Re: [PATCH 1/2] libata: Remove dependence on host_set->dev for SAS

[Jeff Garzik <jgarzik@pobox.com>]

Bartlomiej Zolnierkiewicz wrote:
> On 11/24/05, Jeff Garzik <jgarzik@pobox.com> wrote:
> 
>>Douglas Gilbert wrote:
>>
>>>I don't think a SATL is that easy. One SCSI command can
>>>translate into zero or more ATA commands. If it translates
>>>to multiple commands, then there is the possibility of an
>>>error prior to the last in the sequence of ATA commands
>>>(how to report; rollback needed ?). The SATL needs to hold
>>>state and needs a service thread if it is to support the
>>>IMMED bit on some commands (e.g. START STOP UNIT).
>>
>>It needs a conceptual service thread, not necessarily an explicit one.
>>
>>With REQUEST SENSE, I've demonstrated how to report errors with each
>>step in the sequence.  With demo patches I've posted, I've demonstrated
>>(using qc->private_data) how to hold state.
>>
>>
>>
>>>libata still has a ways to go to catch up to SAT rev 7
>>>but has made some good progress lately with the addition
>>>of the ATA pass through commands (lk 2.6.15-rc1 and onward).
>>>smartmontools (just prior to 5.34) now works with '-d ata'
>>>on libata-connected SATA disks. The '-d ata' ** overrides
>>>the guess of a SCSI disk based on the device node (e.g.
>>>/dev/sda) and uses the HDIO_DRIVE_CMD and HDIO_DRIVE_TASK
>>>ioctls. The absence of support for the HDIO_DRIVE_TASKFILE
>>>ioctl means that "selective" self-test can't be done.
>>>I'm not sure if moving smartmontools to the ATA PASS THROUGH
>>>SCSI commands will win back the "selective" self-test
>>>capability. Anyway, going to those ATA PASS THROUGH SCSI
>>
>>ATA passthru can do anything the legacy IDE ioctls can do (and more).
> 
> 
> [ definitely ATA passthru is the way to go but... ]
> 
> discrete taskfiles?

what is this?


> multi-PIO?

what is this?  multi-sector PIO, such as READ MULTIPLE SECTORS?  ATA 
passthru can do that.


> setting transfer speed?

That's not a limitation of passthru, but a limitation of the driver.  I 
don't yet see the value...

	Jeff