Nouveau - Jan 2020 - [RFT 00/13] iomap: Constify ioreadX() iomem argument

Hi Krzysztof,

On Wed, Jan 8, 2020 at 9:07 AM Geert Uytterhoeven <geert at
linux-m68k.org> wrote:
> On Tue, Jan 7, 2020 at 5:53 PM Krzysztof Kozlowski <krzk at
kernel.org> wrote:
> > The ioread8/16/32() and others have inconsistent interface among the
> > architectures: some taking address as const, some not.
> >
> > It seems there is nothing really stopping all of them to take
> > pointer to const.
>
> Shouldn't all of them take const volatile __iomem pointers?
> It seems the "volatile" is missing from all but the
implementations in
> include/asm-generic/io.h.
As my "volatile" comment applies to iowrite*(), too, probably that
should be
done in a separate patch.

Hence with patches 1-5 squashed, and for patches 11-13:
Reviewed-by: Geert Uytterhoeven <geert+renesas at glider.be>

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert at
linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or
something like that.
                                -- Linus Torvalds

On Wed, 8 Jan 2020 at 09:13, Geert Uytterhoeven <geert at linux-m68k.org>
wrote:
>
> Hi Krzysztof,
>
> On Wed, Jan 8, 2020 at 9:07 AM Geert Uytterhoeven <geert at
linux-m68k.org> wrote:
> > On Tue, Jan 7, 2020 at 5:53 PM Krzysztof Kozlowski <krzk at
kernel.org> wrote:
> > > The ioread8/16/32() and others have inconsistent interface among
the
> > > architectures: some taking address as const, some not.
> > >
> > > It seems there is nothing really stopping all of them to take
> > > pointer to const.
> >
> > Shouldn't all of them take const volatile __iomem pointers?
> > It seems the "volatile" is missing from all but the
implementations in
> > include/asm-generic/io.h.
>
> As my "volatile" comment applies to iowrite*(), too, probably
that should be
> done in a separate patch.
>
> Hence with patches 1-5 squashed, and for patches 11-13:
> Reviewed-by: Geert Uytterhoeven <geert+renesas at glider.be>
I'll add to this one also changes to ioreadX_rep() and add another
patch for volatile for reads and writes. I guess your review will be
appreciated once more because of ioreadX_rep()

Thanks,
Krzysztof

Le 08/01/2020 ? 09:18, Krzysztof Kozlowski a ?crit?:
> On Wed, 8 Jan 2020 at 09:13, Geert Uytterhoeven <geert at
linux-m68k.org> wrote:
>>
>> Hi Krzysztof,
>>
>> On Wed, Jan 8, 2020 at 9:07 AM Geert Uytterhoeven <geert at
linux-m68k.org> wrote:
>>> On Tue, Jan 7, 2020 at 5:53 PM Krzysztof Kozlowski <krzk at
kernel.org> wrote:
>>>> The ioread8/16/32() and others have inconsistent interface
among the
>>>> architectures: some taking address as const, some not.
>>>>
>>>> It seems there is nothing really stopping all of them to take
>>>> pointer to const.
>>>
>>> Shouldn't all of them take const volatile __iomem pointers?
>>> It seems the "volatile" is missing from all but the
implementations in
>>> include/asm-generic/io.h.
>>
>> As my "volatile" comment applies to iowrite*(), too, probably
that should be
>> done in a separate patch.
>>
>> Hence with patches 1-5 squashed, and for patches 11-13:
>> Reviewed-by: Geert Uytterhoeven <geert+renesas at glider.be>
> 
> I'll add to this one also changes to ioreadX_rep() and add another
> patch for volatile for reads and writes. I guess your review will be
> appreciated once more because of ioreadX_rep()
> 
volatile should really only be used where deemed necessary:

https://www.kernel.org/doc/html/latest/process/volatile-considered-harmful.html

It is said: " ...  accessor functions might use volatile on 
architectures where direct I/O memory access does work. Essentially, 
each accessor call becomes a little critical section on its own and 
ensures that the access happens as expected by the programmer."

Christophe