# Re: HP 7400c info / Minolta Scan Dual II

From: EdHamrick@aol.com
Date: Thu May 03 2001 - 01:51:08 PDT

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  In a message dated 5/3/2001 3:19:34 AM EST, moitinho@civil.ist.utl.pt writes:

  > I have read the arguments in favour of different drivers, you don't need to
  > try to explain, but I still don't understand why (for instance) the
  > usb-storage driver doesn't work (at least id didn't). Just my problem of
  > thinking that I understand what I don't.

  There's no good reason why a single driver shouldn't serve
  as a scsi->usb device driver for all devices that need to look
  like a scsi device to higher level routines.

  Oliver claims this would be too hard to write, but I've done it
  on Windows and Mac OS and it isn't hard. The upper levels
  of VueScan think they're working with SCSI scanners, and
  at the lowest level I translate scsi commands to USB
  commands. The trick is to design the driver to do this from
  the start. This works today on Windows and Mac OS with
  HP, Epson, Avision, Acer, and AGFA USB scanners. I did
  the same thing with Firewire scanners on Windows, since
  they also encapsulate scsi commands on Firewire (SBP2
  protocol). Someone already did a generic scsi->firewire
  driver on Linux, and a similar scsi-usb driver is all that's needed.

  Note that the advantage of using generic scsi->usb and
  scsi->firewire drivers is that there isn't any need to set
  up configuration files specifying which scanners (and
  what type of scanners) are on the system. The nice
  part of scsi is that it's possible to poll each device to find
  out what kind of device it is, instead of depending on the
  user to set this up (this is a lot more user-friendly). This
  is how VueScan works.

  This driver the kind of thing I'd assign a college intern or
  beginning programmer to do - it's not hard. If nobody on
  this list has any kernel programming experience, I'll do it
  myself in a month or two as soon as I finish some higher
  priority tasks in VueScan. However, if I write it, I plan to
  sell it (it won't be open source). If someone wants to
  write it and make it open source, I'd be happy to provide
  them the technical assistance they'd need to get it working
  with a wide range of usb scanners.

  Regards,
  Ed Hamrick

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