sane-scsi(5)							File Formats Manual						      sane-scsi(5)

NAME

       sane-usb - USB configuration tips for SANE

DESCRIPTION

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

GENERAL INFO

       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 kernel 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-backends-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:

	      usb VENDOR PRODUCT

       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 recog-
       nized 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 connected 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 relevant backend manual page (e.g. sane-mustek_usb for
       Mustek USB scanners).

WHEN TO USE WHICH ACCESS METHOD

       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 supports 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.

KERNEL SCANNER DRIVER TIPS

       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 cor-
       rectly:

	      $ 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-backends-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 ACCESS TIPS

       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 disable 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. Otherwise 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  "dev-
       mode=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-hot-
       plug.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 permissions.

ENVIRONMENT

       SANE_DEBUG_SANEI_USB
	      If  the  library was compiled with debug support enabled, this environment variable controls the debug level for the USB I/O subsys-
	      tem.  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).

SEE ALSO

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

AUTHOR

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

								    15 Sep 2002 						      sane-scsi(5)