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 Linux SCSI HOWTO (part 1/2)
Archive-name: linux/howto/scsi/part1
Last-modified: 2 Oct 95


*** The Linux SCSI HOWTO is posted automatically by the Linux
*** HOWTO coordinator, Greg Hankins <>.  Please
*** direct any comments or questions about this HOWTO to the author,
*** Drew Eckhardt <d...@PoohSticks.ORG>.

- --- BEGIN Linux SCSI HOWTO part 1/2 ---

Archive-name: linux/howto/scsi
Last-modified: 23 Jul 1995
Version: 2.17

Copyright 1994, 1995, Drew Eckhardt

    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
    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 <d...@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publish outdated versions, I get questions from users that are answered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.  



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 with the line

        subscribe linux-scsi

in the text.  You can unsubscribe by sending mail to the same address and

        unsubscribe linux-scsi

in the text.

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.

Table of contents
Section 1                       Common Problems
    Section 1.1                 General Flakiness
    Section 1.2                 The kernel command line
    Section 1.3                 A SCSI device shows up at all possible IDs
    Section 1.4                 A SCSI device shows up at all possible LUNs
    Section 1.5                 You get sense errors when you know the
                                    devices are error free
    Section 1.6                 A kernel configured with networking does
                                    not work.
    Section 1.7                 Device detected, but unable to access.
    Section 1.8                 Sometimes the scsi subsystem locks up
    Section 1.9                 Configuring and building the kernel
    Section 1.10                LUNS other than 0 don't work

Section 2                       Reporting Bugs
    Section 2.1                 Capturing messages
    Section 2.2                 Locating the source of a panic()

Section 3                       Modules
    Section 3.1                 General information.
    Section 3.2                 Status of modules under 1.2 kernels.
    Section 3.3                 Status of modules under 1.3 kernels.

Section 4                       Hosts
    Section 4.1                 Supported and Unsupported Hardware
    Section 4.1.1               Multiple host adapters
    Section 4.2                 Common Problems
    Section 4.3                 Adaptec 152x, 151x, Sound Blaster 16 SCSI,
                                    SCSI Pro, Gigabyte, and other AIC
                                    6260/6360 based products (Standard)
    Section 4.4                 Adaptec 154x, AMI FastDisk VLB,
                                    Buslogic, DTC 329x (Standard)  
    Section 4.5                 Adaptec 174x (Standard)
    Section 4.6                 Adaptec 274x, 284x (Standard), 294x (ALPHA)
    Section 4.7                 Allways IN2000 (ALPHA)
    Section 4.8                 EATA: DPT Smartcache, Smartcache Plus,
                                    Smartcache III (Standard)
    Section 4.9                 Future Domain 16x0 with TMC-1800, TMC-18C30,
                                    TMC-18C50, or TMC-36C70 chip (Standard)
    Section 4.10                Generic NCR5380 / T130B (Standard)
    Section 4.11                NCR53c8xx rel5 (Standard), rel10+ (ALPHA)
    Section 4.12                Seagate ST0x/Future Domain TMC-8xx/TMC-9xx
    Section 4.13                PAS16 (Standard)
    Section 4.14                Trantor T128/T128F/T228 (Standard)
    Section 4.15                Ultrastor 14f, 24f,  34f (Standard)
    Section 4.16                Western Digital 7000 (Standard)
    Section 4.17                AM53/79C974 (ALPHA)
    Section 4.18                qlogic (STANDARD)

Section 5                       Disks
    Section 5.1                 Supported and Unsupported Hardware
    Section 5.2                 Common Problems
    Section 5.3                 Device Files
    Section 5.4                 Partitioning
    Section 5.5                 Disk Geometry

Section 6                       CD ROMs
    Section 6.1                 Supported and Unsupported Hardware
    Section 6.2                 Common Problems
    Section 6.3                 Device Files

Section 7                       Tapes
    Section 7.1                 Supported and Unsupported Hardware
    Section 7.2                 Common Problems
    Section 7.3                 Device Files

Section 8                       Generic
    Section 8.1                 Supported and Unsupported Hardware
    Section 8.2                 Common Problems
    Section 8.3                 Device Files

Section 9                       Buyers' Guide
    Section 9.1                 Transfer types
    Section 9.2                 Scatter/gather
    Section 9.3                 Mailbox vs. non-mailbox
    Section 9.4                 Bus types
    Section 9.5                 Multiple devices
    Section 9.6                 SCSI-I, SCSI-II, FAST and WIDE options, etc.
    Section 9.7                 Driver feature comparison
    Section 9.8                 Board comparison
    Section 9.9                 Summary

Section 10
    Section 10.1                Assignment of minor numbers.

Section 1 : 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.

Section 1.1 : General Flakiness
        If you experience random errors, the most likely causes are
        cabling and termination problems.

        Some products, such as those built arround 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

        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

Section 1.2 : 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 immage 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


        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.


Section 1.3 :  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

        Please change the jumper settings.

Section 1.4 :  A SCSI device shows up at all possible LUNs

        The device has buggy firmware.  

        As an interim sollution, you should try using the kernel
        command line option


        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.Torva...@cs.Helsinki.FI>.

Section 1.5 :  You get sense errors when you know the devices are error free

        Sometimes this is caused by bad cables or impropper termination.

        See Section 1.1 : General Flakiness

Section 1.6 :  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.

Section 1.7 :  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 fif{*filter*} partition entries for

        ./MAKEDEV sdc\*

        "should" create entries for /dev/sdc and all fif{*filter*} 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 Subsection 4 : Device Files in the appropriate

        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

Section 1.8 :   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.

Section 1.9 : 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 =


            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  


        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

Section 1.10 : 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 arround this, you need to
        the max_scsi_luns command line option, or recompile the kernel
        wiuth the CONFIG_SCSI_MULTI_LUN option.

        Usually, you'll put


        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.

Section 2 : 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 Section 2.1 : Capturing
messages and Section 2.2 : 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

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.

Section 2.1 : 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


        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


Reboot into DOS, and using your favorite communications software include
the log file in your trouble mail.

Section 2.2 : 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 hexidecimal number on the EIP: line, in this case 19c905, and search
through /usr/src/linux/ 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


    CFLAGS = -Wall -Wstrict-prototypes -O2 -fomit-frame-pointer -pipe


    CFLAGS = -g -Wall -Wstrict-prototypes -O2 -fomit-frame-pointer -pipe

Rebuild the kernel, incrementally or by doing a

    make clean

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>

    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>


    (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        }
    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 incase the
developers' kernels differ from yours.

Section 3 : Modules

This section gives specific details regarding the support for loadable
kernel modules and how it relates to SCSI.

Section 3.1 : 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 filessytems.

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

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-existant card would{*filter*}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

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.

Section 3.2 : 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 utillity 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.

Section 3.3 : 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 3.2.  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.

Section 4 : Hosts

This section gives specific information about the various host adapters that
are supported in some way or another under linux.

Section 4.1 : Supported and Unsupported Hardware
Drivers in the distribution kernel :

Adaptec 152x, Adaptec 154x (including clones from Bustek and DTC 329x
boards), Adaptec 174x, Adaptec 274x/284x/2940, EATA-DMA protocol compilant
boards (all DPT PMXXXXX/XX and SKXXXXX/XX except the PM2001, some boards
from NEC and ATT), 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.

Alpha drivers :
Richoh GSI-8

Many of the ALPHA drivers are available via anonymous FTP from

Drivers that are being developed, but aren't publically available yet,
and modifications needed to make existing drivers compatable with
other boards :
DPT PM2001

Announcements WILL be made when drivers are available for public
alpha testing.  Until then, please don't use up the developers'
valuable time with mail asking for release dates, etc.


    A NCR53c8xx driver has been developed, and with modifications
    ranging from minor to severe should support these chips

    NCR53c720 - detection changes, initializaion changes, modification
        of the assembler to use the 720's register mapping

    NCR53c710 - detection changes, initialization changes, modification
        of assembler, modification of the NCR code to use fatal
        interrupts or GPIO generated non fatal interrupts for
        command completion.

    NCR53c700, NCR53c700-66 - detection changes, initialization changes,
        modification of NCR code to not use DSA, modification of Linux
        code to handle context switches.

NCR53c9x family


SCSI hosts that will not work :

All parallel->SCSI adapters, Rancho SCSI boards, and Grass Roots SCSI

SCSI hosts that will NEVER work :

Non Adaptec compatable DTC boards (including the 3270 and 3280).

CMD SCSI boards.

Aquiring 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 an 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 commision a driver.

Section 4.1.1 : Multiple host adapters

With some host adapters (see Section 9.7 : 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

        Ultrastor 14/34F, Ultrastor 14F,, Adaptec 151x/152x, Buslogic,
        Adaptec 154x, Adaptec 174x, AIC7XXX, AM53C974, Future Domain 16x0,
        Allways 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

Section 4.2 : Common Problems
Section 4.2.1 : SCSI timeouts
        Make sure interrupts are enabled correctly, and there are no
        IRQ, DMA, or address conflicts with other boards.

Section 4.2.2 : 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

        d c800:0

        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 1.1 :

Section 4.2.3 : 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

        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.

Section 4.2.4 : "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 gurantee that it will work on your

        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

        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

Section 4.2.5 : Installing a device driver not included with the distribution

        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

        as linux-version.tar.gz

        They are also mirrored at 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

        --- ./ 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 diffs files and patch is beyond the
        scope of this document.

        See also Section 1.8 : Configuring and building the kernel

3.2.6 :  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/, and add a line in the

                * SCSI low-level drivers

            section, add a boolean configuration variable for your
            driver.  Ie,

                bool 'Allways 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

            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 #inlclude 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"

            you might add

                #ifdef CONFIG_SCSI_IN2000
                #include "in2000.h"

            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

            you might add

                #ifdef CONFIG_SCSI_IN2000

        See also Section 1.8 : Configuring and building the kernel

Section 4.2.5 : Failure of a PCI board

    Unfortunately, PCI is still in its infancy, and having a few
teething problems.

Section 4.3 : Adaptec 152x, 151x, 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,
Ports : 0x140, 0x340
IRQs : 9, 10, 11, 12
DMA is 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 as appropriate, see Defines

kernel command line : aha152x=<PORTBASE>,<IRQ>,<SCSI-ID>,<RECONNECT>

Usually, SCSI-ID will be 7 and RECONNECT non-zero.

To force detection at 0x340, IRQ 11, at SCSI-ID 7, allowing
disconnect/reconnect, you would use the following command line
option :


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

Section 4.4 : Adaptec 154x, AMI FastDisk VLB, Buslogic, 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 : works with all supported configurations, does not
        require an installed BIOS.

Autoprobe override : none

Note: 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.

Note: Buslogic makes a series of boards that are software compatible with
    the Adaptec 1542, and these come in ISA, VLB and EISA flavors.

Antiquity Problems, fix by upgrading :

1.  Linux kernel revisions prior to .99.10 don't support the 'C'

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 Section 1 : Common Problems,
        Subsection 1.1 : 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 Section 1 : Common Problems,
        Subsection 1.1 : 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
        Section 1.1 : Common Problems : General Flakiness
        Section 1.8 : Common Problems : SCSI 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

Section 4.5 : 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: 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.

Section 4.6 : Adaptec 274x, 284x (Standard) 294x (ALPHA)
        A newer version which also supports the Adaptec 294x boards
is available at

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

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.

Section 4.7 : Allways IN2000  (STANDARD)
Ports : 0x100, 0x110, 0x200, 0x220
IRQs : 10, 11, 14, 15
DMA is 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

Section 4.8 : EATA: DPT Smartcache, Smartcache Plus, Smartcache III (Standard)
Supported boards: all, that support the EATA-DMA protocol (no PM2001).
           DPT Smartcache: PM2011  PM2012A
           Smartcache III: PM2021  PM2022  PM2024
                                   PM2122  PM2124
           SmartRAID     : PM3021  PM3222  PM3224
           many of those boards are also available as SKXXXX versions,
           which are supported as well.

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
Autoprobe Override :
 Compile time : diskgeometry in eata_dma.h for unusual disk geometries
               which came from the usage of the old DPTFMT utility.
The latest version of the EATA-DMA driver and a Slackware bootdisk should
be available on:

Common Problems :
1.  The IDE driver detects the ST-506 interface of the EATA board.
1.1     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.
1.2     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).

2. Some old SK2011 boards have a broken firmware. Please contact DPT's
        customer support for an update.

1.  CONFIG_PCI must be set if you are using a PCI board.

Section 4.9 : 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 is 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

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.

Section 4.10 : Generic NCR5380 / T130B
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 tupples
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

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 compatable registers are offset eight from
        the base address.  So, if your address is 0x350, use


        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.  

Notes : the generic driver doesn't support DMA yet, and pseudo-DMA
        isn't supported in the generic driver.

Section 4.11 : NCR53c8xx (Standard)

Supported and Unsupported Configurations :
Base addresses : 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
ny i
        See Section 5.2.7 : Disks :  System Hangs When Swapping

2.  Older versions of Linux didn't recognize '815 and '825

3.  Distribution kernels include release 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

    Please see all of the READMEs in that directory.  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 with

        subscribe ncr53c810

    in the text.  You can unsubscribe by sending mail to the same address
    and including

        unsubscribe ncr53c810

    in the text.

- --- END Linux SCSI HOWTO part 1/2 ---

Version: 2.6.2
Comment: finger for public key


 Fri, 20 Mar 1998 03:00:00 GMT   
   [ 1 post ] 

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