Newsgroups: comp.os.minix
Subject: Re: SVGA/VGA in minix
References: <92p99h$eh8$1@nnrp1.deja.com>
Organization: Rochester Institute of Technology, Rochester, NY
From: aje9383@osfmail.isc.rit.edu (Andrew Erickson)
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In article <92p99h$eh8$1@nnrp1.deja.com>, bigbinc  <bigbinc@hotmail.com> wrote:
>Ok I think it is time to ask for help.  I am trying to write a simple
>driver for doing anything with graphics under minix.  I just a need a
>point in the right direction?  I will probably have to write a device
>driver maybe under 'dev/graphics' or something.  My ultimate goal is to
>write this driver then have minix load some bootup bitmap stored on
>disk.

Sounds like an excellent project, which probably many people around here
would be interested in the results of.  (I wouldn't be, personally, but
that's becuase I don't run minix on a PC.)

>I will probably use the svga/vga bios calls to do get into vga mode(if that
>is the simplest way).  Hmm, I could go into 16-bit mode make the necessary
>vga bios calls and then return to protected mode. Or I could write to the
>vga registers in protected mode and enter into svga/vga mode.  Lets say I
>want to enter modeX for example.  Anybody have any other ideas.

I believe the mechanics of doing BIOS calls are pretty well documented in
the various existing device drivers.  I think there are a few macros or
functions which make it pretty painless; a bit of hunting around console.c
or wini_bios.c or tty.c should turn up something.

You might have to do some mucking around with the console driver, at any
rate, to prevent it from trashing your pictures or vice-versa.  I'm not
really sure how much the text and graphics displays are separated on PCs;
but I suspect they may (sometimes) share the same memory regions, etc.,
especially if you are using a bunch of virtual terminals.  (It's nowhere
near as bad as on Macintosh hardware, where the only thing that exists is
bitmapped graphics; drawing text is, at the hardware level, drawing
pictures.  It makes writing a very low-level console driver a rather
difficult and annoying job, to say the least, especially given how easy it
is to debug stuff when you can't read any debug output.)

>Berlin Brown.
>Happy New Years to all Minix Users.

-- 
Andrew Erickson
