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<!-- name="Douglas Gilbert" -->
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<!-- subject="Re: Problem with SANE and SCSI scanner" -->
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<title>sane-devel: Re: Problem with SANE and SCSI scanner</title>
<h1>Re: Problem with SANE and SCSI scanner</h1>
<b>Douglas Gilbert</b> (<a href="mailto:dgilbert@interlog.com"><i>dgilbert@interlog.com</i></a>)<br>
<i>Fri, 03 Dec 1999 09:02:36 -0500</i>
<p>
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abel deuring wrote:<br>
<i>&gt; </i><br>
<i>&gt; Manuel Panea wrote:</i><br>
<i>&gt; </i><br>
<i>&gt; &gt; Now for the backend problem at hand: I could of course do those sg ioctl's</i><br>
<i>&gt; &gt; in the backend, but that should rather be done by sane, not by the</i><br>
<i>&gt; &gt; backends. Do you perhaps know whether there are any development plans for</i><br>
<i>&gt; &gt; sane to include support for such ioctl's?</i><br>
<i>&gt; </i><br>
<i>&gt; If you need a quick fix, you might try Douglas's SG driver version 3</i><br>
<i>&gt; (<a href="http://www.torque.net/sg">http://www.torque.net/sg</a>) in combination with the modifications to</i><br>
<i>&gt; sanei_scsi.c which I posted some weeks ago on this mailing list. While</i><br>
<i>&gt; these modifiactions were mainly intended to benefit from other</i><br>
<i>&gt; improvements in the SG driver (it is possible to omit a buffer in</i><br>
<i>&gt; sanei_scsi.c for the data read from the scanner), they should also fix</i><br>
<i>&gt; the problem, that the SG driver must guess the length of SCSI commands.</i><br>
<i>&gt; (Douglas, please correct me if I am wrong, but I think that with the new</i><br>
<i>&gt; header structure, the SG driver takes the length of the SCSI command</i><br>
<i>&gt; from sg_io_hdr.cmd_len.)</i><br>
<p>
That is correct. Unfortunately SCSI 3 16 byte commands are<br>
not yet supported by Linux but with the sg_io_hdr structure<br>
that is not a sg interface restriction (rather a Linux scsi<br>
mid-level restriction that may later be relaxed).<br>
<p>
Since the sg "version 3" driver is not even in the Linux 2.3<br>
development tree yet, it is probably a bit premature to ask<br>
people maintaining backends to use it. [Of course I don't mind<br>
if they do and it is probably a better solution than asking<br>
end users to edit Linux device drivers.] The common sane <br>
backend for Linux could however be changed to detect such <br>
things (e.g. a 6 byte 0xd5 command) and if the sg driver <br>
supports SG_NEXT_CMD_LEN then use it and if it doesn't then <br>
return an error. <br>
<p>
Doug Gilbert<br>
<p>
<pre>
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<li> <b>Next message:</b> <a href="0036.html">Tim Carroll: "hexadecimal C syntax for serial ports"</a>
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