sane-project-backends/doc/sane-scsi.man

.TH sane-scsi 5 "24 May 2001"
.IX sane-scsi
.SH NAME
sane-scsi - SCSI adapter tips for scanners
.SH DESCRIPTION
This manual page contains various operating-system specific tips and
tricks on how to get scanners with a SCSI interface working.
.SH 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,
.B /dev/sg4
or
.B /dev/sge
is such a generic SCSI device).  It is customary to create a symlink
from
.B /dev/scanner
to the generic SCSI device that the scanner is connected to.  In this
case, the configuration file simply lists the line
.BR /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.).
.PP
For Linux, there is an alternate way of specifying scanner devices
(beginning with SANE version 0.73).  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:
.PP
.RS
scsi
.I VENDOR MODEL TYPE BUS CHANNEL ID LUN
.RE
.PP
where
.I VENDOR
is the SCSI vendor string,
.I MODEL
is the SCSI model string,
.I TYPE
is type SCSI device type string,
.I BUS
is the SCSI bus number,
.I CHANNEL
is the SCSI channel number,
.I ID
is the SCSI id, and
.I 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
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
.PP
.RS
scsi MUSTEK * * * * * * 
.RE
.PP
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.
.PP
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:
.PP
.RS
scsi MUSTEK
.RE
.PP
On some platforms (e.g., OpenStep), SANE device names take a special
form.  This is explained below in the relevant platform-specific section.
.PP
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
.BR /dev/sge ,
then the following two commands would set the permission correctly:
.PP
.RS
$ chgrp scanner /dev/sge
.br
$ chmod 660 /dev/sge
.RE
.SH FreeBSD
.PP
.RS
.TP
Adaptec AHA1542CF
Reported to work fine under FreeBSD 2.2.2R with the
.B aha
driver.
.TP
Adaptec 2940
Reported to work fine under FreeBSD 2.2.2.
.TP
Adaptec 1522
The scanner probes ok but any attempt to
access it
.I 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
.B aic
driver.
.TP
Adaptec 1505
Works on FreeBSD 2.2.5R and 3.0 using the
.B aic
driver, provided that Plug-and-Play support is disabled on the card.
If there are no
.I uk
devices, just do a ``sh MAKEDEV uk0'' in the
.B /dev
directory. The scanner should then be accessible as
.B /dev/uk0 if it was probed
during boot.
.TP
Tekram DC390
Reported to work fine under FreeBSD 2.2.2R with the
.B amd
driver.
.SH LINUX
First, make sure your kernel has SCSI generic support enabled.  In
``make xconfig'', this shows up under ``SCSI support->SCSI generic
support''.
.PP
To keep scanning times to a minimum, it is strongly recommended to use a large
buffer size for the generic SCSI driver.  By default, older Linux kernels use
a buffer of size 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
.B SG_BIG_BUFF
in header file
.IR /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.
.PP
From SG driver version 2.0 on, the maximum buffer size can
be changed at program run time, and the restriction to 127 kB is also
removed. 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
.B 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 http::/www.torque.net/sg.
.PP
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:
.PP
.RS
echo "scsi add-single-device 2 0 5 0" > /proc/scsi/scsi
.RE
.PP
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.
.PP
Scanners are known to work with the following SCSI adapters
under Linux:
.PP
.RS
.TP
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.
.TP
ASUS SC200
Reported to work fine with Linux v2.0.
.TP
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.
.TP
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:
.br
.IR http://rzstud1.rz.uni-karlsruhe.de/~uh49/mustek-scsi.html
.br
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.
.TP
NCR/Symbios 810
For this card, make sure the SCSI timeout is reasonably big; 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. For some scanners it
may be necssary to disable disconnect/reconnect. To achieve this use the
option ncr53c8xx="disc:n".
.TP
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.
.SH 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,
.B /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
.BR /dev/sg0a ,
and the device with target-id 1 on that same bus would be
called
.BR /dev/sg0b,
and so on.
.SH ENVIRONMENT
.TP
.B 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.  Smaller levels reduce verbosity.
.SH "SEE ALSO"
sane(7), sane-find-scanner(1), sane-"backendname"(5)
.SH AUTHOR
David Mosberger