Re: [PATCH v2 2/3] acpi: allow building without CONFIG_HAS_IOPORT

[Rafael J. Wysocki]

On Fri, Oct 11, 2024 at 1:12 PM Andy Shevchenko
<andriy.shevchenko@xxxxxxxxxxxxxxx> wrote:
>
> On Fri, Oct 11, 2024 at 09:59:46AM +0000, Arnd Bergmann wrote:
> > On Fri, Oct 11, 2024, at 09:53, Andy Shevchenko wrote:
> > > On Fri, Oct 11, 2024 at 06:18:18AM +0000, Arnd Bergmann wrote:
>
> ...
>
> > >> +  if (!IS_ENABLED(CONFIG_HAS_IOPORT)) {
> > >> +          *value = BIT_MASK(width);
> > >> +          return AE_NOT_IMPLEMENTED;
> > >
> > > Perhaps it has already been discussed, but why do we need to file value with
> > > semi-garbage when we know it's invalid anyway?
> >
> > It's not strictly necessary, just precaution for possible callers
> > that use the resulting data without checking the error code.
>
> Do you have any examples of that in the kernel?

Yes, there are at least 2 cases.  May not be relevant, though.

> > The all-ones data is what an x86 PC would see when an I/O
> > port is read that is not connected to any device.
>
> Yes, but it's not what your code does.

Care to elaborate?