Re: [RFC PATCH 00/17] Drop uses of pci_read_config_*() return value

Bjorn Helgaas
2020-08-02T19:14:14Z

On Sun, Aug 02, 2020 at 08:46:48PM +0200, Borislav Petkov wrote:
> On Sun, Aug 02, 2020 at 07:28:00PM +0200, Saheed Bolarinwa wrote:
> > Because the value ~0 has a meaning to some drivers and only
>
> No, ~0 means that the PCI read failed. For *every* PCI device I know.

Wait, I'm not convinced yet. I know that if a PCI read fails, you
normally get ~0 data because the host bridge fabricates it to complete
the CPU load.

But what guarantees that a PCI config register cannot contain ~0?
If there's something about that in the spec I'd love to know where it
is because it would simplify a lot of things.

I don't think we should merge any of these patches as-is. If we *do*
want to go this direction, we at least need some kind of macro or
function that tests for ~0 so we have a clue about what's happening
and can grep for it.

Bjorn