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       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 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


       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

         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

       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


       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

              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


       First,  make  sure  your  kernel  has SCSI generic support enabled.  In
       ``make xconfig'', this shows  up  under  ``SCSI  support->SCSI  generic

       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
       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
                     <>):  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
             For some  older
                     scanners  it  may  be  necessary  to disable all the more
                     advanced  features  by  using  e.g.  modprobe  dc395x_trm

              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  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.


              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.

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


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


       David Mosberger

                                  14 Jul 2008                     sane-scsi(5)