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 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


   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  access  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)


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