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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)