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<TITLE>sane-devel: Re: backend fork/reader-process <-> sane_read</TITLE>
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<META NAME="Author" CONTENT="Chris Pinkham (cpinkham@infi.net)">
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<META NAME="Subject" CONTENT="Re: backend fork/reader-process <-> sane_read">
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<H1>Re: backend fork/reader-process <-> sane_read</H1>
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<!-- received="Sat Feb 19 10:10:51 2000" -->
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<!-- name="Chris Pinkham" -->
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<!-- subject="Re: backend fork/reader-process <-> sane_read" -->
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<!-- id="200002191809.NAA07412@panther.panther.net" -->
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<STRONG>From:</STRONG> Chris Pinkham (<A HREF="mailto:cpinkham@infi.net?Subject=Re:%20backend%20fork/reader-process%20<->%20sane_read&In-Reply-To=<200002191809.NAA07412@panther.panther.net>"><EM>cpinkham@infi.net</EM></A>)<BR>
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<STRONG>Date:</STRONG> Sat Feb 19 2000 - 10:09:56 PST
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<LI><STRONG>In reply to:</STRONG> <A HREF="0223.html">Oliver Rauch: "backend fork/reader-process <-> sane_read"</A>
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<P>
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<EM>> b) there is no own reader process, the backend itself calls sanei_scsi_read()
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</EM><BR>
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<P><EM>> All this could be hidden in a sanei_ routine so the backend does not see
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</EM><BR>
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<EM>> anything about that. So a backend would not call sanei_scsi_read(),
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</EM><BR>
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<EM>> instead it would call sanei_scsi_read_buffered().
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</EM><BR>
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<P>This is sort of what I did in my Artec backend. I have a sane_read() function
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<BR>
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and an artec_sane_read() function. sane_read has a buffer. When sane_read
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<BR>
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is called, if the buffer is empty, then artec_sane_read is called to read
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<BR>
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data from the scanner, up to the maximum size of the buffer. If there is
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<BR>
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data already in the buffer, then that data is returned up to the maximum
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<BR>
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amount requested. I wrote this "wrapper" sane_read function when I was
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<BR>
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informed that my backend didn't work over the net. It could really be
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<BR>
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used for any backend by renaming sane_read to sane_read_buffered and
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<BR>
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changing the function's internal calls from artec_sane_read() to just
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<BR>
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plain sane_read(). A few other things such as max read size from the
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<BR>
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scanner might have to be changed, but the individual sane_read() functions
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<BR>
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in each backend should handle that as they do now. The wrapper function
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<BR>
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could also be changed to increase the size of the buffer (I think I use
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<BR>
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only about 32K or 64K right now). If this buffer were bigger, then
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<BR>
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the backend's sane_read() function could be called multiple times in a row
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<BR>
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in order to fill up the buffer. This might cause jerkiness in data being
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<BR>
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returned to the application, but it would probably eliminate some of the
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<BR>
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backtracing of the scan head.
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<BR>
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<P>Chris
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<BR>
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<P>*****************************************************************************
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<BR>
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** Chris Pinkham Linux v2.2.6, Sane v1.0.1, Cajun v3.0-8 **
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<BR>
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** <A HREF="mailto:cpinkham@infi.net?Subject=Re:%20backend%20fork/reader-process%20<->%20sane_read&In-Reply-To=<200002191809.NAA07412@panther.panther.net>">cpinkham@infi.net</A> <A HREF="http://www4.infi.net/~cpinkham/">http://www4.infi.net/~cpinkham/</A> **
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<BR>
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*****************************************************************************
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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:%20backend%20fork/reader-process%20<->%20sane_read&In-Reply-To=<200002191809.NAA07412@panther.panther.net>">majordomo@mostang.com</A>
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</PRE>
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This archive was generated by <A HREF="http://www.hypermail.org/">hypermail 2b29</A>
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: <EM>Sat Feb 19 2000 - 10:12:44 PST</EM>
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