On Iau, 2004-03-18 at 00:00, Jon Smirl wrote:
> For cards where we don't have the protected mode code I have provided a vm86
> solution. This solution works by jumping to C000:3 in the BIOS image. Right now
> this scheme does not work on non-X86 machines (you need emu86). It also does not
> work on a OpenFirmware BIOS.  But it does work for the x86 ROM on an X86
> machine.

For a lot of cards jumping to C000:3 in the ROM doesn't do good things.
Not a problemd directly since its simply a matter of avoiding "C000:3"
as a default and making drivers for hardware where it does work use this
option.

> one up tonight; it's fairly simple to do. The kernel just needs to record the
> pdev of the active PCI video device before any other video drivers get loaded.

Your console may not be on a PCI device, or it may be a non VGA device.
Either way thats a case of figuring out "how do we describe the device".

> An even better solution would be for the kernel itself to call the VBIOS ROMs
> during very early boot before entering protected mode. But someone with more

This has nasty effects and doesn't work for hotplug video devices. A lot
of systems are simply built to boot windows, and thats as far as they
got. This shows up already in the int10 secondary hardware booting quite
often. There are some combinations that work and others that don't.
Sometimes its even down to which combinations of cards, and to hardware 
"quirks". Eg on one of my boards if the secondary video is a PCI card
with bridge the system just cannot get the vga steering right if the
primary VGA device is on AGP. Having checked the settings I suspect its
a hardware not software limitation.

You can virtualise 8086 real mode code at any time, although as I said
before PCI bus access, IRQ management and DMA have to be software
virtualised.



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