[Intel-gfx] [PATCH 1/4] drm/uapi: The ctm matrix uses sign-magnitude representation

[Shankar, Uma]

>-----Original Message-----
>From: Ville Syrjala [mailto:ville.syrjala at linux.intel.com]
>Sent: Friday, February 23, 2018 3:12 AM
>To: intel-gfx at lists.freedesktop.org
>Cc: dri-devel at lists.freedesktop.org; Mihail Atanassov
><mihail.atanassov at arm.com>; Liviu Dudau <liviu.dudau at arm.com>; Brian
>Starkey <brian.starkey at arm.com>; Mali DP Maintainers
><malidp at foss.arm.com>; Lin, Johnson <johnson.lin at intel.com>; Shankar, Uma
><uma.shankar at intel.com>; Sharma, Shashank <shashank.sharma at intel.com>
>Subject: [PATCH 1/4] drm/uapi: The ctm matrix uses sign-magnitude
>representation
>
>From: Ville Syrjälä <ville.syrjala at linux.intel.com>
>
>The documentation for the ctm matrix suggests a two's complement format, but
>at least the i915 implementation is using sign-magnitude instead. And looks like
>malidp is doing the same. Change the docs to match the current implementation,
>and change the type from __s64 to __u64 to drive the point home.
>

Looks ok to me.

Reviewed-by: Uma Shankar <uma.shankar at intel.com>

>Cc: dri-devel at lists.freedesktop.org
>Cc: Mihail Atanassov <mihail.atanassov at arm.com>
>Cc: Liviu Dudau <liviu.dudau at arm.com>
>Cc: Brian Starkey <brian.starkey at arm.com>
>Cc: Mali DP Maintainers <malidp at foss.arm.com>
>Cc: Johnson Lin <johnson.lin at intel.com>
>Cc: Uma Shankar <uma.shankar at intel.com>
>Cc: Shashank Sharma <shashank.sharma at intel.com>
>Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
>---
> include/uapi/drm/drm_mode.h | 7 +++++--
> 1 file changed, 5 insertions(+), 2 deletions(-)
>
>diff --git a/include/uapi/drm/drm_mode.h b/include/uapi/drm/drm_mode.h
>index 2c575794fb52..b5d7d9e0eff5 100644
>--- a/include/uapi/drm/drm_mode.h
>+++ b/include/uapi/drm/drm_mode.h
>@@ -598,8 +598,11 @@ struct drm_mode_crtc_lut {  };
>
> struct drm_color_ctm {
>-	/* Conversion matrix in S31.32 format. */
>-	__s64 matrix[9];
>+	/*
>+	 * Conversion matrix in S31.32 sign-magnitude
>+	 * (not two's complement!) format.
>+	 */
>+	__u64 matrix[9];
> };
>
> struct drm_color_lut {
>--
>2.16.1