/*
* Media device
*
* Copyright (C) 2010 Nokia Corporation
*
* Contacts: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
* Sakari Ailus <sakari.ailus@iki.fi>
*
* 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.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
#ifndef _MEDIA_DEVICE_H
#define _MEDIA_DEVICE_H
#include <linux/list.h>
#include <linux/mutex.h>
#include <linux/spinlock.h>
#include <media/media-devnode.h>
#include <media/media-entity.h>
/**
* DOC: Media Controller
*
* Linux kernel media framework
* ============================
*
* This document describes the Linux kernel media framework, its data structures,
* functions and their usage.
*
*
* Introduction
* ------------
*
* The media controller API is documented in DocBook format in
* Documentation/DocBook/media/v4l/media-controller.xml. This document will focus
* on the kernel-side implementation of the media framework.
*
*
* Abstract media device model
* ---------------------------
*
* Discovering a device internal topology, and configuring it at runtime, is one
* of the goals of the media framework. To achieve this, hardware devices are
* modelled as an oriented graph of building blocks called entities connected
* through pads.
*
* An entity is a basic media hardware building block. It can correspond to
* a large variety of logical blocks such as physical hardware devices
* (CMOS sensor for instance), logical hardware devices (a building block
* in a System-on-Chip image processing pipeline), DMA channels or physical
* connectors.
*
* A pad is a connection endpoint through which an entity can interact with
* other entities. Data (not restricted to video) produced by an entity
* flows from the entity's output to one or more entity inputs. Pads should
* not be confused with physical pins at chip boundaries.
*
* A link is a point-to-point oriented connection between two pads, either
* on the same entity or on different entities. Data flows from a source
* pad to a sink pad.
*
*
* Media device
* ------------
*
* A media device is represented by a struct media_device instance, defined in
* include/media/media-device.h. Allocation of the structure is handled by the
* media device driver, usually by embedding the media_device instance in a
* larger driver-specific structure.
*
* Drivers register media device instances by calling
*
* media_device_register(struct media_device *mdev);
*
* The caller is responsible for initializing the media_device structure before
* registration. The following fields must be set:
*
* - dev must point to the parent device (usually a pci_dev, usb_interface or
* platform_device instance).
*
* - model must be filled with the device model name as a NUL-terminated UTF-8
* string. The device/model revision must not be stored in this field.
*
* The following fields are optional:
*
* - serial is a unique serial number stored as a NUL-terminated ASCII string.
* The field is big enough to store a GUID in text form. If the hardware
* doesn't provide a unique serial number this field must be left empty.
*
* - bus_info represents the location of the device in the system as a
* NUL-terminated ASCII string. For PCI/PCIe devices bus_info must be set to
* "PCI:" (or "PCIe:") followed by the value of pci_name(). For USB devices,
* the usb_make_path() function must be used. This field is used by
* applications to distinguish between otherwise identical devices that don't
* provide a serial number.
*
* - hw_revision is the hardware device revision in a driver-specific format.
* When possible the revision should be formatted with the KERNEL_VERSION
* macro.
*
* - driver_version is formatted with the KERNEL_VERSION macro. The version
* minor must be incremented when new features are added to the userspace API
* without breaking binary compatibility. The version major must be
* incremented when binary compatibility is broken.
*
* Upon successful registration a character device named media[0-9]+ is created.
* The device major and minor numbers are dynamic. The model name is exported as
* a sysfs attribute.
*
* Drivers unregister media device instances by calling
*
* media_device_unregister(struct media_device *mdev);
*
* Unregistering a media device that hasn't been registered is *NOT* safe.
*
*
* Entities, pads and links
* ------------------------
*
* - Entities
*
* Entities are represented by a struct media_entity instance, defined in
* include/media/media-entity.h. The structure is usually embedded into a
* higher-level structure, such as a v4l2_subdev or video_device instance,
* although drivers can allocate entities directly.
*
* Drivers initialize entity pads by calling
*
* media_entity_pads_init(struct media_entity *entity, u16 num_pads,
* struct media_pad *pads);
*
* If no pads are needed, drivers could directly fill entity->num_pads
* with 0 and entity->pads with NULL or to call the above function that
* will do the same.
*
* The media_entity name, type and flags fields should be initialized before
* calling media_device_register_entity(). Entities embedded in higher-level
* standard structures can have some of those fields set by the higher-level
* framework.
*
* As the number of pads is known in advance, the pads array is not allocated
* dynamically but is managed by the entity driver. Most drivers will embed the
* pads array in a driver-specific structure, avoiding dynamic allocation.
*
* Drivers must set the direction of every pad in the pads array before calling
* media_entity_pads_init. The function will initialize the other pads fields.
*
* Unlike the number of pads, the total number of links isn't always known in
* advance by the entity driver. As an initial estimate, media_entity_pads_init
* pre-allocates a number of links equal to the number of pads. The links array
* will be reallocated if it grows beyond the initial estimate.
*
* Drivers register entities with a media device by calling
*
* media_device_register_entity(struct media_device *mdev,
* struct media_entity *entity);
*
* Entities are identified by a unique positive integer ID. Drivers can provide an
* ID by filling the media_entity id field prior to registration, or request the
* media controller framework to assign an ID automatically. Drivers that provide
* IDs manually must ensure that all IDs are unique. IDs are not guaranteed to be
* contiguous even when they are all assigned automatically by the framework.
*
* Drivers unregister entities by calling
*
* media_device_unregister_entity(struct media_entity *entity);
*
* Unregistering an entity will not change the IDs of the other entities, and the
* ID will never be reused for a newly registered entity.
*
* When a media device is unregistered, all its entities are unregistered
* automatically. No manual entities unregistration is then required.
*
* Drivers free resources associated with an entity by calling
*
* media_entity_cleanup(struct media_entity *entity);
*
* This function must be called during the cleanup phase after unregistering the
* entity. Note that the media_entity instance itself must be freed explicitly by
* the driver if required.
*
* Entities have flags that describe the entity capabilities and state.
*
* MEDIA_ENT_FL_DEFAULT indicates the default entity for a given type.
* This can be used to report the default audio and video devices or the
* default camera sensor.
*
* Logical entity groups can be defined by setting the group ID of all member
* entities to the same non-zero value. An entity group serves no purpose in the
* kernel, but is reported to userspace during entities enumeration.
*
* Media device drivers should define groups if several entities are logically
* bound together. Example usages include reporting
*
* - ALSA, VBI and video nodes that carry the same media stream
* - lens and flash controllers associated with a sensor
*
* - Pads
*
* Pads are represented by a struct media_pad instance, defined in
* include/media/media-entity.h. Each entity stores its pads in a pads array
* managed by the entity driver. Drivers usually embed the array in a
* driver-specific structure.
*
* Pads are identified by their entity and their 0-based index in the pads array.
* Both information are stored in the media_pad structure, making the media_pad
* pointer the canonical way to store and pass link references.
*
* Pads have flags that describe the pad capabilities and state.
*
* MEDIA_PAD_FL_SINK indicates that the pad supports sinking data.
* MEDIA_PAD_FL_SOURCE indicates that the pad supports sourcing data.
*
* One and only one of MEDIA_PAD_FL_SINK and MEDIA_PAD_FL_SOURCE must be set for
* each pad.
*
* - Links
*
* Links are represented by a struct media_link instance, defined in
* include/media/media-entity.h. Each entity stores all links originating at or
* targeting any of its pads in a links array. A given link is thus stored
* twice, once in the source entity and once in the target entity. The array is
* pre-allocated and grows dynamically as needed.
*
* Drivers create links by calling
*
* media_create_pad_link(struct media_entity *source, u16 source_pad,
* struct media_entity *sink, u16 sink_pad,
* u32 flags);
*
* An entry in the link array of each entity is allocated and stores pointers
* to source and sink pads.
*
* Links have flags that describe the link capabilities and state.
*
* MEDIA_LNK_FL_ENABLED indicates that the link is enabled and can be used
* to transfer media data. When two or more links target a sink pad, only
* one of them can be enabled at a time.
* MEDIA_LNK_FL_IMMUTABLE indicates that the link enabled state can't be
* modified at runtime. If MEDIA_LNK_FL_IMMUTABLE is set, then
* MEDIA_LNK_FL_ENABLED must also be set since an immutable link is always
* enabled.
*
*
* Graph traversal
* ---------------
*
* The media framework provides APIs to iterate over entities in a graph.
*
* To iterate over all entities belonging to a media device, drivers can use the
* media_device_for_each_entity macro, defined in include/media/media-device.h.
*
* struct media_entity *entity;
*
* media_device_for_each_entity(entity, mdev) {
* // entity will point to each entity in turn
* ...
* }
*
* Drivers might also need to iterate over all entities in a graph that can be
* reached only through enabled links starting at a given entity. The media
* framework provides a depth-first graph traversal API for that purpose.
*
* Note that graphs with cycles (whether directed or undirected) are *NOT*
* supported by the graph traversal API. To prevent infinite loops, the graph
* traversal code limits the maximum depth to MEDIA_ENTITY_ENUM_MAX_DEPTH,
* currently defined as 16.
*
* Drivers initiate a graph traversal by calling
*
* media_entity_graph_walk_start(struct media_entity_graph *graph,
* struct media_entity *entity);
*
* The graph structure, provided by the caller, is initialized to start graph
* traversal at the given entity.
*
* Drivers can then retrieve the next entity by calling
*
* media_entity_graph_walk_next(struct media_entity_graph *graph);
*
* When the graph traversal is complete the function will return NULL.
*
* Graph traversal can be interrupted at any moment. No cleanup function call is
* required and the graph structure can be freed normally.
*
* Helper functions can be used to find a link between two given pads, or a pad
* connected to another pad through an enabled link
*
* media_entity_find_link(struct media_pad *source,
* struct media_pad *sink);
*
* media_entity_remote_pad(struct media_pad *pad);
*
* Refer to the kerneldoc documentation for more information.
*
*
* Use count and power handling
* ----------------------------
*
* Due to the wide differences between drivers regarding power management needs,
* the media controller does not implement power management. However, the
* media_entity structure includes a use_count field that media drivers can use to
* track the number of users of every entity for power management needs.
*
* The use_count field is owned by media drivers and must not be touched by entity
* drivers. Access to the field must be protected by the media device graph_mutex
* lock.
*
*
* Links setup
* -----------
*
* Link properties can be modified at runtime by calling
*
* media_entity_setup_link(struct media_link *link, u32 flags);
*
* The flags argument contains the requested new link flags.
*
* The only configurable property is the ENABLED link flag to enable/disable a
* link. Links marked with the IMMUTABLE link flag can not be enabled or disabled.
*
* When a link is enabled or disabled, the media framework calls the
* link_setup operation for the two entities at the source and sink of the link,
* in that order. If the second link_setup call fails, another link_setup call is
* made on the first entity to restore the original link flags.
*
* Media device drivers can be notified of link setup operations by setting the
* media_device::link_notify pointer to a callback function. If provided, the
* notification callback will be called before enabling and after disabling
* links.
*
* Entity drivers must implement the link_setup operation if any of their links
* is non-immutable. The operation must either configure the hardware or store
* the configuration information to be applied later.
*
* Link configuration must not have any side effect on other links. If an enabled
* link at a sink pad prevents another link at the same pad from being enabled,
* the link_setup operation must return -EBUSY and can't implicitly disable the
* first enabled link.
*
*
* Pipelines and media streams
* ---------------------------
*
* When starting streaming, drivers must notify all entities in the pipeline to
* prevent link states from being modified during streaming by calling
*
* media_entity_pipeline_start(struct media_entity *entity,
* struct media_pipeline *pipe);
*
* The function will mark all entities connected to the given entity through
* enabled links, either directly or indirectly, as streaming.
*
* The media_pipeline instance pointed to by the pipe argument will be stored in
* every entity in the pipeline. Drivers should embed the media_pipeline structure
* in higher-level pipeline structures and can then access the pipeline through
* the media_entity pipe field.
*
* Calls to media_entity_pipeline_start() can be nested. The pipeline pointer must
* be identical for all nested calls to the function.
*
* media_entity_pipeline_start() may return an error. In that case, it will
* clean up any of the changes it did by itself.
*
* When stopping the stream, drivers must notify the entities with
*
* media_entity_pipeline_stop(struct media_entity *entity);
*
* If multiple calls to media_entity_pipeline_start() have been made the same
* number of media_entity_pipeline_stop() calls are required to stop streaming. The
* media_entity pipe field is reset to NULL on the last nested stop call.
*
* Link configuration will fail with -EBUSY by default if either end of the link is
* a streaming entity. Links that can be modified while streaming must be marked
* with the MEDIA_LNK_FL_DYNAMIC flag.
*
* If other operations need to be disallowed on streaming entities (such as
* changing entities configuration parameters) drivers can explicitly check the
* media_entity stream_count field to find out if an entity is streaming. This
* operation must be done with the media_device graph_mutex held.
*
*
* Link validation
* ---------------
*
* Link validation is performed by media_entity_pipeline_start() for any
* entity which has sink pads in the pipeline. The
* media_entity::link_validate() callback is used for that purpose. In
* link_validate() callback, entity driver should check that the properties of
* the source pad of the connected entity and its own sink pad match. It is up
* to the type of the entity (and in the end, the properties of the hardware)
* what matching actually means.
*
* Subsystems should facilitate link validation by providing subsystem specific
* helper functions to provide easy access for commonly needed information, and
* in the end provide a way to use driver-specific callbacks.
*/
struct device;
/**
* struct media_device - Media device
* @dev: Parent device
* @devnode: Media device node
* @model: Device model name
* @serial: Device serial number (optional)
* @bus_info: Unique and stable device location identifier
* @hw_revision: Hardware device revision
* @driver_version: Device driver version
* @topology_version: Monotonic counter for storing the version of the graph
* topology. Should be incremented each time the topology changes.
* @entity_id: Unique ID used on the last entity registered
* @pad_id: Unique ID used on the last pad registered
* @link_id: Unique ID used on the last link registered
* @intf_devnode_id: Unique ID used on the last interface devnode registered
* @entities: List of registered entities
* @interfaces: List of registered interfaces
* @pads: List of registered pads
* @links: List of registered links
* @lock: Entities list lock
* @graph_mutex: Entities graph operation lock
* @link_notify: Link state change notification callback
*
* This structure represents an abstract high-level media device. It allows easy
* access to entities and provides basic media device-level support. The
* structure can be allocated directly or embedded in a larger structure.
*
* The parent @dev is a physical device. It must be set before registering the
* media device.
*
* @model is a descriptive model name exported through sysfs. It doesn't have to
* be unique.
*/
struct media_device {
/* dev->driver_data points to this struct. */
struct device *dev;
struct media_devnode devnode;
char model[32];
char serial[40];
char bus_info[32];
u32 hw_revision;
u32 driver_version;
u32 topology_version;
u32 entity_id;
u32 pad_id;
u32 link_id;
u32 intf_devnode_id;
struct list_head entities;
struct list_head interfaces;
struct list_head pads;
struct list_head links;
/* Protects the graph objects creation/removal */
spinlock_t lock;
/* Serializes graph operations. */
struct mutex graph_mutex;
int (*link_notify)(struct media_link *link, u32 flags,
unsigned int notification);
};
#ifdef CONFIG_MEDIA_CONTROLLER
/* Supported link_notify @notification values. */
#define MEDIA_DEV_NOTIFY_PRE_LINK_CH 0
#define MEDIA_DEV_NOTIFY_POST_LINK_CH 1
/* media_devnode to media_device */
#define to_media_device(node) container_of(node, struct media_device, devnode)
int __must_check __media_device_register(struct media_device *mdev,
struct module *owner);
#define media_device_register(mdev) __media_device_register(mdev, THIS_MODULE)
void media_device_unregister(struct media_device *mdev);
int __must_check media_device_register_entity(struct media_device *mdev,
struct media_entity *entity);
void media_device_unregister_entity(struct media_entity *entity);
struct media_device *media_device_get_devres(struct device *dev);
struct media_device *media_device_find_devres(struct device *dev);
/* Iterate over all entities. */
#define media_device_for_each_entity(entity, mdev) \
list_for_each_entry(entity, &(mdev)->entities, graph_obj.list)
/* Iterate over all interfaces. */
#define media_device_for_each_intf(intf, mdev) \
list_for_each_entry(intf, &(mdev)->interfaces, graph_obj.list)
/* Iterate over all pads. */
#define media_device_for_each_pad(pad, mdev) \
list_for_each_entry(pad, &(mdev)->pads, graph_obj.list)
/* Iterate over all links. */
#define media_device_for_each_link(link, mdev) \
list_for_each_entry(link, &(mdev)->links, graph_obj.list)
#else
static inline int media_device_register(struct media_device *mdev)
{
return 0;
}
static inline void media_device_unregister(struct media_device *mdev)
{
}
static inline int media_device_register_entity(struct media_device *mdev,
struct media_entity *entity)
{
return 0;
}
static inline void media_device_unregister_entity(struct media_entity *entity)
{
}
static inline struct media_device *media_device_get_devres(struct device *dev)
{
return NULL;
}
static inline struct media_device *media_device_find_devres(struct device *dev)
{
return NULL;
}
#endif /* CONFIG_MEDIA_CONTROLLER */
#endif
