Messages in this thread | | | Date | Thu, 7 Apr 2022 15:32:07 +0100 | From | John Garry <> | Subject | Re: [PATCH 03/11] libata: Send internal commands through the block layer |
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On 22/03/2022 11:20, Christoph Hellwig wrote: > On Tue, Mar 22, 2022 at 06:39:37PM +0800, John Garry wrote: >> When SCSI HBA device drivers are required to process an ATA internal >> command they still need a tag for the IO. This often requires the driver >> to set aside a set of tags for these sorts of IOs and manage the tags >> themselves. >> >> If we associate a SCSI command (and request) with an ATA internal command >> then the tag is already provided, so introduce the change to send ATA >> internal commands through the block layer with a set of custom blk-mq ops. >> >> note: I think that the timeout handling needs to be fixed up.
Hi Christoph,
> Any reason to not just send them through an ATA_16 passthrough CDB and > just use all the normal SCSI command handling?
I had a go at implementing this but I have come up against a few issues:
- ATA_16 handling translates the passthrough CDB to a ATA TF. However ata_exec_internal_sg() is passed a TF already. So what to do? Change the callers to generate a ATA_16 CDB? I guess not. Otherwise we could put the already-generated TF in the SCSI cmd CDB somehow and use directly.
- We may have no SCSI device (yet) for the target when issuing an internal command, but only the ATA port+dev. So need a method to pass these pointers to ATA_16 handling
- we would need to change ata_scsi_translate(), ata_scsi_pass_thru() and other friends to deal with ATA_TAG_INTERNAL and its peculiarities - today it just deals with regular qc's.
It still does seem a reasonable idea to use ATA_16, but it looks like significant modifications would be required....
Thanks, John
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