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<H1>Re: reaction to a smaller buffer size</H1>
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<STRONG>From:</STRONG> Henning Meier-Geinitz (<A HREF="mailto:hmg-ml@gmx.de?Subject=Re:%20reaction%20to%20a%20smaller%20buffer%20size&In-Reply-To=&lt;20001118224652.A4375@vortex.swb.de&gt;"><EM>hmg-ml@gmx.de</EM></A>)<BR>
<STRONG>Date:</STRONG> Sat Nov 18 2000 - 13:46:53 PST
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Hi,
<BR>
<P>On Sat, Nov 18, 2000 at 10:11:21PM +0100, Oliver Neukum wrote:
<BR>
<EM>&gt; Hi,
</EM><BR>
<EM>&gt;
</EM><BR>
<EM>&gt; I'd like to ask whether that check
</EM><BR>
<EM>&gt;
</EM><BR>
<EM>&gt; if (real_buffersize != wanted_buffersize)
</EM><BR>
<EM>&gt; {
</EM><BR>
<EM>&gt; DBG(1, &quot;sanei_scsi_open: could not allocate SG buffer memory &quot;
</EM><BR>
<EM>&gt; &quot;wanted: %i got: %i\n&quot;, wanted_buffersize, real_buffersize);
</EM><BR>
<EM>&gt; sanei_scsi_close(*fdp);
</EM><BR>
<EM>&gt; return SANE_STATUS_NO_MEM;
</EM><BR>
<EM>&gt; }
</EM><BR>
<EM>&gt;
</EM><BR>
<EM>&gt; in sanei_scsi.c might be removed. It makes using SANE with scsi drivers
</EM><BR>
<EM>&gt; which don't do scatter/gather very hard.
</EM><BR>
<P>I don't understand this fully. With sanei_scsi_open there is no way to
<BR>
tell the backend that the buffersize is smaller than expected. What
<BR>
happens if the backend sends a bigger buffer than allowed? Is it just
<BR>
slowed down or does the SCSI call return with an error?
<BR>
sanei_scsi_open already reduces the buffer size if
<BR>
proc/sys/kernel/sg-big-buff has a lower value but the backend can't
<BR>
find out about it if I understood correctly.
<BR>
<P>Why don't you use sanei_scsi_open_extended if it is available for your
<BR>
paltform? In this case the backend can try to get a big buffer and
<BR>
knows the actual size it is allowed to use.
<BR>
<P><P>Bye,
<BR>
&nbsp;&nbsp;Henning
<BR>
<P><PRE>
--
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