From: Brian Julin <bri@forcade.calyx.net>
  To  : ggi-develop@eskimo.com
  Date: Sun, 13 Sep 1998 18:26:35 -0400 (EDT)

Re: Multi-Adaptor Compatibilty Matrix

On Sun, 13 Sep 1998, Karsten Petersen wrote:
> - how can an IBM/vga.c be the secondary driver? i thought beeing the
>   primary means beeing the one the bios booted through and the secondary
>   then is the other, but to be the secondary implies to move the vga-regs
>   what i thought is impossible vor ibm/vga.c ?!?!?

The IBM vga driver can be the secondary if the MDA display is the
primary; a few computers like to boot this way when the MDA is
present and there are jumpers on the original IBM vga cards to make
it load in MDA iospace for use with a CGA monitor.  Also, when you 
have a chipset in a laptop and plug it into a docking station with 
another VGA, sometimes the laptop VGA is kept active but is residing 
at the monochrome IO ports; most of these cases (the WD drivers will 
have multiheading by exploiting this) aren't going to be using the 
IBM/vga driver but a more specific driver tho.  You have to dance
circles around resource conmtentions for the 0x3cx PIO range.

See VGADOC's VGAREGS.TXT and look at register 0x3c2 bit 0.

BTW, anyone had any luck on PCI machines getting access to ISA 
chips IO space after mapping the primary PCI adaptor out of
PIO space?  When I turn off PIO on my Mach32 there is no response
from the ISA card.  Could just be it's not initialized but I 
couldn't wake it up even though I knew how...

> - it would be interresting to also have some kind of card-based database
>   which contains *what* a card/driver *allows* and what not.
>   (e.g.: et6000: only primary)

If it only allows primary, then the column for using it as a secondary 
should have an "N" meaning the driver author says it can't be used this way,
and the header to this column should be a link to a driver-generic 
comment (or chipset-generic comment if you're on a sub-table.)  

I still need to work a bit on the inheritance mechanisms and 
make the HTML tree data structure easier to index before this
works, though (and enter more data.)  Due to the way HTML tables are layed
out it's much easier to work with rows than columns so I made more
progress on the row inheritance this first go.

--
Brian S. Julin