From 8b2af8f0ca807eb13b59dc5961d2e99fc2b1bd87 Mon Sep 17 00:00:00 2001
From: Edward Falk
Date: Wed, 15 Jun 2005 14:26:39 -0700
Subject: [PATCH] Minor libata documentation patch

I fleshed out libata.tmpl a bit while I was taking notes.
---
 Documentation/DocBook/libata.tmpl | 96 +++++++++++++++++++++++++++++++++++++--
 1 file changed, 93 insertions(+), 3 deletions(-)

(limited to 'Documentation')

diff --git a/Documentation/DocBook/libata.tmpl b/Documentation/DocBook/libata.tmpl
index 6df1dfd18b65..375ae760dc1e 100644
--- a/Documentation/DocBook/libata.tmpl
+++ b/Documentation/DocBook/libata.tmpl
@@ -84,6 +84,14 @@ void (*port_disable) (struct ata_port *);
 	Called from ata_bus_probe() and ata_bus_reset() error paths,
 	as well as when unregistering from the SCSI module (rmmod, hot
 	unplug).
+	This function should do whatever needs to be done to take the
+	port out of use.  In most cases, ata_port_disable() can be used
+	as this hook.
+	</para>
+	<para>
+	Called from ata_bus_probe() on a failed probe.
+	Called from ata_bus_reset() on a failed bus reset.
+	Called from ata_scsi_release().
 	</para>
 
 	</sect2>
@@ -98,6 +106,13 @@ void (*dev_config) (struct ata_port *, struct ata_device *);
 	found.  Typically used to apply device-specific fixups prior to
 	issue of SET FEATURES - XFER MODE, and prior to operation.
 	</para>
+	<para>
+	Called by ata_device_add() after ata_dev_identify() determines
+	a device is present.
+	</para>
+	<para>
+	This entry may be specified as NULL in ata_port_operations.
+	</para>
 
 	</sect2>
 
@@ -135,6 +150,8 @@ void (*tf_read) (struct ata_port *ap, struct ata_taskfile *tf);
 	registers / DMA buffers.  ->tf_read() is called to read the
 	hardware registers / DMA buffers, to obtain the current set of
 	taskfile register values.
+	Most drivers for taskfile-based hardware (PIO or MMIO) use
+	ata_tf_load() and ata_tf_read() for these hooks.
 	</para>
 
 	</sect2>
@@ -147,6 +164,8 @@ void (*exec_command)(struct ata_port *ap, struct ata_taskfile *tf);
 	<para>
 	causes an ATA command, previously loaded with
 	->tf_load(), to be initiated in hardware.
+	Most drivers for taskfile-based hardware use ata_exec_command()
+	for this hook.
 	</para>
 
 	</sect2>
@@ -161,6 +180,10 @@ Allow low-level driver to filter ATA PACKET commands, returning a status
 indicating whether or not it is OK to use DMA for the supplied PACKET
 command.
 	</para>
+	<para>
+	This hook may be specified as NULL, in which case libata will
+	assume that atapi dma can be supported.
+	</para>
 
 	</sect2>
 
@@ -175,6 +198,14 @@ u8   (*check_err)(struct ata_port *ap);
 	Reads the Status/AltStatus/Error ATA shadow register from
 	hardware.  On some hardware, reading the Status register has
 	the side effect of clearing the interrupt condition.
+	Most drivers for taskfile-based hardware use
+	ata_check_status() for this hook.
+	</para>
+	<para>
+	Note that because this is called from ata_device_add(), at
+	least a dummy function that clears device interrupts must be
+	provided for all drivers, even if the controller doesn't
+	actually have a taskfile status register.
 	</para>
 
 	</sect2>
@@ -188,7 +219,13 @@ void (*dev_select)(struct ata_port *ap, unsigned int device);
 	Issues the low-level hardware command(s) that causes one of N
 	hardware devices to be considered 'selected' (active and
 	available for use) on the ATA bus.  This generally has no
-meaning on FIS-based devices.
+	meaning on FIS-based devices.
+	</para>
+	<para>
+	Most drivers for taskfile-based hardware use
+	ata_std_dev_select() for this hook.  Controllers which do not
+	support second drives on a port (such as SATA contollers) will
+	use ata_noop_dev_select().
 	</para>
 
 	</sect2>
@@ -204,6 +241,8 @@ void (*phy_reset) (struct ata_port *ap);
 	for device presence (PATA and SATA), typically a soft reset
 	(SRST) will be performed.  Drivers typically use the helper
 	functions ata_bus_reset() or sata_phy_reset() for this hook.
+	Many SATA drivers use sata_phy_reset() or call it from within
+	their own phy_reset() functions.
 	</para>
 
 	</sect2>
@@ -227,6 +266,25 @@ PCI IDE DMA Status register.
 These hooks are typically either no-ops, or simply not implemented, in
 FIS-based drivers.
 	</para>
+	<para>
+Most legacy IDE drivers use ata_bmdma_setup() for the bmdma_setup()
+hook.  ata_bmdma_setup() will write the pointer to the PRD table to
+the IDE PRD Table Address register, enable DMA in the DMA Command
+register, and call exec_command() to begin the transfer.
+	</para>
+	<para>
+Most legacy IDE drivers use ata_bmdma_start() for the bmdma_start()
+hook.  ata_bmdma_start() will write the ATA_DMA_START flag to the DMA
+Command register.
+	</para>
+	<para>
+Many legacy IDE drivers use ata_bmdma_stop() for the bmdma_stop()
+hook.  ata_bmdma_stop() clears the ATA_DMA_START flag in the DMA
+command register.
+	</para>
+	<para>
+Many legacy IDE drivers use ata_bmdma_status() as the bmdma_status() hook.
+	</para>
 
 	</sect2>
 
@@ -250,6 +308,10 @@ int (*qc_issue) (struct ata_queued_cmd *qc);
 	helper function ata_qc_issue_prot() for taskfile protocol-based
 	dispatch.  More advanced drivers implement their own ->qc_issue.
 	</para>
+	<para>
+	ata_qc_issue_prot() calls ->tf_load(), ->bmdma_setup(), and
+	->bmdma_start() as necessary to initiate a transfer.
+	</para>
 
 	</sect2>
 
@@ -279,6 +341,21 @@ void (*irq_clear) (struct ata_port *);
 	before the interrupt handler is registered, to be sure hardware
 	is quiet.
 	</para>
+	<para>
+	The second argument, dev_instance, should be cast to a pointer
+	to struct ata_host_set.
+	</para>
+	<para>
+	Most legacy IDE drivers use ata_interrupt() for the
+	irq_handler hook, which scans all ports in the host_set,
+	determines which queued command was active (if any), and calls
+	ata_host_intr(ap,qc).
+	</para>
+	<para>
+	Most legacy IDE drivers use ata_bmdma_irq_clear() for the
+	irq_clear() hook, which simply clears the interrupt and error
+	flags in the DMA status register.
+	</para>
 
 	</sect2>
 
@@ -292,6 +369,7 @@ void (*scr_write) (struct ata_port *ap, unsigned int sc_reg,
 	<para>
 	Read and write standard SATA phy registers.  Currently only used
 	if ->phy_reset hook called the sata_phy_reset() helper function.
+	sc_reg is one of SCR_STATUS, SCR_CONTROL, SCR_ERROR, or SCR_ACTIVE.
 	</para>
 
 	</sect2>
@@ -307,17 +385,29 @@ void (*host_stop) (struct ata_host_set *host_set);
 	->port_start() is called just after the data structures for each
 	port are initialized.  Typically this is used to alloc per-port
 	DMA buffers / tables / rings, enable DMA engines, and similar
-	tasks.  
+	tasks.  Some drivers also use this entry point as a chance to
+	allocate driver-private memory for ap->private_data.
+	</para>
+	<para>
+	Many drivers use ata_port_start() as this hook or call
+	it from their own port_start() hooks.  ata_port_start()
+	allocates space for a legacy IDE PRD table and returns.
 	</para>
 	<para>
 	->port_stop() is called after ->host_stop().  It's sole function
 	is to release DMA/memory resources, now that they are no longer
-	actively being used.
+	actively being used.  Many drivers also free driver-private
+	data from port at this time.
+	</para>
+	<para>
+	Many drivers use ata_port_stop() as this hook, which frees the
+	PRD table.
 	</para>
 	<para>
 	->host_stop() is called after all ->port_stop() calls
 have completed.  The hook must finalize hardware shutdown, release DMA
 and other resources, etc.
+	This hook may be specified as NULL, in which case it is not called.
 	</para>
 
 	</sect2>
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