linux-kernel - Re: [PATCH] soc: renesas: rmobile-sysc: fix -Wvoid-pointer-to-enum-cast warning

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Date:   Wed, 27 Sep 2023 11:28:25 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Ulf Hansson <ulf.hansson@...aro.org>
Cc:     Justin Stitt <justinstitt@...gle.com>,
        Magnus Damm <magnus.damm@...il.com>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Tom Rix <trix@...hat.com>, linux-renesas-soc@...r.kernel.org,
        linux-kernel@...r.kernel.org, llvm@...ts.linux.dev,
        Linux PM list <linux-pm@...r.kernel.org>
Subject: Re: [PATCH] soc: renesas: rmobile-sysc: fix -Wvoid-pointer-to-enum-cast
 warning

Hi Ulf,

On Tue, Sep 26, 2023 at 1:22 PM Ulf Hansson <ulf.hansson@...aro.org> wrote:
> On Mon, 18 Sept 2023 at 11:21, Geert Uytterhoeven <geert@...ux-m68k.org> wrote:
> > On Wed, Aug 30, 2023 at 10:24 AM Geert Uytterhoeven
> > <geert@...ux-m68k.org> wrote:
> > > On Tue, Aug 15, 2023 at 12:11 AM Justin Stitt <justinstitt@...gle.com> wrote:
> > > > When building with clang 18 I see the following warning:
> > > > |      drivers/soc/renesas/rmobile-sysc.c:193:22: warning: cast to smaller integer
> > > > |               type 'enum pd_types' from 'const void *' [-Wvoid-pointer-to-enum-cast]
> > > > |        193 |                 add_special_pd(np, (enum pd_types)id->data);
> > > >
> > > > This is due to the fact that `id->data` is a void* and `enum pd_types`
> > > > has the size of an integer. This cast from pointer-width to int-width
> > > > causes truncation and possible data loss. Instead, cast to `uintptr_t`
> > > > which has the same width as void*.
> > > >
> > > > Link: https://github.com/ClangBuiltLinux/linux/issues/1910
> > > > Reported-by: Nathan Chancellor <nathan@...nel.org>
> > >
> > > scripts/checkpatch.pl:
> > >
> > >     WARNING: Reported-by: should be immediately followed by Closes:
> > > with a URL to the report
> > >
> > > Hence changing the Link: tag to a Closes: tag.
> > >
> > > > Signed-off-by: Justin Stitt <justinstitt@...gle.com>
> > > > ---
> > > > Note: It should be noted that there is likely no data loss occurring in
> > > > this case since the enum only has a few fields. The narrowing cast from
> > > > pointer to int will not lose any data.
> > >
> > > Indeed, the theoretical narrowing could only happen on a 64-bit
> > > platform, while this driver is only used on arm32.
> > >
> > > Reviewed-by: Geert Uytterhoeven <geert+renesas@...der.be>
> > > i.e. will queue in renesas-devel for v6.7.
> >
> > As the Generic PM Domain providers were moved to drivers/pmdomain/
> > in v6.6-rc2, and now have their own maintainer, I have moved this
> > commit from renesas-drivers-for-v6.7 to renesas-pmdomain-for-v6.7[1],
> > with s/soc/pmdomain/ in the oneline-summary.
> >
> > Ulf: if you prefer, you can still take this patch directly.
> > Else I will send a PR after rc3 and/or rc5, like I do with my other
> > renesas-<foo>-for-<version> branches.
> > Thanks!
>
> Apologize for the delay, been traveling lately. Anyway, I can
> certainly pick up the patch and carry it for v6.7. Just let me know,
> if/when you have dropped the patch from your tree.

Thanks, dropped.

P.S. And now I notice it was never part of linux-next, due to an
     oversight in my scripting. Fixed that, too ;-)

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-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