Re: [PATCH v2] drm: Fix drm_fixp2int_round() making it add 0.5

[Melissa Wen]

On 03/16, Arthur Grillo wrote:
> As well noted by Pekka[1], the rounding of drm_fixp2int_round is wrong.
> To round a number, you need to add 0.5 to the number and floor that,
> drm_fixp2int_round() is adding 0.0000076. Make it add 0.5.
> 
> [1]: https://lore.kernel.org/all/20240301135327.22efe0dd.pekka.paalanen@xxxxxxxxxxxxx/
> 
> Fixes: 8b25320887d7 ("drm: Add fixed-point helper to get rounded integer values")
> Suggested-by: Pekka Paalanen <pekka.paalanen@xxxxxxxxxxxxx>
> Reviewed-by: Harry Wentland <harry.wentland@xxxxxxx>
> Signed-off-by: Arthur Grillo <arthurgrillo@xxxxxxxxxx>

Great, thanks!

Reviewed-by: Melissa Wen <mwen@xxxxxxxxxx>

I'll apply to drm-misc-next.

Melissa

> ---
> Changes in v2:
> - Add Fixes tag (Melissa Wen)
> - Remove DRM_FIXED_POINT_HALF (Melissa Wen)
> - Link to v1: https://lore.kernel.org/all/20240306-louis-vkms-conv-v1-1-5bfe7d129fdd@xxxxxxxxxx/
> ---
>  include/drm/drm_fixed.h | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/include/drm/drm_fixed.h b/include/drm/drm_fixed.h
> index 0c9f917a4d4b..81572d32db0c 100644
> --- a/include/drm/drm_fixed.h
> +++ b/include/drm/drm_fixed.h
> @@ -71,7 +71,6 @@ static inline u32 dfixed_div(fixed20_12 A, fixed20_12 B)
>  }
>  
>  #define DRM_FIXED_POINT		32
> -#define DRM_FIXED_POINT_HALF	16
>  #define DRM_FIXED_ONE		(1ULL << DRM_FIXED_POINT)
>  #define DRM_FIXED_DECIMAL_MASK	(DRM_FIXED_ONE - 1)
>  #define DRM_FIXED_DIGITS_MASK	(~DRM_FIXED_DECIMAL_MASK)
> @@ -90,7 +89,7 @@ static inline int drm_fixp2int(s64 a)
>  
>  static inline int drm_fixp2int_round(s64 a)
>  {
> -	return drm_fixp2int(a + (1 << (DRM_FIXED_POINT_HALF - 1)));
> +	return drm_fixp2int(a + DRM_FIXED_ONE / 2);
>  }
>  
>  static inline int drm_fixp2int_ceil(s64 a)
> 
> ---
> base-commit: f89632a9e5fa6c4787c14458cd42a9ef42025434
> change-id: 20240315-drm_fixed-c680ba078ecb
> 
> Best regards,
> -- 
> Arthur Grillo <arthurgrillo@xxxxxxxxxx>
>