[PATCH] drm: fix lut value extraction function

[Lionel Landwerlin]

Ping?

On 22/03/16 14:10, Lionel Landwerlin wrote:
> When extracting the value at full precision (16 bits), no need to
> round the value.
>
> This was spotted by Jani when running sparse. Unfortunately this fix
> doesn't get rid of the warning.
>
> Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin at intel.com>
> Reported-by: Jani Nikula <jani.nikula at intel.com>
> Cc: Daniel Stone <daniels at collabora.com>
> Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
> Cc: Matt Roper <matthew.d.roper at intel.com>
> Cc: dri-devel at lists.freedesktop.org
> Fixes: 5488dc16fde7 ("drm: introduce pipe color correction properties")
> ---
>   include/drm/drm_crtc.h | 8 ++++++--
>   1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
> index e0170bf..da63b4d 100644
> --- a/include/drm/drm_crtc.h
> +++ b/include/drm/drm_crtc.h
> @@ -2600,10 +2600,14 @@ static inline struct drm_property *drm_property_find(struct drm_device *dev,
>   static inline uint32_t drm_color_lut_extract(uint32_t user_input,
>   					     uint32_t bit_precision)
>   {
> -	uint32_t val = user_input + (1 << (16 - bit_precision - 1));
> +	uint32_t val = user_input;
>   	uint32_t max = 0xffff >> (16 - bit_precision);
>   
> -	val >>= 16 - bit_precision;
> +	/* Round only if we're not using full precision. */
> +	if (bit_precision < 16) {
> +		val += 1UL << (16 - bit_precision - 1);
> +		val >>= 16 - bit_precision;
> +	}
>   
>   	return clamp_val(val, 0, max);
>   }