On Wed, Nov 09, 2016 at 04:05:06PM -0600, Bjorn Helgaas wrote:
[...]
ACPI defined a Producer/Consumer bit that was intended to distinguish the bridge apertures from the bridge registers [4, 5]. However, BIOSes didn't use that bit correctly, and the result is that OSes have to assume that everything in a PCI host bridge _CRS is a window. That leaves no way to describe the bridge registers in the PNP0A03/PNP0A08 device itself.
ACPI 6.1 states that in the revision changes 4.0a Apr.2010 (xiii) "Consumer/Producer bit is ignored (Restored 2.0C change that had been lost)" and still that bit is marked as valid. If it is not reliable it should be set as "ignored" in the specs (as it was on ACPI 2.0C, BTW), as it is it is just a source of confusion.
Thanks again ! Lorenzo