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sane-scsi(5)									     sane-scsi(5)

       sane-usb - USB configuration tips for SANE

       This manual page contains information on how to access scanners with a USB interface.

       This  manual  page describes the access of USB scanners over the sanei_usb interface. Most
       SANE USB backends use the sanei_usb interface, only sm3600 accesses the	USB  directly  by
       libusb.	Have  a  look at sane-sm3600 and section "LIBUSB ACCESS TIPS" of this manual page
       for that backend.

       Two methods for accessing USB devices are used by sanei_usb: direct access using the  ker-
       nel  scanner  driver  and  access  over	libusb. sanei_usb tries both methods, if they are
       available. Currently USB access is tested for Linux  (kernel,  libusb),	FreeBSD  (kernel,
       libsub),  NetBSD (libusb), and OpenBSD (kernel, libusb). Libusb access should also work on
       Mac OS X (Darwin) and any other operating system  supported  by	libusb	but  hasn't  been
       tested	yet.   For   installation   issues,   also  check  the	/usr/share/doc/sane-back-
       ends-1.0.9/README.platform files.

       Most backends will detect USB scanners automatically using "usb" configuration file lines.
       This method allows to identify scanners by the USB vendor and product numbers.  The syntax
       for specifying a scanner this way is:


       where VENDOR is the USB vendor id, and PRODUCT is the USB product id of the scanner.  Both
       ids  are non-negative integer numbers in decimal or hexadecimal format. The correct values
       for these fields can be found by looking into  the  syslog  (e.g.,  /var/log/messages)  or
       under  Linux by issuing the command "cat /proc/bus/usb/devices/".  This is an example of a
       config file line:

	      usb 0x055f 0x0006

       would have the effect that all USB devices in the system with a vendor id of 0x55f  and	a
       product	id  of 0x0006 would be probed and recognized by the backend. The same config line
       in decimal format looks like this:

	      usb 1375 6

       If your scanner is not detected automatically, it may be necessary to edit the appropriate
       backend	configuration  file  before using SANE for the first time.  For most systems, the
       configuration file should list the name of the USB device file that the	scanner  is  con-
       nected  to (e.g., under Linux, /dev/usb/scanner0 or /dev/usbscanner0 is such a USB device,
       the device file for FreeBSD is e.g.  /dev/uscanner0).  If libusb is used, the device  name
       looks like the following example: libusb:001:002

       Do  not	create a symlink from /dev/scanner to the USB device because this link is used by
       the SCSI backends. The scanner may be confused if it receives SCSI commands.

       For a detailed description of each backend's configuration file, please refer to the rele-
       vant backend manual page (e.g. sane-mustek_usb for Mustek USB scanners).

       Generally  speaking,  if your scanner works with one method, there is no need to switch to
       the other one.

       Libusb is the more general approach and will be able to access any scanner. Also, it  sup-
       ports  more  platforms. However, the library must be available and installed on the system
       and setting permissions isn't easy at least on Linux.

       Autodetecting scanners and using USB control messages with the kernel access  method  only
       works  with  recent  (>=v2.4.12) Linux kernels. If you need one of these two features on a
       different platform, use libusb instead.

       Ensure that the access permissions for the USB device are set appropriately.  We recommend
       to add a group "scanner" to /etc/group which contains all users that should have access to
       the scanner.  The permission of the device should then be set  to  allow  group	read  and
       write  access.	For  example, if the scanner is at USB device /dev/usb/scanner0, then the
       following two commands would set the permission correctly:

	      $ chgrp scanner /dev/usb/scanner0
	      $ chmod 660 /dev/usb/scanner0

       If your scanner isn't detected automatically by your operating  system's  scanner  driver,
       you  need  to  tell the kernel the vendor and product ids of your scanner. For Linux, this
       can be done with modprobe parameters: First, remove the scanner	module	(rmmod	scanner),
       then  load  it  again:  modprobe scanner vendor=0x0001 product=0x0002. Use the appropriate
       vendor and product ids (e.g. from syslog or cat /proc/bus/usb/devices).	For  OpenBSD  the
       kernel	 must	 be   recompiled.   For   details   look   at	/usr/share/doc/sane-back-
       ends-1.0.9/README.openbsd. Similar approaches should be used for the other BSDs.

       Linux kernel messages in syslog like "kernel: scanner.c: open_scanner(1): Unable to access
       minor  data"  can be ignored. They are generated when SANE scans all available USB devices
       for scanners.

       Libusb can only access your scanner if it's not claimed by the kernel scanner  driver.  If
       you  want to use libusb, unload the kernel driver (e.g. rmmod scanner under Linux) or dis-
       able the driver when compiling a new kernel. For Linux, your kernel needs support for  the
       USB  filesystem (usbfs) and that filesystem must be mounted. That's done automatically, if
       /etc/fstab contains a line like this:

	      none /proc/bus/usb usbfs defaults  0  0

       The permissions for the device files used by libusb must be adjusted for user access. Oth-
       erwise	only  root  can  use  SANE  devices.  For  Linux,  the	devices  are  located  in
       /proc/bus/usb/. There are directories named e.g. "001" (the  bus  name)	containing  files
       "001",  "002"  etc. (the device files). The right device files can be found out by running
       scanimage -L as root. Setting permissions with "chmod" is  not  permanent,  however.  They
       will  be  resetted after reboot or replugging the scanner. It's also possible to mount the
       usbfs with the option "devmode=0666", e.g. by using the following line in /etc/fstab:

	      none /proc/bus/usb usbfs defaults,devmode=0666  0  0

       However, this way everyone has access to all USB devices. Another way to  set  permissions
       is  to  use  the  hotplug utilities (http://linux-hotplug.sourceforge.net/), which support
       dynamic setting of access permissions. Last, the frontends can be run  as  root.  However,
       that's not recommended for security reasons.

       For  the  BSDs, the device files are named /dev/ugen*. Use chmod to apply appropriate per-

	      If the library was compiled with debug support enabled, this  environment  variable
	      controls	the debug level for the USB I/O subsystem.  E.g., a value of 128 requests
	      all debug output to be printed.  Smaller levels reduce  verbosity.  Values  greater
	      than 4 enable libusb debugging (if available).

       sane(7), sane-find-scanner(1), sane-"backendname"(5), sane-scsi(5)

       Henning Meier-Geinitz. Some parts were copied from the sane-scsi manual page.

					   15 Sep 2002				     sane-scsi(5)
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