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    SubjectRe: [PATCH v2] libata: Simulate REPORT LUNS for ATAPI devices
    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".

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