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<TITLE>sane-devel: Re: SANE standard / get_select_fd / sane_read</TITLE>
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<META NAME="Author" CONTENT="Christian Nassau (nassau@math.uni-frankfurt.de)">
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<META NAME="Subject" CONTENT="Re: SANE standard / get_select_fd / sane_read">
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<H1>Re: SANE standard / get_select_fd / sane_read</H1>
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<!-- received="Mon Jan 15 03:49:26 2001" -->
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<!-- sent="Mon, 15 Jan 2001 12:48:02 +0100" -->
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<!-- isosent="20010115114802" -->
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<!-- name="Christian Nassau" -->
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<!-- email="nassau@math.uni-frankfurt.de" -->
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<!-- subject="Re: SANE standard / get_select_fd / sane_read" -->
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<!-- id="200101151148.MAA20298@newton.math.uni-frankfurt.de" -->
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<!-- inreplyto="3A5C98F7.AFB25619@wolfsburg.de" -->
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<STRONG>From:</STRONG> Christian Nassau (<A HREF="mailto:nassau@math.uni-frankfurt.de?Subject=Re:%20SANE%20standard%20/%20get_select_fd%20/%20sane_read&In-Reply-To=<200101151148.MAA20298@newton.math.uni-frankfurt.de>"><EM>nassau@math.uni-frankfurt.de</EM></A>)<BR>
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<STRONG>Date:</STRONG> Mon Jan 15 2001 - 03:48:02 PST
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<LI><STRONG>Next message:</STRONG> <A HREF="0147.html">Christian Nassau: "Re: snapscan"</A>
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<LI><STRONG>Previous message:</STRONG> <A HREF="0145.html">David Mosberger-Tang: "test"</A>
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<LI><STRONG>In reply to:</STRONG> <A HREF="0113.html">Oliver Rauch: "Re: SANE standard / get_select_fd / sane_read"</A>
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Hello Oliver,
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<P>thanks for your remarks on the subject. I've come to accept
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that a frontend may request any number of bytes. However,
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I would still insist that deadlocks (in non-blocking mode)
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are inherent in the current standard.
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<BR>
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<P>Your reply to this was
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<BR>
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<BR>
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<EM>> Wrong.
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</EM><BR>
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<EM>> Non Blocking mode means that the backend may return with 0 bytes
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</EM><BR>
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<EM>> transfered (because it has no data in the moment and it returns
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</EM><BR>
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<EM>> to give the frontend the chance to react to user action, refresh display
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</EM><BR>
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<EM>> etc.)
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</EM><BR>
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<P>I think this is inconsistent. Either say
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<BR>
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<P><EM>> Right.
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</EM><BR>
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<EM>> Non Blocking mode means that the backend may return with 0 bytes
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</EM><BR>
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<EM>> transfered (plus some comments that I may ignore, since they only
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</EM><BR>
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<EM>> refelct the presumed intention of the specs)
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</EM><BR>
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<P>or
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<BR>
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<P><EM>> Wrong.
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</EM><BR>
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<EM>> In non blocking mode the backend may only return with 0 bytes
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</EM><BR>
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<EM>> transfered if it has no data available at the moment.
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</EM><BR>
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<P>In my reading this last version would be either wrong or tautological,
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<BR>
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(but essentially (or substantially?) wrong.)
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<BR>
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<P>Our difference of reading could be this: the notion of "having
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<BR>
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data available" is nowhere made precise in the SANE specification,
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<BR>
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so I take it to be essentially tautological: a backend had data
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<BR>
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available (by definition) if a call to sane_read transferred at
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<BR>
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least one byte.
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<BR>
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<P>I still think the sane_read specification ought to be changed.
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<BR>
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For this, see the reply to Henning Meier-Geinitz' message,
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<BR>
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which I'll write next,
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<BR>
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<P>Christian
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<BR>
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<P><P><P><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:%20SANE%20standard%20/%20get_select_fd%20/%20sane_read&In-Reply-To=<200101151148.MAA20298@newton.math.uni-frankfurt.de>">majordomo@mostang.com</A>
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</PRE>
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<LI><STRONG>Next message:</STRONG> <A HREF="0147.html">Christian Nassau: "Re: snapscan"</A>
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<LI><STRONG>Previous message:</STRONG> <A HREF="0145.html">David Mosberger-Tang: "test"</A>
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<LI><STRONG>In reply to:</STRONG> <A HREF="0113.html">Oliver Rauch: "Re: SANE standard / get_select_fd / sane_read"</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 Jan 15 2001 - 03:51:12 PST</EM>
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