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

Maciej W. Rozycki
2022-05-06T13:15:04Z

On Fri, 6 May 2022, David Laight wrote:

> > The PCI configuration space was retrofitted into x86 systems (and is
> > accessed in an awkward manner with them), but with a new design such a
> > clean approach is most welcome IMHO. Thank you for your explanation.
>
> Actually I think x86 was the initial system for PCI.
> The PCI config space 'mess' is all about trying to make
> something that wouldn't break existing memory maps.

It was retrofitted in that x86 systems already existed for ~15 years when
PCI came into picture. Therefore the makers of the CPU ISA couldn't have
envisaged the need for config access instructions like they did for memory
and port access.

Maciej