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Expanding the hardware capabilities of DISPLAY/PRINTER
======================================================
FreeDOS DISPLAY.SYS and PRINTER.SYS have some routines which are dependant on
the hardware type that they work on. This hardware is selected in the first
parameter of the commandline.
For example:
DEVICE=C:\FDOS\DISPLAY.SYS CON=(EGA,437,1)
specifies a hardware type "EGA".
Currently, there are five hardware types implemented in DISPLAY.SYS, and none
in PRINTER.SYS. The types in DISPLAY.SYS in fact refer to the same
producedures, but define different "subfont" sizes, which helps you save some
RAM. You can also do this specifying the number of subfonts (ready in DISPLAY
0.09, to come very soon). These will come ready on DISPLAY.SYS 0.09.
They are
EGA (automatic detection of number of subfonts, depending whether
you use EGA or VGA)
EGA 8 (these two are equivalent to DISPLAY.SYS CON=(EGA,437,(1,1)) )
LCD
EGA 14 (this is equivalent to DISPLAY.SYS CON=(EGA,437,(1,2)) )
VGA (this is equivalent to DISPLAY.SYS CON=(EGA,437,(1,3)) )
The specific procedures for EGA, as well as the Int10h handler of DISPLAY.SYS,
are the original code of DISPLAY by Ilya V. Vasilyev (all the other stuff is
what I have added).
The notes below explain how to donate code to DISPLAY.SYS and PRINTER.SYS if
you want to enlarge the capabilities with
How can I contribute a new hardware type?
=========================================
In order to contribute a new type, the following structure is required:
HwName DB "xxxxxxxx"
CPHwName DB "xxxxxxxx"
InitP DW
InitParam DW
HwName: 0-padded hardware name (such as "EGA") as it should appear in the
DISPLAY.SYS or PRINTER.SYS command line
CPHwName: space (#32)-padded name of the hardware to be identified in the
codepage entry header of the CPI files
InitP: Near pointer to the hardware device initialisation procedure
InitParam: A param to be passed to the previous procedure, so that the same
procedure can be used for different table entries
Appart from the table, you need to create three procedures:
HWInit (NON-RESIDENT)
A procedure to be executed when DISPLAY is loaded, that detects the
hardware and initialises the required data
SwSelect (RESIDENT)
A procedure to load certain codepage whose data resides in certain
buffer supplied by the core component
HwSelect (RESIDENT)
A procedure to load certain codepage whose data is determined by
hardware
Please send to me two files, written in NASM language, and please use no names
for each field in the table, and a specific name for each procedure. A first
file should contain the table above filled as appropriate, and the HWInit
procedure. The second file should contain the two resident procedures (and any
other resident procedure or variable that is required).
What procedures can I call?
===========================
Respect to procedures, in HwInit you can use ANY procedure throuhgout the file.
In particular, you may find useful to use these:
OutStrDX: write a string (which ends in '$').
IN: DX: near address of the '$'-terminated string
OUT: -
WriteNumber: writes a number in decimal
IN: AX: a number under 1000 to be displayed (3 digits at most)
OUT: -
NOTES: the "SyntaxErrorStr" string space is reused, and this string can no
longer be used after this procedure is called
In the resident routines, you can only call resident procedures (there's
nothing else interesting in the driver that you may want to call).
In DISPLAY.SYS ONLY: you should make calls to the old Int10h handler by using
call FAR [cs:dOld10]
Of course, you can call any resident routine from HwInit, but the converse is
not true.
What variables can/should I use?
================================
When designing your routines, there is a number of variables that you can use,
and even a number of variables that you are expected to fill. See the table
below.
Flags of the variable
---------------------
FLAG Meaning
------------------------------------------------------------------------
+ You should mandatorily fill in this variable in HwInit with the
appropriate value, or else DISPLAY/PRINTER will not work
* Non-resident variables that you can optionally fill in, if the
information is available
& Resident variable that you can ONLY write on the HwInit procedure
(but not in the resident routines)
------------------------------------------------------------------------
Useable variables
--------------------------------------------------------------------------
VarName Flag Type Meaning
--------------------------------------------------------------------------
pRefreshHWcp + WORD Near pointer to the software codepage
selection routine
pRefreshSWcp + WORD Near pointer to the hardware codepage
selection routine
wMinFontSize * WORD (DISPLAY.SYS ONLY) minimum number of subfonts
that DISPLAY.SYS should admit. If the user
specifies less than this value, then user's
option will be ignored, and this variable will
be used
bMaxHWcpNumber * BYTE Maximum number of hardware hardcoded codepages
bAdapter + BYTE (DISPLAY.SYS ONLY) Adapter type (or compatible),
which is used by the DISPLAY int10h handler in
order to provide the appropriate font info (for
example, does not offer the 8x16 font if adapter
is NOT VGA). See the constants below
wTableSize + WORD (PRINTER.SYS ONLY) This variable exists in both
drivers, but you only have to fill in it in
PRINTER.SYS. As in PRINTER there are no subfonts,
you have to specify a maximum size of the font
info, so that PRINTER can reserve required RAM
buffers of the correct size to store the font
info.
DISPLAY will automatically override any value
you give with a value based on the number of
subfonts.
wHardCPs & WORD You can specify here ONE default hardware
codepage for the device on startup (but leave it
0 if it is unknown)
--------------------------------------------------------------------------
Adapter type constants (for bAdapter)
----------------------
Adapter type Value
---------------------
NO 0
MDA 2
HGA 4
CGA 6
EGA 8
MCGA 10
VGA 12
VESA 14
What are the interfaces to the procedures?
==========================================
In this section it is described the interfaces of each of the three
procedures, and the registers they may use. Please note that there isn't
much stack space so you shouldn't abuse the stack.
HwInit
------
Detects the hardware device, initialises the device and some variables.
IN: AX: the parameter stored in the device structure above
OUT: CFlag=0 on success
CFlag=1 on failure, if the device was not found, or couldn't be
initialised. In such case:
DX: near (relative to current CS) pointer to a string
explaining the error (and ending in '$')
REGISTERS: You must preserve SI if you use it, but can use the other
registers freely (except SS, SP, BP)
RefreshHWcp
-----------
Refreshes certain hardware (hardcoded) codepage, if possible
IN: CX: the number of hardware codepage to be restored, starting on 0
OUT: CFlag set on error, clear on success
REGISTERS: AX,CX,DS,ES,DI can be freely used, the others must be
preserved
RefreshSWcp
-----------
Sets a user defined codepage from user loaded font info
IN: AL: screen mode (as set by the functions ah=00h, ax=4f02h of the
interrupt 10h), -1 if mode is unknown
OUT: CFlag set on error, clear on success
REGISTERS: AX,CX,DS,ES,DI can be freely used, the others must be
preserved
NOTE: The font information about the font to be set is stored in
the following variables, that must be used:
bFont8x8: times 2048 DB ; space for the 8x8 font
bFont8x14: times 3584 DB ; space for the 8x14 font
bFont8x16: times 4096 DB ; space for the 8x16 font
when are these routines to be inserted?
=======================================
When you have them ready, please mail them to me to (aitorsm -AT- inicia.es),
and they will be launched with the next version of DISPLAY.SYS and PRINTER.SYS
starting on version 0.09, which at the moment in which these notes are
written, is not yet ready.
are you going to write more of these routines?
==============================================
Personally I am fully satisfied with having support for EGA/VGA displays, and
am not planning to write any more hardware support, although you can easily
write your own routines, that can be easily attached to the current
DISPLAY/PRINTER scheme.
However, as there's no PRINTER.SYS hardware management routine, I would
consider writing one for PRINTER.SYS *provided that*:
(a) You plan to use it, and you can show you really need it
(b) You have CPI fonts to use with it, which the FreeDOS project can
benefit from
(c) Someone (maybe me, maybe you) has enough technical information about
the routines, because I have very little information about it...
===================
Aitor SANTAMARIA MERINO
The FreeDOS Project, 7th of AUGUST, 2003
Version 1.1: 15th of September, 2003
(thanks to Martin Stromberg)
version 1.2: 11th of October, 2003
(thanks to Martin Stromberg)
|
