Re: [RFC] libata new EH document

Luben Tuikov
2005-09-01T03:33:22Z

--- Jeff Garzik <jgarzik@pobox.com> wrote:

> Tejun Heo wrote:
> > IMHO, it's a good idea to maintain one qc to one ATA/ATAPI command
> > mapping as long as possible. And, in the suggested framework, it's
> > guaranteed that no other command can come inbetween CHECK_SENSE and
> > REQUEST_SENSE.
> >
> > Requesting sense from EH, calling scsi_decide_disposition() on the
> > sense and following the verdict should achieve the same effect as
> > emulating autosense. Is there any compelling reason to break one qc to
> > one command mapping?
>
>
> Yes, you should have one qc <-> one ATA/ATAPI command. That's why, in

Agree.

> the NCQ scenario, I wanted to make sure that one qc was always reserved
> for error handling: REQUEST SENSE or READ LOG EXT, most importantly.

Yes.

> For SAT layer MODE SELECT translations, that implies multiple calls to
> qc_new/qc_issue/qc_complete before completing the overall SCSI command.
> The same for handling sata_sil mod15write: I am beginning to feel
> like the mod15write workaround might be best implemented in a manner
> that caused libata-scsi (not sata_sil) to create/issue/complete multiple
> ATA commands.
>
> The only problem you run into is that a qc may be active during EH, when
> you need another qc. So avoiding recursive details becomes an issue.

Hmm...

Luben