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-$Id: README.aha152x,v 1.2 1999/12/25 15:32:30 fischer Exp fischer $
-Adaptec AHA-1520/1522 SCSI driver for Linux (aha152x)
-
-Copyright 1993-1999 Jürgen Fischer <fischer@norbit.de>
-TC1550 patches by Luuk van Dijk (ldz@xs4all.nl)
-
-
-In Revision 2 the driver was modified a lot (especially the
-bottom-half handler complete()).
-
-The driver is much cleaner now, has support for the new
-error handling code in 2.3, produced less cpu load (much
-less polling loops), has slightly higher throughput (at
-least on my ancient test box; a i486/33Mhz/20MB).
-
-
-CONFIGURATION ARGUMENTS:
-
-IOPORT base io address (0x340/0x140)
-IRQ interrupt level (9-12; default 11)
-SCSI_ID scsi id of controller (0-7; default 7)
-RECONNECT allow targets to disconnect from the bus (0/1; default 1 [on])
-PARITY enable parity checking (0/1; default 1 [on])
-SYNCHRONOUS enable synchronous transfers (0/1; default 1 [on])
-DELAY: bus reset delay (default 100)
-EXT_TRANS: enable extended translation (0/1: default 0 [off])
- (see NOTES)
-
-COMPILE TIME CONFIGURATION (go into AHA152X in drivers/scsi/Makefile):
-
--DAUTOCONF
- use configuration the controller reports (AHA-152x only)
-
--DSKIP_BIOSTEST
- Don't test for BIOS signature (AHA-1510 or disabled BIOS)
-
--DSETUP0="{ IOPORT, IRQ, SCSI_ID, RECONNECT, PARITY, SYNCHRONOUS, DELAY, EXT_TRANS }"
- override for the first controller
-
--DSETUP1="{ IOPORT, IRQ, SCSI_ID, RECONNECT, PARITY, SYNCHRONOUS, DELAY, EXT_TRANS }"
- override for the second controller
-
--DAHA152X_DEBUG
- enable debugging output
-
--DAHA152X_STAT
- enable some statistics
-
-
-LILO COMMAND LINE OPTIONS:
-
-aha152x=<IOPORT>[,<IRQ>[,<SCSI-ID>[,<RECONNECT>[,<PARITY>[,<SYNCHRONOUS>[,<DELAY> [,<EXT_TRANS]]]]]]]
-
- The normal configuration can be overridden by specifying a command line.
- When you do this, the BIOS test is skipped. Entered values have to be
- valid (known). Don't use values that aren't supported under normal
- operation. If you think that you need other values: contact me.
- For two controllers use the aha152x statement twice.
-
-
-SYMBOLS FOR MODULE CONFIGURATION:
-
-Choose from 2 alternatives:
-
-1. specify everything (old)
-
-aha152x=IOPORT,IRQ,SCSI_ID,RECONNECT,PARITY,SYNCHRONOUS,DELAY,EXT_TRANS
- configuration override for first controller
-
-
-aha152x1=IOPORT,IRQ,SCSI_ID,RECONNECT,PARITY,SYNCHRONOUS,DELAY,EXT_TRANS
- configuration override for second controller
-
-2. specify only what you need to (irq or io is required; new)
-
-io=IOPORT0[,IOPORT1]
- IOPORT for first and second controller
-
-irq=IRQ0[,IRQ1]
- IRQ for first and second controller
-
-scsiid=SCSIID0[,SCSIID1]
- SCSIID for first and second controller
-
-reconnect=RECONNECT0[,RECONNECT1]
- allow targets to disconnect for first and second controller
-
-parity=PAR0[PAR1]
- use parity for first and second controller
-
-sync=SYNCHRONOUS0[,SYNCHRONOUS1]
- enable synchronous transfers for first and second controller
-
-delay=DELAY0[,DELAY1]
- reset DELAY for first and second controller
-
-exttrans=EXTTRANS0[,EXTTRANS1]
- enable extended translation for first and second controller
-
-
-If you use both alternatives the first will be taken.
-
-
-NOTES ON EXT_TRANS:
-
-SCSI uses block numbers to address blocks/sectors on a device.
-The BIOS uses a cylinder/head/sector addressing scheme (C/H/S)
-scheme instead. DOS expects a BIOS or driver that understands this
-C/H/S addressing.
-
-The number of cylinders/heads/sectors is called geometry and is required
-as base for requests in C/H/S addressing. SCSI only knows about the
-total capacity of disks in blocks (sectors).
-
-Therefore the SCSI BIOS/DOS driver has to calculate a logical/virtual
-geometry just to be able to support that addressing scheme. The geometry
-returned by the SCSI BIOS is a pure calculation and has nothing to
-do with the real/physical geometry of the disk (which is usually
-irrelevant anyway).
-
-Basically this has no impact at all on Linux, because it also uses block
-instead of C/H/S addressing. Unfortunately C/H/S addressing is also used
-in the partition table and therefore every operating system has to know
-the right geometry to be able to interpret it.
-
-Moreover there are certain limitations to the C/H/S addressing scheme,
-namely the address space is limited to up to 255 heads, up to 63 sectors
-and a maximum of 1023 cylinders.
-
-The AHA-1522 BIOS calculates the geometry by fixing the number of heads
-to 64, the number of sectors to 32 and by calculating the number of
-cylinders by dividing the capacity reported by the disk by 64*32 (1 MB).
-This is considered to be the default translation.
-
-With respect to the limit of 1023 cylinders using C/H/S you can only
-address the first GB of your disk in the partition table. Therefore
-BIOSes of some newer controllers based on the AIC-6260/6360 support
-extended translation. This means that the BIOS uses 255 for heads,
-63 for sectors and then divides the capacity of the disk by 255*63
-(about 8 MB), as soon it sees a disk greater than 1 GB. That results
-in a maximum of about 8 GB addressable diskspace in the partition table
-(but there are already bigger disks out there today).
-
-To make it even more complicated the translation mode might/might
-not be configurable in certain BIOS setups.
-
-This driver does some more or less failsafe guessing to get the
-geometry right in most cases:
-
-- for disks<1GB: use default translation (C/32/64)
-
-- for disks>1GB:
- - take current geometry from the partition table
- (using scsicam_bios_param and accept only `valid' geometries,
- ie. either (C/32/64) or (C/63/255)). This can be extended translation
- even if it's not enabled in the driver.
-
- - if that fails, take extended translation if enabled by override,
- kernel or module parameter, otherwise take default translation and
- ask the user for verification. This might on not yet partitioned
- disks.
-
-
-REFERENCES USED:
-
- "AIC-6260 SCSI Chip Specification", Adaptec Corporation.
-
- "SCSI COMPUTER SYSTEM INTERFACE - 2 (SCSI-2)", X3T9.2/86-109 rev. 10h
-
- "Writing a SCSI device driver for Linux", Rik Faith (faith@cs.unc.edu)
-
- "Kernel Hacker's Guide", Michael K. Johnson (johnsonm@sunsite.unc.edu)
-
- "Adaptec 1520/1522 User's Guide", Adaptec Corporation.
-
- Michael K. Johnson (johnsonm@sunsite.unc.edu)
-
- Drew Eckhardt (drew@cs.colorado.edu)
-
- Eric Youngdale (eric@andante.org)
-
- special thanks to Eric Youngdale for the free(!) supplying the
- documentation on the chip.