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aahhaa115544xx -- Device Driver


The device  driver aahhaa115544xx lets you use SCSI  interface devices attached to
an Adaptec AHA-154x series host  adapter.  This driver has major number 13.
It can  be accessed  either as  a block-special device  or as  a character-
special device.  The minor number specifies the device and partition number
for disk-type  devices, letting you  use up to  eight SCSI-IDs, with  up to
four logical unit numbers (LUNs) per  SCSI-ID and up to four partitions per
LUN.

The  first  ooppeenn call  on  a  SCSI disk  device  allocates  memory for  the
partition table and reads it into memory.

_C_o_n_t_r_o_l_l_e_r _C_o_n_f_i_g_u_r_a_t_i_o_n
Prior  to installing  the Adaptec  host  adapter in  your system,  you must
configure  the  I/O base  address,  interrupt vector,  and  DMA channel  as
follows:

       I/O base address:0x330
       DMA channel:    5
       Interrupt vector:IRQ11

In addition, if you are using any synchronous SCSI peripherals, disable the
synchronous transfer option on the Adaptec host adapter.

After verifying that your controller works with COHERENT, you may select an
alternate I/O base address or an alternate interrupt vector.  Device-driver
variables SSDDBBAASSEE and SSDDIIRRQQ correspond to the I/O base address and interrupt
vector, respectively.   Variable SSDDDDMMAA sets  the number of  the DMA channel
being used.   See Lexicon article hhss  for an example of  how to configure a
device driver.

When processing  BIOS I/O requests  prior to booting  COHERENT, the Adaptec
host  adapter uses  translation  mode drive  parameters:  number of  heads,
cylinders, and  sectors per track.   Most current versions  of the AHA-154x
use values of  64 heads and 32 sectors per  track, and calculate the number
of cylinders based upon drive capacity.  Note that these numbers are called
``translation-mode'' parameters  because they have  nothing to do  with the
geometry of  the physical drive.  Some early versions  of the AHA-154x, and
some versions distributed by Tandy, use  16 heads and 32 sectors per track.
Device driver variable SSDD_HHDDSS is initialized to 64 as shipped; it should be
patched  to  a value  of  16  for adapters  whose  BIOS  code uses  16-head
translation mode.   The translation-mode parameters  used by the  BIOS code
present on  your host adapter can  be obtained using the  iinnffoo command from
the  tertiary boot  in  versions 3.2.1  and  later of  COHERENT.  (See  the
article  on ttbboooott  for details.)  Note that  the BIOS  code is  executed by
COHERENT only  during initial bootstrap.  After  that, drive parameters are
of  no consequence  since SCSI  I/O requests are  based upon  logical block
number, rather than on cylinder/head/sector addressing.

The installation  procedure for COHERENT  versions 3.2.0 and  later patches
all necessary variables for  the accompanying version of the aahhaa115544xx driver
by executing the command:

    /etc/mkdev scsi

_M_i_n_o_r _D_e_v_i_c_e _N_u_m_b_e_r_s
The minor device number is decoded as follows:

       _B_i_t _n_u_m_b_e_r:  7 6 5 4 3 2 1 0
       _M_e_a_n_i_n_g:     S I I I L L P P

where  _S indicates  the ``special''  bit, _I_I_I  indicates a  three-bit field
containing the SCSI-ID  in the range of zero through  seven, _L_L indicates a
two-bit field containing  a LUN in the range of  zero through three, and _P_P
indicates a two-bit field that contains either a partition number for disk-
type devices or a set of special modes for devices other than disks.

The ``special'' bit and the partition number interact as follows:

_D_e_s_c_r_i_p_t_i_o_n        _S _B_i_t  _P_P  _D_e_v_i_c_e      _T_y_p_e
partition a        0      00 /dev/sd?a    disk
partition b        0      01 /dev/sd?b    disk
partition c        0      10 /dev/sd?c    disk
partition d        0      11 /dev/sd?d    disk
partition table    1      00 /dev/sd?x    disk
no rewind          1      01 /dev/sd?n    tape
RESERVED           1      10     ---      ----
rewind on close    1      11 /dev/sd?     tape

_L_o_a_d_i_n_g _t_h_e _D_r_i_v_e_r
On  COHERENT releases  which support loadable  device drivers,  the aahhaa115544xx
device driver  must be loaded  on a system  that does not have  a SCSI hard
disk as the root device.  To do so, use the command /eettcc/ddrrvvlldd, as follows:

                   /etc/drvld -r /drv/aha154x

_F_i_l_e_s
/ddeevv/ssdd* -- bblloocckk-ssppeecciiaall ddeevviicceess
/ddeevv/rrssdd* -- cchhaarraacctteerr-ssppeecciiaall ddeevviicceess

_S_e_e _A_l_s_o
ddeevviiccee ddrriivveerrss, ddrrvvlldd, ssccssii, ttbboooott

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