From mboxrd@z Thu Jan  1 00:00:00 1970
Message-ID: <1854fc76e5c50f866c1cccbf01ce82a4@plan9.bell-labs.com>
From: "Russ Cox" <rsc@plan9.bell-labs.com>
To: 9fans@cse.psu.edu
Subject: Re: [9fans] questions on sis630 driver...
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Date: Fri,  2 Aug 2002 20:28:42 -0400
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Look at any of the other vga drivers.  You have to allocate
yourself some physical addresses with upamalloc.  Then you
set up the segment structures so that user programs can
call segattach.  Addvgaseg will do the grungy work for you.

Most of the cards get their addresses configured by the
PCI BIOS at boot time, so you just have to read the addresses
out of the card, upamalloc, and addvgaseg.  Look at the vgat2r4.c
driver for a good simple example.  The linear function takes care
of this.

If the SiS card doesn't have its own video memory and you need
to give it normal memory, you might want to look at the vgai81x.c
driver for an example.

/sys/src/cmd/aux/vga/notes.txt has some notes about writing
VGA drivers.  I posted them to 9fans a while ago too.  I just
put notes.txt out; the next scan will find it.

Russ