Re: [LinuxBIOS] RE : Re: VGA bios and i/o access for powerpc

[ollie]

On Tue, 2006-09-05 at 20:02 +0200, jean-francois simon wrote:
>     Those legacy IO ports are NOT necessary mapped to the PCI IO
>     address.
>     Some VGA card does and some others come with some kind of
>     remapping
>     or offset. Your system chipset should have a way to map legacy
>     VGA IO
>     ports to memory address. You have to read the doc to the PPC
>     chipset 
>     carefully to find it out.
>
> I have read the chipset doc and there is no such VGA support.
> But could you plse explain more on the different ways for VGA cards to
> map the VGA registers? Since the registers are located on a PCI agent
> (the graphic card), there must be a way to access them by generating
> PCI cycles?
> Thanks

I don't know how exactly those legacy IO address is implemented by the
HW and/or the bus protocol. But the Appendix G of PCI sepc says it is
possible for PCI device to decode those legacy ports independent of
the base address register.

Ollie
>