Re: [PATCH v3 5/5] lib, pci: unify generic pci_iounmap()

["Arnd Bergmann" <arnd@arndb.de>]

On Mon, Dec 4, 2023, at 14:39, Philipp Stanner wrote:
> On Mon, 2023-12-04 at 13:38 +0100, Philipp Stanner wrote:

>> + */
>> +#if defined(ARCH_WANTS_GENERIC_IOMEM_IS_IOPORT)
>> +bool iomem_is_ioport(void __iomem *addr)
>>  {
>> -       IO_COND(addr, /* nothing */, iounmap(addr));
>> +       unsigned long port = (unsigned long __force)addr;
>> +
>> +       if (port > PIO_OFFSET && port < PIO_RESERVED)
>
> by the way:
> Reading that again my instinctive feeling would be that it should be
> port >= PIO_OFFSET.
>
> This is, however, the exactly copied logic from the IO_COND macro in
> lib/iomap.c. Is it possible that this macro contains a bug here?

Right, I think that would make more sense, but there is no
practical difference as long as I/O port 0 is always unused,
which is at least true on x86 because of PCIBIOS_MIN_IO.
Commit bb356ddb78b2 ("RISC-V: PCI: Avoid handing out address
0 to devices") describes how setting PCIBIOS_MIN_IO to 0
caused other problems.

I would just leave the logic consistent with IO_COND here,
or maybe use IO_COND() directly, like

      IO_COND(addr, return true, /* nothing */);
      return false;

     Arnd