On Tue, May 4, 2021 at 9:40 AM Niklas Schnelle [off-list ref] wrote:

On Mon, 2021-05-03 at 18:07 +0200, Arnd Bergmann wrote:

quoted

- 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.

I mixed the above in with the current commit message:

    Without MMU support PCI_IOBASE is left undefined because PCI_IO_END is
    VMEMMAP_START. Nevertheless the in*()/out*() helper macros are left
    defined with uses of PCI_IOBASE. At the moment this only compiles
    because asm-generic/io.h defines PCI_IOBASE as 0 if it is undefined and
    so at macro expansion PCI_IOBASE is defined. This leads to compilation
    errors when asm-generic/io.h is changed to leave PCI_IOBASE undefined.
    More importantly it is currently broken at runtime, as accessing a fixed
    I/O port number of an ISA device on NOMMU RISC-V would turn into a NULL
    pointer dereference. Instead only define the in*()/out*() helper macros
    with MMU support and fall back to the asm-generic/io.h helper stubs
    otherwise.

Looks good, thanks. Maybe split into two or three paragraphs for readability.

     Arnd