[sane-devel] Additional SCSI status?

[abel deuring]

abel deuring wrote:
> 
> 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.
> 
> Dave,
> 
> 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.

Sorry, I am obviously too tired to read and write mails ;) So, an
addition: That the sense handler cannot "see" the target status byte, in
indeed a flaw of sanei_scsi.c. I have some ideas to improve the
sanei_scsi interface for Sane 2, and forwarding the SCSI status byte to
the backend is indeed part of the ideas, but I am currently too busy
with other stuff to write down what I have in my mind.

Abel