sane-scsi - SCSI adapter tips for scanners
This manual page contains various operating-system specific tips and tricks on
how to get scanners with a SCSI interface working.
For scanners with a SCSI interface, 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 generic SCSI
device that the scanner is connected to (e.g., under Linux, /dev/sg4
is such a generic SCSI device). It is customary to create a
symlink from /dev/scanner
to the generic SCSI device that the scanner
is connected to. In this case, the configuration file simply lists the line
. For a detailed description of each backend's
configuration file, please refer to the relevant backend manual page (e.g.,
(5) for Epson scanners, sane-hp
(5) for HP scanners,
For some operating systems (e.g. Linux and OS/2), there is an alternate way of
specifying scanner devices. This alternate way allows one to identify scanners
by the SCSI vendor and model string and/or by the SCSI device address
(consisting of bus number, channel number, id, and logical unit number). The
syntax for specifying a scanner in this way is:
scsi VENDOR MODEL TYPE BUS CHANNEL ID
is the SCSI vendor string, MODEL
is the SCSI model
is type SCSI device type string, BUS
is the SCSI
bus number (named "host" in /proc/scsi/scsi), CHANNEL
SCSI channel number, ID
is the SCSI id, and LUN
is the logical
unit number of the scanner device. The first two fields are strings which must
be enclosed in double-quotes if they contain any whitespace. The remaining
four fields are non-negative integer numbers. The correct values for these
fields can be found by using operating system specific tools, e.g. for Linux
by looking at the output of the command "cat /proc/scsi/scsi". To
simplify configuration, a field's value can be replaced with an asterisk
symbol (``*''). An asterisk has the effect that any value is allowed for that
particular field. This can have the effect that a single scsi-line matches
multiple devices. When this happens, each matching device will be probed by
the backend one by one and registered if the backend thinks it is a compatible
device. For example, the line
scsi MUSTEK MFS-06000CX Scanner 0 00 03
would attach the Mustek SCSI scanner with the following /proc/scsi/scsi entry:
Host: scsi0 Channel: 00 Id: 03 Lun: 00
Vendor: MUSTEK Model: MFS-06000CX Rev: 4.04
Type: Scanner ANSI SCSI revision: 0
Usually it's sufficient to use vendor and model strings only or even only the
vendor string. The following example
scsi MUSTEK * * * * * *
would have the effect that all SCSI devices in the system with a vendor string
of MUSTEK would be probed and recognized by the backend.
If the remainder of a scsi-string consists of asterisks only, the asterisks can
be omitted. For example, the following line is equivalent to the one specified
On some platforms (e.g., OpenStep), SANE device names take a special form. This
is explained below in the relevant platform-specific section.
When using a SCSI scanner, ensure that the access permission for the generic
SCSI device is 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 generic
SCSI device /dev/sg0
, then the following two commands would set the
$ chgrp scanner /dev/sg0
$ chmod 660 /dev/sg0
When your system uses the device filesystem (devfs), you have to edit
There you should search the line
REGISTER ^sg[^/]* PERMISSIONS root.root
and add a new line (eg. for changing permissions of sg4):
REGISTER ^sg4 PERMISSIONS root.scanner
Auto-configuration using the "scsi *" lines in the config files only
works if the user running the frontend has read/write access to /dev/xpt0.
Instead, you can also set a link /dev/scanner
to the appropriate
- Adaptec AHA1542CF
- Reported to work fine under FreeBSD 2.2.2R with the
- Adaptec 2940
- Reported to work fine under FreeBSD 2.2.2.
- Adaptec 1522
- The scanner probes ok but any attempt to access it
hangs the entire system. It looks like something is disabling
interrupts and then not re-enabling them, so it looks like a bug in the
FreeBSD aic driver.
- Adaptec 1505
- Works on FreeBSD 2.2.5R and 3.0 using the aic
driver, provided that Plug-and-Play support is disabled on the card. If
there are no uk devices, just do a ``sh MAKEDEV uk0'' in the
/dev directory. The scanner should then be accessible as
/dev/uk0 if it was probed during boot.
- Tekram DC390
- Reported to work fine under FreeBSD 2.2.2R with the
First, make sure your kernel has SCSI generic support enabled. In ``make
xconfig'', this shows up under ``SCSI support->SCSI generic support''.
To keep scanning times to a minimum, it is strongly recommended to use a large
buffer size for the generic SCSI driver. From SG driver version 2.0 on, the
maximum buffer size can be changed at program run time, and there is no
restriction in size. This driver version is part of the Linux kernels from
version 2.2.7 on. If the new SG driver is available some backends (e.g.
sane-umax, sane-mustek, sane-sharp) automatically request larger scsi buffers.
If a backend does not automatically request a larger scsi buffer, set the
environment variable SANE_SG_BUFFERSIZE
to the desired buffer size in
bytes. It is not recommended to use more than 1 MB, because for large values
the probability increases that the SG driver cannot allocate the necessary
buffer(s). For ISA cards, even 1 MB might be a too large value. For a detailed
discussion of memory issues of the SG driver, see http://www.torque.net/sg.
For Linux kernels before version 2.2.7 the size of the buffer is only 32KB. This
works, but for many cheaper scanners this causes scanning to be slower by
about a factor of four than when using a size of 127KB. Linux defines the size
of this buffer by macro SG_BIG_BUFF
in header file
. Unless a system is seriously short on memory,
it is recommended to increase this value to the maximum legal value of
128*1024-512=130560 bytes. After changing this value, it is necessary to
recompile both the kernel (or the SCSI generic module) and the SCSI backends.
Keep in mind that this is only necessary with older Linux kernels.
A common issue with SCSI scanners is what to do when you booted the system while
the scanner was turned off? In such a case, the scanner won't be recognized by
the kernel and SANE won't be able to access it. Fortunately, Linux provides a
simple mechanism to probe a SCSI device on demand. Suppose you have a scanner
connected to SCSI bus 2 and the scanner has a SCSI id of 5. When the system is
up and running and the scanner is turned on, you can issue the command:
echo "scsi add-single-device 2 0 5
0" > /proc/scsi/scsi
and the kernel will probe and recognize your scanner (this needs to be done as
root). It's also possible to dynamically remove a SCSI device by using the
``remove-single-device'' command. For details, please refer to to the
Scanners are known to work with the following SCSI adapters under Linux. This
list isn't complete, usually any SCSI adapter supported by Linux should work.
- Acard/Advance SCSI adapters
- Some old versions of the kernel driver (atp870u.c) cut the
inquiry information. Therefore the scanner couldn't be detected correctly.
Use a current kernel.
- Adaptec AHA-1505/AHA-1542/AHA-2940
- Reported to work fine with Linux since v2.0. If you
encounter kernel freezes or other unexpected behaviour get the latest
Linux kernel (2.2.17 seems to work) or reduce SCSI buffer size to 32
- ASUS SC200
- Reported to work fine with Linux v2.0.
- BusLogic BT958
- To configure the BusLogic card, you may need to follow
these instructions (contributed by Jeremy <firstname.lastname@example.org>):
During boot, when your BusLogic adapter is being initialized, press Ctrl-B
to enter your BusLogic adapter setup. Choose the address which your
BusLogic containing your scanner is located. Choose ``SCSI Device
Configuration''. Choose ``Scan SCSI Bus''. Choose whatever SCSI id that
contains your scanner and then choose ``View/Modify SCSI configuration''.
Change ``Negotiation'' to ``async'' and change ``Disconnect'' to ``off''.
Press Esc, save, and Esc again until you are asked to reboot.
- NCR/Symbios 53c400/53c400a or Domex DTC3181E/L/LE
(DTCT436/436P) ISA SCSI card
- This card is supplied by Mustek (and other vendors). It's
supported since Linux 2.2. The SCSI cards are supported by the module
g_NCR5380. It's necessary to tell the kernel the io port and type of card.
Example for a 53c400a: ``modprobe g_NCR5380 ncr_addr=0x280
ncr_53c400a=1''. Once the kernel detects the card, it should work all
right. However, while it should work, do not expect good performance out
of this card---it has no interrupt line and therefore while a scan is in
progress, the system becomes almost unusable. You may change the values of
the USLEEP macros in drivers/scsi/g_NCR5380.c. Some documentation is in
this file and NCR5380.c.
- NCR/Symbios 810
- For some scanners it may be necessary to disable
disconnect/reconnect. To achieve this use the option
ncr53c8xx="disc:n". Some people reported that their scanner only
worked with the 53c7,8xx driver, not the ncr53c8xx. Try both if you have
For Linux kernels before 2.0.33 it may be necessary to increase the SCSI
timeout. The default timeout for the Linux kernels before 2.0.33 is 10
seconds, which is way too low when scanning large area. If you get
messages of the form ``restart (ncr dead ?)'' in your /var/log/messages
file or on the system console, it's an indication that the timeout is too
short. In this case, find the line ``if (np->latetime>10)'' in file
ncr53c8xx.c (normally in directory /usr/src/linux/drivers/scsi) and change
the constant 10 to, say, 60 (one minute). Then rebuild the kernel/module
and try again.
- Tekram DC315
- The driver can be downloaded from
http://www.garloff.de/kurt/linux/dc395/. For some older scanners it may be
necessary to disable all the more advanced features by using e.g. modprobe
- Tekram DC390
- Version 1.11 of the Tekram driver seems to work fine
mostly, except that the scan does not terminate properly (it causes a SCSI
timeout after 10 minutes). The generic AM53C974 also seems to work fine
and does not suffer from the timeout problems.
Under Solaris, OpenStep and NeXTStep, the generic SCSI device name refers to a
SCSI bus, not to an individual device. For example, /dev/sg0
the first SCSI bus. To tell SANE which device to use, append the character
'a'+target-id to the special device name. For example, the SCSI device
connected to the first SCSI controller and with target-id 0 would be called
, and the device with target-id 1 on that same bus would be
and so on.
- If the library was compiled with debug support enabled,
this environment variable controls the debug level for the generic SCSI
I/O subsystem. E.g., a value of 128 requests all debug output to be
printed by the backend. A value of 255 also prints kernel messages from
the SCSI subsystem (where available). Smaller levels reduce
- sets the timeout value for SCSI commands in seconds.
Overriding the default value of 120 seconds should only be necessary for
very slow scanners.