[coreboot] Question on VGA BIOS extraction

[Stefan Reinauer]

* Iru Cai <mytbk920423 at gmail.com> [150330 18:24]:
> Hi,
> 
> I'm trying to build Coreboot for ThinkPad X220. I first backup the vendor BIOS,
> then use UEFITool to extract a VBIOS. The romheader program detects the ROM's
> PCI data structure and reports the device id is 8086:0106, but the VGA
> controller's device id is 8086:0126. I extracted the video ROM from a running
> X220 memory and use romheader to test it, the result is still 8086:0106. How
> could this happen?

The same VGA OPROM binary is used for a whole set of different chipsets.
However, the PCI header specification does not have a way to express
that. The main system firmware has to know that, for a 0x0126 device it
has to look for the 0x0106 OPROM. Hence coreboot has a mapping function
for most newer (Intel) chipsets.

Stefan