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[Xen-devel] Re: [Bochs-developers] [Patch] [BIOS] support BCV for rombios


Thank you for your comments.

>On Thursday 11 December 2008 00:02:40 Sebastian Herbszt wrote:
>> > +   ;; Point ES:DI at "$PnP", which tells the ROM that we are a PnP BIOS.
>> > +   mov  bx, #0xf000
>> > +   mov  es, bx
>> > +   lea  di, pnp_string
>> Should ax, bx and dx get set to some sane value, e.g. 0? Those are only
>> needed for PnP ISA devices, but some broken option rom might expect
>> something there.
Hmm. I don't find specification in the BBS spec.
But as you said, we may need to add preserving registers.
The patch is for PCI devices.
For ISA device, we would need to check if it is a PCI or ISA device.

>I haven't checked the spec, but if the parameters are meant to match the 
>initialisation vector or other similar entry points (e.g. the UNDI loader 
>entry point for PXE ROMs) then %ax should contain the PCI bus:dev.fn number.

The BBS spec says:
"Note that for PCI cards, AX will not contain the PFA. PCI devices that 
need their PFA during execution of their BCV should store the PFA passed 
earlier when their option ROM’s initialization vector was called."

Best Regards,

Akio Takebe

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