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

From: Christophe Leroy
Date: Wed Jan 08 2020 - 03:35:59 EST




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