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sane-scsi(5)		 SANE Scanner Access Now Easy		  sane-scsi(5)



NAME
       sane-scsi - SCSI adapter tips for scanners

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

GENERAL INFO
       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 cus-
       tomary 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 man-
       ual  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 iden-
       tify scanners by the SCSI vendor and model string and/or	 by  the  SCSI
       device address (consisting of bus number, channel number, id, and logi-
       cal unit number).  The syntax for specifying a scanner in this way is:

	      scsi VENDOR MODEL TYPE BUS CHANNEL ID LUN

       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  sim-
       plify  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  equiva-
       lent 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  sec-
       tion.

       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


FREEBSD INFO
       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	appro-
       priate /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.


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


       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  rec-
       ommended	 to use more than 1 MB, because for large values the probabil-
       ity  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
       http://www.torque.net/sg.

       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
		     <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). It's
		     supported since Linux 2.2.	 The SCSI cards are  supported
		     by the module g_NCR5380.  It's necessary to tell the ker-
		     nel 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 doc-
		     umentation is in this file and NCR5380.c.

	      NCR/Symbios 810
		     For some scanners it may be necessary to disable  discon-
		     nect/reconnect.   To   achieve   this   use   the	option
		     ncr53c8xx="disc:n". Some people reported that their scan-
		     ner  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/mes-
		     sages  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 (nor-
		     mally  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
		     http://www.garloff.de/kurt/linux/dc395/.	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.


SOLARIS, OPENSTEP AND NEXTSTEP INFO
       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.

ENVIRONMENT
       SANE_DEBUG_SANEI_SCSI
	      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.

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


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


AUTHOR
       David Mosberger



sane-backends 1.0.18		  28 Oct 2003			  sane-scsi(5)
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