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<TITLE>sane-devel: Re: [dev] sanei_scsi.c and Linux versions < 2.2.7</TITLE>
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<META NAME="Author" CONTENT="abel deuring (a.deuring@satzbau-gmbh.de)">
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<META NAME="Subject" CONTENT="Re: [dev] sanei_scsi.c and Linux versions < 2.2.7">
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<H1>Re: [dev] sanei_scsi.c and Linux versions < 2.2.7</H1>
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<!-- received="Mon Jul 16 03:02:23 2001" -->
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<!-- name="abel deuring" -->
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<!-- subject="Re: [dev] sanei_scsi.c and Linux versions < 2.2.7" -->
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<STRONG>From:</STRONG> abel deuring (<A HREF="mailto:a.deuring@satzbau-gmbh.de?Subject=Re:%20[dev]%20sanei_scsi.c%20and%20Linux%20versions%20<%202.2.7&In-Reply-To=<3B52CFAC.3161961D@satzbau-gmbh.de>"><EM>a.deuring@satzbau-gmbh.de</EM></A>)<BR>
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<STRONG>Date:</STRONG> Mon Jul 16 2001 - 04:27:40 PDT
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<P>
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<LI><STRONG>Next message:</STRONG> <A HREF="0139.html">Major A: "Re: Nikon Coolscan SCSI commands"</A>
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<UL>
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<LI><STRONG>Previous message:</STRONG> <A HREF="0137.html">Jean-Marie Fenaille: "Guillemot MaxiScanA4"</A>
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<LI><STRONG>In reply to:</STRONG> <A HREF="0135.html">Douglas Gilbert: "Re: [dev] sanei_scsi.c and Linux versions < 2.2.7"</A>
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<HR NOSHADE><P>
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<P>
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Douglas Gilbert wrote:
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<BR>
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<EM>> > Well, the error report could of course be added to sanei_scsi_req_enter,
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</EM><BR>
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<EM>> > but a backend should check for this error in sanei_scsi_req_wait too: If
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</EM><BR>
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<EM>> > you queue two or more commands and the low level driver does not support
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</EM><BR>
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<EM>> > command queueing, sanei_scsi_req_enter puts the second and following
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</EM><BR>
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<EM>> > commands into its internal queue, so it cannot return an error from the
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</EM><BR>
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<EM>> > SG driver.
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</EM><BR>
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<EM>>
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</EM><BR>
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<EM>> The reserved buffer is only good for one SCSI command
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</EM><BR>
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<EM>> at a time (per file descriptor) and only if it is big
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</EM><BR>
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<EM>> enough to hold the size of transfer being requested.
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</EM><BR>
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<EM>>
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</EM><BR>
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<EM>> Thus when commands are queued there is a risk that
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</EM><BR>
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<EM>> subsequent commands will fail with ENOMEM. This "out of
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</EM><BR>
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<EM>> memory" situation is more likely to occur with ISA
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</EM><BR>
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<EM>> SCSI adapters which can only use the bottom 16 MB of
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</EM><BR>
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<EM>> memory for DMA. This is not a hard error and should
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</EM><BR>
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<EM>> not be treated as such [IMO]. The reserve buffer
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</EM><BR>
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<EM>> more or less guarantees SANE can queue 1 command.
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</EM><BR>
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<EM>> If memory is not available to queue 2 or more commands
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</EM><BR>
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<EM>> then wait ....
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</EM><BR>
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<P>Doug,
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<BR>
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<P>thanks for helping my memory :) I knew there were even more reasons to
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<BR>
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check ENOMEM late, but I could not remember them while I wrote my mail.
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<BR>
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<P>Abel
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<BR>
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<P><PRE>
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--
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Source code, list archive, and docs: <A HREF="http://www.mostang.com/sane/">http://www.mostang.com/sane/</A>
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To unsubscribe: echo unsubscribe sane-devel | mail <A HREF="mailto:majordomo@mostang.com?Subject=Re:%20[dev]%20sanei_scsi.c%20and%20Linux%20versions%20<%202.2.7&In-Reply-To=<3B52CFAC.3161961D@satzbau-gmbh.de>">majordomo@mostang.com</A>
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</PRE>
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<HR NOSHADE>
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<UL>
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<!-- next="start" -->
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<LI><STRONG>Next message:</STRONG> <A HREF="0139.html">Major A: "Re: Nikon Coolscan SCSI commands"</A>
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<LI><STRONG>Previous message:</STRONG> <A HREF="0137.html">Jean-Marie Fenaille: "Guillemot MaxiScanA4"</A>
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<LI><STRONG>In reply to:</STRONG> <A HREF="0135.html">Douglas Gilbert: "Re: [dev] sanei_scsi.c and Linux versions < 2.2.7"</A>
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<EM>
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This archive was generated by <A HREF="http://www.hypermail.org/">hypermail 2b29</A>
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: <EM>Mon Jul 16 2001 - 03:04:42 PDT</EM>
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