sane-scsi(5)             SANE Scanner Access Now Easy             sane-scsi(5)



NAME
       sane-scsi - SCSI adapter tips for scanners

DESCRIPTION
       This manual page contains various operating-system specific tips and
       tricks on how to get scanners with a SCSI interface working.

GENERAL INFO
       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 scanners, etc.).

       For some operating systems (e.g. Linux and OS/2), there is an alternate
       way of specifying scanner devices.  This alternate way 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 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 00

       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 previously:

              scsi MUSTEK

       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 permission correctly:

              $ chgrp scanner /dev/sg0
              $ chmod 660 /dev/sg0

       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

FREEBSD INFO
       Auto-configuration using the "scsi *" lines in the config files only
       works if the user running the frontend has read/write acces to
       /dev/xpt0. Instead, you can also set a link /dev/scanner to the
       appropriate /dev/uk device.

              Adaptec AHA1542CF
                     Reported to work fine under FreeBSD 2.2.2R with the aha
                     driver.

              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 amd
                     driver.


LINUX INFO
       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 /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
       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 SCSI-2.4-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 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 kB.

              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
                     <jeremy@xxedgexx.com>): 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 trouble.
                     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 dc395x_trm
                     dc395x_trm=7,5,1,32.

              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.


SOLARIS, OPENSTEP AND NEXTSTEP INFO
       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 target-
       id 1 on that same bus would be called /dev/sg0b, and so on.

ENVIRONMENT
       SANE_DEBUG_SANEI_SCSI
              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_SCSICMD_TIMEOUT
              sets the timeout value for SCSI commands in seconds. Overriding
              the default value of 120 seconds should only be necessary for
              very slow scanners.


SEE ALSO
       sane(7), sane-find-scanner(1), sane-"backendname"(5), sane-usb(5)


AUTHOR
       David Mosberger



                                  14 Jul 2008                     sane-scsi(5)
