Re: [PATCH v2] libata: Simulate REPORT LUNS for ATAPI devices

["Darrick J. Wong" <djwong@us.ibm.com>]

Patrick Mansfield wrote:
> On Mon, Dec 04, 2006 at 03:32:20PM -0800, Darrick J. Wong wrote:
>> The Quantum GoVault SATAPI removable disk device returns ATA_ERR in
>> response to a REPORT LUNS packet.  If this happens to an ATAPI device
>> that is attached to a SAS controller (this is the case with sas_ata),
>> the device does not load because SCSI won't touch a "SCSI device"
>> that won't report its LUNs.  Since most ATAPI devices don't support
>> multiple LUNs anyway, we might as well fake a response like we do for
>> ATA devices.
> 
> If the REPORT LUNS fails, we should fall back to a sequential scan.
> 
> Is (or why isn't) the error propagated back to scsi?

I believe the error is reported back to SCSI, which attempts to follow
up with TEST UNIT READY.  Unfortunately, for some reason the device then
gets dropped.  libata normally calls __scsi_add_device with lun=0, but
SAS calls scsi_scan_target with lun=SCAN_WILD_CARD, which is why SCSI
sends REPORT LUNs in the first place.

As an alternative I suppose we could detect ATA devices in sas_rphy_add
and change that SCAN_WILD_CARD to "0".

--D
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