linux-kernel - Re: [PATCH 1/7] drm: Fix drm_fixp2int

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Date: Fri, 8 Mar 2024 15:57:00 -0500
From: Harry Wentland <harry.wentland@....com>
To: Arthur Grillo <arthurgrillo@...eup.net>,
 Rodrigo Siqueira <rodrigosiqueiramelo@...il.com>,
 Melissa Wen <melissa.srw@...il.com>, Maíra Canal
 <mairacanal@...eup.net>, Haneen Mohammed <hamohammed.sa@...il.com>,
 Daniel Vetter <daniel@...ll.ch>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
 David Airlie <airlied@...il.com>, Jonathan Corbet <corbet@....net>,
 pekka.paalanen@...oniitty.fi, Louis Chauvet <louis.chauvet@...tlin.com>
Cc: dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
 jeremie.dautheribes@...tlin.com, miquel.raynal@...tlin.com,
 thomas.petazzoni@...tlin.com, seanpaul@...gle.com, marcheu@...gle.com,
 nicolejadeyee@...gle.com, Pekka Paalanen <pekka.paalanen@...labora.com>
Subject: Re: [PATCH 1/7] drm: Fix drm_fixp2int_round() making it add 0.5

On 2024-03-06 15:03, 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@collabora.com/
> 
> Suggested-by: Pekka Paalanen <pekka.paalanen@...labora.com>
> Signed-off-by: Arthur Grillo <arthurgrillo@...eup.net>

Reviewed-by: Harry Wentland <harry.wentland@....com>

I had a different jab at this [1], but your patch is cleaner.

https://patchwork.freedesktop.org/patch/579978/?series=123446&rev=4

Harry

> ---
>   include/drm/drm_fixed.h | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/drm/drm_fixed.h b/include/drm/drm_fixed.h
> index 0c9f917a4d4b..de3a79909ac9 100644
> --- a/include/drm/drm_fixed.h
> +++ b/include/drm/drm_fixed.h
> @@ -90,7 +90,7 @@ 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)
>