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<H2><A NAME="s6">6. Boot Arguments for SCSI Peripherals.</A></H2>
<P>This section contains the descriptions of the boot args that
are used for passing information about the installed SCSI
host adapters, and SCSI devices.
<P>
<H2><A NAME="ss6.1">6.1 Arguments for Upper and Mid-level Drivers</A>
</H2>
<P>The upper level drivers handle all things SCSI, regardless
of whether they be disk, tape, or CD-ROM.
The mid level drivers handle things like disks, CD-ROMs and
tapes without getting into low level host adapter
device driver specifics.
<P>
<H3>Maximum Probed LUNs (`max_scsi_luns=')</H3>
<P>Each SCSI device can have a number of `sub-devices' contained
within itself. The most common example is any of the
SCSI CD-ROMs that handle more than one disk at a time.
Each CD is addressed as a `Logical Unit Number' (LUN) of
that particular device. But most devices, such as hard disks,
tape drives and such are only one device, and will be
assigned to LUN zero.
<P>The problem arises with single LUN devices with bad firmware.
Some poorly designed SCSI devices (old and unfortunately new)
can not handle being probed for LUNs not equal to zero. They
will respond by locking up, and possibly taking the whole
SCSI bus down with them.
<P>The kernel has a configuration option that allows you
to set the maximum number of probed LUNs. The default is to
only probe LUN zero, to avoid the problem described above.
<P>To specify the number of probed LUNs at boot, one enters
`max_scsi_luns=n' as a boot arg, where n is a number between
one and eight. To avoid problems as described above, one would
use n=1 to avoid upsetting such broken devices
<P>
<H3>SCSI Logging (`scsi_logging=')</H3>
<P>Supplying a non-zero value to this boot argument turns on
logging of all SCSI events (error, scan, mlqueue, mlcomplete,
llqueue, llcomplete, hlqueue, hlcomplete). Note that
better control of which events are logged can be obtained
via the <CODE>/proc/scsi/scsi</CODE> interface if you aren't
interested in the events that take place at boot before
the <CODE>/proc/</CODE> filesystem is accessible.
<P>
<H3>Parameters for the SCSI Tape Driver (`st=')</H3>
<P>Some boot time configuration of the SCSI tape driver can
be achieved by using the following:
<P>
<HR>
<PRE>
st=buf_size[,write_threshold[,max_bufs]]
</PRE>
<HR>
<P>The first two numbers are specified in units of kB.
The default <CODE>buf_size</CODE> is 32kB, and the maximum size
that can be specified is a ridiculous 16384kB.
The <CODE>write_threshold</CODE> is the value at which the buffer is
committed to tape, with a default value of 30kB.
The maximum number of buffers varies with the number of drives
detected, and has a default of two. An example usage would be:
<P>
<HR>
<PRE>
st=32,30,2
</PRE>
<HR>
<P>Full details can be found in the <CODE>README.st</CODE> file that is
in the <CODE>scsi</CODE> directory of the kernel source tree.
<P>
<H2><A NAME="ss6.2">6.2 Arguments for SCSI Host Adapter Drivers</A>
</H2>
<P>
<P>These are arguments for low level SCSI host device drivers,
and as such are typically only used by those that compile
their own kernel with the SCSI driver built in. These
people are advised to check the source for the latest
list of options that can be supplied to their driver.
<P><CODE>aha152x=</CODE> Adaptec aha151x, aha152x, aic6260, aic6360, SB16-SCSI
<P><CODE>aha1542=</CODE> Adaptec aha1540, aha1542
<P><CODE>aic7xxx=</CODE> Adaptec aha274x, aha284x, aic7xxx
<P><CODE>advansys=</CODE> AdvanSys SCSI Host Adaptors
<P><CODE>in2000=</CODE> Always IN2000 Host Adaptor
<P><CODE>AM53C974=</CODE> AMD AM53C974 based hardware
<P><CODE>BusLogic=</CODE> ISA/PCI/EISA BusLogic SCSI Hosts
<P><CODE>eata=</CODE> EATA SCSI Cards
<P><CODE>tmc8xx=</CODE> Future Domain TMC-8xx, TMC-950
<P><CODE>fdomain=</CODE> Future Domain TMC-16xx, TMC-3260, AHA-2920
<P><CODE>ppa=</CODE> IOMEGA Parallel Port / ZIP drive
<P><CODE>ncr5380=</CODE> NCR5380 based controllers
<P><CODE>ncr53c400=</CODE> NCR53c400 based controllers
<P><CODE>ncr53c406a=</CODE> NCR53c406a based controllers
<P><CODE>pas16=</CODE> Pro Audio Spectrum
<P><CODE>st0x=</CODE> Seagate ST-0x
<P><CODE>t128=</CODE> Trantor T128
<P><CODE>u14-34f=</CODE> Ultrastor SCSI cards
<P><CODE>wd7000=</CODE> Western Digital WD7000 cards
<P>
<P>
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