# Re: General USB questions and comments

From: Henning Meier-Geinitz (hmg-ml@gmx.de)
Date: Sun Jan 07 2001 - 03:36:56 PST

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  Hi,

  On Sat, Jan 06, 2001 at 05:27:34PM +0100, Oliver Neukum wrote:
  > > Some questions (mostly based on Linux and the USB driver "scanner"):
  > >
  > > * Is there any way to get the vendor and device ids for a given device
  > > file name? One problem for SANE-USB backends is that they can't easily
  >
  > No that I know of. Could you live with an IOCTL for that ?
  > I wouldn't be hard to add to the kernel.

  I think this would be fine. With this addition we could implement
  something like
  usb 1000 0001
  for the backend.conf files to check the standard device files for this
  scanner.

  > > * For find-scanner the idea was to scan /proc/bus/usb/devices. Look for
  > > new devices (starting with "T:" lines) and save all devices
  > > containing an "I: ... Driver=usbscanner" line. Get vendor and
  > > product ids from the "P:" line. Question: How to get the device file
  > > from this information? Can I just assume that the first usbscanner entry
  >
  > You can't. Device numbers depend on the order plugging in and out.
  >
  > > in this list is /dev/usbscanner0? Can the number of one device
  > > change if another one is conncted?
  >
  > You cannot assume that the first device is usbscanner0. While a device is
  > plugged in, it's device node doesn't change. Note: You can't tell easily
  > whether it was replugged.

  I may be wrong but all this doesn't look like scanner.o had more then
  one scanner in mind. Looks pretty weird.

  Bye,
  Henning

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