forked from luck/tmp_suning_uos_patched
libata.rst: add c function and struct cross-references
Instead of just using text for functions and structs, use the C domain tags, in order to allow cross-referencing with the kernel-doc markups. Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
This commit is contained in:
Mauro Carvalho Chehab
parent
0ec88413f0
commit
6b46c2b156
|
|
@ -18,18 +18,19 @@ internals, and a couple sample ATA low-level drivers.
|
|||
libata Driver API
|
||||
=================
|
||||
|
||||
struct ata_port_operations is defined for every low-level libata
|
||||
:c:type:`struct ata_port_operations <ata_port_operations>`
|
||||
is defined for every low-level libata
|
||||
hardware driver, and it controls how the low-level driver interfaces
|
||||
with the ATA and SCSI layers.
|
||||
|
||||
FIS-based drivers will hook into the system with ->qc_prep() and
|
||||
->qc_issue() high-level hooks. Hardware which behaves in a manner
|
||||
FIS-based drivers will hook into the system with ``->qc_prep()`` and
|
||||
``->qc_issue()`` high-level hooks. Hardware which behaves in a manner
|
||||
similar to PCI IDE hardware may utilize several generic helpers,
|
||||
defining at a bare minimum the bus I/O addresses of the ATA shadow
|
||||
register blocks.
|
||||
|
||||
struct ata_port_operations
|
||||
----------------------------
|
||||
:c:type:`struct ata_port_operations <ata_port_operations>`
|
||||
----------------------------------------------------------
|
||||
|
||||
Disable ATA port
|
||||
~~~~~~~~~~~~~~~~
|
||||
|
|
@ -39,13 +40,13 @@ Disable ATA port
|
|||
void (*port_disable) (struct ata_port *);
|
||||
|
||||
|
||||
Called from ata_bus_probe() error path, as well as when unregistering
|
||||
Called from :c:func:`ata_bus_probe` error path, 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.
|
||||
:c:func:`ata_port_disable` can be used as this hook.
|
||||
|
||||
Called from ata_bus_probe() on a failed probe. Called from
|
||||
ata_scsi_release().
|
||||
Called from :c:func:`ata_bus_probe` on a failed probe. Called from
|
||||
:c:func:`ata_scsi_release`.
|
||||
|
||||
Post-IDENTIFY device configuration
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
|
|
@ -73,22 +74,22 @@ Set PIO/DMA mode
|
|||
|
||||
|
||||
Hooks called prior to the issue of SET FEATURES - XFER MODE command. The
|
||||
optional ->mode_filter() hook is called when libata has built a mask of
|
||||
the possible modes. This is passed to the ->mode_filter() function
|
||||
optional ``->mode_filter()`` hook is called when libata has built a mask of
|
||||
the possible modes. This is passed to the ``->mode_filter()`` function
|
||||
which should return a mask of valid modes after filtering those
|
||||
unsuitable due to hardware limits. It is not valid to use this interface
|
||||
to add modes.
|
||||
|
||||
dev->pio_mode and dev->dma_mode are guaranteed to be valid when
|
||||
->set_piomode() and when ->set_dmamode() is called. The timings for
|
||||
``dev->pio_mode`` and ``dev->dma_mode`` are guaranteed to be valid when
|
||||
``->set_piomode()`` and when ``->set_dmamode()`` is called. The timings for
|
||||
any other drive sharing the cable will also be valid at this point. That
|
||||
is the library records the decisions for the modes of each drive on a
|
||||
channel before it attempts to set any of them.
|
||||
|
||||
->post_set_mode() is called unconditionally, after the SET FEATURES -
|
||||
``->post_set_mode()`` is called unconditionally, after the SET FEATURES -
|
||||
XFER MODE command completes successfully.
|
||||
|
||||
->set_piomode() is always called (if present), but ->set_dma_mode()
|
||||
``->set_piomode()`` is always called (if present), but ``->set_dma_mode()``
|
||||
is only called if DMA is possible.
|
||||
|
||||
Taskfile read/write
|
||||
|
|
@ -100,11 +101,11 @@ Taskfile read/write
|
|||
void (*sff_tf_read) (struct ata_port *ap, struct ata_taskfile *tf);
|
||||
|
||||
|
||||
->tf_load() is called to load the given taskfile into hardware
|
||||
registers / DMA buffers. ->tf_read() is called to read the hardware
|
||||
``->tf_load()`` is called to load the given taskfile into hardware
|
||||
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_sff_tf_load() and ata_sff_tf_read() for these hooks.
|
||||
:c:func:`ata_sff_tf_load` and :c:func:`ata_sff_tf_read` for these hooks.
|
||||
|
||||
PIO data read/write
|
||||
~~~~~~~~~~~~~~~~~~~
|
||||
|
|
@ -117,8 +118,8 @@ PIO data read/write
|
|||
All bmdma-style drivers must implement this hook. This is the low-level
|
||||
operation that actually copies the data bytes during a PIO data
|
||||
transfer. Typically the driver will choose one of
|
||||
ata_sff_data_xfer_noirq(), ata_sff_data_xfer(), or
|
||||
ata_sff_data_xfer32().
|
||||
:c:func:`ata_sff_data_xfer_noirq`, :c:func:`ata_sff_data_xfer`, or
|
||||
:c:func:`ata_sff_data_xfer32`.
|
||||
|
||||
ATA command execute
|
||||
~~~~~~~~~~~~~~~~~~~
|
||||
|
|
@ -128,9 +129,9 @@ ATA command execute
|
|||
void (*sff_exec_command)(struct ata_port *ap, struct ata_taskfile *tf);
|
||||
|
||||
|
||||
causes an ATA command, previously loaded with ->tf_load(), to be
|
||||
causes an ATA command, previously loaded with ``->tf_load()``, to be
|
||||
initiated in hardware. Most drivers for taskfile-based hardware use
|
||||
ata_sff_exec_command() for this hook.
|
||||
:c:func:`ata_sff_exec_command` for this hook.
|
||||
|
||||
Per-cmd ATAPI DMA capabilities filter
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
|
|
@ -159,7 +160,7 @@ Read specific ATA shadow registers
|
|||
Reads the Status/AltStatus 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_sff_check_status() for this hook.
|
||||
:c:func:`ata_sff_check_status` for this hook.
|
||||
|
||||
Write specific ATA shadow register
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
|
|
@ -184,7 +185,7 @@ 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.
|
||||
|
||||
Most drivers for taskfile-based hardware use ata_sff_dev_select() for
|
||||
Most drivers for taskfile-based hardware use :c:func:`ata_sff_dev_select` for
|
||||
this hook.
|
||||
|
||||
Private tuning method
|
||||
|
|
@ -222,28 +223,28 @@ Control PCI IDE BMDMA engine
|
|||
|
||||
|
||||
When setting up an IDE BMDMA transaction, these hooks arm
|
||||
(->bmdma_setup), fire (->bmdma_start), and halt (->bmdma_stop) the
|
||||
hardware's DMA engine. ->bmdma_status is used to read the standard PCI
|
||||
(``->bmdma_setup``), fire (``->bmdma_start``), and halt (``->bmdma_stop``) the
|
||||
hardware's DMA engine. ``->bmdma_status`` is used to read the standard PCI
|
||||
IDE DMA Status register.
|
||||
|
||||
These hooks are typically either no-ops, or simply not implemented, in
|
||||
FIS-based drivers.
|
||||
|
||||
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.
|
||||
Most legacy IDE drivers use :c:func:`ata_bmdma_setup` for the
|
||||
:c:func:`bmdma_setup` hook. :c:func:`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 :c:func:`exec_command` to begin the transfer.
|
||||
|
||||
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.
|
||||
Most legacy IDE drivers use :c:func:`ata_bmdma_start` for the
|
||||
:c:func:`bmdma_start` hook. :c:func:`ata_bmdma_start` will write the
|
||||
ATA_DMA_START flag to the DMA Command register.
|
||||
|
||||
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.
|
||||
Many legacy IDE drivers use :c:func:`ata_bmdma_stop` for the
|
||||
:c:func:`bmdma_stop` hook. :c:func:`ata_bmdma_stop` clears the ATA_DMA_START
|
||||
flag in the DMA command register.
|
||||
|
||||
Many legacy IDE drivers use ata_bmdma_status() as the bmdma_status()
|
||||
hook.
|
||||
Many legacy IDE drivers use :c:func:`ata_bmdma_status` as the
|
||||
:c:func:`bmdma_status` hook.
|
||||
|
||||
High-level taskfile hooks
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
|
|
@ -255,19 +256,19 @@ High-level taskfile hooks
|
|||
|
||||
|
||||
Higher-level hooks, these two hooks can potentially supercede several of
|
||||
the above taskfile/DMA engine hooks. ->qc_prep is called after the
|
||||
the above taskfile/DMA engine hooks. ``->qc_prep`` is called after the
|
||||
buffers have been DMA-mapped, and is typically used to populate the
|
||||
hardware's DMA scatter-gather table. Most drivers use the standard
|
||||
ata_qc_prep() helper function, but more advanced drivers roll their
|
||||
:c:func:`ata_qc_prep` helper function, but more advanced drivers roll their
|
||||
own.
|
||||
|
||||
->qc_issue is used to make a command active, once the hardware and S/G
|
||||
``->qc_issue`` is used to make a command active, once the hardware and S/G
|
||||
tables have been prepared. IDE BMDMA drivers use the helper function
|
||||
ata_qc_issue_prot() for taskfile protocol-based dispatch. More
|
||||
advanced drivers implement their own ->qc_issue.
|
||||
:c:func:`ata_qc_issue_prot` for taskfile protocol-based dispatch. More
|
||||
advanced drivers implement their own ``->qc_issue``.
|
||||
|
||||
ata_qc_issue_prot() calls ->tf_load(), ->bmdma_setup(), and
|
||||
->bmdma_start() as necessary to initiate a transfer.
|
||||
:c:func:`ata_qc_issue_prot` calls ``->tf_load()``, ``->bmdma_setup()``, and
|
||||
``->bmdma_start()`` as necessary to initiate a transfer.
|
||||
|
||||
Exception and probe handling (EH)
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
|
|
@ -278,7 +279,7 @@ Exception and probe handling (EH)
|
|||
void (*phy_reset) (struct ata_port *ap);
|
||||
|
||||
|
||||
Deprecated. Use ->error_handler() instead.
|
||||
Deprecated. Use ``->error_handler()`` instead.
|
||||
|
||||
::
|
||||
|
||||
|
|
@ -286,18 +287,18 @@ Deprecated. Use ->error_handler() instead.
|
|||
void (*thaw) (struct ata_port *ap);
|
||||
|
||||
|
||||
ata_port_freeze() is called when HSM violations or some other
|
||||
:c:func:`ata_port_freeze` is called when HSM violations or some other
|
||||
condition disrupts normal operation of the port. A frozen port is not
|
||||
allowed to perform any operation until the port is thawed, which usually
|
||||
follows a successful reset.
|
||||
|
||||
The optional ->freeze() callback can be used for freezing the port
|
||||
The optional ``->freeze()`` callback can be used for freezing the port
|
||||
hardware-wise (e.g. mask interrupt and stop DMA engine). If a port
|
||||
cannot be frozen hardware-wise, the interrupt handler must ack and clear
|
||||
interrupts unconditionally while the port is frozen.
|
||||
|
||||
The optional ->thaw() callback is called to perform the opposite of
|
||||
->freeze(): prepare the port for normal operation once again. Unmask
|
||||
The optional ``->thaw()`` callback is called to perform the opposite of
|
||||
``->freeze()``: prepare the port for normal operation once again. Unmask
|
||||
interrupts, start DMA engine, etc.
|
||||
|
||||
::
|
||||
|
|
@ -305,10 +306,10 @@ interrupts, start DMA engine, etc.
|
|||
void (*error_handler) (struct ata_port *ap);
|
||||
|
||||
|
||||
->error_handler() is a driver's hook into probe, hotplug, and recovery
|
||||
``->error_handler()`` is a driver's hook into probe, hotplug, and recovery
|
||||
and other exceptional conditions. The primary responsibility of an
|
||||
implementation is to call ata_do_eh() or ata_bmdma_drive_eh() with
|
||||
a set of EH hooks as arguments:
|
||||
implementation is to call :c:func:`ata_do_eh` or :c:func:`ata_bmdma_drive_eh`
|
||||
with a set of EH hooks as arguments:
|
||||
|
||||
'prereset' hook (may be NULL) is called during an EH reset, before any
|
||||
other actions are taken.
|
||||
|
|
@ -327,7 +328,7 @@ called to perform the low-level EH reset.
|
|||
|
||||
Perform any hardware-specific actions necessary to finish processing
|
||||
after executing a probe-time or EH-time command via
|
||||
ata_exec_internal().
|
||||
:c:func:`ata_exec_internal`.
|
||||
|
||||
Hardware interrupt handling
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
|
|
@ -338,20 +339,20 @@ Hardware interrupt handling
|
|||
void (*irq_clear) (struct ata_port *);
|
||||
|
||||
|
||||
->irq_handler is the interrupt handling routine registered with the
|
||||
system, by libata. ->irq_clear is called during probe just before the
|
||||
``->irq_handler`` is the interrupt handling routine registered with the
|
||||
system, by libata. ``->irq_clear`` is called during probe just before the
|
||||
interrupt handler is registered, to be sure hardware is quiet.
|
||||
|
||||
The second argument, dev_instance, should be cast to a pointer to
|
||||
struct ata_host_set.
|
||||
:c:type:`struct ata_host_set <ata_host_set>`.
|
||||
|
||||
Most legacy IDE drivers use ata_sff_interrupt() for the irq_handler
|
||||
Most legacy IDE drivers use :c:func:`ata_sff_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_sff_host_intr(ap,qc).
|
||||
|
||||
Most legacy IDE drivers use ata_sff_irq_clear() for the irq_clear()
|
||||
hook, which simply clears the interrupt and error flags in the DMA
|
||||
status register.
|
||||
Most legacy IDE drivers use :c:func:`ata_sff_irq_clear` for the
|
||||
:c:func:`irq_clear` hook, which simply clears the interrupt and error flags
|
||||
in the DMA status register.
|
||||
|
||||
SATA phy read/write
|
||||
~~~~~~~~~~~~~~~~~~~
|
||||
|
|
@ -365,8 +366,8 @@ SATA phy read/write
|
|||
|
||||
|
||||
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.
|
||||
``->phy_reset`` hook called the :c:func:`sata_phy_reset` helper function.
|
||||
sc_reg is one of SCR_STATUS, SCR_CONTROL, SCR_ERROR, or SCR_ACTIVE.
|
||||
|
||||
Init and shutdown
|
||||
~~~~~~~~~~~~~~~~~
|
||||
|
|
@ -378,21 +379,21 @@ Init and shutdown
|
|||
void (*host_stop) (struct ata_host_set *host_set);
|
||||
|
||||
|
||||
->port_start() is called just after the data structures for each port
|
||||
``->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. Some drivers also
|
||||
use this entry point as a chance to allocate driver-private memory for
|
||||
ap->private_data.
|
||||
``ap->private_data``.
|
||||
|
||||
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.
|
||||
Many drivers use :c:func:`ata_port_start` as this hook or call it from their
|
||||
own :c:func:`port_start` hooks. :c:func:`ata_port_start` allocates space for
|
||||
a legacy IDE PRD table and returns.
|
||||
|
||||
->port_stop() is called after ->host_stop(). Its sole function is to
|
||||
``->port_stop()`` is called after ``->host_stop()``. Its sole function is to
|
||||
release DMA/memory resources, now that they are no longer actively being
|
||||
used. Many drivers also free driver-private data from port at this time.
|
||||
|
||||
->host_stop() is called after all ->port_stop() calls have completed.
|
||||
``->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.
|
||||
|
|
@ -407,7 +408,8 @@ exceptions doc first.
|
|||
Origins of commands
|
||||
-------------------
|
||||
|
||||
In libata, a command is represented with struct ata_queued_cmd or qc.
|
||||
In libata, a command is represented with
|
||||
:c:type:`struct ata_queued_cmd <ata_queued_cmd>` or qc.
|
||||
qc's are preallocated during port initialization and repetitively used
|
||||
for command executions. Currently only one qc is allocated per port but
|
||||
yet-to-be-merged NCQ branch allocates one for each tag and maps each qc
|
||||
|
|
@ -423,17 +425,17 @@ How commands are issued
|
|||
-----------------------
|
||||
|
||||
Internal commands
|
||||
First, qc is allocated and initialized using ata_qc_new_init().
|
||||
Although ata_qc_new_init() doesn't implement any wait or retry
|
||||
First, qc is allocated and initialized using :c:func:`ata_qc_new_init`.
|
||||
Although :c:func:`ata_qc_new_init` doesn't implement any wait or retry
|
||||
mechanism when qc is not available, internal commands are currently
|
||||
issued only during initialization and error recovery, so no other
|
||||
command is active and allocation is guaranteed to succeed.
|
||||
|
||||
Once allocated qc's taskfile is initialized for the command to be
|
||||
executed. qc currently has two mechanisms to notify completion. One
|
||||
is via qc->complete_fn() callback and the other is completion
|
||||
qc->waiting. qc->complete_fn() callback is the asynchronous path
|
||||
used by normal SCSI translated commands and qc->waiting is the
|
||||
is via ``qc->complete_fn()`` callback and the other is completion
|
||||
``qc->waiting``. ``qc->complete_fn()`` callback is the asynchronous path
|
||||
used by normal SCSI translated commands and ``qc->waiting`` is the
|
||||
synchronous (issuer sleeps in process context) path used by internal
|
||||
commands.
|
||||
|
||||
|
|
@ -441,21 +443,21 @@ Internal commands
|
|||
qc is issued.
|
||||
|
||||
SCSI commands
|
||||
All libata drivers use ata_scsi_queuecmd() as hostt->queuecommand
|
||||
callback. scmds can either be simulated or translated. No qc is
|
||||
involved in processing a simulated scmd. The result is computed
|
||||
right away and the scmd is completed.
|
||||
All libata drivers use :c:func:`ata_scsi_queuecmd` as
|
||||
``hostt->queuecommand`` callback. scmds can either be simulated or
|
||||
translated. No qc is involved in processing a simulated scmd. The
|
||||
result is computed right away and the scmd is completed.
|
||||
|
||||
For a translated scmd, ata_qc_new_init() is invoked to allocate a
|
||||
For a translated scmd, :c:func:`ata_qc_new_init` is invoked to allocate a
|
||||
qc and the scmd is translated into the qc. SCSI midlayer's
|
||||
completion notification function pointer is stored into
|
||||
qc->scsidone.
|
||||
``qc->scsidone``.
|
||||
|
||||
qc->complete_fn() callback is used for completion notification. ATA
|
||||
commands use ata_scsi_qc_complete() while ATAPI commands use
|
||||
atapi_qc_complete(). Both functions end up calling qc->scsidone to
|
||||
notify upper layer when the qc is finished. After translation is
|
||||
completed, the qc is issued with ata_qc_issue().
|
||||
``qc->complete_fn()`` callback is used for completion notification. ATA
|
||||
commands use :c:func:`ata_scsi_qc_complete` while ATAPI commands use
|
||||
:c:func:`atapi_qc_complete`. Both functions end up calling ``qc->scsidone``
|
||||
to notify upper layer when the qc is finished. After translation is
|
||||
completed, the qc is issued with :c:func:`ata_qc_issue`.
|
||||
|
||||
Note that SCSI midlayer invokes hostt->queuecommand while holding
|
||||
host_set lock, so all above occur while holding host_set lock.
|
||||
|
|
@ -495,34 +497,34 @@ ATAPI PIO
|
|||
How commands are completed
|
||||
--------------------------
|
||||
|
||||
Once issued, all qc's are either completed with ata_qc_complete() or
|
||||
Once issued, all qc's are either completed with :c:func:`ata_qc_complete` or
|
||||
time out. For commands which are handled by interrupts,
|
||||
ata_host_intr() invokes ata_qc_complete(), and, for PIO tasks,
|
||||
pio_task invokes ata_qc_complete(). In error cases, packet_task may
|
||||
:c:func:`ata_host_intr` invokes :c:func:`ata_qc_complete`, and, for PIO tasks,
|
||||
pio_task invokes :c:func:`ata_qc_complete`. In error cases, packet_task may
|
||||
also complete commands.
|
||||
|
||||
ata_qc_complete() does the following.
|
||||
:c:func:`ata_qc_complete` does the following.
|
||||
|
||||
1. DMA memory is unmapped.
|
||||
|
||||
2. ATA_QCFLAG_ACTIVE is cleared from qc->flags.
|
||||
|
||||
3. qc->complete_fn() callback is invoked. If the return value of the
|
||||
3. :c:func:`qc->complete_fn` callback is invoked. If the return value of the
|
||||
callback is not zero. Completion is short circuited and
|
||||
ata_qc_complete() returns.
|
||||
:c:func:`ata_qc_complete` returns.
|
||||
|
||||
4. __ata_qc_complete() is called, which does
|
||||
4. :c:func:`__ata_qc_complete` is called, which does
|
||||
|
||||
1. qc->flags is cleared to zero.
|
||||
1. ``qc->flags`` is cleared to zero.
|
||||
|
||||
2. ap->active_tag and qc->tag are poisoned.
|
||||
2. ``ap->active_tag`` and ``qc->tag`` are poisoned.
|
||||
|
||||
3. qc->waiting is cleared & completed (in that order).
|
||||
3. ``qc->waiting`` is cleared & completed (in that order).
|
||||
|
||||
4. qc is deallocated by clearing appropriate bit in ap->qactive.
|
||||
4. qc is deallocated by clearing appropriate bit in ``ap->qactive``.
|
||||
|
||||
So, it basically notifies upper layer and deallocates qc. One exception
|
||||
is short-circuit path in #3 which is used by atapi_qc_complete().
|
||||
is short-circuit path in #3 which is used by :c:func:`atapi_qc_complete`.
|
||||
|
||||
For all non-ATAPI commands, whether it fails or not, almost the same
|
||||
code path is taken and very little error handling takes place. A qc is
|
||||
|
|
@ -531,33 +533,33 @@ otherwise.
|
|||
|
||||
However, failed ATAPI commands require more handling as REQUEST SENSE is
|
||||
needed to acquire sense data. If an ATAPI command fails,
|
||||
ata_qc_complete() is invoked with error status, which in turn invokes
|
||||
atapi_qc_complete() via qc->complete_fn() callback.
|
||||
:c:func:`ata_qc_complete` is invoked with error status, which in turn invokes
|
||||
:c:func:`atapi_qc_complete` via ``qc->complete_fn()`` callback.
|
||||
|
||||
This makes atapi_qc_complete() set scmd->result to
|
||||
This makes :c:func:`atapi_qc_complete` set ``scmd->result`` to
|
||||
SAM_STAT_CHECK_CONDITION, complete the scmd and return 1. As the
|
||||
sense data is empty but scmd->result is CHECK CONDITION, SCSI midlayer
|
||||
will invoke EH for the scmd, and returning 1 makes ata_qc_complete()
|
||||
sense data is empty but ``scmd->result`` is CHECK CONDITION, SCSI midlayer
|
||||
will invoke EH for the scmd, and returning 1 makes :c:func:`ata_qc_complete`
|
||||
to return without deallocating the qc. This leads us to
|
||||
ata_scsi_error() with partially completed qc.
|
||||
:c:func:`ata_scsi_error` with partially completed qc.
|
||||
|
||||
ata_scsi_error()
|
||||
------------------
|
||||
:c:func:`ata_scsi_error`
|
||||
------------------------
|
||||
|
||||
ata_scsi_error() is the current transportt->eh_strategy_handler()
|
||||
:c:func:`ata_scsi_error` is the current ``transportt->eh_strategy_handler()``
|
||||
for libata. As discussed above, this will be entered in two cases -
|
||||
timeout and ATAPI error completion. This function calls low level libata
|
||||
driver's eng_timeout() callback, the standard callback for which is
|
||||
ata_eng_timeout(). It checks if a qc is active and calls
|
||||
ata_qc_timeout() on the qc if so. Actual error handling occurs in
|
||||
ata_qc_timeout().
|
||||
driver's :c:func:`eng_timeout` callback, the standard callback for which is
|
||||
:c:func:`ata_eng_timeout`. It checks if a qc is active and calls
|
||||
:c:func:`ata_qc_timeout` on the qc if so. Actual error handling occurs in
|
||||
:c:func:`ata_qc_timeout`.
|
||||
|
||||
If EH is invoked for timeout, ata_qc_timeout() stops BMDMA and
|
||||
If EH is invoked for timeout, :c:func:`ata_qc_timeout` stops BMDMA and
|
||||
completes the qc. Note that as we're currently in EH, we cannot call
|
||||
scsi_done. As described in SCSI EH doc, a recovered scmd should be
|
||||
either retried with scsi_queue_insert() or finished with
|
||||
scsi_finish_command(). Here, we override qc->scsidone with
|
||||
scsi_finish_command() and calls ata_qc_complete().
|
||||
either retried with :c:func:`scsi_queue_insert` or finished with
|
||||
:c:func:`scsi_finish_command`. Here, we override ``qc->scsidone`` with
|
||||
:c:func:`scsi_finish_command` and calls :c:func:`ata_qc_complete`.
|
||||
|
||||
If EH is invoked due to a failed ATAPI qc, the qc here is completed but
|
||||
not deallocated. The purpose of this half-completion is to use the qc as
|
||||
|
|
@ -565,11 +567,11 @@ place holder to make EH code reach this place. This is a bit hackish,
|
|||
but it works.
|
||||
|
||||
Once control reaches here, the qc is deallocated by invoking
|
||||
__ata_qc_complete() explicitly. Then, internal qc for REQUEST SENSE
|
||||
:c:func:`__ata_qc_complete` explicitly. Then, internal qc for REQUEST SENSE
|
||||
is issued. Once sense data is acquired, scmd is finished by directly
|
||||
invoking scsi_finish_command() on the scmd. Note that as we already
|
||||
invoking :c:func:`scsi_finish_command` on the scmd. Note that as we already
|
||||
have completed and deallocated the qc which was associated with the
|
||||
scmd, we don't need to/cannot call ata_qc_complete() again.
|
||||
scmd, we don't need to/cannot call :c:func:`ata_qc_complete` again.
|
||||
|
||||
Problems with the current EH
|
||||
----------------------------
|
||||
|
|
@ -583,7 +585,7 @@ Problems with the current EH
|
|||
- When handling timeouts, no action is taken to make device forget
|
||||
about the timed out command and ready for new commands.
|
||||
|
||||
- EH handling via ata_scsi_error() is not properly protected from
|
||||
- EH handling via :c:func:`ata_scsi_error` is not properly protected from
|
||||
usual command processing. On EH entrance, the device is not in
|
||||
quiescent state. Timed out commands may succeed or fail any time.
|
||||
pio_task and atapi_task may still be running.
|
||||
|
|
@ -622,6 +624,8 @@ libata Core Internals
|
|||
.. kernel-doc:: drivers/ata/libata-core.c
|
||||
:internal:
|
||||
|
||||
.. kernel-doc:: drivers/ata/libata-eh.c
|
||||
|
||||
libata SCSI translation/emulation
|
||||
=================================
|
||||
|
||||
|
|
|
|||
Loading…
Reference in New Issue
Block a user