James Bottomley wrote:
On Wed, 2007-01-03 at 00:42 -0500, Mark Lord wrote:
James Bottomley wrote:
I don't think I quite understand what you're trying to do here. My
understanding is that ATA_12 and ATA_16 are part of the SAT layer. i.e.
they're used when we're speaking SCSI to an underlying ATA device to
send taskfiles. However, ATAPI devices don't use SAT ... every SCSI
command you send to an ATAPI device goes out as an ATA PACKET command
without being translated.
ATAPI devices also implement quite a few ATA (non-packet) commands.
This patch gives us a way to issue them in response to SG_IO ATA passthru
and the existing (non working) libata HDIO_DRIVE_CMD and HDIO_DRIVE_TASK
ioctl calls.
I know that ... but when you send ATA_16 down to an ATAPI device via
SG_IO the code paths in libata don't unwrap it and send it out as a
taskfile ... they put ATA_16 out as a packet command.
He is aware of that. That's what his two patches address.
Without this patch, SCSI blocks the ATA_16 passthru attempts,
because it thinks the CDB is too large for the 12-byte packet protocol
that ATAPI devices use. This limit (12 bytes) is totally non-applicable
to ATA protocol commands.
Is there a missing piece to this patch, where you scan the incoming
commands to ATAPI devices and actually do translation for ATA_16?
Look at the existing libata-core.c ioctl's for HDIO_DRIVE_CMD
and HDIO_DRIVE_TASK, used by hdparm and others.
Those send out taskfile commands ... my point is that the SAT SCSI
No, those HDIO_xxx ioctls cause libata to send ATA_{12,16} SCSI commands
to the SCSI simulator (which then unwraps them, and sends a taskfile).
Jeff
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