[Open-graphics] From PCI to VGA registers

[Timothy Normand Miller]

On 8/9/07, Paul Brook <paul at codesourcery.com> wrote:

>
> I don't know the exact details, but I'm fairly sure the system bios handles
> this.  ie. it only initializes the VGA bios for one card. Other devices are
> just setup as regular PCI devices, and it's up to the OS to "boot" secondary
> VGA devices. Many BIOS have a setting that lets you choose whether to prefer
> AGP or PCI VGA cards.

That sounds right.

>
> My guess is that there's a bit in the in the option ROM header that says "I'm
> a VGA card". Either that or it just goes off the PCI class.

Yeah, those are the base class, subclass, and interface he was talking
about.  I think these numbers are readable from PCI config space.

-- 
Timothy Normand Miller
http://www.cse.ohio-state.edu/~millerti
Open Graphics Project