.TH sane\-usb 5 "14 Jul 2008"  "" "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 focuses on two main topics: getting the scanner detected by the
operating system kernel and using it with SANE.
.PP
This page applies to USB most backends and scanners, as they use the generic
sanei_usb interface. However, there is one exception: USB Scanners
supported by the
.BR sane\-microtek2 (5)
backend need a special USB kernel driver.

.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 (1).
.PP
Run
.BR sane\-find\-scanner (1).
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
.BR sane\-find\-scanner (1)
doesn't list your scanner? Does it work as root? If yes, there is a permission issue.
See the
.B LIBUSB
section for details.
.PP
Nothing is found even as root? Check that your kernel supports USB and that
libusb is installed (see section
.BR LIBUSB ).

.SH "USB ACCESS METHODS"
For accessing USB devices, the USB library libusb is used. There used to exist
another method to access USB devices: the kernel scanner driver. The kernel
scanner driver method is deprecated and shouldn't be used anymore. It may be
removed from SANE at any time. In Linux, the kernel scanner driver has been
removed in the 2.6.* kernel series. Only libusb access is documented in this
manual page.

.SH LIBUSB
SANE can only use libusb 0.1.6 or newer. It needs to be installed at
build-time. Modern Linux distributions and other operating systems come with
libusb.
.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
.I /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
.I /proc/bus/usb/
or in
.IR /dev/bus/usb ,
if you use
udev. 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:
.I "scanimage \-L:
as root. Setting permissions with
.BR chmod (1)
is not permanent, however. They will be reset after reboot or replugging the scanner.
.PP
Usually
.BR udev (7)
or for older distributions the hotplug utilities are used, which
support dynamic setting of access permissions. SANE comes with udev and hotplug
scripts in the directory
.I tools/udev
and
.IR tools/hotplug .
They can be used for setting permissions, see
.IR /usr/share/doc/libsane/README.linux ,
.IR tools/README
and the
.I README
in the
.I tools/hotplug
directory for more details.
.PP
For the
.BR BSDs ,
the device files used by libusb are named
.IR /dev/ugen* .
Use
.BR chmod (1)
to apply appropriate permissions.

.SH "SANE ISSUES"
.PP
This section assumes that your scanner is detected by
.BR sane\-find\-scanner (1).
It doesn't make sense to go on, if this is not the case. While
.BR sane\-find\-scanner (1)
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.sane\-project.org/ ),
and the individual backend manpages.
.PP
Most backends can detect USB scanners automatically using "usb" configuration
file lines. This method allows one 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 running
.BR sane\-find\-scanner (1),
looking into the syslog (e.g.,
.IR /var/log/messages )
or under Linux by issuing the command
.IR "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 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:
.IR "export SANE_DEBUG_SANEI_USB=4" .
.PP
.TP
.B SANE_USB_WORKAROUND
If your scanner does not work when plugged into a USB3 port, try
setting the environment variable
.B SANE_USB_WORKAROUND
to 1. This may work around issues which happen with particular kernel
versions. Example:
.I export SANE_USB_WORKAROUND=1.
.TP
.B SANE_XEROX_USB_HALT_WORKAROUND
If your old (pre-2010) Xerox / Samsung / HP scanner is detected
only once and subsequent usage requires replugging the cable, try
setting the environment variable
.B SANE_XEROX_USB_HALT_WORKAROUND
to 1. This may work around issues which happen with particular USB
controllers. Example:
.I export SANE_XEROX_USB_HALT_WORKAROUND=1.

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

.SH AUTHOR
Henning Meier-Geinitz
.RI < henning@meier\-geinitz.de >