linux-kernel - Re: [PATCH 3/3] i2c: rcar: Fix Wvoid-pointer-to-enum-cast warning

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Message-ID: <CAMuHMdX7t=mabqFE5O-Cii3REMuyaePHmqX+j_mqyrn6XXzsoA@mail.gmail.com>
Date: Thu, 27 Nov 2025 10:02:26 +0100
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Krzysztof Kozlowski <krzysztof.kozlowski@....qualcomm.com>
Cc: Andi Shyti <andi.shyti@...nel.org>, Ray Jui <rjui@...adcom.com>, 
	Scott Branden <sbranden@...adcom.com>, 
	Broadcom internal kernel review list <bcm-kernel-feedback-list@...adcom.com>, 
	Wolfram Sang <wsa+renesas@...g-engineering.com>, 
	Geert Uytterhoeven <geert+renesas@...der.be>, Magnus Damm <magnus.damm@...il.com>, 
	Nathan Chancellor <nathan@...nel.org>, Nick Desaulniers <nick.desaulniers+lkml@...il.com>, 
	Bill Wendling <morbo@...gle.com>, Justin Stitt <justinstitt@...gle.com>, linux-i2c@...r.kernel.org, 
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org, 
	linux-renesas-soc@...r.kernel.org, llvm@...ts.linux.dev
Subject: Re: [PATCH 3/3] i2c: rcar: Fix Wvoid-pointer-to-enum-cast warning

Hi Krzysztof,

On Wed, 26 Nov 2025 at 19:23, Krzysztof Kozlowski
<krzysztof.kozlowski@....qualcomm.com> wrote:
> 'i2c_types' is an enum, thus cast of pointer on 64-bit compile test with
> clang and W=1 causes:
>
>   i2c-rcar.c:1144:18: error: cast to smaller integer type 'enum rcar_i2c_type' from 'const void *' [-Werror,-Wvoid-pointer-to-enum-cast]
>
> One of the discussions in 2023 on LKML suggested warning is not suitable
> for kernel.  Nothing changed in this regard since that time, so assume
> the warning will stay and we want to have warnings-free builds.
>
> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@....qualcomm.com>

Thanks for your patch!

=
> --- a/drivers/i2c/busses/i2c-rcar.c
> +++ b/drivers/i2c/busses/i2c-rcar.c
> @@ -1141,7 +1141,7 @@ static int rcar_i2c_probe(struct platform_device *pdev)
>         if (IS_ERR(priv->io))
>                 return PTR_ERR(priv->io);
>
> -       priv->devtype = (enum rcar_i2c_type)of_device_get_match_data(dev);
> +       priv->devtype = (kernel_ulong_t)of_device_get_match_data(dev);

Any specific reason you picked "kernel_ulong_t" instead of "unsigned long"?
The former seems to be the least common option.
FWIW, the most common option is "uintptr_t", which torvalds doesn't like...

>         init_waitqueue_head(&priv->wait);
>
>         adap = &priv->adap;

Reviewed-by: Geert Uytterhoeven <geert+renesas@...der.be>

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