Documentation / scsi / ibmmca.txt

Based on kernel version 2.6.26. Page generated on 2008-07-16 21:13 EST.

	
	               -=< The IBM Microchannel SCSI-Subsystem >=-
		       
		                 for the IBM PS/2 series
			 
		  	   Low Level Software-Driver for Linux
			 
	     Copyright (c) 1995 Strom Systems, Inc. under the terms of the GNU 
	  General Public License. Originally written by Martin Kolinek, December 1995.
	   Officially modified and maintained by Michael Lang since January 1999.
		   
	 	                       Version 4.0a
		
	   Last update: January 3, 2001
	   
	   Before you Start
	   ----------------
	   This is the common README.ibmmca file for all driver releases of the 
	   IBM MCA SCSI driver for Linux. Please note, that driver releases 4.0
	   or newer do not work with kernel versions older than 2.4.0, while driver
	   versions older than 4.0 do not work with kernels 2.4.0 or later! If you
	   try to compile your kernel with the wrong driver source, the 
	   compilation is aborted and you get a corresponding error message. This is
	   no bug in the driver; it prevents you from using the wrong source code
	   with the wrong kernel version.
	
	   Authors of this Driver
	   ----------------------
	    - Chris Beauregard (improvement of the SCSI-device mapping by the driver)
	    - Martin Kolinek (origin, first release of this driver)
	    - Klaus Kudielka (multiple SCSI-host management/detection, adaption to
	                      Linux Kernel 2.1.x, module support)
	    - Michael Lang (assigning original pun/lun mapping, dynamical ldn
	                    assignment, rewritten adapter detection, this file, 
			    patches, official driver maintenance and subsequent 
			    debugging, related with the driver)
	
	   Table of Contents
	   -----------------
	   1 Abstract
	   2 Driver Description
	     2.1  IBM SCSI-Subsystem Detection
	     2.2  Physical Units, Logical Units, and Logical Devices
	     2.3  SCSI-Device Recognition and dynamical ldn Assignment
	     2.4  SCSI-Device Order
	     2.5  Regular SCSI-Command-Processing
	     2.6  Abort & Reset Commands
	     2.7  Disk Geometry
	     2.8  Kernel Boot Option
	     2.9  Driver Module Support
	     2.10 Multiple Hostadapter Support
	     2.11 /proc/scsi-Filesystem Information
	     2.12 /proc/mca-Filesystem Information
	     2.13 Supported IBM SCSI-Subsystems
	     2.14 Linux Kernel Versions
	   3 Code History
	   4 To do
	   5 Users' Manual
	     5.1 Commandline Parameters
	     5.2 Troubleshooting
	     5.3 Bug reports
	     5.4 Support WWW-page
	   6 References
	   7 Credits to
	     7.1 People
	     7.2 Sponsors & Supporters
	   8 Trademarks
	   9 Disclaimer
	
	                              * * *
	
	   1 Abstract
	   ----------
	   This README-file describes the IBM SCSI-subsystem low level driver for
	   Linux. The descriptions which were formerly kept in the source code have
	   been taken out of this file to simplify the codes readability. The driver
	   description has been updated, as most of the former description was already
	   quite outdated. The history of the driver development is also kept inside
	   here. Multiple historical developments have been summarized to shorten the
	   text size a bit. At the end of this file you can find a small manual for
	   this driver and hints to get it running on your machine.
	
	   2 Driver Description
	   --------------------
	   2.1 IBM SCSI-Subsystem Detection
	   --------------------------------
	   This is done in the ibmmca_detect() function. It first checks, if the
	   Microchannel-bus support is enabled, as the IBM SCSI-subsystem needs the
	   Microchannel. In a next step, a free interrupt is chosen and the main
	   interrupt handler is connected to it to handle answers of the SCSI-
	   subsystem(s). If the F/W SCSI-adapter is forced by the BIOS to use IRQ11
	   instead of IRQ14, IRQ11 is used for the IBM SCSI-2 F/W adapter. In a 
	   further step it is checked, if the adapter gets detected by force from
	   the kernel commandline, where the I/O port and the SCSI-subsystem id can 
	   be specified. The next step checks if there is an integrated SCSI-subsystem
	   installed. This register area is fixed through all IBM PS/2 MCA-machines 
	   and appears as something like a virtual slot 10 of the MCA-bus. On most
	   PS/2 machines, the POS registers of slot 10 are set to 0xff or 0x00 if not
	   integrated SCSI-controller is available. But on certain PS/2s, like model 
	   9595, this slot 10 is used to store other information which at earlier
	   stage confused the driver and resulted in the detection of some ghost-SCSI. 
	   If POS-register 2 and 3 are not 0x00 and not 0xff, but all other POS
	   registers are either 0xff or 0x00, there must be an integrated SCSI-
	   subsystem present and it will be registered as IBM Integrated SCSI-
	   Subsystem. The next step checks, if there is a slot-adapter installed on 
	   the MCA-bus. To get this, the first two POS-registers, that represent the 
	   adapter ID are checked. If they fit to one of the ids, stored in the 
	   adapter list, a SCSI-subsystem is assumed to be found in a slot and will be 
	   registered. This check is done through all possible MCA-bus slots to allow 
	   more than one SCSI-adapter to be present in the PS/2-system and this is 
	   already the first point of problems. Looking into the technical reference 
	   manual for the IBM PS/2 common interfaces, the POS2 register must have 
	   different interpretation of its single bits to avoid overlapping I/O
	   regions. While one can assume, that the integrated subsystem has a fix 
	   I/O-address at 0x3540 - 0x3547, further installed IBM SCSI-adapters must 
	   use a different I/O-address. This is expressed by bit 1 to 3 of POS2 
	   (multiplied by 8 + 0x3540). Bits 2 and 3 are reserved for the integrated 
	   subsystem, but not for the adapters! The following list shows, how the 
	   bits of POS2 and POS3 should be interpreted.
	   
	   The POS2-register of all PS/2 models' integrated SCSI-subsystems has the 
	   following interpretation of bits:
	                           Bit 7 - 4 : Chip Revision ID (Release)
	                           Bit 3 - 2 : Reserved
	                           Bit 1     : 8k NVRAM Disabled
	                           Bit 0     : Chip Enable (EN-Signal)
	   The POS3-register is interpreted as follows (for most IBM SCSI-subsys.):
	                           Bit 7 - 5 : SCSI ID
	                           Bit 4 - 0 : Reserved = 0
	   The slot-adapters have different interpretation of these bits. The IBM SCSI
	   adapter (w/Cache) and the IBM SCSI-2 F/W adapter use the following
	   interpretation of the POS2 register:
	                           Bit 7 - 4 : ROM Segment Address Select
				   Bit 3 - 1 : Adapter I/O Address Select (*8+0x3540)
				   Bit 0     : Adapter Enable (EN-Signal)
	   and for the POS3 register:
	                           Bit 7 - 5 : SCSI ID 
				   Bit 4     : Fairness Enable (SCSI ID3 f. F/W)
				   Bit 3 - 0 : Arbitration Level
	   The most modern product of the series is the IBM SCSI-2 F/W adapter, it 
	   allows dual-bus SCSI and SCSI-wide addressing, which means, PUNs may be
	   between 0 and 15. Here, Bit 4 is the high-order bit of the 4-bit wide
	   adapter PUN expression. In short words, this means, that IBM PS/2 machines 
	   can only support 1 single integrated subsystem by default. Additional
	   slot-adapters get ports assigned by the automatic configuration tool.
	
	   One day I found a patch in ibmmca_detect(), forcing the I/O-address to be 
	   0x3540 for integrated SCSI-subsystems, there was a remark placed, that on 
	   integrated IBM SCSI-subsystems of model 56, the POS2 register was showing 5.
	   This means, that really for these models, POS2 has to be interpreted
	   sticking to the technical reference guide. In this case, the bit 2 (4) is 
	   a reserved bit and may not be interpreted. These differences between the 
	   adapters and the integrated controllers are taken into account by the 
	   detection routine of the driver on from version >3.0g. 
	
	   Every time, a SCSI-subsystem is discovered, the ibmmca_register() function
	   is called. This function checks first, if the requested area for the I/O-
	   address of this SCSI-subsystem is still available and assigns this I/O-
	   area to the SCSI-subsystem. There are always 8 sequential I/O-addresses
	   taken for each individual SCSI-subsystem found, which are:
	   
	     Offset            Type                  Permissions
	       0     Command Interface Register 1    Read/Write
	       1     Command Interface Register 2    Read/Write
	       2     Command Interface Register 3    Read/Write
	       3     Command Interface Register 4    Read/Write
	       4     Attention Register              Read/Write
	       5     Basic Control Register          Read/Write
	       6     Interrupt Status Register       Read
	       7     Basic Status Register           Read
	   
	   After the I/O-address range is assigned, the host-adapter is assigned
	   to a local structure which keeps all adapter information needed for the
	   driver itself and the mid- and higher-level SCSI-drivers. The SCSI pun/lun
	   and the adapters' ldn tables are initialized and get probed afterwards by
	   the check_devices() function. If no further adapters are found, 
	   ibmmca_detect() quits.
	   
	   2.2 Physical Units, Logical Units, and Logical Devices
	   ------------------------------------------------------
	   There can be up to 56 devices on the SCSI bus (besides the adapter):
	   there are up to 7 "physical units" (each identified by physical unit 
	   number or pun, also called the scsi id, this is the number you select
	   with hardware jumpers), and each physical unit can have up to 8 
	   "logical units" (each identified by logical unit number, or lun, 
	   between 0 and 7). The IBM SCSI-2 F/W adapter offers this on up to two
	   busses and provides support for 30 logical devices at the same time, where
	   in wide-addressing mode you can have 16 puns with 32 luns on each device.
	   This section describes the handling of devices on non-F/W adapters.
	   Just imagine, that you can have 16 * 32 = 512 devices on a F/W adapter
	   which means a lot of possible devices for such a small machine.
	
	   Typically the adapter has pun=7, so puns of other physical units
	   are between 0 and 6(15). On a wide-adapter a pun higher than 7 is
	   possible, but is normally not used. Almost all physical units have only 
	   one logical unit, with lun=0. A CD-ROM jukebox would be an example of a 
	   physical unit with more than one logical unit.
	
	   The embedded microprocessor of the IBM SCSI-subsystem hides the complex
	   two-dimensional (pun,lun) organization from the operating system.
	   When the machine is powered-up (or rebooted), the embedded microprocessor 
	   checks, on its own, all 56 possible (pun,lun) combinations, and the first 
	   15 devices found are assigned into a one-dimensional array of so-called 
	   "logical devices", identified by "logical device numbers" or ldn. The last 
	   ldn=15 is reserved for the subsystem itself. Wide adapters may have 
	   to check up to 15 * 8 = 120 pun/lun combinations.
	   
	   2.3 SCSI-Device Recognition and Dynamical ldn Assignment
	   --------------------------------------------------------
	   One consequence of information hiding is that the real (pun,lun)    
	   numbers are also hidden. The two possibilities to get around this problem
	   are to offer fake pun/lun combinations to the operating system or to 
	   delete the whole mapping of the adapter and to reassign the ldns, using
	   the immediate assign command of the SCSI-subsystem for probing through
	   all possible pun/lun combinations.  An ldn is a "logical device number"
	   which is used by IBM SCSI-subsystems to access some valid SCSI-device.
	   At the beginning of the development of this driver, the following approach 
	   was used:
	   
	   First, the driver checked the ldn's (0 to 6) to find out which ldn's
	   have devices assigned. This was done by the functions check_devices() and
	   device_exists(). The interrupt handler has a special paragraph of code
	   (see local_checking_phase_flag) to assist in the checking. Assume, for
	   example, that three logical devices were found assigned at ldn 0, 1, 2.
	   These are presented to the upper layer of Linux SCSI driver
	   as devices with bogus (pun, lun) equal to (0,0), (1,0), (2,0). 
	   On the other hand, if the upper layer issues a command to device
	   say (4,0), this driver returns DID_NO_CONNECT error.
	
	   In a second step of the driver development, the following improvement has
	   been applied: The first approach limited the number of devices to 7, far
	   fewer than the 15 that it could use, then it just mapped ldn -> 
	   (ldn/8,ldn%8) for pun,lun.  We ended up with a real mishmash of puns
	   and luns, but it all seemed to work.
	
	   The latest development, which is implemented from the driver version 3.0
	   and later, realizes the device recognition in the following way:
	   The physical SCSI-devices on the SCSI-bus are probed via immediate_assign- 
	   and device_inquiry-commands, that is all implemented in a completely new
	   made check_devices() subroutine. This delivers an exact map of the physical
	   SCSI-world that is now stored in the get_scsi[][]-array. This means,
	   that the once hidden pun,lun assignment is now known to this driver.
	   It no longer believes in default-settings of the subsystem and maps all
	   ldns to existing pun,lun "by foot". This assures full control of the ldn
	   mapping and allows dynamical remapping of ldns to different pun,lun, if
	   there are more SCSI-devices installed than ldns available (n>15). The
	   ldns from 0 to 6 get 'hardwired' by this driver to puns 0 to 7 at lun=0,
	   excluding the pun of the subsystem. This assures, that at least simple 
	   SCSI-installations have optimum access-speed and are not touched by
	   dynamical remapping. The ldns 7 to 14 are put to existing devices with 
	   lun>0 or to non-existing devices, in order to satisfy the subsystem, if 
	   there are less than 15 SCSI-devices connected. In the case of more than 15 
	   devices, the dynamical mapping goes active. If the get_scsi[][] reports a 
	   device to be existent, but it has no ldn assigned, it gets an ldn out of 7
	   to 14. The numbers are assigned in cyclic order, therefore it takes 8 
	   dynamical reassignments on the SCSI-devices until a certain device 
	   loses its ldn again. This assures that dynamical remapping is avoided 
	   during intense I/O between up to 15 SCSI-devices (means pun,lun 
	   combinations). A further advantage of this method is that people who
	   build their kernel without probing on all luns will get what they expect,
	   because the driver just won't assign everything with lun>0 when 
	   multiple lun probing is inactive.
	 
	   2.4 SCSI-Device Order
	   ---------------------
	   Because of the now correct recognition of physical pun,lun, and 
	   their report to mid-level- and higher-level-drivers, the new reported puns
	   can be different from the old, faked puns. Therefore, Linux will eventually
	   change /dev/sdXXX assignments and prompt you for corrupted superblock
	   repair on boottime. In this case DO NOT PANIC, YOUR DISKS ARE STILL OK!!!
	   You have to reboot (CTRL-D) with an old kernel and set the /etc/fstab-file
	   entries right. After that, the system should come up as errorfree as before.
	   If your boot-partition is not coming up, also edit the /etc/lilo.conf-file
	   in a Linux session booted on old kernel and run lilo before reboot. Check
	   lilo.conf anyway to get boot on other partitions with foreign OSes right
	   again. But there exists a feature of this driver that allows you to change
	   the assignment order of the SCSI-devices by flipping the PUN-assignment.
	   See the next paragraph for a description.
	 
	   The problem for this is, that Linux does not assign the SCSI-devices in the
	   way as described in the ANSI-SCSI-standard. Linux assigns /dev/sda to 
	   the device with at minimum id 0. But the first drive should be at id 6,
	   because for historical reasons, drive at id 6 has, by hardware, the highest
	   priority and a drive at id 0 the lowest. IBM was one of the rare producers,
	   where the BIOS assigns drives belonging to the ANSI-SCSI-standard. Most 
	   other producers' BIOS does not (I think even Adaptec-BIOS). The 
	   IBMMCA_SCSI_ORDER_STANDARD flag, which you set while configuring the
	   kernel enables to choose the preferred way of SCSI-device-assignment. 
	   Defining this flag would result in Linux determining the devices in the 
	   same order as DOS and OS/2 does on your MCA-machine. This is also standard 
	   on most industrial computers and OSes, like e.g. OS-9. Leaving this flag 
	   undefined will get your devices ordered in the default way of Linux. See 
	   also the remarks of Chris Beauregard from Dec 15, 1997 and the followups 
	   in section 3.
	   
	   2.5 Regular SCSI-Command-Processing
	   -----------------------------------
	   Only three functions get involved: ibmmca_queuecommand(), issue_cmd(),
	   and interrupt_handler().
	
	   The upper layer issues a scsi command by calling function 
	   ibmmca_queuecommand(). This function fills a "subsystem control block"
	   (scb) and calls a local function issue_cmd(), which writes a scb 
	   command into subsystem I/O ports. Once the scb command is carried out, 
	   the interrupt_handler() is invoked. If a device is determined to be 
	   existant and it has not assigned any ldn, it gets one dynamically.
	   For this, the whole stuff is done in ibmmca_queuecommand().
	
	   2.6 Abort & Reset Commands
	   --------------------------
	   These are implemented with busy waiting for interrupt to arrive.
	   ibmmca_reset() and ibmmca_abort() do not work sufficiently well
	   up to now and need still a lot of development work. This seems
	   to be a problem with other low-level SCSI drivers too, however
	   this should be no excuse.
	
	   2.7 Disk Geometry
	   -----------------
	   The ibmmca_biosparams() function should return the same disk geometry 
	   as the bios. This is needed for fdisk, etc. The returned geometry is 
	   certainly correct for disks smaller than 1 gigabyte. In the meantime,
	   it has been proved, that this works fine even with disks larger than
	   1 gigabyte.
	
	   2.8 Kernel Boot Option
	   ----------------------
	   The function ibmmca_scsi_setup() is called if option ibmmcascsi=n 
	   is passed to the kernel. See file linux/init/main.c for details.
	   
	   2.9 Driver Module Support
	   -------------------------
	   Is implemented and tested by K. Kudielka. This could probably not work
	   on kernels <2.1.0.
	  
	   2.10 Multiple Hostadapter Support
	   ---------------------------------
	   This driver supports up to eight interfaces of type IBM-SCSI-Subsystem. 
	   Integrated-, and MCA-adapters are automatically recognized. Unrecognizable
	   IBM-SCSI-Subsystem interfaces can be specified as kernel-parameters.
	 
	   2.11 /proc/scsi-Filesystem Information
	   --------------------------------------
	   Information about the driver condition is given in 
	   /proc/scsi/ibmmca/<host_no>. ibmmca_proc_info() provides this information.
	   
	   This table is quite informative for interested users. It shows the load
	   of commands on the subsystem and whether you are running the bypassed
	   (software) or integrated (hardware) SCSI-command set (see below). The
	   amount of accesses is shown. Read, write, modeselect is shown separately
	   in order to help debugging problems with CD-ROMs or tapedrives.
	   
	   The following table shows the list of 15 logical device numbers, that are
	   used by the SCSI-subsystem. The load on each ldn is shown in the table,
	   again, read and write commands are split. The last column shows the amount
	   of reassignments, that have been applied to the ldns, if you have more than
	   15 pun/lun combinations available on the SCSI-bus.
	   
	   The last two tables show the pun/lun map and the positions of the ldns
	   on this pun/lun map. This may change during operation, when a ldn is
	   reassigned to another pun/lun combination. If the necessity for dynamical
	   assignments is set to 'no', the ldn structure keeps static.
	   
	   2.12 /proc/mca-Filesystem Information
	   -------------------------------------
	   The slot-file contains all default entries and in addition chip and I/O-
	   address information of the SCSI-subsystem. This information is provided
	   by ibmmca_getinfo().
	   
	   2.13 Supported IBM SCSI-Subsystems
	   ----------------------------------
	   The following IBM SCSI-subsystems are supported by this driver:
	   
	     - IBM Fast/Wide SCSI-2 Adapter
	     - IBM 7568 Industrial Computer SCSI Adapter w/Cache
	     - IBM Expansion Unit SCSI Controller
	     - IBM SCSI Adapter w/Cache
	     - IBM SCSI Adapter
	     - IBM Integrated SCSI Controller
	     - All clones, 100% compatible with the chipset and subsystem command
	       system of IBM SCSI-adapters (forced detection)
	     
	   2.14 Linux Kernel Versions
	   --------------------------
	   The IBM SCSI-subsystem low level driver is prepared to be used with
	   all versions of Linux between 2.0.x and 2.4.x. The compatibility checks
	   are fully implemented up from version 3.1e of the driver. This means, that
	   you just need the latest ibmmca.h and ibmmca.c file and copy it in the
	   linux/drivers/scsi directory. The code is automatically adapted during 
	   kernel compilation. This is different from kernel 2.4.0! Here version 
	   4.0 or later of the driver must be used for kernel 2.4.0 or later. Version
	   4.0 or later does not work together with older kernels! Driver versions
	   older than 4.0 do not work together with kernel 2.4.0 or later. They work
	   on all older kernels.
	
	   3 Code History
	   --------------
	   Jan 15 1996:  First public release.
	   - Martin Kolinek
	
	   Jan 23 1996:  Scrapped code which reassigned scsi devices to logical
	   device numbers. Instead, the existing assignment (created
	   when the machine is powered-up or rebooted) is used. 
	   A side effect is that the upper layer of Linux SCSI 
	   device driver gets bogus scsi ids (this is benign), 
	   and also the hard disks are ordered under Linux the 
	   same way as they are under dos (i.e., C: disk is sda, 
	   D: disk is sdb, etc.).
	   - Martin Kolinek
	
	   I think that the CD-ROM is now detected only if a CD is 
	   inside CD_ROM while Linux boots. This can be fixed later,
	   once the driver works on all types of PS/2's.
	   - Martin Kolinek
	
	   Feb 7 1996:   Modified biosparam function. Fixed the CD-ROM detection. 
	   For now, devices other than harddisk and CD_ROM are 
	   ignored. Temporarily modified abort() function 
	   to behave like reset().
	   - Martin Kolinek
	
	   Mar 31 1996:  The integrated scsi subsystem is correctly found
	   in PS/2 models 56,57, but not in model 76. Therefore
	   the ibmmca_scsi_setup() function has been added today.
	   This function allows the user to force detection of
	   scsi subsystem. The kernel option has format
	   ibmmcascsi=n
	   where n is the scsi_id (pun) of the subsystem. Most likely, n is 7.
	   - Martin Kolinek
	
	   Aug 21 1996:  Modified the code which maps ldns to (pun,0).  It was
	   insufficient for those of us with CD-ROM changers.
	   - Chris Beauregard
	 
	   Dec 14 1996: More improvements to the ldn mapping.  See check_devices
	   for details.  Did more fiddling with the integrated SCSI detection,
	   but I think it's ultimately hopeless without actually testing the
	   model of the machine.  The 56, 57, 76 and 95 (ultimedia) all have
	   different integrated SCSI register configurations.  However, the 56
	   and 57 are the only ones that have problems with forced detection.
	   - Chris Beauregard
	 
	   Mar 8-16 1997: Modified driver to run as a module and to support 
	   multiple adapters. A structure, called ibmmca_hostdata, is now
	   present, containing all the variables, that were once only
	   available for one single adapter. The find_subsystem-routine has vanished.
	   The hardware recognition is now done in ibmmca_detect directly.
	   This routine checks for presence of MCA-bus, checks the interrupt
	   level and continues with checking the installed hardware.
	   Certain PS/2-models do not recognize a SCSI-subsystem automatically.
	   Hence, the setup defined by command-line-parameters is checked first.
	   Thereafter, the routine probes for an integrated SCSI-subsystem.
	   Finally, adapters are checked. This method has the advantage to cover all
	   possible combinations of multiple SCSI-subsystems on one MCA-board. Up to
	   eight SCSI-subsystems can be recognized and announced to the upper-level
	   drivers with this improvement. A set of defines made changes to other
	   routines as small as possible.
	   - Klaus Kudielka
	   
	   May 30 1997: (v1.5b)
	   1) SCSI-command capability enlarged by the recognition of MODE_SELECT.
	      This needs the RD-Bit to be disabled on IM_OTHER_SCSI_CMD_CMD which 
	      allows data to be written from the system to the device. It is a
	      necessary step to be allowed to set blocksize of SCSI-tape-drives and 
	      the tape-speed, without confusing the SCSI-Subsystem.
	   2) The recognition of a tape is included in the check_devices routine.
	      This is done by checking for TYPE_TAPE, that is already defined in
	      the kernel-scsi-environment. The markup of a tape is done in the 
	      global ldn_is_tape[] array. If the entry on index ldn 
	      is 1, there is a tapedrive connected.
	   3) The ldn_is_tape[] array is necessary to distinguish between tape- and 
	      other devices. Fixed blocklength devices should not cause a problem
	      with the SCB-command for read and write in the ibmmca_queuecommand
	      subroutine. Therefore, I only derivate the READ_XX, WRITE_XX for
	      the tape-devices, as recommended by IBM in this Technical Reference,
	      mentioned below. (IBM recommends to avoid using the read/write of the
	      subsystem, but the fact was, that read/write causes a command error from
	      the subsystem and this causes kernel-panic.)
	   4) In addition, I propose to use the ldn instead of a fix char for the
	      display of PS2_DISK_LED_ON(). On 95, one can distinguish between the
	      devices that are accessed. It shows activity and easyfies debugging.   
	   The tape-support has been tested with a SONY SDT-5200 and a HP DDS-2
	   (I do not know yet the type). Optimization and CD-ROM audio-support, 
	   I am working on ...
	   - Michael Lang
	   
	   June 19 1997: (v1.6b)
	   1) Submitting the extra-array ldn_is_tape[] -> to the local ld[]
	      device-array. 
	   2) CD-ROM Audio-Play seems to work now.
	   3) When using DDS-2 (120M) DAT-Tapes, mtst shows still density-code
	      0x13 for ordinary DDS (61000 BPM) instead 0x24 for DDS-2. This appears 
	      also on Adaptec 2940 adaptor in a PCI-System. Therefore, I assume that 
	      the problem is independent of the low-level-driver/bus-architecture.
	   4) Hexadecimal ldn on PS/2-95 LED-display.
	   5) Fixing of the PS/2-LED on/off that it works right with tapedrives and
	      does not confuse the disk_rw_in_progress counter.
	   - Michael Lang
	  
	   June 21 1997: (v1.7b)
	   1) Adding of a proc_info routine to inform in /proc/scsi/ibmmca/<host> the
	      outer-world about operational load statistics on the different ldns,
	      seen by the driver. Everybody that has more than one IBM-SCSI should
	      test this, because I only have one and cannot see what happens with more
	      than one IBM-SCSI hosts.
	   2) Definition of a driver version-number to have a better recognition of 
	      the source when there are existing too much releases that may confuse
	      the user, when reading about release-specific problems. Up to know,
	      I calculated the version-number to be 1.7. Because we are in BETA-test
	      yet, it is today 1.7b.
	   3) Sorry for the heavy bug I programmed on June 19 1997! After that, the
	      CD-ROM did not work any more! The C7-command was a fake impression
	      I got while programming. Now, the READ and WRITE commands for CD-ROM are
	      no longer running over the subsystem, but just over 
	      IM_OTHER_SCSI_CMD_CMD. On my observations (PS/2-95), now CD-ROM mounts
	      much faster(!) and hopefully all fancy multimedia-functions, like direct
	      digital recording from audio-CDs also work. (I tried it with cdda2wav
	      from the cdwtools-package and it filled up the harddisk immediately :-).)
	      To easify boolean logics, a further local device-type in ld[], called
	      is_cdrom has been included.
	   4) If one uses a SCSI-device of unsupported type/commands, one
	      immediately runs into a kernel-panic caused by Command Error. To better
	      understand which SCSI-command caused the problem, I extended this
	      specific panic-message slightly.
	   - Michael Lang
	 
	   June 25 1997: (v1.8b)
	   1) Some cosmetical changes for the handling of SCSI-device-types.
	      Now, also CD-Burners / WORMs and SCSI-scanners should work. For
	      MO-drives I have no experience, therefore not yet supported.
	      In logical_devices I changed from different type-variables to one
	      called 'device_type' where the values, corresponding to scsi.h,
	      of a SCSI-device are stored.
	   2) There existed a small bug, that maps a device, coming after a SCSI-tape
	      wrong. Therefore, e.g. a CD-ROM changer would have been mapped wrong
	      -> problem removed.
	   3) Extension of the logical_device structure. Now it contains also device,
	      vendor and revision-level of a SCSI-device for internal usage.
	   - Michael Lang
	
	   June 26-29 1997: (v2.0b)
	   1) The release number 2.0b is necessary because of the completely new done
	      recognition and handling of SCSI-devices with the adapter. As I got
	      from Chris the hint, that the subsystem can reassign ldns dynamically,
	      I remembered this immediate_assign-command, I found once in the handbook.
	      Now, the driver first kills all ldn assignments that are set by default
	      on the SCSI-subsystem. After that, it probes on all puns and luns for
	      devices by going through all combinations with immediate_assign and
	      probing for devices, using device_inquiry. The found physical(!) pun,lun
	      structure is stored in get_scsi[][] as device types. This is followed
	      by the assignment of all ldns to existing SCSI-devices. If more ldns
	      than devices are available, they are assigned to non existing pun,lun
	      combinations to satisfy the adapter. With this, the dynamical mapping
	      was possible to implement. (For further info see the text in the 
	      source code and in the description below. Read the description
	      below BEFORE installing this driver on your system!)
	   2) Changed the name IBMMCA_DRIVER_VERSION to IBMMCA_SCSI_DRIVER_VERSION.
	   3) The LED-display shows on PS/2-95 no longer the ldn, but the SCSI-ID
	      (pun) of the accessed SCSI-device. This is now senseful, because the 
	      pun known within the driver is exactly the pun of the physical device
	      and no longer a fake one.
	   4) The /proc/scsi/ibmmca/<host_no> consists now of the first part, where
	      hit-statistics of ldns is shown and a second part, where the maps of 
	      physical and logical SCSI-devices are displayed. This could be very 
	      interesting, when one is using more than 15 SCSI-devices in order to 
	      follow the dynamical remapping of ldns.
	   - Michael Lang
	 
	   June 26-29 1997: (v2.0b-1)
	   1) I forgot to switch the local_checking_phase_flag to 1 and back to 0
	      in the dynamical remapping part in ibmmca_queuecommand for the 
	      device_exist routine. Sorry.
	   - Michael Lang
	 
	   July 1-13 1997: (v3.0b,c)
	   1) Merging of the driver-developments of Klaus Kudielka and Michael Lang 
	      in order to get a optimum and unified driver-release for the 
	      IBM-SCSI-Subsystem-Adapter(s).
	         For people, using the Kernel-release >=2.1.0, module-support should 
	      be no problem. For users, running under <2.1.0, module-support may not 
	      work, because the methods have changed between 2.0.x and 2.1.x.
	   2) Added some more effective statistics for /proc-output.
	   3) Change typecasting at necessary points from (unsigned long) to
	      virt_to_bus().
	   4) Included #if... at special points to have specific adaption of the
	      driver to kernel 2.0.x and 2.1.x. It should therefore also run with 
	      later releases.
	   5) Magneto-Optical drives and medium-changers are also recognized, now.
	      Therefore, we have a completely gapfree recognition of all SCSI-
	      device-types, that are known by Linux up to kernel 2.1.31.
	   6) The flag SCSI_IBMMCA_DEV_RESET has been inserted. If it is set within
	      the configuration, each connected SCSI-device will get a reset command
	      during boottime. This can be necessary for some special SCSI-devices.
	      This flag should be included in Config.in.
	      (See also the new Config.in file.)
	   Probable next improvement: bad disk handler.
	   - Michael Lang
	 
	   Sept 14 1997: (v3.0c)
	   1) Some debugging and speed optimization applied.
	   - Michael Lang
	
	   Dec 15, 1997
	    - chrisb[AT]truespectra[DOT]com
	    - made the front panel display thingy optional, specified from the
	    command-line via ibmmcascsi=display.  Along the lines of the /LED
	    option for the OS/2 driver.
	    - fixed small bug in the LED display that would hang some machines.
	    - reversed ordering of the drives (using the
	    IBMMCA_SCSI_ORDER_STANDARD define).  This is necessary for two main
	    reasons:
		- users who've already installed Linux won't be screwed.  Keep
		in mind that not everyone is a kernel hacker.
		- be consistent with the BIOS ordering of the drives.  In the
		BIOS, id 6 is C:, id 0 might be D:.  With this scheme, they'd be
		backwards.  This confuses the crap out of those heathens who've
		got a impure Linux installation (which, <wince>, I'm one of).
	    This whole problem arises because IBM is actually non-standard with
	    the id to BIOS mappings.  You'll find, in fdomain.c, a similar
	    comment about a few FD BIOS revisions.  The Linux (and apparently
	    industry) standard is that C: maps to scsi id (0,0).  Let's stick
	    with that standard.
	    - Since this is technically a branch of my own, I changed the
	    version number to 3.0e-cpb.
	
	   Jan 17, 1998: (v3.0f)
	   1) Addition of some statistical info for /proc in proc_info.
	   2) Taking care of the SCSI-assignment problem, dealed by Chris at Dec 15
	      1997. In fact, IBM is right, concerning the assignment of SCSI-devices 
	      to driveletters. It is conform to the ANSI-definition of the SCSI-
	      standard to assign drive C: to SCSI-id 6, because it is the highest
	      hardware priority after the hostadapter (that has still today by
	      default everywhere id 7). Also realtime-operating systems that I use, 
	      like LynxOS and OS9, which are quite industrial systems use top-down
	      numbering of the harddisks, that is also starting at id 6. Now, one
	      sits a bit between two chairs. On one hand side, using the define
	      IBMMCA_SCSI_ORDER_STANDARD makes Linux assigning disks conform to
	      the IBM- and ANSI-SCSI-standard and keeps this driver downward
	      compatible to older releases, on the other hand side, people is quite
	      habituated in believing that C: is assigned to (0,0) and much other
	      SCSI-BIOS do so. Therefore, I moved the IBMMCA_SCSI_ORDER_STANDARD 
	      define out of the driver and put it into Config.in as subitem of 
	      'IBM SCSI support'. A help, added to Documentation/Configure.help 
	      explains the differences between saying 'y' or 'n' to the user, when 
	      IBMMCA_SCSI_ORDER_STANDARD prompts, so the ordinary user is enabled to 
	      choose the way of assignment, depending on his own situation and gusto.
	   3) Adapted SCSI_IBMMCA_DEV_RESET to the local naming convention, so it is
	      now called IBMMCA_SCSI_DEV_RESET.
	   4) Optimization of proc_info and its subroutines.
	   5) Added more in-source-comments and extended the driver description by
	      some explanation about the SCSI-device-assignment problem.
	   - Michael Lang
	   
	   Jan 18, 1998: (v3.0g)
	   1) Correcting names to be absolutely conform to the later 2.1.x releases.
	      This is necessary for 
	            IBMMCA_SCSI_DEV_RESET -> CONFIG_IBMMCA_SCSI_DEV_RESET
	            IBMMCA_SCSI_ORDER_STANDARD -> CONFIG_IBMMCA_SCSI_ORDER_STANDARD
	   - Michael Lang
	 
	   Jan 18, 1999: (v3.1 MCA-team internal)
	   1) The multiple hosts structure is accessed from every subroutine, so there
	      is no longer the address of the device structure passed from function
	      to function, but only the hostindex. A call by value, nothing more. This
	      should really be understood by the compiler and the subsystem should get
	      the right values and addresses.
	   2) The SCSI-subsystem detection was not complete and quite hugely buggy up
	      to now, compared to the technical manual. The interpretation of the pos2
	      register is not as assumed by people before, therefore, I dropped a note
	      in the ibmmca_detect function to show the registers' interpretation.
	      The pos-registers of integrated SCSI-subsystems do not contain any 
	      information concerning the IO-port offset, really. Instead, they contain
	      some info about the adapter, the chip, the NVRAM .... The I/O-port is
	      fixed to 0x3540 - 0x3547. There can be more than one adapters in the 
	      slots and they get an offset for the I/O area in order to get their own
	      I/O-address area. See chapter 2 for detailed description. At least, the 
	      detection should now work right, even on models other than 95. The 95ers
	      came happily around the bug, as their pos2 register contains always 0 
	      in the critical area. Reserved bits are not allowed to be interpreted, 
	      therefore, IBM is allowed to set those bits as they like and they may 
	      really vary between different PS/2 models. So, now, no interpretation 
	      of reserved bits - hopefully no trouble here anymore.
	   3) The command error, which you may get on models 55, 56, 57, 70, 77 and
	      P70 may have been caused by the fact, that adapters of older design do
	      not like sending commands to non-existing SCSI-devices and will react
	      with a command error as a sign of protest. While this error is not
	      present on IBM SCSI Adapter w/cache, it appears on IBM Integrated SCSI
	      Adapters. Therefore, I implemented a workaround to forgive those 
	      adapters their protests, but it is marked up in the statistics, so
	      after a successful boot, you can see in /proc/scsi/ibmmca/<host_number>
	      how often the command errors have been forgiven to the SCSI-subsystem.
	      If the number is bigger than 0, you have a SCSI subsystem of older
	      design, what should no longer matter.
	   4) ibmmca_getinfo() has been adapted very carefully, so it shows in the 
	      slotn file really, what is senseful to be presented.
	   5) ibmmca_register() has been extended in its parameter list in order to
	      pass the right name of the SCSI-adapter to Linux.
	   - Michael Lang
	
	   Feb 6, 1999: (v3.1)
	   1) Finally, after some 3.1Beta-releases, the 3.1 release. Sorry, for 
	      the delayed release, but it was not finished with the release of 
	      Kernel 2.2.0.
	   - Michael Lang
	   
	   Feb 10, 1999 (v3.1)
	   1) Added a new commandline parameter called 'bypass' in order to bypass
	      every integrated subsystem SCSI-command consequently in case of
	      troubles.
	   2) Concatenated read_capacity requests to the harddisks. It gave a lot
	      of troubles with some controllers and after I wanted to apply some
	      extensions, it jumped out in the same situation, on my w/cache, as like 
	      on D. Weinehalls' Model 56, having integrated SCSI. This gave me the 
	      decisive hint to move the code-part out and declare it global. Now
	      it seems to work far better and more stable. Let us see what
	      the world thinks of it...
	   3) By the way, only Sony DAT-drives seem to show density code 0x13. A
	      test with a HP drive gave right results, so the problem is vendor-
	      specific and not a problem of the OS or the driver.
	   - Michael Lang
	   
	   Feb 18, 1999 (v3.1d)
	   1) The abort command and the reset function have been checked for 
	      inconsistencies. From the logical point of thinking, they work
	      at their optimum, now, but as the subsystem does not answer with an
	      interrupt, abort never finishes, sigh...
	   2) Everything, that is accessed by a busmaster request from the adapter
	      is now declared as global variable, even the return-buffer in the
	      local checking phase. This assures, that no accesses to undefined memory
	      areas are performed.
	   3) In ibmmca.h, the line unchecked_isa_dma is added with 1 in order to
	      avoid memory-pointers for the areas higher than 16MByte in order to
	      be sure, it also works on 16-Bit Microchannel bus systems.
	   4) A lot of small things have been found, but nothing that endangered the
	      driver operations. Just it should be more stable, now.
	   - Michael Lang
	      
	   Feb 20, 1999 (v3.1e)
	   1) I took the warning from the Linux Kernel Hackers Guide serious and 
	      checked the cmd->result return value to the done-function very carefully.
	      It is obvious, that the IBM SCSI only delivers the tsb.dev_status, if
	      some error appeared, else it is undefined. Now, this is fixed. Before
	      any SCB command gets queued, the tsb.dev_status is set to 0, so the 
	      cmd->result won't screw up Linux higher level drivers.
	   2) The reset-function has slightly improved. This is still planed for 
	      abort. During the abort and the reset function, no interrupts are 
	      allowed. This is however quite hard to cope with, so the INT-status
	      register is read. When the interrupt gets queued, one can find its
	      status immediately on that register and is enabled to continue in the
	      reset function. I had no chance to test this really, only in a bogus 
	      situation, I got this function running, but the situation was too much
	      worse for Linux :-(, so tests will continue.
	   3) Buffers got now consistent. No open address mapping, as before and
	      therefore no further troubles with the unassigned memory segmentation
	      faults that scrambled probes on 95XX series and even on 85XX series,
	      when the kernel is done in a not so perfectly fitting way.
	   4) Spontaneous interrupts from the subsystem, appearing without any
	      command previously queued are answered with a DID_BAD_INTR result.
	   5) Taken into account ZP Gus' proposals to reverse the SCSI-device
	      scan order. As it does not work on Kernel 2.1.x or 2.2.x, as proposed
	      by him, I implemented it in a slightly derived way, which offers in 
	      addition more flexibility.
	   - Michael Lang
	
	   Apr 23, 2000 (v3.2pre1)
	   1) During a very long time, I collected a huge amount of bug reports from
	      various people, trying really quite different things on their SCSI-
	      PS/2s. Today, all these bug reports are taken into account and should be
	      mostly solved. The major topics were:
	      - Driver crashes during boottime by no obvious reason.
	      - Driver panics while the midlevel-SCSI-driver is trying to inquire
	        the SCSI-device properties, even though hardware is in perfect state.
	      - Displayed info for the various slot-cards is interpreted wrong.
	      The main reasons for the crashes were two:
	      1) The commands to check for device information like INQUIRY, 
	         TEST_UNIT_READY, REQUEST_SENSE and MODE_SENSE cause the devices
		 to deliver information of up to 255 bytes. Midlevel drivers offer
		 1024 bytes of space for the answer, but the IBM-SCSI-adapters do
		 not accept this, as they stick quite near to ANSI-SCSI and report
		 a COMMAND_ERROR message which causes the driver to panic. The main
		 problem was located around the INQUIRY command. Now, for all the
		 mentioned commands, the buffersize sent to the adapter is at 
		 maximum 255 which seems to be a quite reasonable solution. 
		 TEST_UNIT_READY gets a buffersize of 0 to make sure that no 
		 data is transferred in order to avoid any possible command failure.
	      2) On unsuccessful TEST_UNIT_READY, the mid-level driver has to send
	         a REQUEST_SENSE in order to see where the problem is located. This
		 REQUEST_SENSE may have various length in its answer-buffer. IBM
		 SCSI-subsystems report a command failure if the returned buffersize
		 is different from the sent buffersize, but this can be suppressed by
		 a special bit, which is now done and problems seem to be solved.
	   2) Code adaption to all kernel-releases. Now, the 3.2 code compiles on 
	      2.0.x, 2.1.x, 2.2.x and 2.3.x kernel releases without any code-changes.
	   3) Commandline-parameters are recognized again, even under Kernel 2.3.x or
	      higher.
	   - Michael Lang   
	
	   April 27, 2000 (v3.2pre2)
	   1) Bypassed commands get read by the adapter by one cycle instead of two.
	      This increases SCSI-performance.
	   2) Synchronous datatransfer is provided for sure to be 5 MHz on older
	      SCSI and 10 MHz on internal F/W SCSI-adapter.
	   3) New commandline parameters allow to force the adapter to slow down while
	      in synchronous transfer. Could be helpful for very old devices.
	   - Michael Lang
	   
	   June 2, 2000 (v3.2pre5)
	   1) Added Jim Shorney's contribution to make the activity indicator
	      flashing in addition to the LED-alphanumeric display-panel on
	      models 95A. To be enabled to choose this feature freely, a new
	      commandline parameter is added, called 'activity'.
	   2) Added the READ_CONTROL bit for test_unit_ready SCSI-command.
	   3) Added some suppress_exception bits to read_device_capacity and
	      all device_inquiry occurrences in the driver code.
	   4) Complaints about the various KERNEL_VERSION implementations are
	      taken into account. Every local_LinuxKernelVersion occurrence is
	      now replaced by KERNEL_VERSION, defined in linux/version.h. 
	      Corresponding changes were applied to ibmmca.h, too. This was a
	      contribution to all kernel-parts by Philipp Hahn.
	   - Michael Lang
	   
	   July 17, 2000 (v3.2pre8)
	   A long period of collecting bug reports from all corners of the world
	   now lead to the following corrections to the code:
	   1) SCSI-2 F/W support crashed with a COMMAND ERROR. The reason for this 
	      was that it is possible to disable Fast-SCSI for the external bus.
	      The feature-control command, where this crash appeared regularly, tried
	      to set the maximum speed of 10MHz synchronous transfer speed and that
	      reports a COMMAND ERROR if external bus Fast-SCSI is disabled. Now,
	      the feature-command probes down from maximum speed until the adapter 
	      stops to complain, which is at the same time the maximum possible
	      speed selected in the reference program. So, F/W external can run at
	      5 MHz (slow-) or 10 MHz (fast-SCSI). During feature probing, the 
	      COMMAND ERROR message is used to detect if the adapter does not complain.
	   2) Up to now, only combined busmode is supported, if you use external
	      SCSI-devices, attached to the F/W-controller. If dual bus is selected,
	      only the internal SCSI-devices get accessed by Linux. For most 
	      applications, this should do fine. 
	   3) Wide-SCSI-addressing (16-Bit) is now possible for the internal F/W
	      bus on the F/W adapter. If F/W adapter is detected, the driver
	      automatically uses the extended PUN/LUN <-> LDN mapping tables, which
	      are now new from 3.2pre8. This allows PUNs between 0 and 15 and should
	      provide more fun with the F/W adapter.
	   4) Several machines use the SCSI: POS registers for internal/undocumented
	      storage of system relevant info. This confused the driver, mainly on
	      models 9595, as it expected no onboard SCSI only, if all POS in
	      the integrated SCSI-area are set to 0x00 or 0xff. Now, the mechanism
	      to check for integrated SCSI is much more restrictive and these problems
	      should be history.
	   - Michael Lang          
	
	   July 18, 2000 (v3.2pre9)
	   This develop rather quickly at the moment. Two major things were still
	   missing in 3.2pre8:
	   1) The adapter PUN for F/W adapters has 4-bits, while all other adapters
	      have 3-bits. This is now taken into account for F/W.
	   2) When you select CONFIG_IBMMCA_SCSI_ORDER_STANDARD, you should 
	      normally get the inverse probing order of your devices on the SCSI-bus.
	      The ANSI device order gets scrambled in version 3.2pre8!! Now, a new
	      and tested algorithm inverts the device-order on the SCSI-bus and
	      automatically avoids accidental access to whatever SCSI PUN the adapter 
	      is set and works with SCSI- and Wide-SCSI-addressing.
	   - Michael Lang
	
	   July 23, 2000 (v3.2pre10 unpublished) 
	   1) LED panel display supports wide-addressing in ibmmca=display mode.
	   2) Adapter-information and autoadaption to address-space is done.
	   3) Auto-probing for maximum synchronous SCSI transfer rate is working.
	   4) Optimization to some embedded function calls is applied.
	   5) Added some comment for the user to wait for SCSI-devices being probed.
	   6) Finished version 3.2 for Kernel 2.4.0. It least, I thought it is but...
	   - Michael Lang
	   
	   July 26, 2000 (v3.2pre11)
	   1) I passed a horrible weekend getting mad with NMIs on kernel 2.2.14 and
	      a model 9595. Asking around in the community, nobody except of me has
	      seen such errors. Weird, but I am trying to recompile everything on
	      the model 9595. Maybe, as I use a specially modified gcc, that could
	      cause problems. But, it was not the reason. The true background was,
	      that the kernel was compiled for i386 and the 9595 has a 486DX-2. 
	      Normally, no troubles should appear, but for this special machine,
	      only the right processor support is working fine!
	   2) Previous problems with synchronous speed, slowing down from one adapter 
	      to the next during probing are corrected. Now, local variables store
	      the synchronous bitmask for every single adapter found on the MCA bus.
	   3) LED alphanumeric panel support for XX95 systems is now showing some
	      alive rotator during boottime. This makes sense, when no monitor is 
	      connected to the system. You can get rid of all display activity, if
	      you do not use any parameter or just ibmmcascsi=activity, for the 
	      harddrive activity LED, existent on all PS/2, except models 8595-XXX.
	      If no monitor is available, please use ibmmcascsi=display, which works
	      fine together with the linuxinfo utility for the LED-panel.
	   - Michael Lang
	   
	   July 29, 2000 (v3.2)
	   1) Submission of this driver for kernel 2.4test-XX and 2.2.17.
	   - Michael Lang
	   
	   December 28, 2000 (v3.2d / v4.0)
	   1) The interrupt handler had some wrong statement to wait for. This
	      was done due to experimental reasons during 3.2 development but it
	      has shown that this is not stable enough. Going back to wait for the
	      adapter to be not busy is best.
	   2) Inquiry requests can be shorter than 255 bytes of return buffer. Due
	      to a bug in the ibmmca_queuecommand routine, this buffer was forced
	      to 255 at minimum. If the memory address, this return buffer is pointing
	      to does not offer more space, invalid memory accesses destabilized the
	      kernel.
	   3) version 4.0 is only valid for kernel 2.4.0 or later. This is necessary
	      to remove old kernel version dependent waste from the driver. 3.2d is
	      only distributed with older kernels but keeps compatibility with older
	      kernel versions. 4.0 and higher versions cannot be used with older 
	      kernels anymore!! You must have at least kernel 2.4.0!!
	   4) The commandline argument 'bypass' and all its functionality got removed
	      in version 4.0. This was never really necessary, as all troubles were
	      based on non-command related reasons up to now, so bypassing commands
	      did not help to avoid any bugs. It is kept in 3.2X for debugging reasons.
	   5) Dynamical reassignment of ldns was again verified and analyzed to be
	      completely inoperational. This is corrected and should work now.
	   6) All commands that get sent to the SCSI adapter were verified and
	      completed in such a way, that they are now completely conform to the
	      demands in the technical description of IBM. Main candidates were the
	      DEVICE_INQUIRY, REQUEST_SENSE and DEVICE_CAPACITY commands. They must
	      be transferred by bypassing the internal command buffer of the adapter
	      or else the response can be a random result. GET_POS_INFO would be more
	      safe in usage, if one could use the SUPRESS_EXCEPTION_SHORT, but this
	      is not allowed by the technical references of IBM. (Sorry, folks, the
	      model 80 problem is still a task to be solved in a different way.)
	   7) v3.2d is still hold back for some days for testing, while 4.0 is 
	      released.
	   - Michael Lang
	   
	   January 3, 2001 (v4.0a)
	   1) A lot of complains after the 2.4.0-prerelease kernel came in about
	      the impossibility to compile the driver as a module. This problem is
	      solved. In combination with that problem, some unprecise declaration
	      of the function option_setup() gave some warnings during compilation.
	      This is solved, too by a forward declaration in ibmmca.c.
	   2) #ifdef argument concerning CONFIG_SCSI_IBMMCA is no longer needed and
	      was entirely removed.
	   3) Some switch statements got optimized in code, as some minor variables
	      in internal SCSI-command handlers.
	   - Michael Lang
	
	   4 To do
	   -------
	        - IBM SCSI-2 F/W external SCSI bus support in separate mode!
		- It seems that the handling of bad disks is really bad -
		  non-existent, in fact. However, a low-level driver cannot help
		  much, if such things happen.
	
	   5 Users' Manual
	   ---------------
	   5.1 Commandline Parameters
	   --------------------------
	   There exist several features for the IBM SCSI-subsystem driver.
	   The commandline parameter format is:
	   
	         ibmmcascsi=<command1>,<command2>,<command3>,...
		 
	   where commandN can be one of the following:
	   
	         display    Owners of a model 95 or other PS/2 systems with an
		            alphanumeric LED display may set this to have their
			    display showing the following output of the 8 digits:
			      
			                ------DA
					
			    where '-' stays dark, 'D' shows the SCSI-device id
			    and 'A' shows the SCSI hostindex, being currently 
			    accessed. During boottime, this will give the message
			    
			                SCSIini*
					
	                    on the LED-panel, where the * represents a rotator, 
			    showing the activity during the probing phase of the
			    driver which can take up to two minutes per SCSI-adapter.
		 adisplay   This works like display, but gives more optical overview 
		            of the activities on the SCSI-bus. The display will have
			    the following output:
			    
			                6543210A
					
			    where the numbers 0 to 6 light up at the shown position,
			    when the SCSI-device is accessed. 'A' shows again the SCSI
			    hostindex. If display nor adisplay is set, the internal
			    PS/2 harddisk LED is used for media-activities. So, if
			    you really do not have a system with a LED-display, you
			    should not set display or adisplay. Keep in mind, that
			    display and adisplay can only be used alternatively. It
			    is not recommended to use this option, if you have some
			    wide-addressed devices e.g. at the SCSI-2 F/W adapter in
			    your system. In addition, the usage of the display for
			    other tasks in parallel, like the linuxinfo-utility makes 
			    no sense with this option.
		 activity   This enables the PS/2 harddisk LED activity indicator.
		            Most PS/2 have no alphanumeric LED display, but some
			    indicator. So you should use this parameter to activate it.
			    If you own model 9595 (Server95), you can have both, the 
			    LED panel and the activity indicator in parallel. However,
			    some PS/2s, like the 8595 do not have any harddisk LED 
			    activity indicator, which means, that you must use the
			    alphanumeric LED display if you want to monitor SCSI-
			    activity.
		 bypass     This is obsolete from driver version 4.0, as the adapters
		            got that far understood, that the selection between 
			    integrated and bypassed commands should now work completely
			    correct! For historical reasons, the old description is
			    kept here:
		            This commandline parameter forces the driver never to use
		            SCSI-subsystems' integrated SCSI-command set. Except of
			    the immediate assign, which is of vital importance for
			    every IBM SCSI-subsystem to set its ldns right. Instead,
			    the ordinary ANSI-SCSI-commands are used and passed by the
			    controller to the SCSI-devices, therefore 'bypass'. The
			    effort, done by the subsystem is quite bogus and at a
			    minimum and therefore it should work everywhere. This
			    could maybe solve troubles with old or integrated SCSI-
			    controllers and nasty harddisks. Keep in mind, that using 
			    this flag will slow-down SCSI-accesses slightly, as the 
			    software generated commands are always slower than the 
			    hardware. Non-harddisk devices always get read/write-
			    commands in bypass mode. On the most recent releases of 
			    the Linux IBM-SCSI-driver, the bypass command should be
			    no longer a necessary thing, if you are sure about your
			    SCSI-hardware!
		 normal     This is the parameter, introduced on the 2.0.x development
		            rail by ZP Gu. This parameter defines the SCSI-device
			    scan order in the new industry standard. This means, that
			    the first SCSI-device is the one with the lowest pun.
			    E.g. harddisk at pun=0 is scanned before harddisk at
			    pun=6, which means, that harddisk at pun=0 gets sda
			    and the one at pun=6 gets sdb.
		 ansi       The ANSI-standard for the right scan order, as done by
		            IBM, Microware and Microsoft, scans SCSI-devices starting
			    at the highest pun, which means, that e.g. harddisk at
			    pun=6 gets sda and a harddisk at pun=0 gets sdb. If you
			    like to have the same SCSI-device order, as in DOS, OS-9
			    or OS/2, just use this parameter.
	         fast       SCSI-I/O in synchronous mode is done at 5 MHz for IBM-
	                    SCSI-devices. SCSI-2 Fast/Wide Adapter/A external bus
	                    should then run at 10 MHz if Fast-SCSI is enabled,
	                    and at 5 MHz if Fast-SCSI is disabled on the external
	                    bus. This is the default setting when nothing is 
	                    specified here.
	         medium     Synchronous rate is at 50% approximately, which means
	                    2.5 MHz for IBM SCSI-adapters and 5.0 MHz for F/W ext.
	                    SCSI-bus (when Fast-SCSI speed enabled on external bus).
	         slow       The slowest possible synchronous transfer rate is set. 
	                    This means 1.82 MHz for IBM SCSI-adapters and 2.0 MHz
	                    for F/W external bus at Fast-SCSI speed on the external
			    bus.
			    
	   A further option is that you can force the SCSI-driver to accept a SCSI-
	   subsystem at a certain I/O-address with a predefined adapter PUN. This
	   is done by entering 
	
	                  commandN   = I/O-base
			  commandN+1 = adapter PUN
			  
	   e.g. ibmmcascsi=0x3540,7 will force the driver to detect a SCSI-subsystem 
	   at I/O-address 0x3540 with adapter PUN 7. Please only use this method, if
	   the driver does really not recognize your SCSI-adapter! With driver version
	   3.2, this recognition of various adapters was hugely improved and you
	   should try first to remove your commandline arguments of such type with a 
	   newer driver. I bet, it will be recognized correctly. Even multiple and 
	   different types of IBM SCSI-adapters should be recognized correctly, too.
	   Use the forced detection method only as last solution!
	   
	   Examples:
	   
	        ibmmcascsi=adisplay
		
	   This will use the advanced display mode for the model 95 LED alphanumeric
	   display.
	   
	        ibmmcascsi=display,0x3558,7
		
	   This will activate the default display mode for the model 95 LED display
	   and will force the driver to accept a SCSI-subsystem at I/O-base 0x3558
	   with adapter PUN 7.
	   
	   5.2 Troubleshooting
	   -------------------
	   The following FAQs should help you to solve some major problems with this
	   driver.
	   
	     Q: "Reset SCSI-devices at boottime" halts the system at boottime, why?
	     A: This is only tested with the IBM SCSI Adapter w/cache. It is not
	        yet proven to run on other adapters, however you may be lucky.
		In version 3.1d this has been hugely improved and should work better,
		now. Normally you really won't need to activate this flag in the
		kernel configuration, as all post 1989 SCSI-devices should accept
		the reset-signal, when the computer is switched on. The SCSI-
		subsystem generates this reset while being initialized. This flag
		is really reserved for users with very old, very strange or self-made
		SCSI-devices.
	     Q: Why is the SCSI-order of my drives mirrored to the device-order
	        seen from OS/2 or DOS ?
	     A: It depends on the operating system, if it looks at the devices in
	        ANSI-SCSI-standard (starting from pun 6 and going down to pun 0) or
		if it just starts at pun 0 and counts up. If you want to be conform
		with OS/2 and DOS, you have to activate this flag in the kernel
		configuration or you should set 'ansi' as parameter for the kernel.
		The parameter 'normal' sets the new industry standard, starting
		from pun 0, scanning up to pun 6. This allows you to change your 
		opinion still after having already compiled the kernel.
	     Q: Why can't I find IBM MCA SCSI support in the config menu?
	     A: You have to activate MCA bus support, first.
	     Q: Where can I find the latest info about this driver?
	     A: See the file MAINTAINERS for the current WWW-address, which offers
	        updates, info and Q/A lists. At this file's origin, the webaddress
		was: http://www.uni-mainz.de/~langm000/linux.html
	     Q: My SCSI-adapter is not recognized by the driver, what can I do?
	     A: Just force it to be recognized by kernel parameters. See section 5.1.
	        If this really happens, do also send e-mail to the maintainer, as
		forced detection should be never necessary. Forced detection is in
		principal some flaw of the driver adapter detection and goes into 
		bug reports.
	     Q: The driver screws up, if it starts to probe SCSI-devices, is there
	        some way out of it?
	     A: Yes, that was some recognition problem of the correct SCSI-adapter
	        and its I/O base addresses. Upgrade your driver to the latest release
		and it should be fine again.
	     Q: I get a message: panic IBM MCA SCSI: command error .... , what can
	        I do against this?
	     A: Previously, I followed the way by ignoring command errors by using
	        ibmmcascsi=forgiveall, but this command no longer exists and is
		obsolete. If such a problem appears, it is caused by some segmentation
		fault of the driver, which maps to some unallowed area. The latest