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71 wiersze
3.4 KiB
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<!-- received="Thu Feb 26 22:56:52 1998 PST" -->
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<!-- sent="Fri, 27 Feb 1998 00:27:26 +0100 (MET)" -->
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<!-- name="Rogier Wolff" -->
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<!-- email="R.E.Wolff@BitWizard.nl" -->
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<!-- subject="Re: Mustek scanner: success!" -->
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<!-- inreplyto="Pine.LNX.3.96.980226150215.1430A-100000@info04.uni-trier.de" -->
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<title>sane-devel: Re: Mustek scanner: success!</title>
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<h1>Re: Mustek scanner: success!</h1>
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<b>Rogier Wolff</b> (<a href="mailto:R.E.Wolff@BitWizard.nl"><i>R.E.Wolff@BitWizard.nl</i></a>)<br>
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<i>Fri, 27 Feb 1998 00:27:26 +0100 (MET)</i>
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<p>
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<ul>
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<li> <b>Messages sorted by:</b> <a href="date.html#184">[ date ]</a><a href="index.html#184">[ thread ]</a><a href="subject.html#184">[ subject ]</a><a href="author.html#184">[ author ]</a>
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<li> <b>Next message:</b> <a href="0185.html">REINHARD.ARZBERGER@quelle.de: "Microtek 630"</a>
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<li> <b>Previous message:</b> <a href="0183.html">Rogan Dawes: "Dynamic loading libraries for AIX"</a>
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</ul>
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Norbert Mueller wrote:<br>
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<i>> Just an idea: Does anybody know whether there is a possibility to change </i><br>
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<i>> the fixed sized buffer in sg.c to a circular list of e.g. 20 buffers of </i><br>
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<i>> size such that the scanner may write to the list while at the same time </i><br>
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<i>> the application reads from the list? As usually most CPU's are capable to </i><br>
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<i>> read the data faster than the scanner can deliver, the circular list would </i><br>
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<i>> never be full and backtracking would no longer happen.</i><br>
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<p>
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Sounds "neat", but it isn't as simple as that.<br>
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<p>
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The SCSI low level drivers would then need to be able to do<br>
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"scatter-gather". I think that the API isn't that smart. Also, you<br>
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could get into trouble that way: You'd have to tell the scanner: "Ok,<br>
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I want 1Mb of data". and then you have to trust the user-level<br>
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application to actually gather and store that data before your buffer<br>
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overflows. What do you do if the application suddenly goes comatose?<br>
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<p>
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Another problem is that you'd be telling the scanner to send a whole<br>
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lot of data, where you don't know how long that's going to take. The<br>
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lowlevel SCSI driver (e.g. the NCR810 one) might time out after say 10<br>
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seconds (It assumes a command like a "read" will finish within about<br>
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10 seconds: This is valid for most disks.... ;-).<br>
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<p>
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Regards,<br>
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<p>
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Roger. <br>
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<p>
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<p>
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<pre>
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--
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<p>
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<pre>
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--
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</pre>
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<p>
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<ul>
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<li> <b>Next message:</b> <a href="0185.html">REINHARD.ARZBERGER@quelle.de: "Microtek 630"</a>
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<li> <b>Previous message:</b> <a href="0183.html">Rogan Dawes: "Dynamic loading libraries for AIX"</a>
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