Re: [PATCH v6 5/6] fbdev: Move framebuffer I/O helpers into <asm/fb.h>

["Arnd Bergmann" <arnd@xxxxxxxx>]

On Thu, May 11, 2023, at 14:35, Geert Uytterhoeven wrote:
> CC Artur, who's working on HP Jornada 680.
>
> On Wed, May 10, 2023 at 5:55 PM Arnd Bergmann <arnd@xxxxxxxx> wrote:
>> On Wed, May 10, 2023, at 16:27, Thomas Zimmermann wrote:
>> > Am 10.05.23 um 16:15 schrieb Arnd Bergmann:
>> >> On Wed, May 10, 2023, at 16:03, kernel test robot wrote:
>
> See also commit 4aafae27d0ce73f8 ("sh: hd64461 tidying."), which
> claims they are no longer needed.
>
> Don't the I/O port macros just treat the port as an absolute base address
> when sh_io_port_base isn't set?

As far as I can tell, sh_io_port_base gets initialized to '-1'
specifically to prevent that from working by accident. So it's
almost treated as an absolute base address, but the off-by-one
offset ensures this never actually works unless it was first
set to the correct value.

      Arnd