + +A mediated bus driver for mdev should use this structure in the function calls +to register and unregister itself with the core driver: + +* Register:: + + extern int mdev_register_driver(struct mdev_driver *drv, + struct module *owner); + +* Unregister:: + + extern void mdev_unregister_driver(struct mdev_driver *drv); + +The mediated bus driver is responsible for adding mediated devices to the VFIO +group when devices are bound to the driver and removing mediated devices from +the VFIO when devices are unbound from the driver. + + +Physical Device Driver Interface +-------------------------------- + +The physical device driver interface provides the mdev_parent_ops[3] structure +to define the APIs to manage work in the mediated core driver that is related +to the physical device. + +The structures in the mdev_parent_ops structure are as follows: + +* dev_attr_groups: attributes of the parent device +* mdev_attr_groups: attributes of the mediated device +* supported_config: attributes to define supported configurations + +The functions in the mdev_parent_ops structure are as follows: + +* create: allocate basic resources in a driver for a mediated device +* remove: free resources in a driver when a mediated device is destroyed + +(Note that mdev-core provides no implicit serialization of create/remove +callbacks per mdev parent device, per mdev type, or any other categorization. +Vendor drivers are expected to be fully asynchronous in this respect or +provide their own internal resource protection.) + +The callbacks in the mdev_parent_ops structure are as follows: + +* open: open callback of mediated device +* close: close callback of mediated device +* ioctl: ioctl callback of mediated device +* read : read emulation callback +* write: write emulation callback +* mmap: mmap emulation callback + +A driver should use the mdev_parent_ops structure in the function call to +register itself with the mdev core driver:: + + extern int mdev_register_device(struct device *dev, + const struct mdev_parent_ops *ops); + +However, the mdev_parent_ops structure is not required in the function call +that a driver should use to unregister itself with the mdev core driver:: + + extern void mdev_unregister_device(struct device *dev); + + +Mediated Device Management Interface Through sysfs +================================================== + +The management interface through sysfs enables user space software, such as +libvirt, to query and configure mediated devices in a hardware-agnostic fashion. +This management interface provides flexibility to the underlying physical +device's driver to support features such as: + +* Mediated device hot plug +* Multiple mediated devices in a single virtual machine +* Multiple mediated devices from different physical devices + +Links in the mdev_bus Class Directory +------------------------------------- +The /sys/class/mdev_bus/ directory contains links to devices that are registered +with the mdev core driver. + +Directories and files under the sysfs for Each Physical Device +-------------------------------------------------------------- + +:: + + |- [parent physical device] + |--- Vendor-specific-attributes [optional] + |--- [mdev_supported_types] + | |--- [<type-id>] + | | |--- create + | | |--- name + | | |--- available_instances + | | |--- device_api + | | |--- description + | | |--- [devices] + | |--- [<type-id>] + | | |--- create + | | |--- name + | | |--- available_instances + | | |--- device_api + | | |--- description + | | |--- [devices] + | |--- [<type-id>] + | |--- create + | |--- name + | |--- available_instances + | |--- device_api + | |--- description + | |--- [devices] + +* [mdev_supported_types] + + The list of currently supported mediated device types and their details. + + [<type-id>], device_api, and available_instances are mandatory attributes + that should be provided by vendor driver. + +* [<type-id>] + + The [<type-id>] name is created by adding the device driver string as a prefix + to the string provided by the vendor driver. This format of this name is as + follows:: + + sprintf(buf, "%s-%s", dev_driver_string(parent->dev), group->name); + + (or using mdev_parent_dev(mdev) to arrive at the parent device outside + of the core mdev code) + +* device_api + + This attribute should show which device API is being created, for example, + "vfio-pci" for a PCI device. + +* available_instances + + This attribute should show the number of devices of type <type-id> that can be + created. + +* [device] + + This directory contains links to the devices of type <type-id> that have been + created. + +* name + + This attribute should show human readable name. This is optional attribute. + +* description + + This attribute should show brief features/description of the type. This is + optional attribute. + +Directories and Files Under the sysfs for Each mdev Device +---------------------------------------------------------- + +:: + + |- [parent phy device] + |--- [$MDEV_UUID] + |--- remove + |--- mdev_type {link to its type} + |--- vendor-specific-attributes [optional] + +* remove (write only) + +Writing '1' to the 'remove' file destroys the mdev device. The vendor driver can +fail the remove() callback if that device is active and the vendor driver +doesn't support hot unplug. + +Example:: + + # echo 1 > /sys/bus/mdev/devices/$mdev_UUID/remove + +Mediated device Hot plug +------------------------ + +Mediated devices can be created and assigned at runtime. The procedure to hot +plug a mediated device is the same as the procedure to hot plug a PCI device. + +Translation APIs for Mediated Devices +===================================== + +The following APIs are provided for translating user pfn to host pfn in a VFIO +driver:: + + extern int vfio_pin_pages(struct device *dev, unsigned long *user_pfn, + int npage, int prot, unsigned long *phys_pfn); + + extern int vfio_unpin_pages(struct device *dev, unsigned long *user_pfn, + int npage); + +These functions call back into the back-end IOMMU module by using the pin_pages +and unpin_pages callbacks of the struct vfio_iommu_driver_ops[4]. Currently +these callbacks are supported in the TYPE1 IOMMU module. To enable them for +other IOMMU backend modules, such as PPC64 sPAPR module, they need to provide +these two callback functions. + +Using the Sample Code +===================== + +mtty.c in samples/vfio-mdev/ directory is a sample driver program to +demonstrate how to use the mediated device framework. + +The sample driver creates an mdev device that simulates a serial port over a PCI +card. + +1. Build and load the mtty.ko module. + + This step creates a dummy device, /sys/devices/virtual/mtty/mtty/ + + Files in this device directory in sysfs are similar to the following:: + + # tree /sys/devices/virtual/mtty/mtty/ + /sys/devices/virtual/mtty/mtty/ + |-- mdev_supported_types + | |-- mtty-1 + | | |-- available_instances + | | |-- create + | | |-- device_api + | | |-- devices + | | `-- name + | `-- mtty-2 + | |-- available_instances + | |-- create + | |-- device_api + | |-- devices + | `-- name + |-- mtty_dev + | `-- sample_mtty_dev + |-- power + | |-- autosuspend_delay_ms + | |-- control + | |-- runtime_active_time + | |-- runtime_status + | `-- runtime_suspended_time + |-- subsystem -> ../../../../class/mtty + `-- uevent + +2. Create a mediated device by using the dummy device that you created in the + previous step:: + + # echo "83b8f4f2-509f-382f-3c1e-e6bfe0fa1001" > \ + /sys/devices/virtual/mtty/mtty/mdev_supported_types/mtty-2/create + +3. Add parameters to qemu-kvm:: + + -device vfio-pci,\ + sysfsdev=/sys/bus/mdev/devices/83b8f4f2-509f-382f-3c1e-e6bfe0fa1001 + +4. Boot the VM. + + In the Linux guest VM, with no hardware on the host, the device appears + as follows:: + + # lspci -s 00:05.0 -xxvv + 00:05.0 Serial controller: Device 4348:3253 (rev 10) (prog-if 02 [16550]) + Subsystem: Device 4348:3253 + Physical Slot: 5 + Control: I/O+ Mem- BusMaster- SpecCycle- MemWINV- VGASnoop- ParErr- + Stepping- SERR- FastB2B- DisINTx- + Status: Cap- 66MHz- UDF- FastB2B- ParErr- DEVSEL=medium >TAbort- + <TAbort- <MAbort- >SERR- <PERR- INTx- + Interrupt: pin A routed to IRQ 10 + Region 0: I/O ports at c150 [size=8] + Region 1: I/O ports at c158 [size=8] + Kernel driver in use: serial + 00: 48 43 53 32 01 00 00 02 10 02 00 07 00 00 00 00 + 10: 51 c1 00 00 59 c1 00 00 00 00 00 00 00 00 00 00 + 20: 00 00 00 00 00 00 00 00 00 00 00 00 48 43 53 32 + 30: 00 00 00 00 00 00 00 00 00 00 00 00 0a 01 00 00 + + In the Linux guest VM, dmesg output for the device is as follows: + + serial 0000:00:05.0: PCI INT A -> Link[LNKA] -> GSI 10 (level, high) -> IRQ 10 + 0000:00:05.0: ttyS1 at I/O 0xc150 (irq = 10) is a 16550A + 0000:00:05.0: ttyS2 at I/O 0xc158 (irq = 10) is a 16550A + + +5. In the Linux guest VM, check the serial ports:: + + # setserial -g /dev/ttyS* + /dev/ttyS0, UART: 16550A, Port: 0x03f8, IRQ: 4 + /dev/ttyS1, UART: 16550A, Port: 0xc150, IRQ: 10 + /dev/ttyS2, UART: 16550A, Port: 0xc158, IRQ: 10 + +6. Using minicom or any terminal emulation program, open port /dev/ttyS1 or + /dev/ttyS2 with hardware flow control disabled. + +7. Type data on the minicom terminal or send data to the terminal emulation + program and read the data. + + Data is loop backed from hosts mtty driver. + +8. Destroy the mediated device that you created:: + + # echo 1 > /sys/bus/mdev/devices/83b8f4f2-509f-382f-3c1e-e6bfe0fa1001/remove + +References +========== + +1. See Documentation/driver-api/vfio.rst for more information on VFIO. +2. struct mdev_driver in include/linux/mdev.h +3. struct mdev_parent_ops in include/linux/mdev.h +4. struct vfio_iommu_driver_ops in include/linux/vfio.h diff --git a/Documentation/driver-api/vfio.rst b/Documentation/driver-api/vfio.rst new file mode 100644 index 000000000000..f1a4d3c3ba0b --- /dev/null +++ b/Documentation/driver-api/vfio.rst @@ -0,0 +1,520 @@ +================================== +VFIO - "Virtual Function I/O" [1]_ +================================== + +Many modern system now provide DMA and interrupt remapping facilities +to help ensure I/O devices behave within the boundaries they've been +allotted. This includes x86 hardware with AMD-Vi and Intel VT-d, +POWER systems with Partitionable Endpoints (PEs) and embedded PowerPC +systems such as Freescale PAMU. The VFIO driver is an IOMMU/device +agnostic framework for exposing direct device access to userspace, in +a secure, IOMMU protected environment. In other words, this allows +safe [2]_, non-privileged, userspace drivers. + +Why do we want that? Virtual machines often make use of direct device +access ("device assignment") when configured for the highest possible +I/O performance. From a device and host perspective, this simply +turns the VM into a userspace driver, with the benefits of +significantly reduced latency, higher bandwidth, and direct use of +bare-metal device drivers [3]_. + +Some applications, particularly in the high performance computing +field, also benefit from low-overhead, direct device access from +userspace. Examples include network adapters (often non-TCP/IP based) +and compute accelerators. Prior to VFIO, these drivers had to either +go through the full development cycle to become proper upstream +driver, be maintained out of tree, or make use of the UIO framework, +which has no notion of IOMMU protection, limited interrupt support, +and requires root privileges to access things like PCI configuration +space. + +The VFIO driver framework intends to unify these, replacing both the +KVM PCI specific device assignment code as well as provide a more +secure, more featureful userspace driver environment than UIO. + +Groups, Devices, and IOMMUs +--------------------------- + +Devices are the main target of any I/O driver. Devices typically +create a programming interface made up of I/O access, interrupts, +and DMA. Without going into the details of each of these, DMA is +by far the most critical aspect for maintaining a secure environment +as allowing a device read-write access to system memory imposes the +greatest risk to the overall system integrity. + +To help mitigate this risk, many modern IOMMUs now incorporate +isolation properties into what was, in many cases, an interface only +meant for translation (ie. solving the addressing problems of devices +with limited address spaces). With this, devices can now be isolated +from each other and from arbitrary memory access, thus allowing +things like secure direct assignment of devices into virtual machines. + +This isolation is not always at the granularity of a single device +though. Even when an IOMMU is capable of this, properties of devices, +interconnects, and IOMMU topologies can each reduce this isolation. +For instance, an individual device may be part of a larger multi- +function enclosure. While the IOMMU may be able to distinguish +between devices within the enclosure, the enclosure may not require +transactions between devices to reach the IOMMU. Examples of this +could be anything from a multi-function PCI device with backdoors +between functions to a non-PCI-ACS (Access Control Services) capable +bridge allowing redirection without reaching the IOMMU. Topology +can also play a factor in terms of hiding devices. A PCIe-to-PCI +bridge masks the devices behind it, making transaction appear as if +from the bridge itself. Obviously IOMMU design plays a major factor +as well. + +Therefore, while for the most part an IOMMU may have device level +granularity, any system is susceptible to reduced granularity. The +IOMMU API therefore supports a notion of IOMMU groups. A group is +a set of devices which is isolatable from all other devices in the +system. Groups are therefore the unit of ownership used by VFIO. + +While the group is the minimum granularity that must be used to +ensure secure user access, it's not necessarily the preferred +granularity. In IOMMUs which make use of page tables, it may be +possible to share a set of page tables between different groups, +reducing the overhead both to the platform (reduced TLB thrashing, +reduced duplicate page tables), and to the user (programming only +a single set of translations). For this reason, VFIO makes use of +a container class, which may hold one or more groups. A container +is created by simply opening the /dev/vfio/vfio character device. + +On its own, the container provides little functionality, with all +but a couple version and extension query interfaces locked away. +The user needs to add a group into the container for the next level +of functionality. To do this, the user first needs to identify the +group associated with the desired device. This can be done using +the sysfs links described in the example below. By unbinding the +device from the host driver and binding it to a VFIO driver, a new +VFIO group will appear for the group as /dev/vfio/$GROUP, where +$GROUP is the IOMMU group number of which the device is a member. +If the IOMMU group contains multiple devices, each will need to +be bound to a VFIO driver before operations on the VFIO group +are allowed (it's also sufficient to only unbind the device from +host drivers if a VFIO driver is unavailable; this will make the +group available, but not that particular device). TBD - interface +for disabling driver probing/locking a device. + +Once the group is ready, it may be added to the container by opening +the VFIO group character device (/dev/vfio/$GROUP) and using the +VFIO_GROUP_SET_CONTAINER ioctl, passing the file descriptor of the +previously opened container file. If desired and if the IOMMU driver +supports sharing the IOMMU context between groups, multiple groups may +be set to the same container. If a group fails to set to a container +with existing groups, a new empty container will need to be used +instead. + +With a group (or groups) attached to a container, the remaining +ioctls become available, enabling access to the VFIO IOMMU interfaces. +Additionally, it now becomes possible to get file descriptors for each +device within a group using an ioctl on the VFIO group file descriptor. + +The VFIO device API includes ioctls for describing the device, the I/O +regions and their read/write/mmap offsets on the device descriptor, as +well as mechanisms for describing and registering interrupt +notifications. + +VFIO Usage Example +------------------ + +Assume user wants to access PCI device 0000:06:0d.0:: + + $ readlink /sys/bus/pci/devices/0000:06:0d.0/iommu_group + ../../../../kernel/iommu_groups/26 + +This device is therefore in IOMMU group 26. This device is on the +pci bus, therefore the user will make use of vfio-pci to manage the +group:: + + # modprobe vfio-pci + +Binding this device to the vfio-pci driver creates the VFIO group +character devices for this group:: + + $ lspci -n -s 0000:06:0d.0 + 06:0d.0 0401: 1102:0002 (rev 08) + # echo 0000:06:0d.0 > /sys/bus/pci/devices/0000:06:0d.0/driver/unbind + # echo 1102 0002 > /sys/bus/pci/drivers/vfio-pci/new_id + +Now we need to look at what other devices are in the group to free +it for use by VFIO:: + + $ ls -l /sys/bus/pci/devices/0000:06:0d.0/iommu_group/devices + total 0 + lrwxrwxrwx. 1 root root 0 Apr 23 16:13 0000:00:1e.0 -> + ../../../../devices/pci0000:00/0000:00:1e.0 + lrwxrwxrwx. 1 root root 0 Apr 23 16:13 0000:06:0d.0 -> + ../../../../devices/pci0000:00/0000:00:1e.0/0000:06:0d.0 + lrwxrwxrwx. 1 root root 0 Apr 23 16:13 0000:06:0d.1 -> + ../../../../devices/pci0000:00/0000:00:1e.0/0000:06:0d.1 + +This device is behind a PCIe-to-PCI bridge [4]_, therefore we also +need to add device 0000:06:0d.1 to the group following the same +procedure as above. Device 0000:00:1e.0 is a bridge that does +not currently have a host driver, therefore it's not required to +bind this device to the vfio-pci driver (vfio-pci does not currently +support PCI bridges). + +The final step is to provide the user with access to the group if +unprivileged operation is desired (note that /dev/vfio/vfio provides +no capabilities on its own and is therefore expected to be set to +mode 0666 by the system):: + + # chown user:user /dev/vfio/26 + +The user now has full access to all the devices and the iommu for this +group and can access them as follows:: + + int container, group, device, i; + struct vfio_group_status group_status = + { .argsz = sizeof(group_status) }; + struct vfio_iommu_type1_info iommu_info = { .argsz = sizeof(iommu_info) }; + struct vfio_iommu_type1_dma_map dma_map = { .argsz = sizeof(dma_map) }; + struct vfio_device_info device_info = { .argsz = sizeof(device_info) }; + + /* Create a new container */ + container = open("/dev/vfio/vfio", O_RDWR); + + if (ioctl(container, VFIO_GET_API_VERSION) != VFIO_API_VERSION) + /* Unknown API version */ + + if (!ioctl(container, VFIO_CHECK_EXTENSION, VFIO_TYPE1_IOMMU)) + /* Doesn't support the IOMMU driver we want. */ + + /* Open the group */ + group = open("/dev/vfio/26", O_RDWR); + + /* Test the group is viable and available */ + ioctl(group, VFIO_GROUP_GET_STATUS, &group_status); + + if (!(group_status.flags & VFIO_GROUP_FLAGS_VIABLE)) + /* Group is not viable (ie, not all devices bound for vfio) */ + + /* Add the group to the container */ + ioctl(group, VFIO_GROUP_SET_CONTAINER, &container); + + /* Enable the IOMMU model we want */ + ioctl(container, VFIO_SET_IOMMU, VFIO_TYPE1_IOMMU); + + /* Get addition IOMMU info */ + ioctl(container, VFIO_IOMMU_GET_INFO, &iommu_info); + + /* Allocate some space and setup a DMA mapping */ + dma_map.vaddr = mmap(0, 1024 * 1024, PROT_READ | PROT_WRITE, + MAP_PRIVATE | MAP_ANONYMOUS, 0, 0); + dma_map.size = 1024 * 1024; + dma_map.iova = 0; /* 1MB starting at 0x0 from device view */ + dma_map.flags = VFIO_DMA_MAP_FLAG_READ | VFIO_DMA_MAP_FLAG_WRITE; + + ioctl(container, VFIO_IOMMU_MAP_DMA, &dma_map); + + /* Get a file descriptor for the device */ + device = ioctl(group, VFIO_GROUP_GET_DEVICE_FD, "0000:06:0d.0"); + + /* Test and setup the device */ + ioctl(device, VFIO_DEVICE_GET_INFO, &device_info); + + for (i = 0; i < device_info.num_regions; i++) { + struct vfio_region_info reg = { .argsz = sizeof(reg) }; + + reg.index = i; + + ioctl(device, VFIO_DEVICE_GET_REGION_INFO, ®); + + /* Setup mappings... read/write offsets, mmaps + * For PCI devices, config space is a region */ + } + + for (i = 0; i < device_info.num_irqs; i++) { + struct vfio_irq_info irq = { .argsz = sizeof(irq) }; + + irq.index = i; + + ioctl(device, VFIO_DEVICE_GET_IRQ_INFO, &irq); + + /* Setup IRQs... eventfds, VFIO_DEVICE_SET_IRQS */ + } + + /* Gratuitous device reset and go... */ + ioctl(device, VFIO_DEVICE_RESET); + +VFIO User API +------------------------------------------------------------------------------- + +Please see include/linux/vfio.h for complete API documentation. + +VFIO bus driver API +------------------------------------------------------------------------------- + +VFIO bus drivers, such as vfio-pci make use of only a few interfaces +into VFIO core. When devices are bound and unbound to the driver, +the driver should call vfio_add_group_dev() and vfio_del_group_dev() +respectively:: + + extern int vfio_add_group_dev(struct device *dev, + const struct vfio_device_ops *ops, + void *device_data); + + extern void *vfio_del_group_dev(struct device *dev); + +vfio_add_group_dev() indicates to the core to begin tracking the +iommu_group of the specified dev and register the dev as owned by +a VFIO bus driver. The driver provides an ops structure for callbacks +similar to a file operations structure:: + + struct vfio_device_ops { + int (*open)(void *device_data); + void (*release)(void *device_data); + ssize_t (*read)(void *device_data, char __user *buf, + size_t count, loff_t *ppos); + ssize_t (*write)(void *device_data, const char __user *buf, + size_t size, loff_t *ppos); + long (*ioctl)(void *device_data, unsigned int cmd, + unsigned long arg); + int (*mmap)(void *device_data, struct vm_area_struct *vma); + }; + +Each function is passed the device_data that was originally registered +in the vfio_add_group_dev() call above. This allows the bus driver +an easy place to store its opaque, private data. The open/release +callbacks are issued when a new file descriptor is created for a +device (via VFIO_GROUP_GET_DEVICE_FD). The ioctl interface provides +a direct pass through for VFIO_DEVICE_* ioctls. The read/write/mmap +interfaces implement the device region access defined by the device's +own VFIO_DEVICE_GET_REGION_INFO ioctl. + + +PPC64 sPAPR implementation note +------------------------------- + +This implementation has some specifics: + +1) On older systems (POWER7 with P5IOC2/IODA1) only one IOMMU group per + container is supported as an IOMMU table is allocated at the boot time, + one table per a IOMMU group which is a Partitionable Endpoint (PE) + (PE is often a PCI domain but not always). + + Newer systems (POWER8 with IODA2) have improved hardware design which allows + to remove this limitation and have multiple IOMMU groups per a VFIO + container. + +2) The hardware supports so called DMA windows - the PCI address range + within which DMA transfer is allowed, any attempt to access address space + out of the window leads to the whole PE isolation. + +3) PPC64 guests are paravirtualized but not fully emulated. There is an API + to map/unmap pages for DMA, and it normally maps 1..32 pages per call and + currently there is no way to reduce the number of calls. In order to make + things faster, the map/unmap handling has been implemented in real mode + which provides an excellent performance which has limitations such as + inability to do locked pages accounting in real time. + +4) According to sPAPR specification, A Partitionable Endpoint (PE) is an I/O + subtree that can be treated as a unit for the purposes of partitioning and + error recovery. A PE may be a single or multi-function IOA (IO Adapter), a + function of a multi-function IOA, or multiple IOAs (possibly including + switch and bridge structures above the multiple IOAs). PPC64 guests detect + PCI errors and recover from them via EEH RTAS services, which works on the + basis of additional ioctl commands. + + So 4 additional ioctls have been added: + + VFIO_IOMMU_SPAPR_TCE_GET_INFO + returns the size and the start of the DMA window on the PCI bus. + + VFIO_IOMMU_ENABLE + enables the container. The locked pages accounting + is done at this point. This lets user first to know what + the DMA window is and adjust rlimit before doing any real job. + + VFIO_IOMMU_DISABLE + disables the container. + + VFIO_EEH_PE_OP + provides an API for EEH setup, error detection and recovery. + + The code flow from the example above should be slightly changed:: + + struct vfio_eeh_pe_op pe_op = { .argsz = sizeof(pe_op), .flags = 0 }; + + ..... + /* Add the group to the container */ + ioctl(group, VFIO_GROUP_SET_CONTAINER, &container); + + /* Enable the IOMMU model we want */ + ioctl(container, VFIO_SET_IOMMU, VFIO_SPAPR_TCE_IOMMU) + + /* Get addition sPAPR IOMMU info */ + vfio_iommu_spapr_tce_info spapr_iommu_info; + ioctl(container, VFIO_IOMMU_SPAPR_TCE_GET_INFO, &spapr_iommu_info); + + if (ioctl(container, VFIO_IOMMU_ENABLE)) + /* Cannot enable container, may be low rlimit */ + + /* Allocate some space and setup a DMA mapping */ + dma_map.vaddr = mmap(0, 1024 * 1024, PROT_READ | PROT_WRITE, + MAP_PRIVATE | MAP_ANONYMOUS, 0, 0); + + dma_map.size = 1024 * 1024; + dma_map.iova = 0; /* 1MB starting at 0x0 from device view */ + dma_map.flags = VFIO_DMA_MAP_FLAG_READ | VFIO_DMA_MAP_FLAG_WRITE; + + /* Check here is .iova/.size are within DMA window from spapr_iommu_info */ + ioctl(container, VFIO_IOMMU_MAP_DMA, &dma_map); + + /* Get a file descriptor for the device */ + device = ioctl(group, VFIO_GROUP_GET_DEVICE_FD, "0000:06:0d.0"); + + .... + + /* Gratuitous device reset and go... */ + ioctl(device, VFIO_DEVICE_RESET); + + /* Make sure EEH is supported */ + ioctl(container, VFIO_CHECK_EXTENSION, VFIO_EEH); + + /* Enable the EEH functionality on the device */ + pe_op.op = VFIO_EEH_PE_ENABLE; + ioctl(container, VFIO_EEH_PE_OP, &pe_op); + + /* You're suggested to create additional data struct to represent + * PE, and put child devices belonging to same IOMMU group to the + * PE instance for later reference. + */ + + /* Check the PE's state and make sure it's in functional state */ + pe_op.op = VFIO_EEH_PE_GET_STATE; + ioctl(container, VFIO_EEH_PE_OP, &pe_op); + + /* Save device state using pci_save_state(). + * EEH should be enabled on the specified device. + */ + + .... + + /* Inject EEH error, which is expected to be caused by 32-bits + * config load. + */ + pe_op.op = VFIO_EEH_PE_INJECT_ERR; + pe_op.err.type = EEH_ERR_TYPE_32; + pe_op.err.func = EEH_ERR_FUNC_LD_CFG_ADDR; + pe_op.err.addr = 0ul; + pe_op.err.mask = 0ul; + ioctl(container, VFIO_EEH_PE_OP, &pe_op); + + .... + + /* When 0xFF's returned from reading PCI config space or IO BARs + * of the PCI device. Check the PE's state to see if that has been + * frozen. + */ + ioctl(container, VFIO_EEH_PE_OP, &pe_op); + + /* Waiting for pending PCI transactions to be completed and don't + * produce any more PCI traffic from/to the affected PE until + * recovery is finished. + */ + + /* Enable IO for the affected PE and collect logs. Usually, the + * standard part of PCI config space, AER registers are dumped + * as logs for further analysis. + */ + pe_op.op = VFIO_EEH_PE_UNFREEZE_IO; + ioctl(container, VFIO_EEH_PE_OP, &pe_op); + + /* + * Issue PE reset: hot or fundamental reset. Usually, hot reset + * is enough. However, the firmware of some PCI adapters would + * require fundamental reset. + */ + pe_op.op = VFIO_EEH_PE_RESET_HOT; + ioctl(container, VFIO_EEH_PE_OP, &pe_op); + pe_op.op = VFIO_EEH_PE_RESET_DEACTIVATE; + ioctl(container, VFIO_EEH_PE_OP, &pe_op); + + /* Configure the PCI bridges for the affected PE */ + pe_op.op = VFIO_EEH_PE_CONFIGURE; + ioctl(container, VFIO_EEH_PE_OP, &pe_op); + + /* Restored state we saved at initialization time. pci_restore_state() + * is good enough as an example. + */ + + /* Hopefully, error is recovered successfully. Now, you can resume to + * start PCI traffic to/from the affected PE. + */ + + .... + +5) There is v2 of SPAPR TCE IOMMU. It deprecates VFIO_IOMMU_ENABLE/ + VFIO_IOMMU_DISABLE and implements 2 new ioctls: + VFIO_IOMMU_SPAPR_REGISTER_MEMORY and VFIO_IOMMU_SPAPR_UNREGISTER_MEMORY + (which are unsupported in v1 IOMMU). + + PPC64 paravirtualized guests generate a lot of map/unmap requests, + and the handling of those includes pinning/unpinning pages and updating + mm::locked_vm counter to make sure we do not exceed the rlimit. + The v2 IOMMU splits accounting and pinning into separate operations: + + - VFIO_IOMMU_SPAPR_REGISTER_MEMORY/VFIO_IOMMU_SPAPR_UNREGISTER_MEMORY ioctls + receive a user space address and size of the block to be pinned. + Bisecting is not supported and VFIO_IOMMU_UNREGISTER_MEMORY is expected to + be called with the exact address and size used for registering + the memory block. The userspace is not expected to call these often. + The ranges are stored in a linked list in a VFIO container. + + - VFIO_IOMMU_MAP_DMA/VFIO_IOMMU_UNMAP_DMA ioctls only update the actual + IOMMU table and do not do pinning; instead these check that the userspace + address is from pre-registered range. + + This separation helps in optimizing DMA for guests. + +6) sPAPR specification allows guests to have an additional DMA window(s) on + a PCI bus with a variable page size. Two ioctls have been added to support + this: VFIO_IOMMU_SPAPR_TCE_CREATE and VFIO_IOMMU_SPAPR_TCE_REMOVE. + The platform has to support the functionality or error will be returned to + the userspace. The existing hardware supports up to 2 DMA windows, one is + 2GB long, uses 4K pages and called "default 32bit window"; the other can + be as big as entire RAM, use different page size, it is optional - guests + create those in run-time if the guest driver supports 64bit DMA. + + VFIO_IOMMU_SPAPR_TCE_CREATE receives a page shift, a DMA window size and + a number of TCE table levels (if a TCE table is going to be big enough and + the kernel may not be able to allocate enough of physically contiguous + memory). It creates a new window in the available slot and returns the bus + address where the new window starts. Due to hardware limitation, the user + space cannot choose the location of DMA windows. + + VFIO_IOMMU_SPAPR_TCE_REMOVE receives the bus start address of the window + and removes it. + +------------------------------------------------------------------------------- + +.. [1] VFIO was originally an acronym for "Virtual Function I/O" in its + initial implementation by Tom Lyon while as Cisco. We've since + outgrown the acronym, but it's catchy. + +.. [2] "safe" also depends upon a device being "well behaved". It's + possible for multi-function devices to have backdoors between + functions and even for single function devices to have alternative + access to things like PCI config space through MMIO registers. To + guard against the former we can include additional precautions in the + IOMMU driver to group multi-function PCI devices together + (iommu=group_mf). The latter we can't prevent, but the IOMMU should + still provide isolation. For PCI, SR-IOV Virtual Functions are the + best indicator of "well behaved", as these are designed for + virtualization usage models. + +.. [3] As always there are trade-offs to virtual machine device + assignment that are beyond the scope of VFIO. It's expected that + future IOMMU technologies will reduce some, but maybe not all, of + these trade-offs. + +.. [4] In this case the device is below a PCI bridge, so transactions + from either function of the device are indistinguishable to the iommu:: + + -[0000:00]-+-1e.0-[06]--+-0d.0 + \-0d.1 + + 00:1e.0 PCI bridge: Intel Corporation 82801 PCI Bridge (rev 90) diff --git a/Documentation/driver-api/xillybus.rst b/Documentation/driver-api/xillybus.rst new file mode 100644 index 000000000000..2446ee303c09 --- /dev/null +++ b/Documentation/driver-api/xillybus.rst @@ -0,0 +1,379 @@ +========================================== +Xillybus driver for generic FPGA interface +========================================== + +:Author: Eli Billauer, Xillybus Ltd. (http://xillybus.com) +:Email: eli.billauer@gmail.com or as advertised on Xillybus' site. + +.. Contents: + + - Introduction + -- Background + -- Xillybus Overview + + - Usage + -- User interface + -- Synchronization + -- Seekable pipes + + - Internals + -- Source code organization + -- Pipe attributes + -- Host never reads from the FPGA + -- Channels, pipes, and the message channel + -- Data streaming + -- Data granularity + -- Probing + -- Buffer allocation + -- The "nonempty" message (supporting poll) + + +Introduction +============ + +Background +---------- + +An FPGA (Field Programmable Gate Array) is a piece of logic hardware, which +can be programmed to become virtually anything that is usually found as a +dedicated chipset: For instance, a display adapter, network interface card, +or even a processor with its peripherals. FPGAs are the LEGO of hardware: +Based upon certain building blocks, you make your own toys the way you like +them. It's usually pointless to reimplement something that is already +available on the market as a chipset, so FPGAs are mostly used when some +special functionality is needed, and the production volume is relatively low +(hence not justifying the development of an ASIC). + +The challenge with FPGAs is that everything is implemented at a very low +level, even lower than assembly language. In order to allow FPGA designers to +focus on their specific project, and not reinvent the wheel over and over +again, pre-designed building blocks, IP cores, are often used. These are the +FPGA parallels of library functions. IP cores may implement certain +mathematical functions, a functional unit (e.g. a USB interface), an entire +processor (e.g. ARM) or anything that might come handy. Think of them as a +building block, with electrical wires dangling on the sides for connection to +other blocks. + +One of the daunting tasks in FPGA design is communicating with a fullblown +operating system (actually, with the processor running it): Implementing the +low-level bus protocol and the somewhat higher-level interface with the host +(registers, interrupts, DMA etc.) is a project in itself. When the FPGA's +function is a well-known one (e.g. a video adapter card, or a NIC), it can +make sense to design the FPGA's interface logic specifically for the project. +A special driver is then written to present the FPGA as a well-known interface +to the kernel and/or user space. In that case, there is no reason to treat the +FPGA differently than any device on the bus. + +It's however common that the desired data communication doesn't fit any well- +known peripheral function. Also, the effort of designing an elegant +abstraction for the data exchange is often considered too big. In those cases, +a quicker and possibly less elegant solution is sought: The driver is +effectively written as a user space program, leaving the kernel space part +with just elementary data transport. This still requires designing some +interface logic for the FPGA, and write a simple ad-hoc driver for the kernel. + +Xillybus Overview +----------------- + +Xillybus is an IP core and a Linux driver. Together, they form a kit for +elementary data transport between an FPGA and the host, providing pipe-like +data streams with a straightforward user interface. It's intended as a low- +effort solution for mixed FPGA-host projects, for which it makes sense to +have the project-specific part of the driver running in a user-space program. + +Since the communication requirements may vary significantly from one FPGA +project to another (the number of data pipes needed in each direction and +their attributes), there isn't one specific chunk of logic being the Xillybus +IP core. Rather, the IP core is configured and built based upon a +specification given by its end user. + +Xillybus presents independent data streams, which resemble pipes or TCP/IP +communication to the user. At the host side, a character device file is used +just like any pipe file. On the FPGA side, hardware FIFOs are used to stream +the data. This is contrary to a common method of communicating through fixed- +sized buffers (even though such buffers are used by Xillybus under the hood). +There may be more than a hundred of these streams on a single IP core, but +also no more than one, depending on the configuration. + +In order to ease the deployment of the Xillybus IP core, it contains a simple +data structure which completely defines the core's configuration. The Linux +driver fetches this data structure during its initialization process, and sets +up the DMA buffers and character devices accordingly. As a result, a single +driver is used to work out of the box with any Xillybus IP core. + +The data structure just mentioned should not be confused with PCI's +configuration space or the Flattened Device Tree. + +Usage +===== + +User interface +-------------- + +On the host, all interface with Xillybus is done through /dev/xillybus_* +device files, which are generated automatically as the drivers loads. The +names of these files depend on the IP core that is loaded in the FPGA (see +Probing below). To communicate with the FPGA, open the device file that +corresponds to the hardware FIFO you want to send data or receive data from, +and use plain write() or read() calls, just like with a regular pipe. In +particular, it makes perfect sense to go:: + + $ cat mydata > /dev/xillybus_thisfifo + + $ cat /dev/xillybus_thatfifo > hisdata + +possibly pressing CTRL-C as some stage, even though the xillybus_* pipes have +the capability to send an EOF (but may not use it). + +The driver and hardware are designed to behave sensibly as pipes, including: + +* Supporting non-blocking I/O (by setting O_NONBLOCK on open() ). + +* Supporting poll() and select(). + +* Being bandwidth efficient under load (using DMA) but also handle small + pieces of data sent across (like TCP/IP) by autoflushing. + +A device file can be read only, write only or bidirectional. Bidirectional +device files are treated like two independent pipes (except for sharing a +"channel" structure in the implementation code). + +Synchronization +--------------- + +Xillybus pipes are configured (on the IP core) to be either synchronous or +asynchronous. For a synchronous pipe, write() returns successfully only after +some data has been submitted and acknowledged by the FPGA. This slows down +bulk data transfers, and is nearly impossible for use with streams that +require data at a constant rate: There is no data transmitted to the FPGA +between write() calls, in particular when the process loses the CPU. + +When a pipe is configured asynchronous, write() returns if there was enough +room in the buffers to store any of the data in the buffers. + +For FPGA to host pipes, asynchronous pipes allow data transfer from the FPGA +as soon as the respective device file is opened, regardless of if the data +has been requested by a read() call. On synchronous pipes, only the amount +of data requested by a read() call is transmitted. + +In summary, for synchronous pipes, data between the host and FPGA is +transmitted only to satisfy the read() or write() call currently handled +by the driver, and those calls wait for the transmission to complete before +returning. + +Note that the synchronization attribute has nothing to do with the possibility +that read() or write() completes less bytes than requested. There is a +separate configuration flag ("allowpartial") that determines whether such a +partial completion is allowed. + +Seekable pipes +-------------- + +A synchronous pipe can be configured to have the stream's position exposed +to the user logic at the FPGA. Such a pipe is also seekable on the host API. +With this feature, a memory or register interface can be attached on the +FPGA side to the seekable stream. Reading or writing to a certain address in +the attached memory is done by seeking to the desired address, and calling +read() or write() as required. + + +Internals +========= + +Source code organization +------------------------ + +The Xillybus driver consists of a core module, xillybus_core.c, and modules +that depend on the specific bus interface (xillybus_of.c and xillybus_pcie.c). + +The bus specific modules are those probed when a suitable device is found by +the kernel. Since the DMA mapping and synchronization functions, which are bus +dependent by their nature, are used by the core module, a +xilly_endpoint_hardware structure is passed to the core module on +initialization. This structure is populated with pointers to wrapper functions +which execute the DMA-related operations on the bus. + +Pipe attributes +--------------- + +Each pipe has a number of attributes which are set when the FPGA component +(IP core) is built. They are fetched from the IDT (the data structure which +defines the core's configuration, see Probing below) by xilly_setupchannels() +in xillybus_core.c as follows: + +* is_writebuf: The pipe's direction. A non-zero value means it's an FPGA to + host pipe (the FPGA "writes"). + +* channelnum: The pipe's identification number in communication between the + host and FPGA. + +* format: The underlying data width. See Data Granularity below. + +* allowpartial: A non-zero value means that a read() or write() (whichever + applies) may return with less than the requested number of bytes. The common + choice is a non-zero value, to match standard UNIX behavior. + +* synchronous: A non-zero value means that the pipe is synchronous. See + Synchronization above. + +* bufsize: Each DMA buffer's size. Always a power of two. + +* bufnum: The number of buffers allocated for this pipe. Always a power of two. + +* exclusive_open: A non-zero value forces exclusive opening of the associated + device file. If the device file is bidirectional, and already opened only in + one direction, the opposite direction may be opened once. + +* seekable: A non-zero value indicates that the pipe is seekable. See + Seekable pipes above. + +* supports_nonempty: A non-zero value (which is typical) indicates that the + hardware will send the messages that are necessary to support select() and + poll() for this pipe. + +Host never reads from the FPGA +------------------------------ + +Even though PCI Express is hotpluggable in general, a typical motherboard +doesn't expect a card to go away all of the sudden. But since the PCIe card +is based upon reprogrammable logic, a sudden disappearance from the bus is +quite likely as a result of an accidental reprogramming of the FPGA while the +host is up. In practice, nothing happens immediately in such a situation. But +if the host attempts to read from an address that is mapped to the PCI Express +device, that leads to an immediate freeze of the system on some motherboards, +even though the PCIe standard requires a graceful recovery. + +In order to avoid these freezes, the Xillybus driver refrains completely from +reading from the device's register space. All communication from the FPGA to +the host is done through DMA. In particular, the Interrupt Service Routine +doesn't follow the common practice of checking a status register when it's +invoked. Rather, the FPGA prepares a small buffer which contains short +messages, which inform the host what the interrupt was about. + +This mechanism is used on non-PCIe buses as well for the sake of uniformity. + + +Channels, pipes, and the message channel +---------------------------------------- + +Each of the (possibly bidirectional) pipes presented to the user is allocated +a data channel between the FPGA and the host. The distinction between channels +and pipes is necessary only because of channel 0, which is used for interrupt- +related messages from the FPGA, and has no pipe attached to it. + +Data streaming +-------------- + +Even though a non-segmented data stream is presented to the user at both +sides, the implementation relies on a set of DMA buffers which is allocated +for each channel. For the sake of illustration, let's take the FPGA to host +direction: As data streams into the respective channel's interface in the +FPGA, the Xillybus IP core writes it to one of the DMA buffers. When the +buffer is full, the FPGA informs the host about that (appending a +XILLYMSG_OPCODE_RELEASEBUF message channel 0 and sending an interrupt if +necessary). The host responds by making the data available for reading through +the character device. When all data has been read, the host writes on the +the FPGA's buffer control register, allowing the buffer's overwriting. Flow +control mechanisms exist on both sides to prevent underflows and overflows. + +This is not good enough for creating a TCP/IP-like stream: If the data flow +stops momentarily before a DMA buffer is filled, the intuitive expectation is +that the partial data in buffer will arrive anyhow, despite the buffer not +being completed. This is implemented by adding a field in the +XILLYMSG_OPCODE_RELEASEBUF message, through which the FPGA informs not just +which buffer is submitted, but how much data it contains. + +But the FPGA will submit a partially filled buffer only if directed to do so +by the host. This situation occurs when the read() method has been blocking +for XILLY_RX_TIMEOUT jiffies (currently 10 ms), after which the host commands +the FPGA to submit a DMA buffer as soon as it can. This timeout mechanism +balances between bus bandwidth efficiency (preventing a lot of partially +filled buffers being sent) and a latency held fairly low for tails of data. + +A similar setting is used in the host to FPGA direction. The handling of +partial DMA buffers is somewhat different, though. The user can tell the +driver to submit all data it has in the buffers to the FPGA, by issuing a +write() with the byte count set to zero. This is similar to a flush request, +but it doesn't block. There is also an autoflushing mechanism, which triggers +an equivalent flush roughly XILLY_RX_TIMEOUT jiffies after the last write(). +This allows the user to be oblivious about the underlying buffering mechanism +and yet enjoy a stream-like interface. + +Note that the issue of partial buffer flushing is irrelevant for pipes having +the "synchronous" attribute nonzero, since synchronous pipes don't allow data +to lay around in the DMA buffers between read() and write() anyhow. + +Data granularity +---------------- + +The data arrives or is sent at the FPGA as 8, 16 or 32 bit wide words, as +configured by the "format" attribute. Whenever possible, the driver attempts +to hide this when the pipe is accessed differently from its natural alignment. +For example, reading single bytes from a pipe with 32 bit granularity works +with no issues. Writing single bytes to pipes with 16 or 32 bit granularity +will also work, but the driver can't send partially completed words to the +FPGA, so the transmission of up to one word may be held until it's fully +occupied with user data. + +This somewhat complicates the handling of host to FPGA streams, because +when a buffer is flushed, it may contain up to 3 bytes don't form a word in +the FPGA, and hence can't be sent. To prevent loss of data, these leftover +bytes need to be moved to the next buffer. The parts in xillybus_core.c +that mention "leftovers" in some way are related to this complication. + +Probing +------- + +As mentioned earlier, the number of pipes that are created when the driver +loads and their attributes depend on the Xillybus IP core in the FPGA. During +the driver's initialization, a blob containing configuration info, the +Interface Description Table (IDT), is sent from the FPGA to the host. The +bootstrap process is done in three phases: + +1. Acquire the length of the IDT, so a buffer can be allocated for it. This + is done by sending a quiesce command to the device, since the acknowledge + for this command contains the IDT's buffer length. + +2. Acquire the IDT itself. + +3. Create the interfaces according to the IDT. + +Buffer allocation +----------------- + +In order to simplify the logic that prevents illegal boundary crossings of +PCIe packets, the following rule applies: If a buffer is smaller than 4kB, +it must not cross a 4kB boundary. Otherwise, it must be 4kB aligned. The +xilly_setupchannels() functions allocates these buffers by requesting whole +pages from the kernel, and diving them into DMA buffers as necessary. Since +all buffers' sizes are powers of two, it's possible to pack any set of such +buffers, with a maximal waste of one page of memory. + +All buffers are allocated when the driver is loaded. This is necessary, +since large continuous physical memory segments are sometimes requested, +which are more likely to be available when the system is freshly booted. + +The allocation of buffer memory takes place in the same order they appear in +the IDT. The driver relies on a rule that the pipes are sorted with decreasing +buffer size in the IDT. If a requested buffer is larger or equal to a page, +the necessary number of pages is requested from the kernel, and these are +used for this buffer. If the requested buffer is smaller than a page, one +single page is requested from the kernel, and that page is partially used. +Or, if there already is a partially used page at hand, the buffer is packed +into that page. It can be shown that all pages requested from the kernel +(except possibly for the last) are 100% utilized this way. + +The "nonempty" message (supporting poll) +---------------------------------------- + +In order to support the "poll" method (and hence select() ), there is a small +catch regarding the FPGA to host direction: The FPGA may have filled a DMA +buffer with some data, but not submitted that buffer. If the host waited for +the buffer's submission by the FPGA, there would be a possibility that the +FPGA side has sent data, but a select() call would still block, because the +host has not received any notification about this. This is solved with +XILLYMSG_OPCODE_NONEMPTY messages sent by the FPGA when a channel goes from +completely empty to containing some data. + +These messages are used only to support poll() and select(). The IP core can +be configured not to send them for a slight reduction of bandwidth. diff --git a/Documentation/driver-api/zorro.rst b/Documentation/driver-api/zorro.rst new file mode 100644 index 000000000000..664072b017e3 --- /dev/null +++ b/Documentation/driver-api/zorro.rst @@ -0,0 +1,104 @@ +======================================== +Writing Device Drivers for Zorro Devices +======================================== + +:Author: Written by Geert Uytterhoeven <geert@linux-m68k.org> +:Last revised: September 5, 2003 + + +Introduction +------------ + +The Zorro bus is the bus used in the Amiga family of computers. Thanks to +AutoConfig(tm), it's 100% Plug-and-Play. + +There are two types of Zorro buses, Zorro II and Zorro III: + + - The Zorro II address space is 24-bit and lies within the first 16 MB of the + Amiga's address map. + + - Zorro III is a 32-bit extension of Zorro II, which is backwards compatible + with Zorro II. The Zorro III address space lies outside the first 16 MB. + + +Probing for Zorro Devices +------------------------- + +Zorro devices are found by calling ``zorro_find_device()``, which returns a +pointer to the ``next`` Zorro device with the specified Zorro ID. A probe loop +for the board with Zorro ID ``ZORRO_PROD_xxx`` looks like:: + + struct zorro_dev *z = NULL; + + while ((z = zorro_find_device(ZORRO_PROD_xxx, z))) { + if (!zorro_request_region(z->resource.start+MY_START, MY_SIZE, + "My explanation")) + ... + } + +``ZORRO_WILDCARD`` acts as a wildcard and finds any Zorro device. If your driver +supports different types of boards, you can use a construct like:: + + struct zorro_dev *z = NULL; + + while ((z = zorro_find_device(ZORRO_WILDCARD, z))) { + if (z->id != ZORRO_PROD_xxx1 && z->id != ZORRO_PROD_xxx2 && ...) + continue; + if (!zorro_request_region(z->resource.start+MY_START, MY_SIZE, + "My explanation")) + ... + } + + +Zorro Resources +--------------- + +Before you can access a Zorro device's registers, you have to make sure it's +not yet in use. This is done using the I/O memory space resource management +functions:: + + request_mem_region() + release_mem_region() + +Shortcuts to claim the whole device's address space are provided as well:: + + zorro_request_device + zorro_release_device + + +Accessing the Zorro Address Space +--------------------------------- + +The address regions in the Zorro device resources are Zorro bus address +regions. Due to the identity bus-physical address mapping on the Zorro bus, +they are CPU physical addresses as well. + +The treatment of these regions depends on the type of Zorro space: + + - Zorro II address space is always mapped and does not have to be mapped + explicitly using z_ioremap(). + + Conversion from bus/physical Zorro II addresses to kernel virtual addresses + and vice versa is done using:: + + virt_addr = ZTWO_VADDR(bus_addr); + bus_addr = ZTWO_PADDR(virt_addr); + + - Zorro III address space must be mapped explicitly using z_ioremap() first + before it can be accessed:: + + virt_addr = z_ioremap(bus_addr, size); + ... + z_iounmap(virt_addr); + + +References +---------- + +#. linux/include/linux/zorro.h +#. linux/include/uapi/linux/zorro.h +#. linux/include/uapi/linux/zorro_ids.h +#. linux/arch/m68k/include/asm/zorro.h +#. linux/drivers/zorro +#. /proc/bus/zorro + |