Re: [PATCH v3 2/3] ACPI / OSL: Allow PCI to be disabled

From: Rafael J. Wysocki
Date: Tue Dec 11 2018 - 17:51:54 EST

On Tue, Dec 11, 2018 at 11:22 PM Sinan Kaya <okaya@xxxxxxxxxx> wrote:
> On 12/11/2018 5:16 PM, Rafael J. Wysocki wrote:
> >> AFAIK, ACPI spec says that AML code running on non-existing op-regions to be
> >> discarded last time I checked.
> > I guess you mean "disregarded"?
> >
> I have seen Linux complain about reads/writes to non-existing I2C opregions
> before as a read/write failure for every single AML transaction. I was under the
> impression that we didn't care.
> > So the spec appears to expect the OS to silently ignore the failures
> > in those cases, so why should an error be returned?
> >
> I can certainly return success for this case when CONFIG_PCI is not present.
> >> I know Linux is noisy about these.

Well, users running kernels with CONFIG_PCI unset on platforms
expecting PCI support to be present in the OS may want to know that I
suppose, so that would be a good reason to return an error, but
perhaps just once rather than on every access (maybe unless debugging
is enabled?).