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

From: Niklas Schnelle
Date: Mon May 10 2021 - 04:49:44 EST


This is version 5 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. It also
applies cleanly on v5.13-rc1 for which I boot tested it on s390.

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().


Changes since v4:
- Added Link to patch 4 (Arnd)
- Improved comment on RISC-V patch mentioning current brokeness (Arnd)

Changes since v3:
- Changed the subject of the last patch to better reflect the actual
change i.e. the addition of WARN_ONCE() to the helpers not the
silencing of the clang warning
- Added asm/bug.h to asm-generic/io.h so it doesn't have to be included
previously by all arches to be available for the WARN_ONCE()
- Added patch for risc-v which defines PCI_IOBASE except when compiled
for nommu

Changes since v2:
- Improved comment for SPARC PCI_IOBASE definition as suggested
by David Laight
- Added a patch for ARC which is missing the asm/bug.h include for
WARN_ONCE() (kernel test robot)
- Added ifdefs to ioport_map() and __pci_ioport_map() since apparently
at least test configs enable CONFIG_HAS_IOPORT_MAP even on
architectures which leave PCI_IOBASE unset (kernel test robot for
nds32 and ARC).

Changes since v1:
- Added patch to explicitly set PCI_IOBASE to 0 on sparc as suggested by
Arnd Bergmann
- Instead of working around the warning with a uintptr_t PCI_IOBASE make
inb() and friends explicitly WARN_ONCE() and return 0xff... (Arnd

Niklas Schnelle (3):
sparc: explicitly set PCI_IOBASE to 0
risc-v: Use generic io.h helpers for nommu
asm-generic/io.h: warn in inb() and friends with undefined PCI_IOBASE

arch/riscv/include/asm/io.h | 5 +--
arch/sparc/include/asm/io.h | 8 +++++
include/asm-generic/io.h | 65 ++++++++++++++++++++++++++++++++++---
3 files changed, 72 insertions(+), 6 deletions(-)