linux-kernel - Re: [PATCH] drm/fourcc: fix integer type usage in uapi header

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Date:   Wed, 22 Jun 2022 07:02:04 +0000
From:   Simon Ser <contact@...rsion.fr>
To:     Carlos Llamas <cmllamas@...gle.com>
Cc:     amd-gfx@...ts.freedesktop.org, David Airlie <airlied@...ux.ie>,
        Masahiro Yamada <masahiroy@...nel.org>,
        linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Alex Deucher <alexander.deucher@....com>,
        Bas Nieuwenhuizen <bas@...nieuwenhuizen.nl>
Subject: Re: [PATCH] drm/fourcc: fix integer type usage in uapi header

On Tuesday, June 21st, 2022 at 22:39, Carlos Llamas <cmllamas@...gle.com> wrote:

> Kernel uapi headers are supposed to use __[us]{8,16,32,64} types defined
> by <linux/types.h> as opposed to 'uint32_t' and similar. See [1] for the
> relevant discussion about this topic. In this particular case, the usage
> of 'uint64_t' escaped headers_check as these macros are not being called
> here. However, the following program triggers a compilation error:
>
>   #include <drm/drm_fourcc.h>
>
>   int main()
>   {
>   	unsigned long x = AMD_FMT_MOD_CLEAR(RB);
>   	return 0;
>   }
>
> gcc error:
>   drm.c:5:27: error: ‘uint64_t’ undeclared (first use in this function)
>       5 |         unsigned long x = AMD_FMT_MOD_CLEAR(RB);
>         |                           ^~~~~~~~~~~~~~~~~
>
> This patch changes AMD_FMT_MOD_{SET,CLEAR} macros to use the correct
> integer types, which fixes the above issue.
>
>   [1] https://lkml.org/lkml/2019/6/5/18
>
> Fixes: 8ba16d599374 ("drm/fourcc: Add AMD DRM modifiers.")
> Signed-off-by: Carlos Llamas <cmllamas@...gle.com>

Reviewed-by: Simon Ser <contact@...rsion.fr>

Cc'ing Bas as well

> ---
>  include/uapi/drm/drm_fourcc.h | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/include/uapi/drm/drm_fourcc.h b/include/uapi/drm/drm_fourcc.h
> index f1972154a594..0980678d502d 100644
> --- a/include/uapi/drm/drm_fourcc.h
> +++ b/include/uapi/drm/drm_fourcc.h
> @@ -1444,11 +1444,11 @@ drm_fourcc_canonicalize_nvidia_format_mod(__u64 modifier)
>  #define AMD_FMT_MOD_PIPE_MASK 0x7
>
>  #define AMD_FMT_MOD_SET(field, value) \
> -	((uint64_t)(value) << AMD_FMT_MOD_##field##_SHIFT)
> +	((__u64)(value) << AMD_FMT_MOD_##field##_SHIFT)
>  #define AMD_FMT_MOD_GET(field, value) \
>  	(((value) >> AMD_FMT_MOD_##field##_SHIFT) & AMD_FMT_MOD_##field##_MASK)
>  #define AMD_FMT_MOD_CLEAR(field) \
> -	(~((uint64_t)AMD_FMT_MOD_##field##_MASK << AMD_FMT_MOD_##field##_SHIFT))
> +	(~((__u64)AMD_FMT_MOD_##field##_MASK << AMD_FMT_MOD_##field##_SHIFT))
>
>  #if defined(__cplusplus)
>  }
> --
> 2.37.0.rc0.104.g0611611a94-goog