[Intel-gfx] [PATCH] drm: fix lut value extraction function

[Lionel Landwerlin]

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);
 }
-- 
2.8.0.rc3