[Open-graphics] VGA BIOS

[Paul Brook]

> > I guess you could probably invent a simple DMA interface and feed ogsim
> > commands over that. I wouldn't like to say whether that'll end up
> > anything like the final hardware, but it might give you enough to take a
> > stab at writing the rest of the 3D driver.
>
> I intend to give the 3D engine a PCI BAR, where every engine register
> has an address.  The engine will be complex, and so will DMA, so it
> will be important for us to be able to eliminate variables whe
> debugging.  Thus, the first driver should be all PIO.  Indeed,
> anything that isn't performance critical that needs to use the GPU
> would do well to use the PIO interface, rather than going through the
> trouble to allocate DMA'able memory space, set up the DMA controller,
> etc., etc.


PIO regs are nice for debugging and poking at the card state from within a 
running machine.