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 or /dev/sge 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 /dev/scanner. For a detailed description of each
backend's configuration file, please refer to the relevant backend manual
page (e.g., sane-epson(5) for Epson scanners, sane-hp(5) for HP
For Linux, there is an alternate way of specifying scanner devices.
This alternate way is based on /proc/scsi/scsi and allows 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 LUN
where VENDOR is the SCSI vendor string, MODEL is the SCSI model string,
TYPE is type SCSI device type string, BUS is the SCSI bus number (named
"host" in /proc/scsi/scsi), CHANNEL is the 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 doublequotes
if they contain any whitespace. The remaining four fields are
non-negative integer numbers. The correct values for these fields can
be found 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 00
would attach the Mustek SCSI scanner with the following /proc/scsi/scsi
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 previously:
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/sge, then the following two commands would
set the permission correctly:
$ chgrp scanner /dev/sge
$ chmod 660 /dev/sge
When your system uses the device filesystem (devfs), you have to edit
/etc/devfs/perms. There you should search the line
REGISTER ^sg[^/]* PERMISSIONS root.root 0600
and add a new line (eg. for changing permissions of sg4):
REGISTER ^sg4 PERMISSIONS root.scanner 0660
Reported to work fine under FreeBSD 2.2.2R with the aha
Reported to work fine under FreeBSD 2.2.2.
The scanner probes ok but any attempt to access it hangs
the entire system. It looks like something is disabling
interrupts and then not reenabling them, so it looks like
a bug in the FreeBSD aic driver.
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.
Reported to work fine under FreeBSD 2.2.2R with the amd
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
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 /usr/include/scsi/sg.h. 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
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 SCSI-Programming-HOWTO.
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 versions of the kernel driver (atp870u.c) cut the
inquiry information. Therefore the scanner can't be
detected correctly. See http://www.meier-
geinitz.de/sane/trouble.html#acard for a solution.
Reported to work fine with Linux 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 kB.
Reported to work fine with Linux v2.0.
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). If
you use Linux 2.0.x you may need a patch from Ingmar
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
For some scanners it may be necssary to disable disconnect/reconnect.
To achieve this use the option
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.
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.
Solaris, OpenStep and NeXTStep
Under Solaris, OpenStep and NeXTStep, the generic SCSI device name
refers to a SCSI bus, not to an individual device. For example,
/dev/sg0 refers to 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 /dev/sg0a, and the device with targetid
1 on that same bus would be called /dev/sg0b, 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 verbosity.
sane(7), sane-find-scanner(1), sane-"backendname"(5), sane-usb(5)
12 Nov 2001 sane-scsi(5)
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