John Fremlin wrote:
>abel deuring <a.deuring@satzbau-gmbh.de> writes:
>
>> > Hmm. I don't know if Oliver added anything to my version, but here is
>> > what I sent him (relative to sane-cvs). The patch to
>> > sanei/sanei_scsi.c should not be necessary if sane is setup properly,
>> > and is probably incorrect wrt other sane backends.
>
>[...]
>
>> If this patch to sanei_scsi.c works for your setup (Microtek USB
>> scanner, if my memory is right), it's fine. But it might break the
>> memory management for other backends which use the function
>> sanei_scsi_open. Most backends open the device file for scanner access
>
>To clarify:
>
>The patch is *only* included because I couldn't be bothered to read
>the docs to find the correct fix for the fact that my kernel sg buffer
>size is smaller than that which SANE expects.
Right. Sorry, I missed the point you mentioned above, that the patch to
sanei_scsi.c is not in every case necessary.
>I suppose that the USB scanner will work OK with any SCSI buffer size,
>though this is untested and the blighters at microtek can't be
>bothered to give us the docs, and Oliver can't get it to work at all
>on his setup, so whether they work on any system except mine is open
>to question. ;-)
Yes and no. As Oliver wrote in his response to your mail, the USB/SCSI
converter or driver (or however it is called) limits the buffer size to
32 kB, because it does not support scatter/gather. We can live with this
limit, but since the Microtek backend uses sanei_scsi_open, users must
either set SANE_SG_BUFFERSIZE, or if they install Sane from the sources,
they must use the configure option --enable-scsibuffersize in order to
get a "SCSI via USB" scanner running.
What I tried to point out is, that this inconvenience of a "special
SCSI/USB configuration" (what a big word for an environment variable...)
can be avoided, if a backend uses sanei_scsi_open_extended instead of
sanei_scsi_open. Using the latter function, a backend can easily adapt
to any available buffer size. This way, things would be a little bit
easier for a Linux newbie to get his/her SCSI-over-USB scanner working.
Abel
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This archive was generated by hypermail 2b29 : Sun May 28 2000 - 13:56:50 PDT