sane-project-backends/doc/sane-usb.man

.TH sane-usb 5 "27 Nov 2002"  "@PACKAGEVERSION@" "SANE Scanner Access Now Easy"
.IX sane-usb
.SH NAME
sane-usb \- USB configuration tips for SANE
.SH DESCRIPTION
This manual page contains information on how to access scanners with a USB
interface. It focusses on two main topics: getting the scanner detected by the
operating system kernel and using it with SANE.
.PP
This page applies to most backends and scanners, as they use the generic
sanei_usb interface. However, there are some exceptions: USB Scanners
supported by the avision and microtek2 backends need special USB kernel
drivers, see
.BR sane-avision (5)
and
.BR sane-microtek2 (5)
for details. The sm3600 backend supports only access via libusb. See the
appropriate section in this manpage and
.BR sane-sm3600 (5).

.SH "QUICK START"
This is a short HOWTO-like section. For the full details, read the following
sections. The goal of this section is to get the scanner detected by
.BR sane-find-scanner (5).
.PP
Run sane-find-scanner. If it lists your scanner with the correct vendor and
product ids, you are done. See section
.B "SANE ISSUES"
for details on how to go on.
.PP
Sane-find-scanner lists your scanner, but can't detect the vendor- and product
ids? Scanning may work nevertheless, just try with section
.BR "SANE ISSUES" .
If it doesn't, install libusb (see section
.BR LIBUSB )
or, if you use Linux, upgrade your kernel (see section
.BR "GENERIC KERNEL SCANNER DRIVER" ).
.PP
Sane-find-scanner doesn't list your scanner? Does it work as root? If yes,
there is a permission issue. If sane-find-scanner lists a device name starting with 
.IR libusb: ,
read
.BR LIBUSB ,
otherwise have a look at the section
.BR "GENERIC KERNEL SCANNER DRIVER" ).
.PP
Nothing is found even as root? Either install libusb (see section
.BR LIBUSB ),
or make sure, that the kernel scanner driver knows the ids of your scanner
(see section
.BR "GENERIC KERNEL SCANNER DRIVER" ).

.SH "USB ACCESS METHODS"
Two methods for accessing USB devices are currently in use: direct access
using the kernel scanner driver and access over libusb. By default, both
methods are tried by SANE, if they are available. Currently USB access is
tested for Linux (kernel, libusb), FreeBSD (kernel, libsub), NetBSD (libusb),
OpenBSD (kernel, libusb) and MacOS X (libusb). Testing on MacOS X is very
limited and not all scanners seem to work reliably with the BSDs. For
installation issues, also check the @DOCDIR@/README.platform files.
.PP
Generally speaking, if your scanner works with one method, there is no need to
switch to the other one.
.PP
Libusb is the more general approach and is able to access any scanner. Also,
it supports more platforms.
.PP
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. Also, the
kernel scanner driver may be removed from Linux 2.5/2.6 in future so libusb
will be the only access method.

.SH LIBUSB
SANE can only use libusb 0.1.6 or newer. It needs to be installed at
build-time.
.PP
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). For kernels
older than 2.4.19, replace "usbfs" with "usbdevfs" because the name has
changed. This filesystem must be mounted. That's done automatically at boot
time, if /etc/fstab contains a line like this:
.PP
.RS
none /proc/bus/usb usbfs defaults  0  0
.RE
.PP
The permissions for the device files used by libusb must be adjusted for user
access. Otherwise only root can use SANE devices. For
.IR 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:
.PP
.RS
none /proc/bus/usb usbfs defaults,devmode=0666  0  0
.RE
.PP
However, this way everyone has access to all USB devices. Another way to set
permissions is to use the hotplug utilities
.RI ( 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.
.PP
For the
.BR BSDs ,
the device files are named 
.IR /dev/ugen* .
Use chmod to apply appropriate permissions.

.SH "GENERIC KERNEL SCANNER DRIVER"
Ensure that the access permissions for the USB device are set appropriately.
We recommend to add a group "scanner" to 
.I /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
.BR /dev/usb/scanner0 ,
then the following two commands would set the permission correctly:
.PP
.RS
$ chgrp scanner /dev/usb/scanner0
.br
$ chmod 660 /dev/usb/scanner0
.RE
.PP
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 
.BR Linux ,
this can be done with modprobe parameters: First, remove the scanner module
.RI ( "rmmod scanner" ),
then load it again: 
.IR "modprobe scanner vendor=0x0001 product=0x0002" .
Use the appropriate vendor and product ids (e.g. from 
.IR /var/log/messages ,
.IR dmesg ,
or
.IR "cat /proc/bus/usb/devices" ).
Some scanners supported by the gt68xx backend are not supported by the current
version of the generic scanner driver. See
.BR sane-gt68xx (5)
for details. For these scanners, there will be a message concerning "only 2 or
three endpoints" in syslog.
.PP
For OpenBSD the kernel may need to be recompiled. For details look at
@DOCDIR@/README.openbsd. Similar approaches should be used for the other BSDs.
.PP
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.

.SH "SANE ISSUES"
.PP
This section assumes that your scanner is detected by sane-find-scanner. It
doesn't make sense to go on, if this is not the case. While sane-find-scanner
is able to detect any USB scanner, actual scanning will only work if the
scanner is supported by a SANE backend. Information on the level of support
can be found on the SANE webpage
.RI ( http://www.mostang.com/sane/ ),
and the individual backend manpages.
.PP
Most backends can 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:
.PP
.RS
usb
.I VENDOR PRODUCT
.RE
.PP
where
.I VENDOR
is the USB vendor id, and
.I 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:
.PP
.RS
usb 0x055f 0x0006
.RE
.PP
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. 
.PP
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,
.B /dev/usb/scanner0
or
.B /dev/usbscanner0
is such a USB device, the device file for FreeBSD is e.g.
.BR /dev/uscanner0 ).
If libusb is used, the device name looks like the following example:
.BR libusb:001:002 .
.PP
For a detailed description of each backend's configuration file, please refer
to the relevant backend manual page (e.g. 
.BR sane-mustek_usb (5)
for Mustek USB scanners).
.PP
Do
.B not
create a symlink from
.I /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.

.SH ENVIRONMENT
.TP
.B 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
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). Example: export SANE_DEBUG_SANEI_USB=4.

.SH "SEE ALSO"
.BR sane (7),
.BR sane-find-scanner (1),
.BR sane-"backendname" (5),
.BR sane-scsi (5)

.SH AUTHOR
Henning Meier-Geinitz