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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 is:


       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

              $ 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 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.


       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 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 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.


       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

              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)