Snapscan Code

From: Ian Cartwright (
Date: Sat Dec 09 2000 - 20:00:51 PST

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    It's me again (the guy with the Acer 320U ;-). I've been hunting through the
    code, trying to see if I can something that might help me, and I ran across
    something interesting. I don't think it has anything to do with my particular
    problem, but I thought I'd pass it along...

    When I run xscanimage with SANE_DEBUG_SNAPSCAN set to 255, this is a bit of
    the output I get:

    [snapscan] inquiry: pixels per scan line = 308
    [snapscan] inquiry: bytes per scan line = 924
    [snapscan] inquiry: number of scan lines = 256
    [snapscan] inquiry: effective buffer size = 31416 bytes, 122 lines
    [snapscan] inquiry: expected total scan data: 236544 bytes

    If the effective buffer size is 31416 bytes and there are 924 bytes per line
    shouldn't the buffer be 34 lines, not 122? I looked at the code in
    snapscan-scsi.c and the lines that produce this output (starting at 441) are:

             "%s: effective buffer size = %lu bytes, %lu lines\n",
             (u_long) pss->buf_sz,
             (u_long) (pss->buf_sz ? pss->buf_sz / pss->lines : 0));

    It looks like the number of lines in the buffer is being calculated by
    dividing the effective buffer size by the number of lines in the scan instead
    of by the number of bytes in a line (i.e. pss->bytes_per_line).

    Unless of course the numbers are correct and the labels are ambiguous?



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