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| author |   John Garry <john.garry@huawei.com> | 2022-04-08 17:04:12 +0800 |
|---|---|---|
| committer |   Damien Le Moal <damien.lemoal@opensource.wdc.com> | 2022-04-11 09:27:44 +0900 |
| commit | 4f1a22ee7b576a38dc5705837c9b0de0c7b5b064 (patch) | |
| tree | 6da76c8edd6a5e5b713cfc639d7e6bae769adbc3 /Documentation/driver-api | |
| parent | ata: pata_mpc52xx: Prepare cleanup of powerpc's asm/prom.h (diff) | |
| download | linux-dev-4f1a22ee7b576a38dc5705837c9b0de0c7b5b064.tar.xz linux-dev-4f1a22ee7b576a38dc5705837c9b0de0c7b5b064.zip | |
libata: Improve ATA queued command allocation
Improve ATA queued command allocation as follows:
- For attaining a qc tag for a SAS host we need to allocate a bit in
ata_port.sas_tag_allocated bitmap.
However we already have a unique tag per device in range
[0, ATA_MAX_QUEUE -1] in the scsi cmnd budget token, so just use that
instead.
- It is a bit pointless to have ata_qc_new_init() in libata-core.c since it
pokes scsi internals, so inline it in ata_scsi_qc_new() (in
libata-scsi.c). Also update Doc accordingly.
- Use standard SCSI helpers set_host_byte() and set_status_byte() in
ata_scsi_qc_new().
Christoph Hellwig originally contributed the change to inline
ata_qc_new_init().
Signed-off-by: John Garry <john.garry@huawei.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Diffstat (limited to 'Documentation/driver-api')
| -rw-r--r-- | Documentation/driver-api/libata.rst | 11 |
1 files changed, 0 insertions, 11 deletions
diff --git a/Documentation/driver-api/libata.rst b/Documentation/driver-api/libata.rst index d477e296bda5..311af516a3fd 100644 --- a/Documentation/driver-api/libata.rst +++ b/Documentation/driver-api/libata.rst @@ -424,12 +424,6 @@ How commands are issued ----------------------- Internal commands - 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 @@ -447,11 +441,6 @@ SCSI commands 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, :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->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`` |