Some time ago, "Andrew Goodbody" noted :
I'm pretty sure that the detection of FWH devices requires writing to the address space used and you cannot do that as you cannot set the BIOS WE bit in the chipset. So unless you can get around the SMI protection of that bit then there is no way to detect the chip in use. Even if you did detect it, you still could not program it.
And I responded :
I'll check whether the BIOS also has locked access to SMRAM
- usually it wasn't done at the time. If the SMRAM is
accessible from outside SMM, it would be straightforward to bypass the protection (just replace an RSM instruction as the SMI "handler" ;-)
Which was done successfully a mompent ago... BIOS was not locking the SMM settings on this Intel board fortunately, so replacing a plain RSM instruction at the SMI origin (A000:8000) took just a couple minutes' hacking, then for sure Flashrom was able to detect the FWH, to dump and also to update the flash image successfully :=)
This complete circumvention of the (idiotic) BIOS 'protection' has achieved my original purpose - be able to modify the BIOS ad libitum. I did not have to search for the specific GPIO or similar method which the official BIOS patchers use.
Regards