REPORT LUNS is only required to be supported by multi-LUN devices for LUN 0. It
is optional for multi-LUN device LUN > 0 as well as single-LUN devices, cf.
t10.org SPC-2. Also a SCSI device must always at a minimum have a LUN 0 - it's
unlikely this will ever change because LUN 0 has other specific characteristics
defined in the SCSI standards.
Eric I know you're busy but here's a future change that would be an improvement
to Linux's SCSI device detection and I think would help the situation in the
future with multi-LUN devices. The first command sent to a SCSI device for a
SCSI bus scan should always be an INQUIRY. The last time I checked
(actuallyobserved with a SCSI analyzer) it is a TEST UNIT READY which doesn't
make sense in all cases like for scanners and CD-ROM changers. After the LUN 0
INQUIRY the device should be passed to the Upper Layer driver to complete
initialization for the device that makes sense for that class of device.
Note the INQUIRY data for SPC-2 devices does indicate whether a device supports
REPORT LUNS with the HiSup bit. An Upper Layer driver could detect this bit set
and decide to use the REPORT LUNS command.
Bob Frey
[EMAIL PROTECTED]
P.S. All the latest drafts as well as old drafts of the SCSI standards are
available www.t10.org/drafts.htm
Matthew Jacob wrote:
> >
> > Okay, from my reading of the old SCSI-2 specification final draft.
> >
> > "Each target has one or more logical units, beginning with logical unit 0."
> >
> > To me this implies that if there is MORE than one logical unit, the
> > first logical unit must be 0.
>
> Yes. This might possibly change in SCSI-3- the REPORT LUNS command says it can
> be run on any LUN.
>
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