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

On Tue, 4 Aug 2026, Arnd Bergmann wrote:

> arch/um is the only other one that does not always enable HAS_IOMEM,
> though most m68k targets don't have any support for ISA/PCI style
> MMIO or PIO and probably should not enable it in theory.

 While HAS_IOPORT is indeed a feature that has propagated from Intel x86 
(or really 8080, etc.) to non-x86 systems through ISA/PCI what's been so 
special about ISA/PCI WRT HAS_IOMEM?

 AFAICT HAS_IOMEM is all about just having peripherals located in the 
CPU's regular memory addressing space.  All the DEC MIPS platforms fall 
into this category, never seen PCI/ISA, some have no peripheral bus.

  Maciej