On Wed, Oct 13, 2021 at 04:47:43PM -0500, Rob Herring wrote: > Presumably, there could be some register somewhere where all 1s is > valid? So I think we need the error values. We have to assume ~0 is a valid value for any config registers except the few defined by the spec that have bits required to be 0. There can be all kinds of vendor-defined stuff in config space that can be anything. > Also, I seem to recall only the vendor/device IDs are defined to be > all 1s for non-existent devices. Other errors are undefined? I think this case is actually an instance of the PCI controller fabricating ~0 because a PCI/PCIe error occurred (I think on PCI it's a Master Abort when nothing responds; on PCIe the read terminates as an Unsupported Request (PCIe r5.0, sec 2.3.2)).
