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

[Jeff Garzik <jgarzik@pobox.com>]

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).

	Jeff