Re: [PATCH #upstream 1/2] libata: move command post processing to __ata_qc_complete()

[Jeff Garzik <jeff@garzik.org>]

Tejun Heo wrote:
> Jeff Garzik wrote:
>> Tejun Heo wrote:
>>> Some commands need post-processing after successful completion.  This
>>> was done in ata_scsi_qc_complete() till now but command post
>>> processing doesn't belong to SAT layer.  Move them to
>>> __ata_qc_complete() and, while at it, restructure a bit to ease adding
>>> post-processing for other commands.
>>>
>>> Signed-off-by: Tejun Heo <htejun@gmail.com>
>> BTW, while doing the TEST UNIT READY emulation patch for ATA (recently
>> withdrawn from libata-dev.git#upstream), I found a problem with the
>> interface that was difficult to get around:  TEST UNIT READY simulation
>> code really wants to look at the result TF of CHECK POWER MODE, even if
>> ATA_ERR is asserted, before determining whether or not to call that
>> command an error.
>>
>> Maybe the EH scheduling could be moved until after ->complete_fn, to
>> permit ->complete_fn users to manipulate qc->err_mask etc.?
> 
> Yeah, right.  Device error is a special case.  In many cases, devices
> can operate without any problem after asserting error and for some
> commands error is used to signal certain conditions.  I think the least
> intrusive way would be a qc flag - ATA_QCFLAG_ALLOW_DEVERR, maybe.
> Also, I'm not sure whether EH should kick in when passthru commands fail
> with a device error.  Maybe libata should just report the error to the
> issuer and continue operation?

Good point and agreed -- I definitely think passthru commands want 
device errors immediately.

That vastly increases the utility of passthru to be used in test suites 
and stuff, where you know a lot of operations should fail, by design. 
(i.e. intentionally submitting an invalid command, to test that 'command 
aborted' is returned)

	Jeff