sane-scsi

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 customary to cre
   ate 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 is:

          scsi VENDOR MODEL TYPE BUS CHANNEL ID LUN

   where VENDOR is the SCSI vendor string, MODEL is the SCSI model string, TYPE is the 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 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 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.

LINUX INFO

   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  back
   ends  (e.g.  sane-umax(5), sane-mustek(5), sane-sharp(5)) automatically request larger SCSI buffers. If a backend does not automatically request a larger SCSI buffer, set the environ
   ment 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  dri
   ver  cannot  allocate  the  necessary  buffer(s).  For  ISA  cards,  even  1  MB  might  be  a  too  large  value.   For  a  detailed  discussion  of  the  Linux  SG  SCSI driver see:
   https://tldp.org/HOWTO/SCSI-Generic-HOWTO.

   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 Configu‐
                 ration''.   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 http://www.garloff.de/kurt/linux/dc395/.  For some older scanners it may be necessary to disable all the more advanced features by  us
                 ing 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

                                                                                      14 Jul 2008                                                                             sane-scsi(5)