Hi Steve,
On Mon, 31 Jul 100, Steve Ralston wrote:
> We're having a problem with recent (linux-2.4.0-test2) scsi_scan.c,
> centered around this change:
> /*
> * We used to do a TEST_UNIT_READY before the INQUIRY but that was
> * not really necessary. Spec recommends using INQUIRY to scan for
> * devices (and TEST_UNIT_READY to poll for media change). - Paul G.
> */
> This change has caused additional "ghost" LUNs to be seen by linux.
>
> We have a RAID subsystem that happens to return (e.g.):
> SCSI Error Report =-=-= (ioc0,scsi0:4)
> SCSI_Status=02h (CHECK CONDITION)
> Original_CDB[]: 00 80 00 00 00 00 - "TEST UNIT READY"
> SenseData[A0h]: 70 00 05 00 00 00 00 98 00 00 00 00 25 00 00 00 00 00 ...
> SenseKey=5h (ILLEGAL REQUEST); FRU=00h
> ASC/ASCQ=25h/00h "LOGICAL UNIT NOT SUPPORTED"
> to TEST_UNIT_READY (and READ_CAPACITY, et al), which *used* to cause linux
> to ignore the LUN.
>
> We kindly request that TEST_UNIT_READY *before* INQUIRY be reinstated.
The reason for why this has been changed was, that some SCSI-devices,
mainly those with changeable media, like tapedrives, CD-ROMs or Syquest
drives won't get recognized. The TEST_UNIT_READY may fail on such devices,
if no medium is inserted. The INQUIRY command should always work on
physically present drives, no matter if a medium is present or not and it
therefore offers the safest way to detect some SCSI-device.
Maybe, one could think of some TEST_UNIT_READY to be done on unchangeable
media, before the INQUIRY test is done. This could be some point of
discussion.
Greetings
Michael
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