Re: [PATCH v4 0/3] asm-generic/io.h: Silence -Wnull-pointer-arithmetic warning on PCI_IOBASE

[Arnd Bergmann]

On Fri, Apr 30, 2021 at 1:16 PM Niklas Schnelle <schnelle@xxxxxxxxxxxxx> wrote:
>
> From: Niklas Schnelle <niklas@xxxxxxxxx>
>
> This is version 4 of my attempt to get rid of a clang
> -Wnull-pointer-arithmetic warning for the use of PCI_IOBASE in
> asm-generic/io.h. This was originally found on s390 but should apply to
> all platforms leaving PCI_IOBASE undefined while making use of the inb()
> and friends helpers from asm-generic/io.h.
>
> This applies cleanly and was compile tested on top of v5.12 for the
> previously broken ARC, nds32, h8300 and risc-v architecture
>
> I did boot test this only on x86_64 and s390x the former implements
> inb() itself while the latter would emit a WARN_ONCE() but no drivers
> use inb().

This looks all fine to me, but with the merge window open right now, I
can't add it into linux-next yet, and it wouldn't qualify as a bugfix for 5.13.

Please resend them to me after -rc1 is out so I can merge it for
5.14 through the asm-generic tree.

Please add two small changes to the changelog texts:

- for patch 3, please include a 'Link: tag' to the lore archive of the
  previous discussion, that should cover any questions that people
  may have

- for the risc-v patch, I would suggest explaining that this fixes
  an existing runtime bug, not just a compiler error:
  | This is already broken, as accessing a fixed I/O port number of
  | an ISA device on NOMMU RISC-V would turn into a NULL pointer
  | dereference.
  Feel free to either copy this, or use your own explanation.

       Arnd