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Date:   Tue, 13 Nov 2018 11:45:36 +0000
From:   Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
To:     Mika Westerberg <mika.westerberg@linux.intel.com>
Cc:     Lukas Wunner <lukas@wunner.de>, iommu@lists.linux-foundation.org,
        Joerg Roedel <joro@8bytes.org>,
        David Woodhouse <dwmw2@infradead.org>,
        Lu Baolu <baolu.lu@linux.intel.com>,
        Ashok Raj <ashok.raj@intel.com>,
        Bjorn Helgaas <bhelgaas@google.com>,
        "Rafael J. Wysocki" <rjw@rjwysocki.net>,
        Jacob jun Pan <jacob.jun.pan@intel.com>,
        Andreas Noever <andreas.noever@gmail.com>,
        Michael Jamet <michael.jamet@intel.com>,
        Yehezkel Bernat <YehezkelShB@gmail.com>,
        Christian Kellner <ckellner@redhat.com>,
        Mario.Limonciello@dell.com,
        Anthony Wong <anthony.wong@canonical.com>,
        linux-acpi@vger.kernel.org, linux-pci@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/4] PCI / ACPI: Identify external PCI devices
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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.

Lorenzo