Sorry for top-posting. A quick note that SMBIOS3 is required by SBBR so it can be presumed that compliant platforms will provide quirks via DMI.

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On Dec 21, 2015, at 09:11, Arnd Bergmann [off-list ref] wrote:

On Monday 21 December 2015, Gabriele Paoloni wrote:

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-----Original Message-----
From: linux-kernel-owner at vger.kernel.org [mailto:linux-kernel-
owner at vger.kernel.org] On Behalf Of Tomasz Nowicki

quoted

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Some platforms may not be fully compliant with generic set of PCI
config accessors. For these cases we implement the way to overwrite
accessors set before PCI buses enumeration. Algorithm that overwrite
accessors matches against platform ID (DMI), domain and bus number,
hopefully enough for all cases. All quirks can be defined using:
DECLARE_ACPI_MCFG_FIXUP() and keep self contained.

I've got a couple of comments/questions about this patch..

1) So according to this mechanism quirks would be supported only by 
  vendors whose BIOS are SMBIOS compliant. Now personally I am ok
  with this but I don't know if this is OK in general as it would 
  narrow down the number of platforms that would be able to define
  the quirks...
  Lorenzo, Arnd what is your opinion here?

I'd rather not see the quirks in mainline at all, and only support
SBSA compliant machines, or require the BIOS to work around the hardware
quirks differently (e.g. by trapping config space access through secure
firmware, or going through an AML method to be defined). I'm certainly
ok with making it depend on SMBIOS if we are going to use something like this.

   Arnd