[PATCH] Minor libata documentation patch
I fleshed out libata.tmpl a bit while I was taking notes.
diff --git a/Documentation/DocBook/libata.tmpl b/Documentation/DocBook/libata.tmpl
index 6df1dfd..375ae76 100644
--- a/Documentation/DocBook/libata.tmpl
+++ b/Documentation/DocBook/libata.tmpl
@@ -84,6 +84,14 @@
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 @@
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 @@
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 @@
<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 @@
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 @@
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 @@
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 @@
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 @@
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 @@
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 @@
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 @@
<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 @@
->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>