Willow Schlanger wrote:
>
> Instead of hooking INT 10 via INT 80 do this:
> Put your ROM at C000:8000. Make C000:8003 just contain a RETF.
> Read 3 bytes from C000:3.
> Patch C000:3 with a JUMP to C000:c004.
> Make C000:c004 do a far call to the target of the old C000:3
> instruction. Then _replace_ interrupt 10h with your handler, _without_
> worrying about backing it up.
Hmm.. I don't quite understand what you mean here: what actions do you want to do
*outside* the plex guest os and what do you want to do inside the guest environment? (+
can I "patch" the guest rom bios in my extension rom initialization? - "normally" rom
can
not be written to)
> Now make your handler generate INT 6Dh to call the "old" handler.
>
> Why will this work? Because all 100^ VGA-compatible BIOSes must hook INT
> 10 and INT 6D and make them _both_ go to the same place. Since INT 10 is
> what gets called by programs, we can simply hook that. Elpin's BIOS
> isn't 100% compatible and instead of making INT 10 and INT 6D go to the
> same handler, they made INT 10 go to code that does INT 6Dh and then
> IRETs.
Yes, I figured this out after posting my message (and reading back in the mailinglist
archive). I now hook up to int 10h and just call int 6d when I should call the normal
VGA
bios.
> I guess I can through some code together. Lemme know... if I must...
ok, I was wondering if it would be better to (as suggested on the mailinglist a while
back) output AX to a specific port when calling a VBE function. That way we can have a
plex plugin (written in C++) to handle things for a while (at least while
"prototyping" -
I'm a "little" better at writing C++ then I'm with asm :).. then when we have "enough"
functionality we can start thinking about moving things the extension rom again (we
probably need a plex plugin too, because we need to have a LFB + some way of being
able to
"detect" available video modi).
--
Best regards,
Jeroen Janssen
---
"It's got three keyboards and a hundred extra knobs, including twelve with
'?' on them."
-- The Unseen University Organ, as designed by B. S. Johnson
(Terry Pratchett, Men at Arms)
