Re: [RFC v2 01/39] Kconfig: introduce HAS_IOPORT option and select it as necessary

Maciej W. Rozycki
2022-05-06T13:17:04Z

On Fri, 6 May 2022, Arnd Bergmann wrote:

> > So what happens if the instruction is given an I/O rather than memory BAR
> > as the relevant argument? Is the address space indicator bit (bit #0)
> > simply ignored or what?
>
> Not sure. My best guess is that it would actually work as you'd expect,
> but is deliberately left out of the architecture specification so they don't
> have to to validate the correctness. Note that only a small number of
> PCIe cards are actually supported by IBM, and I think the firmware
> only passes devices to the OS if they are whitelisted.

That makes sense, thanks!

Maciej