Re: [patch] Make MMCONFIG space (extended PCI config space) a driver opt-in issue

Jeff Garzik
2007-12-22T14:20:43Z

Arjan van de Ven wrote:
> Hi,
>
> Linus really wants the extended (4Kb) PCI configuration space (using MCFG acpi table etc) to be opt-in, since there's many issues with it and most drivers don't even use/need it. The idea behind opt-in is that if you don't use it, you don't get to suffer the bugs...
>
> Booted on my 64 bit test machine; sadly it has a defunct BIOS that doesn't have a working MCFG.
>
>
> From: Arjan van de Ven <arjan@linux.intel.com>
> Subject: Make MMCONFIG space a driver opt-in
>
> There are many issues with using the extended PCI configuration space
> (CPU, Chipset and most of all BIOS bugs). This while the vast majority of drivers
> and devices don't even use/need to use the memory mapped access methods since they
> don't use the config space beyond the traditional 256 bytes.
>
> This patch makes accessing the extended config space a driver choice, via the
>
> pci_enable_ext_config(pdev)

Yuck. And, Linus is just being silly. Wait a year then turn on
MMCONFIG :) It took PCI MSI a while to mature, but is finally getting
there.

Jeff