On Sun, 14 Jan 2001, Douglas Gilbert wrote:
>This is interesting. The linux scsi subsystem (as does
>FreeBSD's CAM) implements "autosense" to get its sense
>buffer after a command has failed. This means that when
>a command like "test unit ready" is sent and it returns
>a "check condition" status code then the subsystem will
>automatically issue a "request sense" and give its
>response back as the sense buffer of the original command
>("test unit ready" in this case).
>So SANE backends shouldn't be issuing "request sense"
>commands IMHO. BTW only the first "request sense" gets
>the error response, so sending more of them is useless.
Did a grep in current sources, and found that 12 out of 30-something
backends issue request_sense commands currently.
But a problem is: what about the other OS'es supported by
SANE? AIX, Unixware, OS/2, HP-UX, Solaris, *BSD ? I expect not all of
these use the "autosense" method... And that's probably why these backends
issue request_sense commands.
So do we need to implement some sort of: (pseudocode following)
error = do_scsi_command(cmd);
if ((error < 0) && OS_AUTOSENSE)
sense = cmd->sense;
sense = do_scsi_command(request_sense);
in some generic layer somewhere?
I'm not familiar with SANE internals, so this might already exist, for all
I know :)
>It seems as though a problem that Arnold Schiller has
>sent me is very similar: a SnapScan1236/aha152x
>combination that locks up just after a "request sense"
>is sent to the scanner.
Sounds like the same problem, indeed.
-- Erik I. Bolsų | email: <knan at mo.himolde.no> The UNIX philosophy basically involves giving you enough rope to hang yourself. And then a couple of feet more, just to be sure.
-- Source code, list archive, and docs: http://www.mostang.com/sane/ To unsubscribe: echo unsubscribe sane-devel | mail email@example.com
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