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<TITLE>sane-devel: 1.0.3 snapscan interface</TITLE>
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<META NAME="Author" CONTENT="Lawrence Glaister (lg@jfm.bc.ca)">
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<META NAME="Subject" CONTENT="1.0.3 snapscan interface">
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<H1>1.0.3 snapscan interface</H1>
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<!-- received="Sun Sep 24 17:55:42 2000" -->
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<!-- name="Lawrence Glaister" -->
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<!-- subject="1.0.3 snapscan interface" -->
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<STRONG>From:</STRONG> Lawrence Glaister (<A HREF="mailto:lg@jfm.bc.ca?Subject=Re:%201.0.3%20snapscan%20interface&In-Reply-To=<02b001c0268c$3aed96e0$bf0aa8c0@dufusiii>"><EM>lg@jfm.bc.ca</EM></A>)<BR>
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<STRONG>Date:</STRONG> Sun Sep 24 2000 - 18:02:08 PDT
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<LI><STRONG>Next message:</STRONG> <A HREF="0252.html">Dave Hill: "find-scanner (Was: Re: scanmagic 4800p doesnt work)"</A>
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<LI><STRONG>Next in thread:</STRONG> <A HREF="0255.html">abel deuring: "Re: 1.0.3 snapscan interface"</A>
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Thanks for the pointer Steve,
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I have been digging further and you are right, TxSource is returning 0 bytes
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on a regular basis. It turns out that the read in FDSource_get() is hitting
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<BR>
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the EAGAIN break which leaves the status at SANE_STATUS_GOOD. I wonder why
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<BR>
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the usb interface is returning a read status of "Resource temporarily
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<BR>
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unavailable". Would it make more sense to put a small sleep and a continue
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in place of the break? This would make the code wait for the data or a
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<BR>
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timeout at a lower level.
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<BR>
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-sometime later that evening...
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<BR>
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I just tried a usleep(2000) and a continue added into the EAGAIN condition
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<BR>
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in FDSource_get() instead of the break, and restored the code in
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RGBRouter_get(). This does seem to work. I noticed that the scanner does
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<BR>
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"backtrack" occasionally on large scans and this coincides perfectly with
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<BR>
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hitting the EAGAIN condition. It looks like the scanner is responding to usb
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<BR>
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read requests with a "try again later" and these are getting passed back up
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the chain... it is possible that other versions of usb kernel code will
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block on a read() until data is ready instead of returning with EAGAIN. I
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don't know what the scsi driver does, but if the reads dont return until
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data is available or an error occurs, this would explain the problems I have
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<BR>
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been seeing. I looked at the umax scsi code (I also have a umax 12120s scsi
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<BR>
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scanner) and it looks like it has all been written such that an EAGAIN
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condition with 0 bytes would cause problems. Where would you suggest a fix?
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<BR>
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hanging in the low level USB read? Hanging in FDSource_get? Hanging in
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<BR>
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TXsource_get? Handling the 0 bytes being returned without an error status in
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RGBRouter_get()? The EAGAIN condition occurs with my system even when
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<BR>
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scanning b/w images, but I was not seeing errors because there always was
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some data returned and not 0 bytes. The FSSource_get() seems to be the
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<BR>
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lowest level point in common code for scsi and usb scanners and the usb code
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<BR>
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patches are the lowest level user code for usb specific snapscan scanners.
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<BR>
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=======================================================
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<BR>
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Lawrence Glaister VE7IT email: <A HREF="mailto:lg@jfm.bc.ca?Subject=Re:%201.0.3%20snapscan%20interface&In-Reply-To=<02b001c0268c$3aed96e0$bf0aa8c0@dufusiii>">lg@jfm.bc.ca</A>
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<BR>
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1462 Madrona Drive <A HREF="http://jfm.bc.ca">http://jfm.bc.ca</A>
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<BR>
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Nanoose Bay BC Canada
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<BR>
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V9P 9C9
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<BR>
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=======================================================
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<BR>
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<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:%201.0.3%20snapscan%20interface&In-Reply-To=<02b001c0268c$3aed96e0$bf0aa8c0@dufusiii>">majordomo@mostang.com</A>
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</PRE>
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<LI><STRONG>Next message:</STRONG> <A HREF="0252.html">Dave Hill: "find-scanner (Was: Re: scanmagic 4800p doesnt work)"</A>
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<LI><STRONG>Previous message:</STRONG> <A HREF="0250.html">Nick Lamb: "Re: sane-devel mailing list blocking non-subscribers"</A>
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This archive was generated by <A HREF="http://www.hypermail.org/">hypermail 2b29</A>
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: <EM>Sun Sep 24 2000 - 17:56:25 PDT</EM>
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