Writing UNIX video /graphics drivers

[Kenny Goers]

Netland,

I've recently purchased Coherent, a U*NX ver 7 clone for the PC. 
Currently I would like to write a device driver for my
VGA/SVGA card (Orchid Pro II), that will allow me to use the
graphic modes of the card and I don't know where to begin.  I've
written low level VGA/SVGA code for DOS, what I would like to know is the
kind of routines one implements, under a U*NX system.
Do you write a charcter or block driver?  Which functions do you
put in ioctl?  What general functions are comtained in most UN*X 
video drivers?  Does anyone have a generic one I can hack up?
I intend this to be public domain when finished so your effort
won't be wasted.

Any help welcome,
kenny.
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Kenny Goers (kenny at msc.edu)
Minnesota Supercomputer Center, Inc.