Re: [RFT 00/13] iomap: Constify ioreadX() iomem argument

[Christophe Leroy]

Le 08/01/2020 Ã 09:18, Krzysztof Kozlowski a ÃcritÂ:
> On Wed, 8 Jan 2020 at 09:13, Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> wrote:
> > Hi Krzysztof,
> >
> > On Wed, Jan 8, 2020 at 9:07 AM Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> wrote:
> > > On Tue, Jan 7, 2020 at 5:53 PM Krzysztof Kozlowski <krzk@xxxxxxxxxx> 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@xxxxxxxxx>
>
> 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