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    SubjectRe: [PATCH v2] libata: Simulate REPORT LUNS for ATAPI devices
    James Bottomley wrote:
    > On Mon, 2006-12-04 at 15:32 -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.
    >
    > Actually, there may be a standards conflict here. SPC says that all
    > devices reporting compliance with this standard (as the inquiry data for
    > this device claims) shall support REPORT LUNS. On the other hand, MMC
    > doesn't list REPORT LUNS in its table of mandatory commands.

    MMC-5 rev 4 section 7.1:
    "Some commands that may be implemented by MM drives are
    not described in this standard, but are found in other
    SCSI standards. For a complete list of these commands
    refer to [SPC-3]."

    Hmm, "may be implemented" yet REPORT LUNS is mandatory
    in SPC-3 (and SPC-3 is a normative reference for MMC-5).
    I guess there is wriggle room there.
    In practice, MMC diverges from SPC a lot more than other
    SCSI device type command sets (e.g. SBC and SSC).

    > I'm starting to think that even if they report a SCSI compliance level
    > of 3 or greater, we still shouldn't send REPORT LUNS to devices that
    > return MMC type unless we have a white list override.

    There is also SAT compliance. For the ATA command set (i.e.
    disks) sat-r09 lists REPORT LUNS and refers to SPC-3. For
    ATAPI sat-r09 is far less clear. It does recommend, for
    example, that the ATA Information VPD pages is implemented
    in the SATL for ATAPI devices.

    Doug Gilbert
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