Re: [PATCH 1/4] PCI / ACPI: Identify external PCI devices

[Lorenzo Pieralisi]

On Thu, Nov 15, 2018 at 12:22:39PM +0200, Mika Westerberg wrote:
> On Tue, Nov 13, 2018 at 11:45:36AM +0000, Lorenzo Pieralisi wrote:
> > On Tue, Nov 13, 2018 at 01:27:00PM +0200, Mika Westerberg wrote:
> > 
> > [...]
> > 
> > > > To be frank the concept (and Microsoft _DSD bindings) seems a bit vague
> > > > and not thoroughly defined and I would question its detection at
> > > > PCI/ACPI core level, I would hope this can be clarified at ACPI
> > > > specification level, at least.
> > > 
> > > I guess that is the way they envision to use _DSD. Instead of having
> > > single UUID that covers all properties (like what we have with device
> > > properties) they have one UUID per property "class". I certainly hope we
> > > don't need to keep extending prp_guids[] array each time they invent
> > > another "class" of properties.
> > 
> > It is even worse than that. This is a unilateral/obscure change that
> > won't be part of ACPI specifications (I guess it was easier to add a
> > UUID than add this to the ACPI specifications through the AWSG) but it
> > is still supposed to be applicable to ACPI PCI bindings on any
> > platforms/arches; this way of adding bindings does not work and it
> > has to be rectified.
> 
> I agree.
> 
> For the existing property "classes" such as the one here I don't think
> we can do anything. There are systems already with these included in
> their ACPI tables.
> 
> I wonder if you have any objections regarding this patch?

I have strong objections to the way these bindings have been forced upon
everybody; if that's the way *generic* ACPI bindings are specified I
wonder why there still exists an ACPI specification and related working
group.

I personally (but that's Bjorn and Rafael choice) think that this is
not a change that belongs in PCI core, ACPI bindings are ill-defined
and device tree bindings are non-existing.

At the very least Microsoft should be asked to publish and discuss
these bindings within the ACPI and UEFI forums.

Lorenzo