linux-kernel - Re: thermal/drivers/hisi: Remove bogus const from function return type

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Message-ID: <CAMuHMdU-_Obwo8t=2oE3CfEmZ0nks03HNssS53cKVfbLCi2sdA@mail.gmail.com>
Date:   Tue, 2 Jan 2018 08:36:31 +0100
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Eduardo Valentin <edubezval@...il.com>
Cc:     Zhang Rui <rui.zhang@...el.com>,
        Kevin Wangtao <kevin.wangtao@...aro.org>,
        Arnd Bergmann <arnd@...db.de>,
        Linux PM list <linux-pm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: thermal/drivers/hisi: Remove bogus const from function return type

Hi Eduardo,

On Mon, Jan 1, 2018 at 7:21 PM, Eduardo Valentin <edubezval@...il.com> wrote:
> On Sun, Nov 19, 2017 at 12:04:27PM +0100, Geert Uytterhoeven wrote:
>> With gcc-4.1.2:
>>
>>     drivers/thermal/hisi_thermal.c: In function ‘hisi_thermal_probe’:
>>     drivers/thermal/hisi_thermal.c:530: warning: type qualifiers ignored on function return type
>>
>> Remove the "const" keyword to fix this.
>
> Interesting.
>
> I intentionally asked Daniel to include the modifier because sparse
> pointed this to me:
>
> This patch adds this issue to hisi driver (sparse)
>
> drivers/thermal/hisi_thermal.c:398:24: warning: incorrect type in assignment (different modifiers)
> drivers/thermal/hisi_thermal.c:398:24:    expected int ( *platform_probe )( ... )
> drivers/thermal/hisi_thermal.c:398:24:    got void const *

Sparse doesn't like assigning void pointers to function pointers without a cast.

> which makes sense to me to be const, given that it is receiving the return
> of a function which returns a const void *.
> nclude/linux/of_device.h:extern const void *of_device_get_match_data(const struct device *dev);

That const applies to what is returned by of_device_get_match_data() (a const
void *), not to what is returned by the returned function (an int).

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