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ddeevviiccee ddrriivveerrss -- Overview


A  _d_e_v_i_c_e _d_r_i_v_e_r  is  a program  that  controls the  action of  one of  the
physical devices attached to your computer system.

The following table lists the  device drivers included with this edition of
the  COHERENT system.   The  first field  gives the  device's major  device
number; the  second gives  its name;  and the third  describes it.   When a
major  device number  has  no driver  associated  with it,  that device  is
available for a driver yet to be written.

 0:  mmeemm       Interface to memory and null device
 1:  ttttyy       Controlling terminal device
 2:  nnkkbb/kkbb/mmmm Keyboard and video
 3:  llpp        Parallel line printer
 4:  ffll        Floppy drive
 5:  aassyy       Serial driver (COHERENT 386 only)
 5:  aall00       Serial line 0 (COM1 and COM3) (COHERENT 286 only)
 6:  aall11       Serial line 1 (COM2 and COM4) (COHERENT 286 only)
 7:  hhss        Generic polled multi-port serial card (COHERENT 286 only)
 8:  rrmm        Dual RAM disk
 9:  ppttyy       Pseudoterminals (COHERENT 386 only)
10:  mmss        Microsoft Mouse
11:  aatt        AT hard disk
12:  sstt        Archive Streaming Tape
12:
13:  ssccssii      SCSI device drivers: aahhaa115544xx, ssss
14:
15:
16:
17:
18:
19:
20:
21:
22:
23:  sseemm       System V compatible semaphores
24:  sshhmm       System V subset shared memory
25:  mmssgg       System V compatible messaging
26:
27:
28:
29:
30:
31:

Also included are drivers for the following devices:

ccoonnssoollee   Console driver
cctt        Controlling terminal driver
nnuullll      The ``bit bucket''

These device  drivers are  distributed with  the COHERENT system  in binary
form only.  For proprietary reasons, source code for some drivers cannot be
included with the COHERENT Device Driver Kit.

The command BBuuiilldd links the drivers into a new version of the kernel.

_M_a_j_o_r _a_n_d _M_i_n_o_r _N_u_m_b_e_r_s
COHERENT uses a system of _m_a_j_o_r  and _m_i_n_o_r device numbers to manage devices
and drivers.   In theory,  COHERENT assigns a  unique major number  to each
type of  device, and a unique  minor number to each  instance of that type.
In practice, however, a major number describes a device driver (rather than
a device _p_e_r _s_e).   The  individual devices  serviced  by  that driver  are
identified by a minor number.  Sometimes, certain parts of the minor number
specify configuration.   For example, bits 0 through 6  of the minor number
for COHERENT RAM disks indicate the size of the allocated device.

In COHERENT  286, devices  using different  IRQ's may have  different major
numbers, even  if the devices are  of the same general  type.  For example,
devices ccoomm11*  and ccoomm33* have  major number 5,  while ccoomm22* and  ccoomm44* have
major number 6.

_S_e_r_i_a_l _P_o_r_t_s
The two implementations of  COHERENT come with different drivers for serial
ports.

COHERENT 286 comes with two sets  of drivers.  aall00 and aall11 support ordinary
serial lines.   aall00 supports ports CCOOMM11  and CCOOMM33, and has  major number 5.
aall11 supports ports  CCOOMM22 and CCOOMM44, and has major  number 6.  The driver hhss,
on the other hand, supports generic polled multi-port serial cards.

COHERENT  386 replaces  these drivers  with one driver,  aassyy. It  has major
number 5,  like aall00, but it  supports all four CCOOMM ports,  and a variety of
generic multi-port cards.  The  configuration of ports that aassyy supports is
set when you install COHERENT;  however, you can reconfigure aassyy should you
wish to  add more  hardware to  your system.  See  its Lexicon  article for
details.

_S_e_e _A_l_s_o
aacccceessssiibbllee kkeerrnneell rroouuttiinneess,  bblloocckk-ddeevviiccee rroouuttiinneess, ddrriivveerr-aacccceessss rroouuttiinneess,
hheeaaddeerr ffiilleess,  iinntteerrrruupptt-hhaannddlleerr rroouuttiinneess, II/OO  rroouuttiinneess, kkeerrnneell vvaarriiaabblleess,
mmeemmoorryy-mmaanniippuullaattiioonn   rroouuttiinneess,    rraaccee   ccoonnddiittiioonn,   sseeggmmeenntt-mmaanniippuullaattiioonn
rroouuttiinneess, sswwaapp, tteerrmmiinnaall-ddeevviiccee rroouuttiinneess

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