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    SubjectRe: [PATCH 2/4] x86/amd_nb: add support for newer PCI topologies
    On Wed, Nov 07, 2018 at 05:40:14PM -0800, Guenter Roeck wrote:
    > On 11/7/18 3:14 PM, Bjorn Helgaas wrote:
    > >
    > > >
    > > > There is no INT3401 on any newer atom or core platforms, so you can't
    > > > enumerate on this device. We don't control what ACPI device is present
    > > > on a system. It depends on what the other non-Linux OS is using.
    > >
    > > Sure, you can't *force* OEMs to supply a given ACPI device, but you
    > > can certainly say "if you want this functionality, supply INT3401
    > > devices." That's what you do with PNP0A03 (PCI host bridges), for
    > > example. If an OEM doesn't supply PNP0A03 devices, the system can
    > > boot just fine as long as you don't need PCI.
    > >
    > > This model of using the PCI IDs forces OS vendors to release updates
    > > for every new platform. I guess you must have considered that and
    > > decided whatever benefit you're getting was worth the cost.
    > >
    >
    > I really dislike where this is going. Board vendors - and that included
    > Intel when Intel was still selling boards - have a long history of only
    > making mandatory methods available in ACPI. Pretty much all of them don't
    > make hardware monitoring information available via ACPI. This is a pain
    > especially for laptops where the information is provided by an embedded
    > controller. On systems with Super-IO chips with dedicated hardware
    > monitoring functionality, they often go as far as signing mutual NDAs
    > with chip vendors, which lets both the board and the chip vendor claim
    > that they can not provide chip specifications to third parties, aka
    > users.
    >
    > You are pretty much extending that to CPU temperature monitoring. The
    > fallout, if adopted, will be that it will effectively no longer be
    > possible to monitor the temperature on chips supporting this
    > "feature".
    >
    > I do not think that would be a good idea.

    I wasn't aware of these political implications. Thanks for raising
    them.

    I'm not in a position to balance those implications vs the technical
    question of minimizing the burden of supporting new platforms, so I'll
    try again to bow out of this.

    Bjorn

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