Re: Proper support for PCI-based option rom loading (was Re: [Qemu-devel] Re: qdev property bug?)

[Sebastian Herbszt]

Anthony Liguori wrote:
> Sebastian Herbszt wrote:
> > What about isapc? Or (pci)pc with isa card?
>
> I'm not sure how the bios enumerates isa option roms on bare metal.  

Let's give this a shot:

A typical isa expansion card seems to have a jumper to select a I/O port, IRQ 
and
boot rom location, e.g. 280, 10, cc00.
In its default configuration the PMC directs access to 0xc0000-0xdffff to pci 
and
doesn't respond to those. Those accesses are forwarded to isa. Now they can be
decoded by the expansion card. I assume isa option roms just appear to be there 
and
the bios only needs to scan for them. This seems to be exactly what qemu does 
right
now with "-option-rom".

- Sebastian