[sane-devel] Additional SCSI status?

abel deuring a.deuring@satzbau-gmbh.de
Tue, 14 May 2002 00:08:22 +0200

Dave Close wrote:
> I am dealing with a scanner that seems to return some of its status
> outside the SCSI sense byte area. sanei_scsi reports this information
> via DBG but doesn't provide it to the sense handler. The data is in the
> SCSI header, which is physically adjacent to and preceding the sense
> bytes in sanei_scsi.c, so I can get to it with some C tricks. But, of
> course, those tricks could fail in a future SANE version. Is there a
> better recommended solution?
> Here's the kind of debug output I'm seeing.
> [sanei_scsi] sanei_scsi_req_wait: read 64 bytes
> [sanei_scsi] sanei_scsi_req_wait: SCSI command complained: Success
> [sanei_scsi] sense buffer: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> [sanei_scsi] target status: 02 host status: 0000 driver status: 0018
> [mybackend] sense=00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> The fourth line above shows target status and driver status. This
> information does not appear to be available to the sense handler. If
> sanei_scsi knows enough to call the sense handler in this case, and it
> does, it should provide all the relevant data.


It does not make much sense to forward the words host status and driver
status to the backend, because they are Linux-specific, while the
backends should be able to work with a number of different OSes, which
might provide completely different status information. 

I've inserted the DBG statements, because it makes bug tracing more
convenient: If host status or driver status are non-zero, one should
check for possible inconsistencies in the SCSI command sent (e.g., wrong
CDB length, wrong data length), for possible bugs in sanei_scsi.c or in
the backend; if things look fine, it's time to ask the kernel developers
for help.