On Jul 13, 2014, at 1:15 AM, jabir <[email protected]> wrote:

> Hi,
> 
> Please help me in understanding the policy of system BIOS for scanning
> UEFI driver from a PCI option rom image.
> 1. Does the system BIOS look for UEFI driver image immediately after
> the legacy OpROM image based on PCIR length field of legacy OpROM
> image. OR Can there be gap between legacy and UEFI OpROM images? Does
> system BIOS scan entire option rom to find 0xAA55 signature of UEFI
> driver image?
> 

If follows the PCI Firmware Specification and walks the data structures in the 
ROM defined in the spec. Some legacy BIOSes in the past only supported a single 
ROM image, they did not walk the table so usually the Legacy BIOS op-rom is 1st 
in the ROM. It is legal to have more than 2 ROM images. 

The open source code is here: 
https://svn.code.sf.net/p/edk2/code/trunk/edk2/MdeModulePkg/Bus/Pci/PciBusDxe/PciOptionRomSupport.c
 ProcessOpRomImage()

Thanks,

Andrew Fish

> Thanks,
> Jabir
> 
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