Re: `io{re,un}map()` build error in s390 under `!CONFIG_HAS_IOMEM`

On Thu, 6 Aug 2026, Arnd Bergmann wrote:

> I think the reason is that there are a couple of architectures
> (including non-MIO s390) that take a shortcut for normal
> ioremap() that avoids actually mapping anything, e.g. mips
> and related architectures have a fixed uncached mapping
> of all MMIO space visible to kernel, while some alpha, m68k
> powerpc, and s390 do something other than a pointer dereference
> for MMIO.

 FWIW 32-bit MIPS configurations only have low 512MiB of MMIO accessible 
via a fixed mapping and arrange for a regular mapping via the page table 
for anything beyond.

  Maciej