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<TITLE>sane-devel: Re: HP 7400c info / Minolta Scan Dual II</TITLE>
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<META NAME="Author" CONTENT="EdHamrick@aol.com (EdHamrick@aol.com)">
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<META NAME="Subject" CONTENT="Re: HP 7400c info / Minolta Scan Dual II">
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<H1>Re: HP 7400c info / Minolta Scan Dual II</H1>
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<!-- received="Thu May 3 13:07:27 2001" -->
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<STRONG>From:</STRONG> <A HREF="mailto:EdHamrick@aol.com?Subject=Re:%20HP%207400c%20info%20/%20Minolta%20Scan%20Dual%20II&In-Reply-To=<b9.dcd34b0.282316a6@aol.com>"><EM>EdHamrick@aol.com</EM></A><BR>
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<STRONG>Date:</STRONG> Thu May 03 2001 - 13:16:38 PDT
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<LI><STRONG>Next message:</STRONG> <A HREF="0053.html">Stephen Williams: "Re: SANE API & file format"</A>
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<LI><STRONG>Previous message:</STRONG> <A HREF="0051.html">Henning Meier-Geinitz: "Re: New backend: UMAX 1220P sane'ification take 1"</A>
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In a message dated 5/3/2001 4:52:31 AM EST, <A HREF="mailto:Oliver.Neukum@lrz.uni-muenchen.de?Subject=Re:%20HP%207400c%20info%20/%20Minolta%20Scan%20Dual%20II&In-Reply-To=<b9.dcd34b0.282316a6@aol.com>">Oliver.Neukum@lrz.uni-muenchen.de</A>
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<BR>
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writes:
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<BR>
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<P><EM>> Our disagreement seems to be rather in the type of scanners that should
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</EM><BR>
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<EM>> appear as scsi devices to user space.
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</EM><BR>
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<EM>> If I understand Ed correctly, to him that would be all of them.
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</EM><BR>
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<P>That's correct - but I'd make it a generic scsi->usb driver that
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<BR>
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could easily be modified to add support for other usb peripherals
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<BR>
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that encapsulate scsi over usb.
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<BR>
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<P>The reason USB is so messed up on Linux is that too many people
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<BR>
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took the easy way out instead of planning for the future. For instance,
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<BR>
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whoever wrote the scanner.c driver didn't even add the capability to
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<BR>
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ask the device what it's VID/PID is or to allow reading the interrupt
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<BR>
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channel. As a result, there are a slew of barely working drivers
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<BR>
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for scanners, and even these are kludges that are poorly tested
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<BR>
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(i.e. the HP5300 driver doesn't work with the Scan Dual II).
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<BR>
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<P>The right way to handle USB scanners in the kernel is a single
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<BR>
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device driver that does scsi->usb translation.
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<BR>
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<P><EM>> Firewire is a better design. There is no question about that.
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</EM><BR>
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<EM>> USB has no common protocol for transfering SCSI commands.
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</EM><BR>
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<EM>> In fact I know of _six_ incompatible protocols to do that.
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</EM><BR>
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<P>These are the ones I know of:
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<BR>
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<P> 1) HP/Epson (read/write bulk endpoints)
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<BR>
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2) Avision
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<BR>
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3) Acer/AGFA SnapScan
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<BR>
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4) Nikon LS-40
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<BR>
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5) Microtek (actually at least 2 different types)
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<BR>
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6) Canon FB-series
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<BR>
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<P>For #1, the driver needs to emulate the scsi INQUIRY
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<BR>
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command based on the VID/PID, but this is only a few
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<BR>
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lines of code.
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<BR>
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<P><EM>> The attempt to unify them leads to a monster like usb-storage.
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</EM><BR>
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<EM>> I wanted to add the microtek protocol to usb-storage, but Matt vetoed that.
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</EM><BR>
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<P>It's open source - you can add what you want to whatever you
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<BR>
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want. Working code (if it's more elegant than the code it replaces) rules.
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<BR>
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<P><EM>> I could trivially merge microtek and hp5300 to a common driver.
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</EM><BR>
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<EM>> However there would still be the generic driver (scanner.c) and
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</EM><BR>
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<EM>> the two drivers currently under development for even stranger scanners.
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</EM><BR>
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<P>The only thing remaining for scanner.c is Epson and HP, and
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<BR>
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these are better done in the single scsi->usb driver.
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<BR>
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<P><EM>> Reducing the number of drivers from 5 to 4 isn't IMHO worth the trouble.
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</EM><BR>
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<EM>> Unless you go to one, you need to look it up anyway, thus simplicity in
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</EM><BR>
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<EM>> kernel is more important.
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</EM><BR>
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<P>Yes, going to one scsi->usb driver is the way to go (including
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<BR>
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storage).
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<BR>
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<P><EM>> As for configuration, loading a driver for your usb scanner is the same
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</EM><BR>
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<EM>> trouble as loading a driver for the controller your scsi scanner is
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</EM><BR>
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attached
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<BR>
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<EM>> to.
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</EM><BR>
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<P>The problem is that there's too much user-configuration that needs
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<BR>
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to be done. A user should just run a scanner program, and the
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<BR>
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scanner program should determine what scanners are connected
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<BR>
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to the system.
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<BR>
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<P><EM>> After that for microtek and hp5300 then you can probe as for conventional
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</EM><BR>
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<EM>> scsi. Generic usb scanners are a problem though.
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</EM><BR>
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<P>They're only a problem because the user-mode interface to the
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<BR>
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usb subsystem is so primitive on Linux, and you can't even get
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<BR>
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the VID/PID of a scanner from user space.
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<BR>
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<P><EM>> For generic scanners you _could_ go the easy route.
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</EM><BR>
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<EM>> Emulate INQUIRY based on a table of vend./prod. ids and
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</EM><BR>
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<EM>> map read/write over usb to SCSI_READ/SCSI_WRITE.
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</EM><BR>
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<P>Yes, this is what I do in VueScan on Windows and Mac OS.
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<BR>
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It works quite nicely. Just run VueScan on Windows, Linux
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<BR>
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or Mac OS with any USB scanner and turn on the log file (a
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<BR>
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dump of the scsi commands) and you'll see this. VueScan
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<BR>
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works with scanner.c on Linux, but you have to tell it the
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<BR>
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device name, the VID and the PID. It doesn't work with
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<BR>
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Avision scanners (Scan Dual II, 5300C, 7400C) on Linux
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<BR>
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because scanner.c doesn't allow reading the interrupt
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<BR>
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pipe.
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<BR>
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<P><EM>> It can be done. Even the unusual scanners could be handled with vendor
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</EM><BR>
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<EM>> specific commands. However at some point you end up with a scsi
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</EM><BR>
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interpreter
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<BR>
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<EM>> in kernel.
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</EM><BR>
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<P>It's all very simple table-driven, finite state machine stuff.
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<BR>
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<P>Regards,
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<BR>
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Ed Hamrick
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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:%20HP%207400c%20info%20/%20Minolta%20Scan%20Dual%20II&In-Reply-To=<b9.dcd34b0.282316a6@aol.com>">majordomo@mostang.com</A>
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</PRE>
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<LI><STRONG>Previous message:</STRONG> <A HREF="0051.html">Henning Meier-Geinitz: "Re: New backend: UMAX 1220P sane'ification take 1"</A>
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<SMALL>
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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>Thu May 03 2001 - 13:07:48 PDT</EM>
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</EM>
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