The Linux SCSI HOWTO
Drew Eckhardt,<drew@PoohSticks.ORG> (transformed to linuxdoc-sgml for�
mat by Dieter Faulbaum), <faulbaum@bii.bessy.de>
v2.30, 30 August 1996
1. Introduction
This documentation is free documentation; you can redistribute it
and/or modify it under the terms of the GNU General Public License as
published by the Free Software Foundation; either version 2 of the
License, or (at your option) any later version.
This documentation is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.
You should have received a copy of the GNU General Public License
along with this documentation; if not, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
That said, I'd appreciate it if people would ask me
<drew@PoohSticks.ORG> if there's a newer version available before they
publish it. When people publish outdated versions, I get questions
from users that are answered in newer versions, and it reflects poorly
on the publisher. I'd also prefer that all references to free
distribution sites, and possibly competing distributions/products be
left intact.
IMPORTANT :
BUG REPORTS OR OTHER REQUESTS FOR HELP WHICH FAIL TO FOLLOW THE
PROCEDURES OUTLINED IN THE ``REPORTING BUGS'' SECTION WILL BE IGNORED.
This HOWTO covers the Linux SCSI subsystem, as implemented in Linux
kernel revision 1.2.10 and newer alpha code. Earlier revisions of the
SCSI code are _unsupported_, and may differ significantly in terms of
the drivers implemented, performance, and options available.
For additional information, you may wish to join the linux-scsi
mailing list by mailing majordomo@vger.rutgers.edu with the line
subscribe linux-scsi
in the text. You can unsubscribe by sending mail to the same address
and including
unsubscribe linux-scsi
in the text.
Once you're subscribed, you can send mail to the list at
linux-scsi@vger.rutgers.edu
I'm aware that this document isn't the most user-friendly, and that
there may be inaccuracies and oversights. If you have constructive
comments on how to rectify the situation you're free to mail me about
it.
2. Common Problems
This section lists some of the common problems that people have. If
there is not anything here that answers your questions, you should
also consult the sections for your host adapter and the devices in
that are giving you problems.
2.1. General Flakiness
If you experience random errors, the most likely causes are cabling
and termination problems.
Some products, such as those built around the newer NCR chips, feature
digital filtering and active signal negation, and aren't very
sensitive to cabling problems.
Others, such as the Adaptec 154xC, 154xCF, and 274x, are _extremely_
sensitive and may fail with cables that work with other systems.
I reiterate : some host adapters are _extremely_ sensitive to cabling
and termination problems and therefore, cabling and termination should
be the first things checked when there are problems.
To minimize your problems, you should use cables which
1. Claim SCSI-II compliance
2. Have a characteristic impedance of 132 ohms
3. All come from the same source to avoid impedance mismatches
4. Come from a reputable vendor such as Amphenol
Termination power should be provided by _all_ devices on the SCSI bus,
through a diode to prevent current backflow, so that sufficient power
is available at the ends of the cable where it is needed. To prevent
damage if the bus is shorted, TERMPWR should be driven through a fuse
or other current limiting device.
If multiple devices, external cables, or FAST SCSI 2 are used, active
or forced perfect termination should be used on both ends of the SCSI
bus.
See the Comp.Periphs.Scsi FAQ (available on tsx-11 in
pub/linux/ALPHA/scsi) for more information about active termination.
2.2. The kernel command line
Other parts of the documentation refer to a "kernel command line".
The kernel command line is a set of options you may specify from
either the LILO : prompt after an image name, or in the append field
in your LILO configuration file (LILO .14 and newer use
/etc/lilo.conf, older versions use /etc/lilo/config).
Boot your system with LILO, and hit one of the alt, control, or shift
keys when it first comes up to get a prompt. LILO should respond with
:
At this prompt, you can select a kernel image to boot, or list them
with ?. Ie
:?
ramdisk floppy harddisk
To boot that kernel with the command line options you have selected,
simply enter the name followed by a white space delimited list of
options, terminating with a return.
Options take the form of
variable=valuelist
Where valuelist may be a single value or comma delimited list of
values with no whitespace. With the exception of root device,
individual values are numbers, and may be specified in either decimal
or hexadecimal.
Ie, to boot linux with an Adaptec 1520 clone not recognized at bootup,
you might type
:floppy aha152x=0x340,11,7,1
If you don't care to type all of this at boot time, it is also
possible to use the LILO configuration file "append" option with LILO
.13 and newer.
Ie,
append="aha152x=0x340,11,7,1"
2.3. A SCSI device shows up at all possible IDs
If this is the case, you have strapped the device at the same address
as the controller (typically 7, although some boards use other
addresses, with 6 being used by some Future Domain boards).
Please change the jumper settings.
2.4. A SCSI device shows up at all possible LUNs
The device has buggy firmware.
As an interim solution, you should try using the kernel command line
option
max_scsi_luns=1
If that works, there is a list of buggy devices in the kernel sources
in drivers/scsi/scsi.c in the variable blacklist. Add your device to
this list and mail the patch to Linus Torvalds
<Linus.Torvalds@cs.Helsinki.FI>.
2.5. You get sense errors when you know the devices are error free
Sometimes this is caused by bad cables or improper termination.
See section ``General Flakiness''
2.6. A kernel configured with networking does not work
The auto-probe routines for many of the network drivers are not
passive, and will interfere with operation with some of the SCSI
drivers.
2.7. Device detected, but unable to access
A SCSI device is detected by the kernel, but you are unable to access
it - ie mkfs /dev/sdc, tar xvf /dev/rst2, etc fails.
You don't have a special file in /dev for the device.
Unix devices are identified as either block or character (block
devices go through the buffer cache, character devices do not)
devices, a major number (ie which driver is used - block major 8
corresponds to SCSI disks) and a minor number (ie which unit is being
accessed through a given driver - ie character major 4, minor 0 is the
first virtual console, minor 1 the next, etc). However, accessing
devices through this separate namespace would break the unix/Linux
metaphor of "everything is a file," so character and block device
special files are created under /dev. This lets you access the raw
third SCSI disk device as /dev/sdc, the first serial port as
/dev/ttyS0, etc.
The preferred method for creating a file is using the MAKEDEV script -
cd /dev
and run MAKEDEV (as root) for the devices you want to create - ie
./MAKEDEV sdc
wildcards "should" work - ie
./MAKEDEV sd\*
"should" create entries for all SCSI disk devices (doing this should
create /dev/sda through /dev/sdp, with fifteen partition entries for
each)
./MAKEDEV sdc\*
"should" create entries for /dev/sdc and all fifteen permissible
partitions on /dev/sdc, etc.
I say "should" because this is the standard unix behavior - the
MAKEDEV script in your installation may not conform to this behavior,
or may have restricted the number of devices it will create.
If MAKEDEV won't do the right magic for you, you'll have to create the
device entries by hand with the mknod command.
The block/character type, major, and minor numbers are specified for
the various SCSI devices in section ``Device Files'' in the
appropriate section.
Take those numbers, and use (as root)
mknod /dev/device b|c major minor
ie -
mknod /dev/sdc b 8 32
mknod /dev/rst0 c 9 0
2.8. SCSI System Lockups
This could be one of a number of things. Also see the section for
your specific host adapter for possible further solutions.
There are cases where the lockups seem to occur when multiple devices
are in use at the same time. In this case, you can try contacting the
manufacturer of the devices and see if firmware upgrades are available
which would correct the problem. If possible, try a different scsi
cable, or try on another system. This can also be caused by bad
blocks on disks, or by bad handling of DMA by the motherboard (for
host adapters that do DMA). There are probably many other possible
conditions that could lead to this type of event.
Sometimes these problems occur when there are multiple devices in use
on the bus at the same time. In this case, if your host adapter
driver supports more than one outstanding command on the bus at one
time, try reducing this to 1 and see if this helps. If you have tape
drives or slow cdrom drives on the bus, this might not be a practical
solution.
2.9. Configuring and building the kernel
Unused SCSI drivers eat up valuable memory, aggravating memory
shortage problems on small systems because kernel memory is unpagable.
So, you will want to build a kernel tuned for your system, with only
the drivers you need installed.
cd to /usr/src/linux
If you are using a root device other than the current one, or
something other than 80x25 VGA, and you are writing a boot floppy, you
should edit the makefile, and make sure the
ROOT_DEV =
and
SVGA_MODE =
lines are the way you want them.
If you've installed any patches, you may wish to guarantee that all
files are rebuilt. If this is the case, you should type
make mrproper
Irregardless of weather you ran make mrproper, type
make config
and answer the configuration questions. Then run
make depend
and finally
make
Once the build completes, you may wish to update the lilo
configuration, or write a boot floppy. A boot floppy may be made by
running
make zdisk
2.10. LUNS other than 0 don't work
Many SCSI devices are horrendously broken, lock the SCSI bus up solid,
and do other bad things when you attempt to talk to them at a logical
unit someplace other than zero.
So, by default recent versions of the Linux kernel will not probe luns
other than 0. To work around this, you need to the max_scsi_luns
command line option, or recompile the kernel with the
CONFIG_SCSI_MULTI_LUN option.
Usually, you'll put
max_scsi_luns=8
on your LILO command line.
If your multi-LUN devices still aren't detected correctly after trying
one of these fixes (as the case will be with many old SCSI->MFM, RLL,
ESDI, SMD, and similar bridge boards), you'll be thwarted by this
piece of code
/* Some scsi-1 peripherals do not handle lun != 0.
I am assuming that scsi-2 peripherals do better */
if((scsi_result[2] & 0x07) == 1 &&
(scsi_result[3] & 0x0f) == 0) break;
in scan_scsis() in drivers/scsi/scsi.c. Delete this code, and you
should be fine.
3. Reporting Bugs
The Linux SCSI developers don't necessarily maintain old revisions of
the code due to space constraints. So, if you are not running the
latest publically released Linux kernel (note that many of the Linux
distributions, such as MCC, SLS, Yggdrasil, etc. often lag one or even
twenty patches behind this) chances are we will be unable to solve
your problem. So, before reporting a bug, please check to see if it
exists with the latest publically available kernel.
If after upgrading, and reading this document thoroughly, you still
believe that you have a bug, please mail a bug report to the SCSI
channel of the mailing list where it will be seen by many of the
people who've contributed to the Linux SCSI drivers.
In your bug report, please provide as much information as possible
regarding your hardware configuration, the exact text of
all of the messages that Linux prints when it boots, when the error
condition occurs, and where in the source code the error is. Use the
procedures outlined in ``Capturing messages'' and ``Locating the
source of a panic()''.
Failure to provide the maximum possible amount of information may
result in misdiagnosis of your problem, or developers deciding that
there are other more interesting problems to fix.
The bottom line is that if we can't reproduce your bug, and you can't
point at us what's broken, it won't get fixed.
3.1. Capturing messages
If you are not running a kernel message logging system :
Insure that the /proc filesystem is mounted.
grep proc /etc/mtab
If the /proc filesystem is not mounted, mount it
mkdir /proc
chmod 755 /proc
mount -t proc /proc /proc
Copy the kernel revision and messages into a log file
cat /proc/version > /tmp/log
cat /proc/kmsg >> /tmp/log
Type CNTRL-C after a second or two.
If you are running some logger, you'll have to poke through the
appropriate log files (/etc/syslog.conf should be of some use in
locating them), or use dmesg.
If Linux is not yet bootstrapped, format a floppy diskette under DOS.
Note that if you have a distribution which mounts the root diskette
off of floppy rather than RAM drive, you'll have to format a diskette
readable in the drive not being used to mount root or use their
ramdisk boot option.
Boot Linux off your distribution boot floppy, preferably in single
user mode using a RAM disk as root.
mkdir /tmp/dos
Insert the diskette in a drive not being used to mount root, and mount
it. Ie
mount -t msdos /dev/fd0 /tmp/dos
or
mount -t msdos /dev/fd1 /tmp/dos
Copy your log to it
cp /tmp/log /tmp/dos/log
Unmount the DOS floppy
umount /tmp/dos
And shutdown Linux
shutdown
Reboot into DOS, and using your favorite communications software
include the log file in your trouble mail.
3.2. Locating the source of a panic()
Like other unices, when a fatal error is encountered, Linux calls the
kernel panic() function. Unlike other unices, Linux doesn't dump core
to the swap or dump device and reboot automatically. Instead, a
useful summary of state information is printed for the user to
manually copy down. Ie :
Unable to handle kernel NULL pointer dereference at virtual address c0000004
current->tss,cr3 = 00101000, %cr3 = 00101000
*pde = 00102027
*pte = 00000027
Oops: 0000
EIP: 0010:0019c905
EFLAGS: 00010002
eax: 0000000a ebx: 001cd0e8 ecx: 00000006 edx: 000003d5
esi: 001cd0a8 edi: 00000000 ebp: 00000000 esp: 001a18c0
ds: 0018 es: 0018 fs: 002b gs: 002b ss: 0018
Process swapper (pid: 0, process nr: 0, stackpage=001a09c8)
Stack: 0019c5c6 00000000 0019c5b2 00000000 0019c5a5 001cd0a8 00000002 00000000
001cd0e8 001cd0a8 00000000 001cdb38 001cdb00 00000000 001ce284 0019d001
001cd004 0000e800 fbfff000 0019d051 001cd0a8 00000000 001a29f4 00800000
Call Trace: 0019c5c6 0019c5b2 0018c5a5 0019d001 0019d051 00111508 00111502
0011e800 0011154d 00110f63 0010e2b3 0010ef55 0010ddb7
Code: 8b 57 04 52 68 d2 c5 19 00 e8 cd a0 f7 ff 83 c4 20 8b 4f 04
Aiee, killing interrupt handler
kfree of non-kmalloced memory: 001a29c0, next= 00000000, order=0
task[0] (swapper) killed: unable to recover
Kernel panic: Trying to free up swapper memory space
In swapper task - not syncing
Take the hexadecimal number on the EIP: line, in this case 19c905, and
search through /usr/src/linux/zSystem.map for the highest number not
larger than that address. Ie,
0019a000 T _fix_pointers
0019c700 t _intr_scsi
0019d000 t _NCR53c7x0_intr
That tells you what function its in. Recompile the source file which
defines that function file with debugging enabled, or the whole kernel
if you prefer by editing /usr/src/linux/Makefile and adding a "-g" to
the CFLAGS definition.
#
# standard CFLAGS
#
Ie,
CFLAGS = -Wall -Wstrict-prototypes -O2 -fomit-frame-pointer -pipe
becomes
CFLAGS = -g -Wall -Wstrict-prototypes -O2 -fomit-frame-pointer -pipe
Rebuild the kernel, incrementally or by doing a
make clean
make
Make the kernel bootable by creating an entry in your /etc/lilo.conf
for it
image = /usr/src/linux/zImage
label = experimental
and re-running LILO as root, or by creating a boot floppy
make zImage
Reboot and record the new EIP for the error.
If you have script installed, you may want to start it, as it will log
your debugging session to the typescript file.
Now, run
gdb /usr/src/linux/tools/zSystem
and enter
info line *<your EIP>
Ie,
info line *0x19c905
To which GDB will respond something like
(gdb) info line *0x19c905
Line 2855 of "53c7,8xx.c" starts at address 0x19c905 <intr_scsi+641&>
and ends at 0x19c913 <intr_scsi+655>.
Record this information. Then, enter
list <line number>
Ie,
(gdb) list 2855
2850 /* printk("scsi%d : target %d lun %d unexpected disconnect\n",
2851 host->host_no, cmd->cmd->target, cmd->cmd->lun); */
2852 printk("host : 0x%x\n", (unsigned) host);
2853 printk("host->host_no : %d\n", host->host_no);
2854 printk("cmd : 0x%x\n", (unsigned) cmd);
2855 printk("cmd->cmd : 0x%x\n", (unsigned) cmd->cmd);
2856 printk("cmd->cmd->target : %d\n", cmd->cmd->target);
2857 if (cmd) {;
2858 abnormal_finished(cmd, DID_ERROR << 16);
2859 }
2860 hostdata->dsp = hostdata->script + hostdata->E_schedule /
2861 sizeof(long);
2862 hostdata->dsp_changed = 1;
2863 /* SCSI PARITY error */
2864 }
2865
2866 if (sstat0_sist0 & SSTAT0_PAR) {
2867 fatal = 1;
2868 if (cmd && cmd->cmd) {
2869 printk("scsi%d : target %d lun %d parity error.\n",
Obviously, quit will take you out of GDB.
Record this information too, as it will provide a context in case the
developers' kernels differ from yours.
4. Modules
This section gives specific details regarding the support for loadable
kernel modules and how it relates to SCSI.
4.1. General Information
Loadable modules are a means by which the user or system administrator
can load files into the kernel's memory in such a way that the
kernel's capabilities are expanded. The most common usages of modules
are for drivers to support hardware, or to load filesytems.
There are several advantages of modules for SCSI. One is that a
system administrator trying to maintain a large number of machines can
use a single kernel image for all of the machines, and then load
kernel modules to support hardware that is only present on some
machines.
It is also possible for someone trying to create a distribution to use
a script on the bootable floppy to query for which modules to be
loaded. This saves memory that would otherwise be wasted on unused
drivers, and it would also reduce the possibility that a probe for a
non-existent card would screw up some other card on the system.
Modules also work out nicely on laptops, which tend to have less
memory than desktop machines, and people tend to want to keep the
kernel image as small as possible and load modules as required. Also,
modules makes supporting PCMCIA SCSI cards on laptops somewhat easier,
since you can load and unload the driver as the card is
inserted/removed. [Note: currently the qlogic and 152x drivers support
PCMCIA].
Finally, there is the advantage that kernel developers can more easily
debug and test their drivers, since testing a new driver does not
require rebooting the machine (provided of course that the machine has
not completely crashed as a result of some bug in the driver).
Although modules are very nice, there is one limitation. If your root
disk partition is on a scsi device, you will not be able to use
modularized versions of scsi code required to access the disk. This
is because the system must be able to mount the root partition before
it can load any modules from disk. There are people thinking about
ways of fixing the loader and the kernel so that the kernel can self-
load modules prior to attempting to mount the root filesystem, so at
some point in the future this limitation may be lifted.
4.2. Module support in the 1.2.N kernel
In the 1.2.N series of kernels, there is partial support for SCSI
kernel modules. While none of the high level drivers (such as disk,
tape, etc) can be used as modules, most of the low level drivers (i.e.
1542, 1522) can be loaded and unloaded as required. Each time you
load a low-level driver, the driver first searches for cards that can
be driven. Next, the bus is scanned for each card that is found, and
then the internal data structures are set up so as to make it possible
to actually use the devices attached to the cards that the driver is
managing.
When you are through with a low-level driver, you can unload it. You
should keep in mind that usage counts are maintained based upon
mounted filesystems, open files, etc, so that if you are still using a
device that the driver is managing, the rmmod utility will tell you
that the device is still busy and refuse to unload the driver. When
the driver is unloaded, all of the associated data structures are also
freed so that the system state should be back to where it was before
the module was loaded. This means that the driver could be reloaded
at a later time if required.
4.3. Module support in the 1.3.N kernel
In the 1.3 series of kernels, the scsi code is completely modularized.
This means that you can start with a kernel that has no scsi support
whatsoever, and start loading modules and you will eventually end up
with complete support.
If you wish, you can compile some parts of the SCSI code into the
kernel and then load other parts later - it is all up to you how much
gets loaded at runtime and how much is linked directly into the
kernel.
If you are starting with a kernel that has no support whatsoever for
SCSI, then the first thing you will need to do is to load the scsi
core into the kernel - this is in a module called "scsi_mod". You
will not be able to load any other scsi modules until you have this
loaded into kernel memory. Since this does not contain any low-level
drivers, the act of loading this module will not scan any busses, nor
will it activate any drivers for scsi disks, tapes, etc. If you
answered 'Y' to the CONFIG_SCSI question when you built your kernel,
you will not need to load this module.
At this point you can add modules in more or less any order to achieve
the desired functionality. Usage counts are interlocks are used to
prevent unloading of any component which might still be in use, and
you will get a message from rmmod if a module is still busy.
The high level drivers are in modules named "sd_mod", "sr_mod", "st",
and "sg", for disk, cdrom, tape, and scsi generics support
respectively. When you load a high level driver, the device list for
all attached hosts is examined for devices which the high level driver
can drive, and these are automatically activated.
The use of modules with low level drivers were described in the
section of the ``modules under 1.2 kernels''. When a low-level driver
is loaded, the bus is scanned, and each device is examined by each of
the high level drivers to see if they recognize it as something that
they can drive - anything recognized is automatically attached and
activated.
5. Hosts
This section gives specific information about the various host
adapters that are supported in some way or another under linux.
5.1. Supported and Unsupported Hardware
Drivers in the distribution kernel :
Adaptec 152x, Adaptec 154x (DTC 329x boards usually work, but are
unsupported), Adaptec 174x, Adaptec 274x/284x (294x support requires a
newer version of the driver), BusLogic MultiMaster Host Adapters,
EATA-DMA and EATA-PIO protocol compilant boards (DPT PM2001, PM2011,
PM2012A, PM2012B, PM2021, PM2022, PM2024, PM2122, PM2124, PM2322,
PM2041, PM2042, PM2044, PM2142, PM2144, PM2322, PM3021, PM3122,
PM3222, PM3224, PM3334 some boards from NEC, AT&T, SNI, AST, Olivetti,
and Alphatronix), Future Domain 850, 885, 950, and other boards in
that series (but not the 840, 841, 880, and 881 boards unless you make
the appropriate patch), Future Domain 16x0 with TMC-1800, TMC-18C30,
or TMC-18C50 chips, NCR53c8xx,PAS16 SCSI ports, Seagate ST0x, Trantor
T128/T130/T228 boards, Ultrastor 14F, 24F, and 34F, and Western
Digital 7000.
MCA :
MCA boards which are compatible with a supported board (ie, Adaptec
1640 and BusLogic 640) will work.
Alpha drivers :
Many ALPHA drivers are available at
ftp://tsx-11.mit.edu/pub/linux/ALPHA/scsi
Drivers which will work with modifications
NCR53c8x0/7x0:
A NCR53c8xx driver has been developed, but currently will not work
with NCR53c700, NCR53c700-66, NCR53c710, and NCR53c720 chips. A list
of changes needed to make each of these chips work follows, as well
as a summary of the complexity.
NCR53c720 (trivial) - detection changes, initialization changes, change
fixup code to translate '810 register addresses to
'7xx mapping.
NCR53c710 (trivial) - detection changes, initialization changes,
of assembler, change fixup code to translate '810 register
addresses to '7xx mapping, change interrupt handlers to treat
IID interrupt from INTFLY instruction to emulate it.
NCR53c700, NCR53c700-66 (very messy) - detection changes,
initialization changes, modification of NCR code to not use DSA,
modification of Linux code to handle context switches.
SCSI hosts that will not work :
All parallel->SCSI adapters, Rancho SCSI boards, and Grass Roots SCSI
boards. BusLogic FlashPoint boards, such as the BT-930/932/950, are
currently unsupported.
SCSI hosts that will NEVER work :
Non Adaptec compatible, non NCR53c8xx DTC boards (including the 3270
and 3280).
CMD SCSI boards.
Acquiring programming information requires a non-disclosure agreement
with DTC/CMD. This means that it would be impossible to distribute a
Linux driver if one were written, since complying with the NDA would
mean distributing no source, in violation of the GPL, and complying
with the GPL would mean distributing source, in violation of the NDA.
If you want to run Linux on some other unsupported piece of hardware,
your options are to either write a driver yourself (Eric Youngdale and
I are usually willing to answer technical questions concerning the
Linux SCSI drivers) or to commission a driver (Normal consulting rates
mean that this will not be a viable option for personal use).
5.1.1. Multiple host adapters
With some host adapters (see ``Buyers' Guide : Feature Comparison''),
you can use multiple host adapters of the same type in the same
system. With multiple adapters of the same type in the same system,
generally the one at the lowest address will be scsi0, the one at the
next address scsi1, etc.
In all cases, it is possible to use multiple host adapters of
different types, provided that none of their addresses conflict. SCSI
controllers are scanned in the order specified in the
builtin_scsi_hosts[] array in drivers/scsi/hosts.c, with the order
currently being
BusLogic, Ultrastor 14/34F, Ultrastor 14F,, Adaptec
151x/152x, Adaptec 154x, Adaptec 174x, AIC7XXX, AM53C974,
Future Domain 16x0, Always IN2000, Generic NCR5380, QLOGIC,
PAS16, Seagate, Trantor T128/T130, NCR53c8xx, EATA-DMA,
WD7000, debugging driver.
In most cases (ie, you aren't trying to use both BusLogic and Adaptec
drivers), this can be changed to suit your needs (ie, keeping the same
devices when new SCSI devices are added to the system on a new
controller) by moving the individual entries.
5.2. Common Problems
5.2.1. SCSI timeouts
Make sure interrupts are enabled correctly, and there are no IRQ, DMA,
or address conflicts with other boards.
5.2.2. Failure of autoprobe routines on boards that rely on BIOS for
autoprobe.
If your SCSI adapter is one of the following :
Adaptec 152x, Adaptec 151x, Adaptec AIC-6260, Adaptec
AIC-6360, Future Domain 1680, Future Domain TMC-950, Future
Domain TMC-8xx, Trantor T128, Trantor T128F, Trantor T228F,
Seagate ST01, Seagate ST02, or a Western Digital 7000
and it is not detected on bootup, ie you get a
scsi : 0 hosts
message or a
scsi%d : type
message is not printed for each supported SCSI adapter installed in
the system, you may have a problem with the autoprobe routine not
knowing about your board.
Autodetection will fail for drivers using the BIOS for autodetection
if the BIOS is disabled. Double check that your BIOS is enabled, and
not conflicting with any other peripherial BIOSes.
Autodetection will also fail if the board's "signature" and/or BIOS
address don't match known ones.
If the BIOS is installed, please use DOS and DEBUG to find a signature
that will detect your board -
Ie, if your board lives at 0xc8000, under DOS do
debug
d c800:0
q
and send a message to the SCSI channel of the mailing list with the
ASCII message, with the length and offset from the base address (ie,
0xc8000). Note that the EXACT text is required, and you should
provide both the hex and ASCII portions of the text.
If no BIOS is installed, and you are using an Adaptec 152x, Trantor
T128, or Seagate driver, you can use command line or compile time
overrides to force detection.
Please consult the appropriate subsection for your SCSI board as well
as section ``General Flakiness''.
5.2.3. Failure of boards using memory mapped I/O
(This include the Trantor T128 and Seagate boards, but not the
Adaptec, Generic NCR5380, PAS16, and Ultrastor drivers)
This is often caused when the memory mapped I/O ports are incorrectly
cached. You should have the board's address space marked as
uncachable in the XCMOS settings.
If this is not possible, you will have to disable cache entirely.
If you have manually specified the address of the board, remember that
Linux needs the actual address of the board, and not the 16 byte
segment the documentation may refer to.
Ie, 0xc8000 would be correct, 0xc800 would not work and could cause
memory corruption.
5.2.4. kernel panic : cannot mount root device" when booting an ALPHA
driver boot floppy
You'll need to edit the binary image of the kernel (before or after
writing it out to disk), and modify a few two byte fields (little
endian) to guarantee that it will work on your system.
1. default swap device at offset 502, this should be set to 0x00 0x00
2. ram disk size at offset 504, this should be set to the size of the
boot floppy in K - ie, 5.25" = 1200, 3.5" = 1440.
This means the bytes are
3.5" : 0xA0 0x05
5.25" : 0xB0 0x04
3. root device offset at 508, this should be 0x00 0x00, ie the boot
device.
dd or rawrite the file to a disk. Insert the disk in the first floppy
drive, wait until it prompts you to insert the root disk, and insert
the root floppy from your distribution.
5.2.5. Installing a device driver not included with the distribution
kernel
You need to start with the version of the kernel used by the driver
author. This revision may be alluded to in the documentation included
with the driver.
Various recent kernel revisions can be found at
nic.funet.fi:/pub/OS/Linux/PEOPLE/Linus
as linux-version.tar.gz
They are also mirrored at tsx-11.mit.edu and various other sites.
cd to /usr/src.
Remove your old Linux sources, if you want to keep a backup copy of
them
mv linux linux-old
Untar the archive
gunzip < linux-0.99.12.tar.gz | tar xvfp -
Apply the patches. The patches will be relative to some directory in
the filesystem. By examining the output file lines in the patch file
(grep for ^---), you can tell where this is - ie patches with these
lines
--- ./kernel/blk_drv/scsi/Makefile
--- ./config.in Wed Sep 1 16:19:33 1993
would have the files relative to /usr/src/linux.
Untar the driver sources at an appropriate place - you can type
tar tfv patches.tar
to get a listing, and move files as necessary (The SCSI driver files
should live in /usr/src/linux/kernel/drivers/scsi)
Either cd to the directory they are relative to and type
patch -p0 < patch_file
or tell patch to strip off leading path components. Ie, if the files
started with
--- linux-new/kernel/blk_drv/scsi/Makefile
and you wanted to apply them while in /usr/src/linux, you could cd to
/usr/src/linux and type
patch -p1 < patches
to strip off the "linux-new" component.
After you have applied the patches, look for any patch rejects, which
will be the name of the rejected file with a # suffix appended.
find /usr/src/linux/ -name "*#" -print
If any of these exist, look at them. In some cases, the differences
will be in RCS identifiers and will be harmless, in other cases,
you'll have to manually apply important parts. Documentation on diff
files and patch is beyond the scope of this document.
See also ``Configuring and building the kernel''.
5.2.6. Installing a driver that has no patches
In some cases, a driver author may not offer patches with the .c and
.h files which comprise his driver, or the patches may be against an
older revision of the kernel and not go in cleanly.
1. Copy the .c and .h files into /usr/src/linux/drivers/scsi
2. Add the configuration option
Edit /usr/src/linux/config.in, and add a line in the
*
* SCSI low-level drivers
*
section, add a boolean configuration variable for your driver. Ie,
bool 'Always IN2000 SCSI support' CONFIG_SCSI_IN2000 y
3. Add the makefile entries
Edit /usr/src/linux/drivers/scsi/Makefile, and add an entry like
ifdef CONFIG_SCSI_IN2000
SCSI_OBS := $(SCSI_OBJS) in2000.o
SCSI_SRCS := $(SCSI_SRCS) in2000.c
endif
before the
scsi.a: $(SCSI_OBJS)
line in the makefile, where the .c file is the .c file you copied in,
and the .o file is the basename of the .c file with a .o suffixed.
4. Add the entry points
Edit /usr/src/linux/drivers/scsi/hosts.c, and add a #include for
the header file, conditional on the CONFIG_SCSI preprocessor define
you added to the configuration file. Ie, after
#ifdef CONFIG_SCSI_GENERIC_NCR5380
#include "g_NCR5380.h"
#endif
you might add
#ifdef CONFIG_SCSI_IN2000
#include "in2000.h"
#endif
You will also need to add the Scsi_Host_Template entry into the
scsi_hosts[] array. Take a look into the .h file, and you should find
a #define that looks something like this :
#define IN2000 {"Always IN2000", in2000_detect, \
in2000_info, in2000_command, \
in2000_queuecommand, \
in2000_abort, \
in2000_reset, \
NULL, \
in2000_biosparam, \
1, 7, IN2000_SG, 1, 0, 0}
the name of the preprocessor define, and add it into the scsi_hosts[]
array, conditional on definition of the preprocessor symbol you used
in the configuration file.
Ie, after
#ifdef CONFIG_SCSI_GENERIC_NCR5380
GENERIC_NCR5380,
#endif
you might add
#ifdef CONFIG_SCSI_IN2000
IN2000,
#endif
See also ``Configuring and building the kernel''.
5.2.7. Failure of a PCI board in a Compaq System
A number of Compaq systems map the 32-bit BIOS extensions used to
probe for PCI devices into memory which is inaccessible to the Linux
kernel due to the memory layout. If Linux is unable to detect a
supported PCI SCSI board, and the kernel tells you something like
pcibios_init: entry in high memory, unable to access
Grab
ftp://ftp.compaq.com/pub/softpaq/Software-Solutions/sp0921.zip
which is a self-extracting archive of a program which will relocate
the BIOS32 code.
5.2.8. A SCSI system with PCI boards hangs after the %d Hosts message
Some PCI systems have broken BIOSes which disable interrupts and fail
to reenable them before returning control to the caller. The
following patch fixes this
--- bios32.c.orig Mon Nov 13 22:35:31 1995
+++ bios32.c Thu Jan 18 00:15:09 1996
@@ -56,6 +56,7 @@
#include <linux/pci.h>
#include <asm/segment.h>
+#include <asm/system.h>
#define PCIBIOS_PCI_FUNCTION_ID 0xb1XX
#define PCIBIOS_PCI_BIOS_PRESENT 0xb101
@@ -125,7 +126,9 @@
unsigned long address; /* %ebx */
unsigned long length; /* %ecx */
unsigned long entry; /* %edx */
+ unsigned long flags;
+ save_flags(flags);
__asm__("lcall (%%edi)"
: "=a" (return_code),
"=b" (address),
@@ -134,6 +137,7 @@
: "0" (service),
"1" (0),
"D" (&bios32_indirect));
+ restore_flags(flags);
switch (return_code) {
case 0:
@@ -161,11 +165,13 @@
unsigned char present_status;
unsigned char major_revision;
unsigned char minor_revision;
+ unsigned long flags;
int pack;
if ((pcibios_entry = bios32_service(PCI_SERVICE))) {
pci_indirect.address = pcibios_entry;
+ save_flags(flags);
__asm__("lcall (%%edi)\n\t"
"jc 1f\n\t"
"xor %%ah, %%ah\n"
@@ -176,6 +182,7 @@
: "1" (PCIBIOS_PCI_BIOS_PRESENT),
"D" (&pci_indirect)
: "bx", "cx");
+ restore_flags(flags);
present_status = (pack >> 16) & 0xff;
major_revision = (pack >> 8) & 0xff;
@@ -210,7 +217,9 @@
{
unsigned long bx;
unsigned long ret;
+ unsigned long flags;
+ save_flags(flags);
__asm__ ("lcall (%%edi)\n\t"
"jc 1f\n\t"
"xor %%ah, %%ah\n"
@@ -221,6 +230,7 @@
"c" (class_code),
"S" ((int) index),
"D" (&pci_indirect));
+ restore_flags(flags);
*bus = (bx >> 8) & 0xff;
*device_fn = bx & 0xff;
return (int) (ret & 0xff00) >> 8;
@@ -232,7 +242,9 @@
{
unsigned short bx;
unsigned short ret;
+ unsigned long flags;
+ save_flags(flags);
__asm__("lcall (%%edi)\n\t"
"jc 1f\n\t"
"xor %%ah, %%ah\n"
@@ -244,6 +256,7 @@
"d" (vendor),
"S" ((int) index),
"D" (&pci_indirect));
+ restore_flags(flags);
*bus = (bx >> 8) & 0xff;
*device_fn = bx & 0xff;
return (int) (ret & 0xff00) >> 8;
@@ -254,7 +267,9 @@
{
unsigned long ret;
unsigned long bx = (bus << 8) | device_fn;
+ unsigned long flags;
+ save_flags (flags);
__asm__("lcall (%%esi)\n\t"
"jc 1f\n\t"
"xor %%ah, %%ah\n"
@@ -273,7 +288,9 @@
{
unsigned long ret;
unsigned long bx = (bus << 8) | device_fn;
+ unsigned long flags;
+ save_flags(flags);
__asm__("lcall (%%esi)\n\t"
"jc 1f\n\t"
"xor %%ah, %%ah\n"
@@ -292,7 +309,9 @@
{
unsigned long ret;
unsigned long bx = (bus << 8) | device_fn;
+ unsigned long flags;
+ save_flags(flags);
__asm__("lcall (%%esi)\n\t"
"jc 1f\n\t"
"xor %%ah, %%ah\n"
@@ -303,6 +322,7 @@
"b" (bx),
"D" ((long) where),
"S" (&pci_indirect));
+ restore_flags(flags);
return (int) (ret & 0xff00) >> 8;
}
@@ -311,7 +331,9 @@
{
unsigned long ret;
unsigned long bx = (bus << 8) | device_fn;
+ unsigned long flags;
+ save_flags(flags);
__asm__("lcall (%%esi)\n\t"
"jc 1f\n\t"
"xor %%ah, %%ah\n"
@@ -322,6 +344,7 @@
"b" (bx),
"D" ((long) where),
"S" (&pci_indirect));
+ restore_flags(flags);
return (int) (ret & 0xff00) >> 8;
}
@@ -330,7 +353,9 @@
{
unsigned long ret;
unsigned long bx = (bus << 8) | device_fn;
+ unsigned long flags;
+ save_flags(flags);
__asm__("lcall (%%esi)\n\t"
"jc 1f\n\t"
"xor %%ah, %%ah\n"
@@ -341,6 +366,7 @@
"b" (bx),
"D" ((long) where),
"S" (&pci_indirect));
+ restore_flags(flags);
return (int) (ret & 0xff00) >> 8;
}
@@ -349,7 +375,9 @@
{
unsigned long ret;
unsigned long bx = (bus << 8) | device_fn;
+ unsigned long flags;
+ save_flags(flags);
__asm__("lcall (%%esi)\n\t"
"jc 1f\n\t"
"xor %%ah, %%ah\n"
@@ -360,6 +388,7 @@
"b" (bx),
"D" ((long) where),
"S" (&pci_indirect));
+ restore_flags(flags);
return (int) (ret & 0xff00) >> 8;
}
5.3. Adaptec 152x, 151x, 1505, 282x, Sound Blaster 16 SCSI, SCSI Pro,
Gigabyte, and other AIC 6260/6360 based products (Standard)
Supported Configurations :
BIOS addresses : 0xd8000, 0xdc000, 0xd0000, 0xd4000, 0xc8000, 0xcc000, 0xe0000,
0xe4000.
Ports : 0x140, 0x340
IRQs : 9, 10, 11, 12
DMA : not used
IO : port mapped
Autoprobe :
Works with many boards with an installed BIOS. All
other boards, including the Adaptec 1510, and Sound Blaster16 SCSI
must use a kernel command line or compile time override.
Autoprobe Override :
Compile time :
Define PORTBASE, IRQ, SCSI_ID, RECONNECT, PARITY as appropriate, see Defines
kernel command line :
aha152x=<PORTBASE>[,<IRQ>[,<SCSI-ID>[,<RECONNECT>[,<PARITY>]]]]
SCSI-ID is the SCSI ID of the HOST adapter, not of any devices you
have installed on it. Usually, this should be 7.
To force detection at 0x340, IRQ 11, at SCSI-ID 7, allowing
disconnect/reconnect, you would use the following command line option
:
aha152x=0x340,11,7,1
Antiquity Problems, fix by upgrading :
1. The driver fails with VLB boards. There was a timing problem in
kernels older than revision 1.0.5.
Defines :
AUTOCONF : use configuration the controller reports (only 152x)
IRQ : override interrupt channel (9,10,11 or 12) (default 11)
SCSI_ID : override SCSI ID of AIC-6260 (0-7) (default 7)
RECONNECT : override target disconnect/reselect (set to non-zero to
allow, zero to disable)
DONT_SNARF : Don't register ports (pl12 and below)
SKIP_BIOSTEST : Don't test for BIOS signature (AHA-1510 or disabled BIOS)
PORTBASE : Force port base. Don't try to probe
5.4. Adaptec 154x, AMI FastDisk VLB, DTC 329x (Standard)
Supported Configurations :
Ports : 0x330 and 0x334
IRQs : 9, 10, 11, 12, 14, 15
DMA channels : 5, 6, 7
IO : port mapped, bus master
Autoprobe :
will detect boards at 0x330 and 0x334 only.
Autoprobe override :
aha1542=<PORTBASE>[,<BUSON>,<BUSOFF>[,<DMASPEED>]]
Notes:
1. BusLogic makes a series of boards that are software compatible with
the Adaptec 1542, and these come in ISA, VLB, EISA, and PCI
flavors.
2. No-suffix boards, and early 'A' suffix boards do not support
scatter/gather, and thus don't work. However, they can be made to
work for some definition of the word works if AHA1542_SCATTER is
changed to 0 in drivers/scsi/aha1542.h.
Antiquity Problems, fix by upgrading :
1. Linux kernel revisions prior to .99.10 don't support the 'C'
revision.
2. Linux kernel revisions prior to .99.14k don't support the 'C'
revision options for
� BIOS support for the extended mapping for disks > 1G
� BIOS support for > 2 drives
� BIOS support for autoscanning the SCSI bus
3. Linux kernel revisions prior to .99.15e don't support the 'C' with
the BIOS support for > 2 drives turned on and the BIOS support for
the extended mapping for disks > 1G turned off.
4. Linux kernel revisions prior to .99.14u don't support the 'CF'
revisions of the board.
5. Linux kernel revisions prior to 1.0.5 have a race condition when
multiple devices are accessed at the same time.
Common problems :
1. There are unexpected errors with a 154xC or 154xCF board,
Early examples of the 154xC boards have a high slew rate on one of
the SCSI signals, which results in signal reflections when cables
with the wrong impedance are used.
Newer boards aren't much better, and also suffer from extreme
cabling and termination sensitivity.
See also Common Problems ``#2'' and ``#3'' and ``Common Problems'',
``General Flakiness''.
2. There are unexpected errors with a 154xC or 154x with both internal
and external devices connected.
This is probably a termination problem. In order to use the
software option to disable host adapter termination, you must turn
switch 1 off.
See also Common Problems ``#1'' and ``#3'' and ``Common Problems'',
``General Flakiness''.
3. The SCSI subsystem locks up completely.
There are cases where the lockups seem to occur when multiple
devices are in use at the same time. In this case, you can try
contacting the manufacturer of the devices and see if firmware
upgrades are available which would correct the problem. As a last
resort, you can go into aha1542.h and change AHA1542_MAILBOX to 1.
This will effectively limit you to one outstanding command on the
scsi bus at one time, and may help the situation. If you have tape
drives or slow cdrom drives on the bus, this might not be a
practical solution.
See also Common Problems ``#1'' and ``#2'' and ``Common Problems'',
``Common Problems : SCSI System Lockups''.
4. An "Interrupt received, but no mail" message is printed on bootup
and your SCSI devices are not detected.
Disable the BIOS options to support the extended mapping for disks
> 1G, support for > 2 drives, and for autoscanning the bus. Or,
upgrade to Linux .99.14k or newer.
5. If infinite timeout errors occur on 'C' revision boards, you may
need to go into the Adaptec setup program and enable synchronous
negotiation.
6. Linux 1.2.x gives the message
Unable to determine Adaptec DMA priority. Disabling board.
This is due to a conflict on some systems with the obsolete
BusLogic driver. Either rebuild your kernel without it, or give
the BusLogic driver a command line option telling it to look
somewhere other than where your controller is configured. Ie, if
you have an Adaptec board at port 0x334, and nothing at 0x330, use
a command line option like
buslogic=0x330
7. The system locks up with simultaneous access to multiple devices on
a 1542C or 1540C and disconnection enabled
Some Adaptec firmware revisions have bugs. Upgrading to BIOS v2.11
purportedly fixes these problems.
5.5. Adaptec 174x
Supported Configurations :
Slots : 1-8
Ports : EISA board, not applicable
IRQs : 9, 10, 11, 12, 14, 15
DMA Channels : EISA board, not applicable
IO : port mapped, bus master
Autoprobe :
works with all supported configurations
Autoprobe override :
none
Note:
1. This board has been discontinued by Adaptec.
Common Problems :
1. If the Adaptec 1740 driver prints the message "aha1740: Board
detected, but EBCNTRL = %x, so disabled it."
your board was disabled because it was not running in enhanced
mode. Boards running in standard 1542 mode are not supported.
5.6. Adaptec 274x, 284x (Standard) 294x (ALPHA)
A newer version which also supports the Adaptec 294x boards is
available at
ftp://ftp.ims.com/pub/Linux/aic7xxx
Supported Configurations :
274x 284x 294x
EISA Slots : 1-12 N/A N/A
Ports : N/A ALL ALL
IRQs : ALL ALL ALL
DMA Channels : N/A ALL N/A
IO : port mapped, bus master
Autoprobe Override :
kernel command line :
aha274x=extended
(to force extended mapping)
Notes:
1. BIOS MUST be enabled
2. The B channel on 2742AT boards is ignored.
3. CONFIG_PCI must be set if you are using a PCI board.
5.7. Always IN2000 (Standard)
Supported Configurations :
Ports : 0x100, 0x110, 0x200, 0x220
IRQs : 10, 11, 14, 15
DMA : not used
IO : port mapped
Autoprobe :
BIOS not required
Autoprobe override :
none
Common Problems :
1. There are known problems in systems with IDE drives and with
swapping.
5.8. BusLogic MultiMaster Host Adapters
(this section Copyright 1995 by Leonard N. Zubkoff
<lnz@dandelion.com>) (see README.BusLogic for more complete BusLogic
driver documentation)
BusLogic MultiMaster SCSI Driver for Linux
Version 1.2.2 for Linux 1.2.13
Version 1.3.2 for Linux 1.3.88
ftp://ftp.dandelion.com/BusLogic-1.2.2.tar.gz
ftp://ftp.dandelion.com/BusLogic-1.3.2.tar.gz
16 April 1996
Leonard N. Zubkoff
Dandelion Digital
lnz@dandelion.com
BusLogic, Inc. designs and manufactures a variety of high performance SCSI host
adapters which share a common programming interface across a diverse collection
of bus architectures by virtue of their MultiMaster ASIC technology. This
driver supports all present BusLogic MultiMaster Host Adapters, and should
support any future MultiMaster designs with little or no modification. Host
adapters based on the new FlashPoint architecture are not supported by this
driver; consult the README.FlashPoint file for information about a program to
upgrade Linux users from the unsupported FlashPoint LT to the supported BT-948.
My primary goals in writing this completely new BusLogic driver for Linux are
to achieve the full performance that BusLogic SCSI Host Adapters and modern
SCSI peripherals are capable of, and to provide a highly robust driver that can
be depended upon for high performance mission critical applications. All of
the major performance and error recovery features can be configured from the
Linux kernel command line, allowing individual installations to tune driver
performance and error recovery to their particular needs.
BusLogic has been an excellent company to work with and I highly recommend
their products to the Linux community. In November 1995, I was offered the
opportunity to become a beta test site for their latest MultiMaster product,
the BT-948 PCI Ultra SCSI Host Adapter, and then again for the BT-958 PCI Wide
Ultra SCSI Host Adapter in January 1996. This was mutually beneficial since
BusLogic received a degree and kind of testing that their own testing group
cannot readily achieve, and the Linux community has available high performance
host adapters that have been well tested with Linux even before being brought
to market. This relationship has also given me the opportunity to interact
directly with their technical staff, to understand more about the internal
workings of their products, and in turn to educate them about the needs and
potential of the Linux community. Their interest and support is greatly
appreciated.
Unlike some other vendors, if you contact BusLogic Technical Support with a
problem and are running Linux, they will not tell you that your use of their
products is unsupported. Their latest product marketing literature even states
"BusLogic SCSI host adapters are compatible with all major operating systems
including: ... Linux ...".
BusLogic, Inc. is located at 4151 Burton Drive, Santa Clara, California, 95054,
USA and can be reached by Voice at 408/492-9090 or by FAX at 408/492-1542.
BusLogic maintains a World Wide Web site at http://www.buslogic.com, an
anonymous FTP site at ftp.buslogic.com, and a BBS at 408/492-1984. BusLogic
Technical Support can be reached by electronic mail at techsup@buslogic.com, by
Voice at 408/654-0760, or by FAX at 408/492-1542. Contact information for
offices in Europe and Japan is available on the Web site.
SUPPORTED HOST ADAPTERS
The following list comprises the supported BusLogic SCSI Host Adapters as of
the date of this document. It is recommended that anyone purchasing a BusLogic
Host Adapter not in the following table contact the author beforehand to verify
that it is or will be supported.
"W" Series Host Adapters:
BT-948 PCI Ultra Fast Single-ended SCSI-2
BT-958 PCI Ultra Wide Single-ended SCSI-2
BT-958D PCI Ultra Wide Differential SCSI-2
"C" Series Host Adapters:
BT-946C PCI Fast Single-ended SCSI-2
BT-956C PCI Fast Wide Single-ended SCSI-2
BT-956CD PCI Fast Wide Differential SCSI-2
BT-445C VLB Fast Single-ended SCSI-2
BT-747C EISA Fast Single-ended SCSI-2
BT-757C EISA Fast Wide Single-ended SCSI-2
BT-757CD EISA Fast Wide Differential SCSI-2
BT-545C ISA Fast Single-ended SCSI-2
BT-540CF ISA Fast Single-ended SCSI-2
"S" Series Host Adapters:
BT-445S VLB Fast Single-ended SCSI-2
BT-747S EISA Fast Single-ended SCSI-2
BT-747D EISA Fast Differential SCSI-2
BT-757S EISA Fast Wide Single-ended SCSI-2
BT-757D EISA Fast Wide Differential SCSI-2
BT-545S ISA Fast Single-ended SCSI-2
BT-542D ISA Fast Differential SCSI-2
BT-742A EISA Single-ended SCSI-2 (742A revision H)
BT-542B ISA Single-ended SCSI-2 (542B revision H)
"A" Series Host Adapters:
BT-742A EISA Single-ended SCSI-2 (742A revisions A - G)
BT-542B ISA Single-ended SCSI-2 (542B revisions A - G)
AMI FastDisk Host Adapters that are true BusLogic clones are supported by this
driver.
BT-948/958/958D INSTALLATION NOTES
The BT-948/958/958D PCI Ultra SCSI Host Adapters have some features which may
require attention in some circumstances when installing Linux.
o PCI I/O Port Assignments
When configured to factory default settings, the BT-948/958/958D will only
recognize the PCI I/O port assignments made by the motherboard's PCI BIOS.
The BT-948/958/958D will not respond to any of the ISA compatible I/O ports
that previous BusLogic SCSI Host Adapters respond to. This driver supports
the PCI I/O port assignments, so this is the preferred configuration.
However, if the obsolete BusLogic driver must be used for any reason, such as
a Linux distribution that does not yet use this driver in its boot kernel,
BusLogic has provided an AutoSCSI configuration option to enable a legacy ISA
compatible I/O port.
To enable this backward compatibility option, invoke the AutoSCSI utility via
Ctrl-B at system startup and select "Adapter Configuration", "View/Modify
Configuration", and then change the "ISA Compatible Port" setting from
"Disable" to "Primary" or "Alternate". Once this driver has been installed,
the "ISA Compatible Port" option should be set back to "Disable" to avoid
possible future I/O port conflicts. The older BT-946C/956C/956CD also have
this configuration option, but the factory default setting is "Primary".
o PCI Slot Scanning Order
In systems with multiple BusLogic PCI Host Adapters, the order in which the
PCI slots are scanned may appear reversed with the BT-948/958/958D as
compared to the BT-946C/956C/956CD. For booting from a SCSI disk to work
correctly, it is necessary that the host adapter's BIOS and the kernel agree
on which disk is the boot device, which requires that they recognize the PCI
host adapters in the same order. The motherboard's PCI BIOS provides a
standard way of enumerating the PCI host adapters, which is used by the Linux
kernel. Some PCI BIOS implementations enumerate the PCI slots in order of
increasing bus number and device number, while others do so in the opposite
direction.
Unfortunately, Microsoft decided that Windows 95 would always enumerate the
PCI slots in order of increasing bus number and device number regardless of
the PCI BIOS enumeration, and requires that their scheme be supported by the
host adapter's BIOS to receive Windows 95 certification. Therefore, the
factory default settings of the BT-948/958/958D enumerate the host adapters
by increasing bus number and device number. To disable this feature, invoke
the AutoSCSI utility via Ctrl-B at system startup and select "Adapter
Configuration", "View/Modify Configuration", press Ctrl-F10, and then change
the "Use Bus And Device # For PCI Scanning Seq." option to OFF.
This driver will interrogate the setting of the PCI Scanning Sequence option
so as to recognize the host adapters in the same order as they are enumerated
by the host adapter's BIOS.
BUSLOGIC ANNOUNCEMENTS MAILING LIST
The BusLogic Announcements Mailing List provides a forum for informing Linux
users of new driver releases and other announcements regarding Linux support
for BusLogic SCSI Host Adapters. To join the mailing list, send a message to
"BusLogic-announce-request@dandelion.com" with the line "subscribe" in the
message body.
5.9. BusLogic FlashPoint Host Adapters
(this section Copyright 1995 by Leonard N. Zubkoff
<lnz@dandelion.com>)
There are no Linux drivers for the FlashPoint LT/DL/LW (BT-930/932/950)
available and it is not clear when or if there will be any. The FlashPoint
boards have a different architecture from the MultiMaster boards and have no
onboard CPU, only a SCSI sequencer engine. They are positioned as a desktop
workstation product, and are not particularly well suited for a high
performance multitasking operating system like Linux.
The MultiMaster BT-948/958 have an onboard CPU and the mailbox programming
interface allows for parallelism and pipelining between the host operating
system and the host adapter, whereas the FlashPoint boards require frequent
host CPU intervention. As interrupt latencies rise in a loaded multitasking
system, the BT-948/958 should maintain excellent performance whereas the
FlashPoint's performance will likely drop quite rapidly. Furthermore, the
firmware on the BT-948/958 contains the low level knowledge for proper
interaction with the SCSI bus, whereas with a sequencer engine the Linux driver
must contain some or all of this information, and it often takes quite a long
time to get all the kinks worked out. Given the relatively small difference in
the street price of these products, the BT-948 or BT-958 is clearly the better
choice for Linux.
<begin quotation>
ANNOUNCEMENT
BusLogic FlashPoint/BT-948 Upgrade Program
1 February 1996
Ever since its introduction last October, the BusLogic FlashPoint LT has
been problematic for members of the Linux community, in that no Linux
drivers have been available for this new Ultra SCSI product. Despite it's
officially being positioned as a desktop workstation product, and not being
particularly well suited for a high performance multitasking operating
system like Linux, the FlashPoint LT has been touted by computer system
vendors as the latest thing, and has been sold even on many of their high
end systems, to the exclusion of the older MultiMaster products. This has
caused grief for many people who inadvertently purchased a system expecting
that all BusLogic SCSI Host Adapters were supported by Linux, only to
discover that the FlashPoint was not supported and would not be for quite
some time, if ever.
After this problem was identified, BusLogic contacted its major OEM
customers to make sure the BT-946C/956C MultiMaster cards would still be
made available, and that Linux users who mistakenly ordered systems with
the FlashPoint would be able to upgrade to the BT-946C. While this helped
many purchasers of new systems, it was only a partial solution to the
overall problem of FlashPoint support for Linux users. It did nothing to
assist the people who initially purchased a FlashPoint for a supported
operating system and then later decided to run Linux, or those who had
ended up with a FlashPoint LT, believing it was supported, and were unable
to return it.
In the middle of December, I asked to meet with BusLogic's senior
management to discuss the issues related to Linux and free software support
for the FlashPoint. Rumors of varying accuracy had been circulating
publicly about BusLogic's attitude toward the Linux community, and I felt
it was best that these issues be addressed directly. I sent an email
message after 11pm one evening, and the meeting took place the next
afternoon. Unfortunately, corporate wheels sometimes grind slowly,
especially when a company is being acquired, and so it's taken until now
before the details were completely determined and a public statement could
be made.
BusLogic is not prepared at this time to release the information necessary
for third parties to write drivers for the FlashPoint. The only existing
FlashPoint drivers have been written directly by BusLogic Engineering, and
there is no FlashPoint documentation sufficiently detailed to allow outside
developers to write a driver without substantial assistance. While there
are people at BusLogic who would rather not release the details of the
FlashPoint architecture at all, that debate has not yet been settled either
way. In any event, even if documentation were available today it would
take quite a while for a usable driver to be written, especially since I'm
not convinced that the effort required would be worthwhile.
However, BusLogic does remain committed to providing a high performance
SCSI solution for the Linux community, and does not want to see anyone left
unable to run Linux because they have a Flashpoint LT. Therefore, BusLogic
has put in place a direct upgrade program to allow any Linux user worldwide
to trade in their FlashPoint LT for the new BT-948 MultiMaster PCI Ultra
SCSI Host Adapter. The BT-948 is the Ultra SCSI successor to the BT-946C
and has all the best features of both the BT-946C and FlashPoint LT,
including smart termination and a flash PROM for easy firmware updates, and
is of course compatible with the present Linux driver. The price for this
upgrade has been set at US $45, and the upgrade program will be
administered through BusLogic Technical Support, which can be reached by
electronic mail at techsup@BusLogic.com, by Voice at +1 408 654-0760, or by
FAX at +1 408 492-1542.
I was a beta test site for the BT-948 and versions 1.2.1 and 1.3.1 of my
BusLogic driver already include latent support for the BT-948. Additional
cosmetic support for the Ultra SCSI MultiMaster cards will be added in a
subsequent release. As a result of this cooperative testing process,
several firmware bugs were found and corrected (make sure you have firmware
version 5.05R or later). My heavily loaded Linux test system provided an
ideal environment for testing error recovery processes that are much more
rarely exercised in production systems, but are crucial to overall system
stability. It was especially convenient being able to work directly with
their firmware engineer in demonstrating the problems under control of the
firmware debugging environment; things sure have come a long way since the
last time I worked on firmware for an embedded system. I am presently
working on some performance testing and expect to have some data to report
in the not too distant future.
BusLogic asked me to send this announcement since a large percentage of the
questions regarding support for the FlashPoint have either been sent to me
directly via email, or have appeared in the Linux newsgroups in which I
participate. To summarize, BusLogic is offering Linux users an upgrade
from the unsupported FlashPoint LT (BT-930) to the supported BT-948 for US
$45. Contact BusLogic Technical Support at techsup@BusLogic.com or +1 408
654-0760 to take advantage of their offer.
Leonard N. Zubkoff
lnz@dandelion.com
<end quotation>
5.10. EATA: DPT SmartCache, SmartCache Plus, SmartCache III, Smart�
Cache IV and SmartRAID (Standard)
Supported boards: all, that support the EATA-DMA protocol.
Among them are:
DPT Smartcache (Plus) family:
PM2011 ISA Fast Single-ended SCSI-2
PM2012B EISA Fast Single-ended SCSI-2
DPT Smartcache III family:
PM2021 ISA Fast Single-ended SCSI-2
PM2021W ISA Wide Single-ended SCSI-2
PM2022 EISA Fast Single-ended SCSI-2
PM2022W EISA Wide Single-ended SCSI-2
PM2024 PCI Fast Single-ended SCSI-2
PM2024W PCI Wide Single-ended SCSI-2
PM2122 EISA Fast Single-ended SCSI-2
PM2122W EISA Wide Single-ended SCSI-2
PM2124 PCI Fast Single-ended SCSI-2
PM2124W PCI Wide Single-ended SCSI-2
PM2322 EISA Fast Single-ended SCSI-2
PM2322W EISA Wide Single-ended SCSI-2
DPT Smartcache VI family:
PM2041W ISA Wide Single-ended SCSI-2
PM2041UW ISA Ultra Wide Single-ended SCSI-2
PM2042W EISA Wide Single-ended SCSI-2
PM2042UW EISA Ultra Wide Single-ended SCSI-2
PM2044W PCI Wide Single-ended SCSI-2
PM2044UW PCI Ultra Wide Single-ended SCSI-2
PM2142W EISA Wide Single-ended SCSI-2
PM2142UW EISA Ultra Wide Single-ended SCSI-2
PM2144W PCI Wide Single-ended SCSI-2
PM2144UW PCI Ultra Wide Single-ended SCSI-2
PM2322W EISA Wide Single-ended SCSI-2
PM2322UW EISA Ultra Wide Single-ended SCSI-2
DPT SmartRAID family:
PM3021 ISA Fast Single-ended SCSI-2
PM3021W ISA Wide Single-ended SCSI-2
PM3122 EISA Fast Single-ended SCSI-2
PM3122W EISA Wide Single-ended SCSI-2
PM3222 EISA Fast Single-ended SCSI-2
PM3222W EISA Wide Single-ended SCSI-2
PM3224 PCI Fast Single-ended SCSI-2
PM3224W PCI Wide Single-ended SCSI-2
PM3334W PCI Wide Single-ended SCSI-2
PM3334UW PCI Ultra Wide Single-ended SCSI-2
also the differential versions of the above controllers.
and some controllers from:
NEC, AT&T, SNI, AST, Olivetti, Alphatronix.
Supported Configurations :
Slots : ALL
Ports : ALL
IRQs : ALL level & edge triggered
DMA Channels : ISA ALL, EISA/PCI not applicable
IO : port mapped, bus master
SCSI Channels : ALL
Autoprobe :
works with all supported configurations
The latest version of the EATA-DMA driver is available on:
ftp.i-Connect.Net:/pub/Local/EATA/
Mailinglist: The EATA Mailing List provides a forum to Linux users of
the EATA-DMA and EATA-PIO driver for discussions and announcements of
new releases and other announcements. To join the mailing list, send
a message to "linux-eata-request@i-connect.net" with the line
"subscribe" in the message body.
/proc/scsi support: To get advanced command statistics, do the
following: echo "eata_dma latency" >/proc/scsi/eata_dma/<driver_no>
and to switch it off again: echo "eata_dma nolatency"
>/proc/scsi/eata_dma/<driver_no>
Common Problems :
1. Slackware doesn't find the controller.
Solution: Use one of the ascsi* bootdisks.
2. The IDE driver can detect the ST-506 interface of the EATA board in
old kernels (<v1.3).
a. This will look like similar to one of the following 2 examples:
hd.c: ST-506 interface disk with more than 16 heads detected,
probably due to non-standard sector translation. Giving up.
(disk %d: cyl=%d, sect=63, head=64)
hdc: probing with STATUS instead of ALTSTATUS
hdc: MP0242 A, 0MB w/128KB Cache, CHS=0/0/0
hdc: cannot handle disk with 0 physical heads
hdd: probing with STATUS instead of ALTSTATUS
hdd: MP0242 A, 0MB w/128KB Cache, CHS=0/0/0
hdd: cannot handle disk with 0 physical heads
If the IDE driver gets into trouble because of this, ie. you can't
access your (real) IDE hardware, change the IO Port and/or the IRQ
of the EATA board.
b. If the IDE driver finds hardware it can handle ie. harddisks
with a capacity <=504MB, it will allocate the IO Port and IRQ,
so that the eata driver can't utilize them. In this case also
change IO Port and IRQ (!= 14,15).
3. Some old SK2011 boards have a broken firmware. Please contact DPT's
customer support for an update.
Notes:
1. CONFIG_PCI must be set if you are using a PCI board.
5.11. Future Domain 16x0 with TMC-1800, TMC-18C30, TMC-18C50, or
TMC-36C70 chip
Supported Configurations :
BIOSs : 2.0, 3.0, 3.2, 3.4, 3.5
BIOS Addresses : 0xc8000, 0xca000, 0xce000, 0xde000
Ports : 0x140, 0x150, 0x160, 0x170
IRQs : 3, 5, 10, 11, 12, 14, 15
DMA : not used
IO : port mapped
Autoprobe :
works with all supported configurations, requires installed BIOS
Autoprobe Override :
none
Antiquity Problems, fix by upgrading :
1. Old versions do not support the TMC-18C50 chip, and will fail with
newer boards.
2. Old versions will not have the most current BIOS signatures for
autodetection.
3. Versions prior to the one included in Linux 1.0.9 and 1.1.6 don't
support the new SCSI chip or 3.4 BIOS.
Notes :
1. The Future Domain BIOS often scans for SCSI-devices from highest ID
to 0, in reverse order of other SCSI BIOSes. sda will be the last
"drive letter" (ie, D: rather than C:). You may also need to use a
a disktab override for LILO.
5.12. Generic NCR5380 / T130B (Standard)
Supported and Unsupported Configurations :
Ports : all
IRQs : all
DMA channels : DMA is not used
IO : port mapped
Autoprobe :
none
Autoprobe Override :
Compile time : Define GENERIC_NCR5380_OVERRIDE to be an array of tuples
with port, irq, dma, board type - ie
#define GENERIC_NCR5380_OVERRIDE {{0x330, 5, DMA_NONE, BOARD_NCR5380}}
for a NCR5380 board at port 330, IRQ 5.
#define GENERIC_NCR5380_OVERRIDE {{0x350, 5, DMA_NONE, BOARD_NCR53C400}}
for a T130B at port 0x350.
Older versions of the code eliminate the BOARD_* entry.
The symbolic IRQs IRQ_NONE and IRQ_AUTO may be used.
kernel command line :
ncr5380=port,irq
ncr5380=port,irq,dma
ncr53c400=port,irq
255 may be used for no irq, 254 for irq autoprobe.
Common Problems :
1. Using the T130B board with the old (pre public release 6) generic
NCR5380 driver which doesn't support the ncr53c400 command line
option.
The NCR5380 compatible registers are offset eight from the base
address. So, if your address is 0x350, use
ncr5380=0x358,254
on the kernel command line.
Antiquity problems, fix by upgrading :
1. The kernel locks up during disk access with T130B or other
NCR53c400 boards.
Pre-public release 6 versions of the Generic NCR5380 driver didn't
support interrupts on these boards. Upgrade.
Notes :
1. the generic driver doesn't support DMA yet, and pseudo-DMA isn't
supported in the generic driver.
5.13. NCR53c8xx (Standard)
Supported and Unsupported Configurations :
Base addresses : ALL
IRQs : ALL
DMA channels : PCI, not applicable
IO : port mapped, busmastering
Autoprobe :
requires PCI BIOS, uses PCI BIOS routines to
search for devices and read configuration space
The driver uses the pre-programmed values in some registers for
initialization, so a BIOS must be installed.
Antiquity Problems, fix by upgrading :
1. Older versions of Linux had a problem with swapping See``Disks :
System Hangs When Swapping''
2. Older versions of Linux didn't recognize '815 and '825 boards.
3. Distribution kernels include release 4 or 5 of the driver, which
does not support useful things like disconnect/reconnect (the most
noticeable effect of this being attempts to retension/rewind/file
space a tape lock you out of all SCSI devices), multiple host
adapters, and BIOSless operation.
The latest release of the driver is available at
ftp://tsx-11.mit.edu/pub/linux/ALPHA/scsi/ncr53c810
Currently, this is a 1.2.10 and newer patch, although the next release
will be 1.3.x exclusively. These patches are NOT entirely clean due
to some ELF and other patches which were in the baseline revision of
my source tree, and if you can't manually correct the (four) problems
you should get, you shouldn't use them. Note that only the newest
patch is needed; these are not incremental.
If you wish to run the newer NCR driver with a 1.3.x kernel before
then, Harald Evensen <Harald.Evensen@pvv.unit.no> has adapted the
patches for 1.3.x
ftp://ftp.pvv.unit.no/pub/Linux/ALPHA/ncr
These patches should be clean.
Please see all of the READMEs in these directories. You should also
join the NCR mailing list if you are interested in running the ALPHA
code, since interim bug fixes and announcements of the next release
are posted to this list.
To subscribe, send mail to majordomo@colorado.edu with
subscribe ncr53c810
in the text. You can unsubscribe by sending mail to the same address
and including
unsubscribe ncr53c810
in the text.
Common Problems :
1. Many people have encountered problems where the chip worked fine
under DOS, but failed under Linux with a timeout on test 1 due to a
lost interrupt.
This is often due to a mismatch between the IRQ hardware jumper for
a slot or mainboard device and the value set in the CMOS setup.
DOUBLE CHECK
� The IRQ you are using is used only by your onboard NCR chip, or the
slot an NCR board is installed in
� Any main board jumpers selecting the IRQ for the onboard chip or
slot match your CMOS setup.a
� Some PCI mainboards have an "auto" assignment feature, which will
not work.
It may also be due to PCI INTB, INTC, or INTD being selected on a
PCI board in a system which only supports PCI INTA. If you are
using an NCR board which has jumpers to select between PCI
interrupt lines, make sure you are using INTA.
Finally, PCI should be using level-sensitive rather than edge
triggered interrupts. Check that your board is jumpered for level-
sensitive, and if that fails try edge-triggered because your system
may be broken.
This problem is especially common with Viglen some Viglen
motherboards, where the mainboard IRQ jumper settings are NOT as
documented in the manual. I've been told that what claims to be
IRQ5 is really IRQ9, your mileage will vary.
2. Lockups / other problems occur when using an S3 928, or Tseng
ET4000W32 PCI video board.
There are hardware bugs in at least some revisions of these chips.
Don't use them.
3. You get a message on boot up indicating that the I/O mapping was
disabled because base address 0 bits 0..1 indicated a non I/O
mapping
This is due to a BIOS bug in some machines which results in dword
reads of configuration registers returning the high and low 16 bit
words swapped.
4. Some systems have problems if PCI write posting, or CPU-> PCI
buffering are enabled. If you have problems, disable these
options.
5. Some systems with the NCR SDMS software in an onboard BIOS
ROM and in the system BIOS are unable to boot DOS. Disabling the
image in one place should rectify this problem.
6. If you encounter the message
"scsi%d: IRQ0 not free, detaching"
or
"scsi%d: IRQ255 not free, detaching"
The NCR chip had all 0 or 1 bits stored in the PCI configuration reg�
ister. Either you have configuration problems (see ``Common Problem
1''), or you have a defective mainboard BIOS.
As a work around, you could edit drivers/scsi/ncr53c7,8xx.c, and
change pci_init() so that you have
irq = my_irq;
before
return normal_init (tpnt, board, chip, (int) base,
(int) io_port, (int) irq, DMA_NONE, 1, bus, device_fn,
options);
7. Some systems have hideous, broken, BIOS chips. Don't make any bug
reports until you've made sure you have the newest ROM from your
vendor.
8. The command line overrides ncr53c810=xxx, etc. don't work.
In stock kernels, this is because their entry points are not
included in init/main.c, which is quite intentional :
The driver makes no attempt to avoid autoprobing for a board where
a command line override was used, so if an override is used where
the board actually showed up to the PCI configuration routines,
you'll have big problems.
The only reason you would need an override would be if the PCI
hardware + BIOS were broken, in which case certain error recovery
routines wouldn't work, rendering the override less than useful.
Finally, nearly all of people who _think_ they need a command line
override do because they get configuration or other error messages
from the driver. If the driver says you have a configuration
problem, you have a broken system or a configuration problem and no
override is going to fix this.
If some one has gone and added the appropriate entry points to
init/main.c for command line overrides, they are totally
unsupported and may not work.
9. Certain NCR boards (most notably Nexstor) which don't use an NCR
BIOS get timeouts. Some of these ROMs handle synchronous and
transfers, negotiate for sync. transfers on power up, and leave the
drives in an unknown state. When the distribution Linux NCR driver
attempts to talk with them, it gets timeouts and cannot recover
because it won't do a bus reset or renegotiate.
If you run into this problem, you can either disable synchronous
transfers in the board's setup program, or upgrade to a newer ALPHA
release of the NCR driver which will do synchronous negotiation.
10.
Tyan S1365 '825 boards have problems with timeouts, especially when
disconnects are enabled. Some of these boards have the
documentation regarding the termination enable jumper reversed - so
that termination is off when you need it, and on when it shouldn't
be.
Try reversing the position of the jumper.
Notes:
1. CONFIG_PCI must be set
5.14. Seagate ST0x/Future Domain TMC-8xx/TMC-9xx (Standard)
Supported and Unsupported Configurations :
Base addresses : 0xc8000, 0xca000, 0xcc000, 0xce000, 0xdc000, 0xde000
IRQs : 3, 5
DMA channels : DMA is not used
IO : memory mapped
Autoprobe :
probes for address only, IRQ is assumed to be 5, requires installed BIOS.
Autoprobe Override :
Compile time :
Define OVERRIDE to be the base address, CONTROLLER to
FD or SEAGATE as appropriate, and IRQ to the IRQ.
kernel command line :
st0x=address,irq or tmc8xx=address,irq (only works for .99.13b and newer)
Antiquity Problems, fix by upgrading :
1. Versions prior to the one in the Linux .99.12 kernel had a problem
handshaking with some slow devices, where
This is what happens when you write data out to the bus
a. Write byte to data register, data register is asserted to bus
b. time_remaining = 12us
c. wait while time_remaining > 0 and REQ is not asserted
d. if time_remaining > 0, assert ACK
e. wait while time remaining > 0 and REQ is asserted
f. deassert ACK
The problem was encountered in slow devices that do the command
processing as they read the command, where the REQ/ACK handshake
takes over 12us - REQ didn't go false when the driver expected it
to, so the driver ended up sending multiple bytes of data for each
REQ pulse.
2. With Linux .99.12, a bug was introduced when I fixed the
arbitration code, resulting in failed selections on some systems.
This was fixed in .99.13.
Common Problems :
1. There are command timeouts when Linux attempts to read the
partition table or do other disk access.
The board ships with the defaults set up for MSDOS, ie interrupts
are disabled. To jumper the board for interrupts, on the Seagate
use jumper W3 (ST01) or JP3 (ST02) and short pins F-G to select IRQ
5.
2. The driver can't handle some devices, particularly cheap SCSI tapes
and CDROMs.
The Seagate ties the SCSI bus REQ/ACK handshaking into the PC bus
IO CHANNEL READY and (optionally) 0WS signals. Unfortunately, it
doesn't tell you when the watchdog timer runs out, and you have no
way of knowing for certain that REQ went low, and may end up seeing
one REQ pulse as multiple REQ pulses.
Dealing with this means using a tight loop to look for REQ to go
low, with a timeout incase you don't catch the transition due to an
interrupt, etc. This results in a performance decrease, so it
would be undesirable to apply this to all SCSI devices. Instead,
it is selected on a per-device basis with the "broken" field for
the given SCSI device in the scsi_devices array. If you run into
problems, you should try adding your device to the list of devices
for which broken is not reset to zero (currently, only the TENEX
CDROM drives).
3. A future domain board (specific examples include the 840, 841, 880,
and 881) doesn't work.
A few of the Future domain boards use the Seagate register mapping,
and have the MSG and CD bits of the status register flipped.
You should edit seagate.h, swapping the definitions for STAT_MSG
and STAT_CD, and recompile the kernel with CONTROLLER defined to
SEAGATE and an appropriate IRQ and OVERRIDE specified.
4. When attempting to fdisk your drive, you get error messages
indicating that the HDIO_REQ or HDIO_GETGEO ioctl failed, or
You must set heads sectors and cylinders.
You can do this from the extra functions menu.
See ``Disks Partitioning''
5. After manually specifying the drive geometry, subsequent attempts
to read the partition table result in partition boundary not on a
cylinder boundary, physical and logical boundaries don't match,
etc. error messages.
See ``Disks Partitioning''
6. Some systems which worked prior to .99.13 fail with newer versions
of Linux. Older versions of Linux assigned the CONTROL and DATA
registers in an order different than that outlined in the Seagate
documentation, which broke on some systems. Newer versions make
the assignment in the correct way, but this breaks other systems.
The code in seagate.c looks like this now :
cli();
DATA = (unsigned char) ((1 << target) | (controller_type == SEAGATE ? 0x80 : 0x40));
CONTROL = BASE_CMD | CMD_DRVR_ENABLE | CMD_SEL |
(reselect ? CMD_ATTN : 0);
sti();
Changing this to
cli();
CONTROL = BASE_CMD | CMD_DRVR_ENABLE | CMD_SEL |
(reselect ? CMD_ATTN : 0);
DATA = (unsigned char) ((1 << target) | (controller_type == SEAGATE ? 0x80 : 0x40));
sti();
may fix your problem.
Defines :
FAST or FAST32 will use blind transfers where possible
ARBITRATE will cause the host adapter to arbitrate for the
bus for better SCSI-II compatibility, rather than just
waiting for BUS FREE and then doing its thing. Should
let us do one command per Lun when I integrate my
reorganization changes into the distribution sources.
SLOW_HANDSHAKE will allow compatibility with broken devices that don't
handshake fast enough (ie, some CD ROM's) for the Seagate
code.
SLOW_RATE=x, x some number will let you specify a default
transfer rate if handshaking isn't working correctly.
5.15. PAS16 SCSI (Standard)
Supported and Unsupported Configurations :
Ports : 0x388, 0x384, 0x38x, 0x288
IRQs : 10, 12, 14, 15
IMPORTANT : IRQ MUST be different from the IRQ used for the sound
portion of the board.
DMA : is not used for the SCSI portion of the board
IO : port mapped
Autoprobe :
does not require BIOS
Autoprobe Override :
Compile time : Define PAS16_OVERRIDE to be an array of port, irq
tuples. Ie
#define PAS16_OVERRIDE {{0x388, 10}}
for a board at port 0x388, IRQ 10.
kernel command line :
pas16=port,irq
Defines :
AUTOSENSE - if defined, REQUEST SENSE will be performed automatically
for commands that return with a CHECK CONDITION status.
PSEUDO_DMA - enables PSEUDO-DMA hardware, should give a 3-4X performance
increase compared to polled I/O.
PARITY - enable parity checking. Not supported
SCSI2 - enable support for SCSI-II tagged queuing. Untested
UNSAFE - leave interrupts enabled during pseudo-DMA transfers. You
only really want to use this if you're having a problem with
dropped characters during high speed communications, and even
then, you're going to be better off twiddling with transfersize.
USLEEP - enable support for devices that don't disconnect. Untested.
Common problems :
1. Command timeouts, aborts, etc.
You should install the NCR5380 patches that I posted to the net
some time ago, which should be integrated into some future alpha
release. These patches fix a race condition in earlier NCR5380
driver cores, as well as fixing support for multiple devices on
NCR5380 based boards.
If that fails, you should disable the PSEUDO_DMA option by changing
the #define PSEUDO_DMA line in drivers/scsi/pas16.c to #undef
PSEUDO_DMA.
Note that the later should be considered a last resort, because
there will be a severe performance degradation.
5.16. Trantor T128/T128F/T228 (Standard)
Supported and Unsupported Configurations :
Base addresses : 0xcc000, 00xc8000, 0xdc000, 0xd8000
IRQs : none, 3, 5, 7 (all boards)
10, 12, 14, 15 (T128F only)
DMA : not used.
IO : memory mapped
Autoprobe :
works for all supported configurations, requires installed BIOS.
Autoprobe Override :
Compile time : Define T128_OVERRIDE to be an array of address, irq
tuples. Ie
#define T128_OVERRIDE {{0xcc000, 5}}
for a board at address 0xcc000, IRQ 5.
The symbolic IRQs IRQ_NONE and IRQ_AUTO may be used.
kernel command line :
t128=address,irq
-1 may be used for no irq, -2 for irq autoprobe.
Defines :
AUTOSENSE - if defined, REQUEST SENSE will be performed automatically
for commands that return with a CHECK CONDITION status.
PSEUDO_DMA - enables PSEUDO-DMA hardware, should give a 3-4X performance
increase compared to polled I/O.
PARITY - enable parity checking. Not supported
SCSI2 - enable support for SCSI-II tagged queuing. Untested
UNSAFE - leave interrupts enabled during pseudo-DMA transfers. You
only really want to use this if you're having a problem with
dropped characters during high speed communications, and even
then, you're going to be better off twiddling with transfersize.
USLEEP - enable support for devices that don't disconnect. Untested.
Common Problems :
1. Command timeouts, aborts, etc.
You should install the NCR5380 patches that I posted to the net
some time ago, which should be integrated into some future alpha
release. These patches fix a race condition in earlier NCR5380
driver cores, as well as fixing support for multiple devices on
NCR5380 based boards.
If that fails, you should disable the PSEUDO_DMA option by changing
the #define PSEUDO_DMA line in drivers/scsi/pas16.c to #undef
PSEUDO_DMA.
Note that the later should be considered a last resort, because
there will be a severe performance degradation.
5.17. Ultrastor 14f (ISA), 24f (EISA), 34f (VLB) (Standard)
Supported Configurations :
Ports : 0x130, 0x140, 0x210, 0x230, 0x240, 0x310, 0x330, 0x340
IRQs : 10, 11, 14, 15
DMA channels : 5, 6, 7
IO : port mapped, bus master
Autoprobe :
does not work for boards at port 0x310, BIOS not required.
Autoprobe override :
compile time only, define PORT_OVERRIDE
Common Problems :
1. The address 0x310 is not supported by the autoprobe code, and may
cause conflicts if networking is enabled.
Please use a different address.
2. Using an Ultrastor at address 0x330 may cause the system to hang
when the sound drivers are autoprobing.
Please use a different address.
3. Various other drivers do unsafe probes at various addresses, if you
are having problems with detection or the system is hanging at boot
time, please try a different address.
0x340 is recommended as an address that is known to work.
4. Linux detects no SCSI devices, but detects your SCSI hard disk on
an Ultrastor SCSI board as a normal hard disk, and the hard disk
driver refuses to support it. Note that when this occurs, you will
probably also get a message
hd.c: ST-506 interface disk with more than 16 heads detected,
probably due to non-standard sector translation. Giving up. (disk
%d: cyl=%d, sect=63, head=64)
If this is the case, you are running the Ultrastor board in WD1003
emulation mode. You have
a. Switch the Ultrastor into native mode. This is the recommended
action, since the SCSI driver can be significantly faster than
the IDE driver, especially with the clustered read/write patches
installed. Some users have sustained in excess of 2M/sec
through the file system using these patches.
Note that this will be necessary if you wish to use any non-
hard disk, or more than two hard disk devices on the Ultrastor.
b. Use the kernel command line switch
hd=cylinders,heads,sectors
to override the default setting to bootstrap yourself, keeping num�
ber of cylinders <= 2048, number of heads <= 16, and number of sec�
tors <= 255 such that cylinders * heads * sectors is the same for
both mappings.
You'll also have to manually specify the disk geometry when running
fdisk under Linux. Failure to do so will result in incorrect par�
tition entries being written, which will work correctly with Linux
but fail under MSDOS which looks at the cylinder/head/sector
entries in the table.
Once Linux is up, you can avoid the inconvenience of having to boot
by hand by recompiling the kernel with an appropriately defined
HD_TYPE macro in include/linux/config.h.
5.18. Western Digital 7000 (Standard)
Supported Configurations :
BIOS Addresses : 0xce000
Ports : 0x350
IRQs : 15
DMA Channels : 6
IO : port mapped, bus master
Autoprobe :
requires installed BIOS
Common Problems :
1. There are several revisions of the chip and firmware. Supposedly,
revision 3 boards do not work, revision 5 boards do, chips with no
suffix do not work, chips with an 'A' suffix do.
2. The board supports a few BIOS addresses which aren't on the list of
supported addresses. If you run into this situation, please use
one of the supported addresses and submit a bug report as outlined
in ``Bug Reports''.
5.19. AM53/79C974 (ALPHA)
ftp://tsx-11.mit.edu/pub/linux/ALPHA/scsi/AM53C974-0.3.tar.gz
Supported Configurations :
Ports : all
IRQs : all
DMA Channels : 6
IO : port mapped, bus master (unintelligent)
5.20. qlogic (Standard)
Hey Drew, where is this section (I (D.F.) saw it only in the toc ;-)?
6. Disks
This section gives information that is specific to disk drives.
6.1. Supported and Unsupported Hardware
All direct access SCSI devices with a block size of 256, 512, or 1024
bytes should work. Other block sizes will not work (Note that this
can often be fixed by changing the block and/or sector sizes using the
MODE SELECT SCSI command)
Sector size refers to the number of data bytes allocated per sector on
a device, ie CDROMs use a 2048 byte sector size.
Block size refers to the size of the logical blocks used to interface
with the device. Although this is usually identical to sector size,
some devices map multiple smaller physical sectors (ie, 256 bytes in
the case of 55M Syquest drives) to larger logical blocks or vice versa
(ie, 512 byte blocks on SUN compatible CDROM drives).
Removable media devices, including Bernoulis, flopticals, MO drives,
and Syquests.
In theory, drives up to a terabyte in size should work. There is
definitely no problem with tiny 9G drives.
6.2. Common Problems
6.2.1. Cylinder > 1024 message
When partitioning, you get a warning message about "cylinder > 1024"
or you are unable to boot from a partition including a logical
cylinder past logical cylinder 1024.
This is a BIOS limitation.
See Disk ``Geometry'' and ``Partitioning'' for an explanation.
6.2.2. You are unable to partition "/dev/hd*"
/dev/hd* aren't SCSI devices, /dev/sd* are.
See ``Device Files'' and Disk ``Geometry'' and ``Partitioning'' for
the correct device names and partitioning procedure.
6.2.3. Unable to eject media from a removable media drive
Linux attempts to lock the drive door when a piece of media is mounted
to prevent filesystem corruption due to an inadvertent media change.
Please unmount your disks before ejecting them.
6.2.4. Unable to boot using LILO from a SCSI disk
In some cases, the SCSI driver and BIOS will disagree over the correct
BIOS mapping to use, and will result in LILO hanging after 'LI' at
boot time and/or other problems.
To workaround this, you'll have to determine your BIOS geometry
mapping used under DOS, and make an entry for your disk in
/etc/lilo/disktab.
Alternatively, you may be able to use the "linear" configuration jfile
option.
6.2.5. Fdisk responds with
You must set heads sectors and cylinders.
You can do this from the extra functions menu.
and disk geometry is not 'remembered' when fdisk is rerun.
See ``Partitioning''
6.2.6. Only one drive is detected on a bridge board with multiple
drives connected.
Linux won't search LUNs past zero on SCSI devices which predate ANSI
SCSI revision 1. If you wish devices on alternate LUNs to be
recognized, you will have to modify drivers/scsi/scsi.c:scan_scsis().
6.2.7. System hangs when swapping
We think this has been fixed, try upgrading to 1.1.38.
6.2.8. Connor CFP1060S disks get corrupted
This is due to a microcode bug in the read-ahead and caching code.
>From Soenke Behrens of Conner tech. support :
During the past few weeks, we got several calls from customers stating
that they had severe problems with Conner CFP1060x 1GB SCSI drives
using the Linux operating system. Symptoms were corrupt filesystems
(damaged inodes) reported by e2fsck on each system boot and similar
errors.
There is now a fix available for customers with a CFP1060x (microcode
revisions 9WA1.62/1.66/1.68) and Linux. To apply the upgrade, you
will need a DOS boot disk and ASPI drivers that can access the hard
drive. The upgrade downloads new queuing and lookahead code into the
non-volatile SCSI RAM of the drive.
If you are experiencing problems with a disk that has microcode
revision 9WA1.60, you will have to contact your nearest Conner service
centre to get the disk upgraded. The microcode revision can be found
on the label of the drive and on the underside of the drive on a label
on one of the ICs.
If you are confident that you can perform the upgrade yourself, please
contact Conner Technical Support and have your microcode revision
ready. Conner Technical Support Europe can be reached on +44-1294-315333,
Conner Technical Support in the USA can be reached on 1-800-4CONNER.
Regards
Soenke Behrens
European Technical Support
6.3. Device Files
SCSI disks use block device major 8, and there are no "raw" devices
ala BSD.
16 minor numbers are allocated to each SCSI disk, with minor % 16 == 0
being the whole disk, minors 1 <= (minor % 16) <= 4 the four primary
partitions, minors 5 <= (minor % 16) <= 15 any extended partitions.
Ie, a configuration may work out like this (with one host adapter)
Device Target, Lun SCSI disk
84M Seagate 0 0 /dev/sda
SCSI->SMD bridge disk 0 3 0 /dev/sdb
SCSI->SMD bridge disk 1 3 1 /dev/sdc
Wangtek tape 4 0 none
213M Maxtor 6 0 /dev/sdd
Etc.
The standard naming convention is
/dev/sd{letter} for the entire disk device ((minor % 16) == 0)
/dev/sd{letter}{partition} for the partitions on that device (1 <=
(minor % 16) <= 15)
Ie
/dev/sda block device major 8 minor 0
/dev/sda1 block device major 8 minor 1
/dev/sda2 block device major 8 minor 2
/dev/sdb block device major 8 minor 16
etc.
6.4. Partitioning
You can partition your SCSI disks using the partitioning program of
your choice, under DOS, OS/2, Linux or any other operating system
supporting the standard partitioning scheme.
The correct way to run the Linux fdisk program is by specifying the
device on the command line. Ie, to partition the first SCSI disk,
fdisk /dev/sda
If you don't explicitly specify the device, the partitioning program
may default to /dev/hda, which isn't a SCSI disk.
In some cases, fdisk will respond with
You must set heads sectors and cylinders.
You can do this from the extra functions menu.
Command (m for help):
and/or give a message to the effect that the HDIO_REQ or HDIO_GETGEO
ioctl failed. In these cases, you must manually specify the disk
geometry as outlined in ``Disk Geometry'' when running fdisk, and also
in /etc/disktab if you wish to boot kernels off that disk with LILO.
If you have manually specified the disk geometry, subsequent attempts
to run fdisk will give the same error message. This is normal, since
PCs don't store the disk geometry information in the partition table.
In and of itself, will cause _NO PROBLEMS_, and you will have no
problems accessing partitions you created on the drive with Linux.
Some vendors' poor installation code will choke on this, in which case
you should contact your vendor and insist that they fix the code.
In some cases, you will get a warning message about a partition ending
past cylinder 1024. If you create one of these partitions, you will
be unable to boot Linux kernels off of that partition using LILO.
Note, however, that this restriction does not preclude the creation of
a root partition partially or entirely above the 1024 cylinder mark,
since it is possible to create a small /boot partition below the 1024
cylinder mark or to boot kernels off existing partitions.
6.5. Disk Geometry
Under Linux, each disk is viewed as the SCSI host adapter sees it : N
blocks, numbered from 0 to N-1, all error free, where as DOS/BIOS
predate intelligent disks and apply an arbitrary head / cylinder /
sector mapping to this linear addressing.
This can pose a problem when you partition the drives under Linux,
since there is no portable way to get DOS/BIOS's idea of the mapped
geometry. In most cases, a HDIO_GETGEO ioctl() can be implemented to
return this mapping. Unfortunately, when the vendor (ie Seagate) has
chosen a perverse, non-standard, and undocumented mapping, this is not
possible and geometry must be manually specified
If manual specification of the is required, you have one of several
options :
1. If you don't care about using DOS, or booting kernels from the
drive with LILO, create a translation such that heads * cylinders *
sectors * 512 < size of your drive in bytes (a megabyte is defined
as 2^20 bytes).
1 <= heads <= 256
1 <= cylinders <= 1024
1 <= sectors <= 63
2. Use the BIOS mapping. In some cases, this will mean reconfiguring
the disk so that it is at SCSI ID 0, and disabling the second IDE
drive (if you have one).
You can either use a program like NU, or you can use the following
program :
begin 664 dparam.com
MBAZ``##_B+^!`+N!`(H'0SP@=/D\,'5:@#]X=`6`/UAU4(!_`3AU2H!_`P!U
M1(I7`H#J,(#Z`7<Y@,*`M`C-$PCD=3-14HC()#\PY.@R`.@J`%J(\/[`,.3H
M)0#H'0!8AL2Q!M+L0.@7`+K"`;0)S2'#NIP!ZR"ZQ0'K&[K5`>L6N]T!,=*Y
M"@#W\8#",$N(%PG`=>^)VK0)S2'#=7-A9V4Z(&1P87)A;2`P>#@P#0H@("!O
L<B`@9'!A<F%M(#!X.#$-"B1);G9A;&ED(&1R:79E#0HD("`D```````D``!O
`
end
When run it prints the sectors, heads, and cylinders of the drive
whose BIOS address was specified on the command line (0x80 is the
first disk, 0x81 the second).
Ie, dparam 0x80
60 17 1007
Would mean that C: had 60 sectors, 17 heads, and 1007 cylinders.
7. CD ROMs
This section gives information that is specific to cdrom drives.
7.1. Supported and Unsupported Hardware
SCSI CDs with a block size of 512 or 2048 bytes should work. Other
block sizes will not work.
7.2. Common Problems
7.2.1. Unable to mount cdrom
The correct syntax to mount an ISO-9660 CDROM is
mount -t iso9660 /dev/sr0 /mount_point -o ro
Note that for this to work, you must have the kernel configured with
support for SCSI, your host adapter, the SCSI CDROM driver, and the
iso9660 filesystem.
Note that as of Linux 1.1.32, read-only devices such as CDROMs CANNOT
be mounted with the default read/write options.
7.2.2. Unable to eject cdrom
Linux attempts to lock the drive door when a piece of media is mounted
to prevent filesystem corruption due to an inadvertent media change.
7.2.3. Unable to play audio
The programs Workman or xcdplayer will do this for you.
7.2.4. Workman or Xcdplayer do not work
The functions to control audio functions are part of the SCSI-II
command set, so any drive that is not SCSI-II will probably not work
here. Also, many SCSI-I and some SCSI-II CDROM drives use a
proprietary command set for accessing audio functions instead of the
SCSI-II command set. For NEC drives, there is a version of xcdplayer
specially adapted to use this command set floating around - try
looking on tsx-11.mit.edu in pub/linux/BETA/cdrom.
These programs may work with some of the non-SCSI cdrom drives if the
driver implements the same ioctls as the scsi drivers.
7.2.5. Additional drives on CD ROM changers do not work
Most CD changers assign each disc to a logical unit. Insure that you
have special files made for each platter (see ``Device Files'') and
see ``LUNS other than 0 don't work''.
7.3. Device Files
SCSI CD ROMs use major 11.
Minors are allocated dynamically (See ``Disks'', ``Device Files'' for
an example) with the first CDROM found being minor 0, the second minor
1, etc.
The standard naming convention is
/dev/sr{digit}, although some distributions have used /dev/scd{digit},
with examples being
/dev/sr0 /dev/scd0
/dev/sr1 /dev/scd1
8. Tapes
This section gives information that is specific to scsi tape drives.
8.1. Supported and Unsupported Hardware
Drives using both fixed and variable length blocks smaller than the
the driver buffer length (set to 32K in the distribution sources) are
supported.
Parameters (block size, buffering, density) are set with ioctls
(usually with the mt program), and remain in effect after the device
is closed and reopened.
Virtually all drives should work, including :
� Archive Viper QIC drives, including the 150M and 525M models
� Exabyte 8mm drives
� Wangtek 5150S drives
� Wangdat DAT drives
8.2. Common Problems
8.2.1. Tape drive not recognized at boot time
Try booting with a tape in the drive.
8.2.2. Tapes with multiple files cannot be read properly
When reading a tape with multiple files, the first tar is successful,
a second tar fails silently, and retrying the second tar is
successful.
User level programs, such as tar, don't understand file marks. The
first tar reads up until the end of the file. The second tar attempts
to read at the file mark, gets nothing, but the tape spaces over the
file mark. The third tar is successful since the tape is at the start
of the next file.
Use mt on the no-rewind device to space forward to the next file.
8.2.3. Decompression fails
Decompressing programs cannot handle the zeros padding the last block
of the file.
To prevent warnings and errors, wrap your compressed files in a .tar
file - ie, rather than doing
tar cfvz /dev/nrst0 file.1 file.2 ...
do
tar cfvz tmp.tar.z file.1 file.2 ...
tar cf /dev/nrst0 tmp.tar.z
8.2.4. Problems taking tapes to/from other systems
You can't read a tape made with another operating system or another
operating system can't read a tape written in Linux.
Different systems often use different block sizes. On a tape device
using a fixed blocksize, you will get errors when reading blocks
written using a different block size.
To read these tapes, you must set the blocksize of the tape driver to
match the blocksize used when the tape was written, or to variable.
NOTE : this is the hardware block size, not the blocking factor used
with tar, dump, etc.
You can do this with the mt command -
mt setblk <size>
or
mt setblk 0
to get variable block length support.
Note that these mt flags are NOT supported under the GNU version of mt
which is included with some Linux distributions. Instead, you must
use the BSD derived Linux SCSI mt command. Source should be available
from
tsx-11.mit.edu:/pub/linux/ALPHA/scsi
Also note that by default, ST_BUFFER_BLOCKS (defined in
/usr/src/linux/drivers/scsi/st_options.h in newer kernels, st.c in
older kernels) is set to allow for a 32K maximum buffer size; you'll
need to edit the source to use larger blocks.
8.2.5. No such device" error message
All attempts to access the tape result in a
"No such device"
or similar error message. Check the type of your tape device - it
MUST be a character device with major and minor numbers matching those
specified in ``Device Files''.
8.2.6. Tape reads at a given density work, writes fail
Many tape drives support reading at lower densities for compatibility
with older hardware, but will not write at those same densities.
This is especially the case with QIC drives, which will read old 60M
tapes but only write new 120, 150, 250, and 525M formats.
8.2.7. Repositioning the tape locks out access to all SCSI devices
This is most common with SCSI drivers which only support one
outstanding command at a time (see ``Multiple devices'' for an
explanation, and ``Driver feature comparison'' to see which drivers
suffer from this limitation), although there may be a few tape drives
out there which refuse to disconnect.
In either case, you can work around the problem by editing
drivers/scsi/st.c and adding a
#define ST_NOWAIT
at the top and rebuilding the kernel.
Note that this will defer error condition reporting until the next
SCSI command is executed. For this reason, you may want to do
something like a
mt status
after a mt file positioning command so you don't overwrite tape files
if the positioning command failed.
You may also wish to consider changing to a better-supported SCSI
board or newer tape drive if you need to use this workaround and are
writing multiple files to tapes.
8.3. Device Files
SCSI tapes use character device major 9.
Due to constraints imposed by Linux's use of a sixteen bit dev_t with
only eight bits allocated to the minor number, the SCSI tape minor
numbers are assigned dynamically starting with the lowest SCSI
HOST/ID/LUN.
Rewinding devices are numbered from 0 - with the first SCSI tape,
/dev/rst0 being c 9 0, the second /dev/rst1 c 9 1, etc. Non-rewinding
devices have the high bit set in the minor number, ie /dev/nrst0 is c
9 128.
The standard naming convention is
/dev/nst{digit} for non-rewinding devices
/dev/st{digit} for rewinding devices
9. Generic
This information gives information that is specific to the generic
scsi driver.
9.1. Supported Hardware
The Generic SCSI device driver provides an interface for sending SCSI
commands to all SCSI devices - disks, tapes, CDROMs, media changer
robots, etc.
Everything electrically compatible with your SCSI board should work.
9.2. Common Problems
None :-).
9.3. Device Files
SCSI generic devices use character major 21. Due to constraints
imposed by Linux's use of a 16 bit dev_t, minor numbers are
dynamically assigned from 0, one per device, with
/dev/sg0
corresponding to the lowest numerical target/lun on the first SCSI
board.
10. Buyers' Guide
A frequent question is:
"Linux supports quite a number of different boards, so which scsi host
adapter should I get."
The answer depends upon how much performance you expect or need,
motherboard, and the scsi peripherals that you plan on attaching to
your machine.
10.1. Transfer types
The biggest factor affecting performance (in terms of throughput and
interactive response time during SCSI I/O) is the transfer type used.
The table below lists the various transfer types, the effects they
have on performance, and some recommendations as to their use.
Transfer type
Description / Performance / Recommendations
Pure Polled
A pure polled I/O board will use the CPU to handle all of the
SCSI processing, including the REQ/ACK handshaking.
Even a fast CPU will be slower handling the REQ/ACK handshake
sequence than a simple finite state machine, resulting in peak
transfer rates of about 150K/sec on a fast machine, perhaps
60K/sec on a slow machine (through the filesystem).
The driver also must sit in a tight loop as long as the SCSI bus
is busy, resulting in near 100% CPU utilization and extremely
poor responsiveness during SCSI I/O. Slow CDROMs which don't
disconnect/reconnect will kill interactive performance with
these boards.
Not recommended.
Interlocked Polled
Boards using interlocked polled I/O are essentially the same as
pure polled I/O boards, only the SCSI REQ/ACK handshaking
signals are interlocked with the PC bus handshaking signals.
All SCSI processing beyond the handshaking is handled by the
CPU.
Peak transfer rates of 500-600K/sec through the filesystem are
possible on these boards.
As with pure polled I/O boards, the driver must sit in a tight
loop as long as the SCSI bus is busy, resulting in CPU
utilization dependent on the transfer rates of the devices, and
when they disconnect/reconnect. CPU utilization may vary
between 25% for single speed CDs which handle
disconnect/reconnect properly to 100% for faster drives or
broken CD ROMs which fail to disconnect/reconnect.
On my 486-66, with a T128, I use 90% of my CPU time to sustain a
throughput of 547K/sec on a drive with a headrate of 1080K/sec
with a T128 board.
Sometimes acceptable for slow tapes and CDROMs when low cost is
essential.
FIFO Polled
Boards using FIFO polled I/O put a small (typically 8K) buffer
between the CPU and the SCSI bus, and often implement some
amount of intelligence. The net effect is that the CPU is only
tied up when it is transferring data at top speed to the FIFO
and when it's handling the rest of the interrupt processing for
FIFO empty conditions, disconnect/reconnect, etc.
Peak transfer rates should be sufficient to handle most SCSI
devices, and have been measured at up to 4M/sec using raw SCSI
commands to read 64K blocks on a fast Seagate Baracuda with an
Adaptec 1520.
CPU utilization is dependent on the transfer rates of the
devices, with faster devices generating more interrupts per unit
time which require more CPU processing time. Although CPU
usage may be high (perhaps 75%) with fast devices, the system
usually remains usable. These boards will provide excellent
interactive performance with broken devices which don't
disconnect/reconnect (typically cheap CDROM drives)
Recommended for persons on a budget.
Slave DMA
Drivers for boards using slave DMA program the PC's DMA
controller for a channel when they do a data transfer, and
return control to the CPU.
Peak transfer rates are usually handicapped by the poor DMA
controller used on PCs, with one such 8-bit board having
problems going faster than 140-150K/sec with one mainboard.
CPU utilization is very reasonable, slightly less than what is
seen with FIFO polled I/O boards. These boards are very
tolerant of broken devices which don't disconnect/reconnect
(typically cheap CSG limitDROM drives).
Acceptable for slow CDROM drives, tapes, etc.
Busmastering DMA
These boards are intelligent. Drivers for these boards throw a
SCSI command, the destination target and lun, and where the data
should end up in a structure, and tell the board "Hey, I have a
command for you." The driver returns control to various running
programs, and eventually the SCSI board gets back and says that
it's done.
Since the intelligence is in the host adapter firmware and not
the driver, drivers for these boards typically support more
features - synchronous transfers, tagged queuing, etc.
With the clustered read/write patches, peak transfer rates
through the file system approach 100% of head rate writing, 75%
reading.
CPU utilization is minimal, irregardless of I/O load, with a
measured 5% CPU usage while accessing a double speed CDROM on an
Adaptec 1540 and 20% while sustaining a 1.2M/sec transfer rate
on a SCSI disk.
Recommended in all cases where money is not extremely tight, the
main board is not broken (some broken main boards do not work
with bus masters), and applications where time to data is more
important than throughput are not being run (bus master overhead
may hit 3-4ms per command).
10.2. Scatter/gather
The second most important driver/hardware feature with respect to
performance is support for scatter/gather I/O. The overhead of
executing a SCSI command is significant - on the order of
milliseconds. Intelligent bus masters like the Adaptec 1540 may take
3-4ms to process a SCSI command before the target even sees it. On
unbuffered devices, this overhead is always enough to slip a
revolution, resulting in a transfer rate of about 60K/sec (assuming a
3600RPM drive) per block transfered at a time. So, to maximize
performance, it is necessary to minimize the number of SCSI commands
needed to transfer a given amount of data by transferring more data
per command. Due to the design of the Linux buffer cache, contiguous
disk blocks are not contiguous in memory. With the clustered
read/write patches, 4K worth of buffers are contiguous. So, the
maximum amount of data which can be transfered per SCSI command is
going to be 1K * # of scatter/gather regions without the clustered
read/write patches, 4K * # of regions with. Experimentally, we've
determined that 64K is a reasonable amount to transfer with a single
SCSI command - meaning 64 scatter/gather buffers with clustered
read/write patches, 16 without. With the change from 16K to 64K
transfers, we saw an improvement from 50% of headrate, through the
filesystem, reading and writing, to 75% and 100% respectively using an
Adaptec 1540 series board.
10.3. Mailbox vs. non-mailbox
A number of intelligent host adapters, such as the Ultrastor, WD7000,
Adaptec 1540, 1740, and BusLogic boards have used a mailbox-metaphor
interface, where SCSI commands are executed by putting a SCSI command
structure in a fixed memory location (mailbox), signaling the board
(ie, raising the outgoing mail flag), and waiting for a return
(incoming mail). With this high level programming interface, users
can often upgrade to a newer board revision to take advantage of new
features, such as FAST + WIDE SCSI, without software changes. Drivers
tend to be simpler to implement, may implement a larger feature set,
and may be more stable.
Other intelligent host adapters, such as the NCR53c7/8xx family, and
Adaptec AIC-7770/7870 chips (including the 274x, 284x, and 2940
boards) use a lower level programming interface. This may prove
faster since processing can be shifted between the board's processor
and faster host CPU, allow better flexibility in implementing certain
features (ie, target mode for arbitrary devices), and these boards can
be built for less money (In some cases, this is passed on to the
consumer (ie, most NCR boards)). On the down side, drivers tend to be
more complex (read : there is more potential for bugs), and must be
modified to take advantage of the features present on newer chips.
10.4. Bus types
Bus type is the next thing to consider, with choices including ISA,
EISA, VESA, and PCI. Marketing types often spout of absurd bandwidth
numbers based on burst transfer rates and fiction, which isn't very
useful. Instead, I've chosen to state "real-world" numbers based on
measured performance with various peripherals.
Bus
Bandwidth, description,
ISA
Bandwidth is slightly better than 5M/sec for busmastering
devices. With an ISA bus, arbitration for busmasters is
performed by the venerable 8237 third party DMA controller,
resulting in relatively high bus acquisition times. Interrupt
drivers are tri-state and edge triggered, meaning interrupts
cannot be shared. Generally, ISA is unbuffered, meaning the
host/memory bus is tied up whenever a transfer is occuring. No
mechanism is provided to prevent bus-hogging.
VESA
Bandwidth is about 30M/sec. Some VESA systems run the bus out
of spec, rendering them incompatible with some boards, so this
should be taken into consideration before purchasing hardware
without a return guarantee. Generally, VESA is unbuffered,
meaning meaning the host/memory bus is tied up whenever a
transfer is occuring.
EISA
Bandwidth is about 30M/sec, with busmastering operations
generally being faster than VESA. Some EISA systems buffer the
bus, allowing burst transfers to the faster host/memory bus and
minimizing impact on CPU performance. EISA interrupt drivers
may be either tri-state edge-triggered or open collector level-
active, allowing interrupt sharing with drivers that support it.
Since EISA allocates a separate address space for each board, it
is usually less prone to resource conflicts than ISA or VESA.
PCI
Bandwidth is about 60M/sec. Most PCI systems implement write
posting buffers on the host bridge, allowing speed mismatches on
either side to have a minimum impact on bus/CPU performance.
PCI interrupt drivers are open collector level-active, allowing
interrupt sharing with drivers that support it. Mechanisms are
provided to prevent bus hogging, and for both master and slave
to suspend a bus-mastering operation.
Since PCI provides a plug-n-play mechanism with writeable
configuration registers on every board, in a separate address
space, a properly implemented PCI system is plug-and play.
PCI is extremely strict as to trace length, loading, mechanical
specifications, etc. and ultimately should be more reliable than
VESA or ISA.
In summary, PCI is the best PC bus, although it does have its
dark side. PCI is still in its infancy, and although most
manufacturers have ironed out the problems, there is still stock
of older, buggy PCI hardware and broken main BIOSes. For this
reason, I _strongly_ recommend a return guarantee on the
hardware. While the latest PCI mainboards are truly plug-and-
play, older PCI boards may require the user to set options with
both jumpers and in software (ie, interrupt assignments).
Although many users have resolved their PCI problems, it has
taken time and for this reason I cannot recommend a PCI purchase
if having the system operational is extremely time critical.
For many slower SCSI devices, such as disks with head rates around
2M/sec or less, CDROMs, and tapes, there will be little difference in
throughputs with the different PC bus interfaces. For faster
contemporary SCSI drives (Typical high end multi-gigabyte drives have
a head rate of 4-5M/sec, and at least one company is currently ALPHA
testing a parallel head unit with a 14M/sec head rate), throughput
will often be significantly better with controllers on faster busses,
with one user noting a 2.5 fold performance improvement when going
from an Adaptec 1542 ISA board to a NCR53c810 PCI board.
With the exception of situations where PCI write-posting or a similar
write-buffering mechanism is being used, when one of the busses in
your system is busy, all of the busses will be unaccessible. So,
although bus saturation may not be interfering with SCSI performance,
it may have a negative effect on interactive performance. Ie, if you
have a 4M/sec SCSI disk under ISA, you'll have lost 80% of your
bandwidth, and in an ISA/VESA system would only be able to bitblt at
6M/sec. In most cases, a similar impact on processing jobs in the
background would also be felt.
Note that having over 16M of memory does not preclude using an ISA
busmastering SCSI board. Unlike various broken operating systems,
Linux will double buffer when using a DMA with an ISA controller and a
transfer is ultimately destined for an area above 16M. Performance on
these transfers only suffers by about 1.5%, ie not noticeably.
Finally, the price difference between bus masters offered with the
different bus interfaces is often minimal.
With all that in mind, based on your priorities you will have certain
bus preferences
Stability, time critical installations, EISA ISA VESA PCI
and poor return policies
Performance, and typical hobbiest PCI EISA VESA ISA
installations
As I pointed out earlier, bus mastering versus other transfer modes is
going to have a bigger impact on total system performance, and should
be considered more important than bus type when purchasing a SCSI
controller.
10.5. Multiple devices
If will you have multiple devices on your SCSI bus, you may want to
see whether the host adapter/driver that you are considering supports
more than one outstanding command at one time. This is almost
essential if you'll be running a tape drive, and very desirable if you
are mixing devices of different speeds, like a CD ROM and a disk
drive. If the linux driver only supports one outstanding command, you
may be locked out of your disk drive while a tape in the tape drive is
rewinding or seeking to end of media (perhaps for half an hour). With
two disk drives, the problem will not be as noticeable, although
throughput would approach the average of the two transfer rates rather
than the sum of the two transfer rates.
10.6. SCSI-I, SCSI-II, SCSI-III FAST and WIDE options, etc.
Over the years, SCSI has evolved, with new revisions of the standard
introducing higher transfer rates, methods to increase throughput,
standardized commands for new devices, and new commands for previously
supported devices.
In and of themselves, the revision levels don't really mean anything.
Excepting minor things like SCSI-II not allowing the single initiator
option of SCSI-I, SCSI is backwards compatible, with new features
being introduced as options and not mandatory. So, the decision to
call a SCSI adapter SCSI, SCSI-II, or SCSI-III is almost entirely a
marketing one.
10.7. Driver feature comparison
Driver feature comparison (supported chips are listed in parenthesis)
Driver Simultaneous SG > 1
Transfer mode Commands limit Boards
total/LUN
AM53C974 Busmastering DMA 12s/1s 255s Y
aha152x FIFO(8k) Polled 7s/1s 255s N
(AIC6260,
AIC6360)
aha1542 Busmastering DMA 8s/1s 16 Y
aha1740 Busmastering DMA 32s 16 N
aha274x Busmastering DMA 4s/1s 255s Y
BusLogic Busmastering DMA 192/31 128s, 8192h Y
(values are for BT-948/958/958D, older boards support fewer commands)
eata_dma Busmastering DMA 64s-8192h/2-64 512s, 8192h Y
fdomain FIFO(8k) Polled 1s 64s N
(TMC1800, except TMC18c30
TMC18c30, with 2k FIFO
TMC18c50,
TMC36c70)
in2000* FIFO(2k) Polled 1s 255s N
g_NCR5380 Pure Polled 16s/2s 255s Y
(NCR5380,
NCR53c80,
NCR5381,
NCR53c400)
gsi8* Slave DMA 16s/2s 255s
(NCR5380)
PAS16 Pure Polled 16s/2s 255s Y
(NCR5380) or Interlocked Polled
(fails on some systems!)
seagate Interlocked Polled 1s/1s 255s N
wd7000 Busmastering DMA 16s/1s 16 Y
t128 Interlocked Polled 16s 255s Y
(NCR5380)
qlogic Interlocked Polled 1s/1s 255s N
ultrastor Busmastering DMA 16s/2s 32 Y
53c7,8xx Busmastering DMA
(NCR53c810,
NCR53c815,
NCR53c820,
NCR53c825)
rel5 1s/1s 127s N
rel10 8s/1s 127s Y
Notes :
1. drivers flagged with an '*' are not included with the distribution
kernel, and binary boot images may be unavailable.
2. numbers suffixed with an 's' are arbitrary limits set in software
which may be changed with a compile time define.
3. hardware limits are indicated by an 'h' suffix, and may differ from
the software limits currently imposed by the Linux drivers.
4. unsuffixed numbers may indicate either hard or soft limits.
5. rel5 of the NCR53c810 driver is included in the stock 1.2.x and
1.3.x kernels; rel10 is available via anonymous FTP.
6. With the exception of the AM53C974, the busmastering DMA boards are
intelligent; with the NCR executing microcode from main memory, the
AIC7770 executing microcode from on-chip RAM, and the rest using a
mailbox-style interface.
10.8. Board comparison
Board Driver Bus Price Notes
Adaptec AIC-6260 aha152x ISA chip, not board
Adaptec AIC-6360 aha152x VLB chip, not board
(Used in most
VESA/ISA multi-IO
boards with SCSI,
Zenon mainboards)
Adaptec 1520 aha152x ISA
Adaptec 1522 aha152x ISA $80 1520 w/FDC
Adaptec 1510 aha152x ISA 1520 w/out boot ROM,
won't autoprobe.
Adaptec 1540C aha1542 ISA
Adaptec 1542C aha1542 ISA 1540C w/FDC
Adaptec 1540CF aha1542 ISA FAST SCSI-II
Adaptec 1542CF aha1542 ISA $200 1540CF w/FDC
Adaptec 1640 aha1542 MCA
Adaptec 1740 aha1740 EISA discontinued
Adaptec 1742 aha1740 EISA discontinued, 1740
w/FDC
Adaptec 2740 aha274x EISA
Adaptec 2742 aha274x EISA w/FDC
Adaptec 2840 aha274x VLB
Adaptec 2842 aha274x VLB w/FDC
Adaptec 2940 aha274x PCI
Always IN2000 in2000 ISA
BusLogic BT-948 BusLogic PCI $180 Ultra SCSI
BusLogic BT-958 BusLogic PCI $230 Wide Ultra SCSI
(see the section ``BusLogic MultiMaster Host Adapters'' for additional
BusLogic board descriptions)
DPT PM2011 eata_dma ISA FAST SCSI-II
PM2012A eata_dma EISA FAST SCSI-II
PM2012B eata_dma EISA FAST SCSI-II
PM2021 eata_dma ISA FAST SCSI-II
PM2022 eata_dma EISA FAST SCSI-II
PM2024 eata_dma PCI FAST SCSI-II
PM2122 eata_dma EISA FAST SCSI-II
PM2322 eata_dma EISA FAST SCSI-II
PM2124 eata_dma PCI FAST SCSI-II
PM2124 eata_dma PCI FAST SCSI-II
PM2124 eata_dma PCI FAST SCSI-II
PM2124 eata_dma PCI FAST SCSI-II
PM2124 eata_dma PCI FAST SCSI-II
PM2124 eata_dma PCI FAST SCSI-II
PM2041W eata_dma ISA Wide Single-ended
SCSI-II
PM2041UW eata_dma ISA Ultra Wide Single-ended
PM2042W eata_dma EISA Wide Single-ended
PM2042UW eata_dma EISA Ultra Wide Single-ended
PM2044W eata_dma PCI Wide Single-ended
PM2044UW eata_dma PCI Ultra Wide Single-ended
PM2142W eata_dma EISA Wide Single-ended
PM2142UW eata_dma EISA Ultra Wide Single-ended
PM2144W eata_dma PCI Wide Single-ended
PM2144UW eata_dma PCI Ultra Wide Single-ended
PM3021 eata_dma ISA multichannel
raid/simm sockets
PM3122 eata_dma EISA multichannel/raid
PM3222 eata_dma EISA multichannel
raid/simm sockets
PM3224 eata_dma PCI multichannel
raid/simm sockets
PM3334 eata_dma PCI Wide Ultra SCSI
multichannel
raid/simm sockets
DTC 3290 aha1542 EISA Although it should work,
due to documentation
release polcies, DTC
hardware is unsupported
DTC 3130 53c7,8xx PCI '810
DTC 3130B 53c7,8xx PCI '815
DTC 3292 aha1542 EISA 3290 w/FDC
DTC 3292 aha1542 EISA 3290 w/FDC
Future Domain 1680 fdomain ISA FDC
Future Domain 3260 fdomain PCI
NCR53c810 (boards sold 53c7,8xx PCI $60 chip, not board. Boards
by FIC, Chaintech, (board) don't include
Nextor, Gigabyte, etc. BIOS, although most
Mainboards with chip by non-NCR equipped main
AMI, ASUS, J-Bond, boards have the SDMS
etc. Common in DEC BIOS
PCI systems)
NCR53c815 ( 53c7,8xx PCI $100 NCR53c810 plus
Intel PCISCSIKIT, bios
NCR8150S, etc)
NCR53c825 53c7,8xx PCI $120 Wide variant of
NCR53c815. Note that
the current Linux
driver does not
negotiate for wide
transfers.
Pro Audio Spectrum 16 pas16 ISA Sound board w/SCSI
Seagate ST01 seagate ISA $20 BIOS only works with
some drives
Seagate ST02 seagate ISA $40 ST01 w/FDC
Sound Blaster 16 SCSI aha152x ISA Sound board w/SCSI
Western Digital 7000 wd7000 ISA w/FDC
Trantor T128 t128 ISA
Trantor T128F t128 ISA T128 w/FDC and
support for high IRQs
Trantor T130B g_NCR5380 ISA
Ultrastor 14F ultrastor ISA w/FDC
Ultrastor 24F ultrastor EISA w/FDC
Ultrastor 34F ultrastor VLB
Notes :
1. Trantor was recently purchased by Adaptec, and some products are
being sold under the Adaptec name.
2. Ultrastor recently filed for Chapter 11 Bankruptcy, so technical
support is non-existent at this time.
3. The price for the busmastering NCR53c810 boards is not a typo,
includes the standard ASPI/CAM driver package for DOS, OS/2 and
Windows (32 bit access), and other drivers are available for free
download.
Some people have had luck with the following companies :
SW (swt@netcom.com) (214) 907-0871 fax (214) 907-9339
As of 23 Dec 1995, their price was $53 on '810 boards.
4. Adaptec's recent SCSI chips show an unusual sensitivity to cabling
and termination problems. For this reason, I cannot recommend the
Adaptec 154x C and CF revisions or the 2xxx series.
Note that the reliability problems do not apply to the older 154x B
revision boards, 174x A revision boards, or to my knowledge
AIC-6360/AIC-6260 based boards (1505, 1510, 1520, etc).
Also, the quality of their technical support has slipped markedly,
with long delays becoming more common, and their employees being
ignorant (suggesting there were non-disclosure policies affecting
certain literature when there were none), and hostile (ie, refusing
to pass questions on to some one else when they couldn't answer
them).
If users desire handholding, or wish to make a political statement,
they should take this point into consideration. Otherwise, the
Adaptec 152x/1510/1505 are nicer than the other ISA boards in the
same price range, and there are some excellent deals on used and
surplus 154x B revision boards and 1742 boards which IMHO outweigh
the support problems.
5. All DPT boards can be upgraded with cache and raid modules, most of
the boards are also available in Wide and/or Differential versions.
6. The various NCR boards are not entirely equivalent. Ie, while the
ASUS SC200 uses active termination, many other NCR53c810 boards use
passive termination. Most '825 boards use active termination, but
some use a ROM for BIOS and others have a FLASH ROM. Most '825
boards have a WIDE external connector, WIDE internal connector, and
narrow internal connector, although a few (ie, CSC's less expensive
model) lack the narrow internal connector.
10.9. Summary
Most ISA, EISA, VESA, and PCI users will probably be served best by a
BusLogic MultiMaster board, due to its performance, features such as
active termination, and Adaptec 1540 compatibility. There are a
number of models available with EISA, ISA, PCI, and VESA local bus
interfaces, in single ended and differential, and 8/16 bit SCSI bus
widths. The most recent Ultra SCSI PCI models, the BT-948/958/958D,
also include Flash ROM for easy firmware updates, as well as automatic
"smart" termination.
People with the need for the highest possible IO performance at their
fingertips should consider the boards from DPT, which are the only
ones that support RAID, caching and more than one SCSI channel.
People with PCI systems should consider NCR53c8xx based boards. These
are bus mastering SCSI controllers, '810s are available quantity one
for $53 (ie, cheaper than the Adaptec 1520). C't magazine benchmarked
the boards as faster than both the Adaptec 2940 and BusLogic BT-946C
(under DOS), and they get reasonable performance under Linux (up to
6M/sec through the file system ). The disadvantages of these boards
versus the BusLogics are that they aren't Adaptec 1540 compatible, may
or may not come with active termination, you'll need the latest driver
revision (standard in 1.3.5x, also available via anonymous FTP for
1.2.x) to make full use of the hardware, and are more likely to have
problems than with a mailbox interface board like a BusLogic or DPT.
Where everything working right on the first try is imperative, a
BusLogic MultiMaster or DPT board is probably optimal due to the
complexity and potential for problems in non-mailbox interface boards
like the NCR53c8xx and Adaptec AIC7xxx .
People wanting non-PCI SCSI on a limited budget will probably be
happiest finding a surplus or used Adaptec 154x B revision or 174x A
revision, or an Adaptec 1520 clone of some sort (about $80) if they
want new hardware. These boards offer reasonable throughput and
interactive performance at a modest price.
11. Assignment of minor numbers
Due to constraints imposed by Linux's use of a sixteen bit dev_t with
only eight bits allocated to the minor number, SCSI disk, tape, CDROM,
and generic minor numbers are assigned dynamically. according to the
following procedure :
For all SCSI host adapters, from scsi0 through scsiN
For all SCSI IDs on this bus, from 0 through 7, except for
this host adapter's ID
For all logical units, from 0 through max_scsi_luns
- Probe the bus, target, and LUN combination by
issuing a TEST UNIT READY command. If we don't
think a unit was here, don't probe any more LUNs
on this bus + SCSI ID.
- Send an INQUIRY command to determine what we've
found; including the device type, vendor, model,
firmware revision, etc.
- Pass the results of this to a special recognition
function for each high level driver present (i.e. disk,
tape, etc). Attach this device to the next available
unit for any drivers that are willing to drive this.
The generic device will attach to all devices.
- If it was SCSI-I, or in a list of devices known
not to handle multiple LUNs, don't probe any more
LUNs on this bus + SCSI ID.
- If it is a device known to have multiple LUNs, then
a scan of the full LUN spectrum is forced, overriding
max_scsi_luns.
There are frequently problems with this approach because if you have a
system where some devices are only present some of the time, then the
minor numbers for a given device will depend upon which devices were
present at boot time. This can present problem, because rc scripts or
the file /etc/fstab might contain instructions for mounting specific
partitions which fails when the disk appears with a different minor
number.
This problem has not yet been fully solved. There is a program which
can be found on tsx-11 that creates a /dev/scsi hierarchy based upon
host number, id and lun. This is a bit clumsy, but it would help to
alleviate some of the problems.
A better solution will probably come out of the /proc/scsi pseudo
directory. This is currently a work in progress, so at present we
cannot say exactly the form of the solution, but at the time of this
writing this appears to be a promising approach for resolving some of
these issues.