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NAME    [Toc]    [Back]

       sane-scsi - SCSI adapter tips for scanners

DESCRIPTION    [Toc]    [Back]

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

GENERAL INFO    [Toc]    [Back]

       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 Linux, there is an alternate way  of  specifying  scanner  devices.
       This  alternate	way is based on /proc/scsi/scsi and 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  doublequotes
  if  they contain any whitespace.  The remaining four fields are
       non-negative integer numbers.  The correct values for these fields  can
       be found 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  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/sge, then the following two commands  would
       set the permission correctly:

	      $ chgrp scanner /dev/sge
	      $ chmod 660 /dev/sge

       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    [Toc]    [Back]

	      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 reenabling 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

LINUX    [Toc]    [Back]

       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-Programming-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 versions of the kernel driver  (atp870u.c)  cut  the
		     inquiry  information.   Therefore	the  scanner  can't be
		     detected	   correctly.	   See	     http://www.meier-
		     geinitz.de/sane/trouble.html#acard for a solution.

	      Adaptec AHA-1505/AHA-1542/AHA-2940
		     Reported  to  work fine with Linux 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). If
		     you use Linux 2.0.x you may  need	a  patch  from	Ingmar
		     Baumgart's homepage:
		     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 necssary to  disable  disconnect/reconnect.
   To   achieve   this   use   the	option
		     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 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
       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 targetid
 1 on that same bus would be called /dev/sg0b, and so on.

ENVIRONMENT    [Toc]    [Back]

	      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.

SEE ALSO    [Toc]    [Back]

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

AUTHOR    [Toc]    [Back]

       David Mosberger

				  12 Nov 2001			  sane-scsi(5)
[ Back ]
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