On 2018-03-06 02:51 AM, Daniel Vetter wrote: > On Fri, Feb 23, 2018 at 11:26:41AM -0500, Harry Wentland wrote: >> On 2018-02-22 04:42 PM, Ville Syrjala wrote: >>> From: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> >>> >>> 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. >>> >>> Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx >>> Cc: Mihail Atanassov <mihail.atanassov@xxxxxxx> >>> Cc: Liviu Dudau <liviu.dudau@xxxxxxx> >>> Cc: Brian Starkey <brian.starkey@xxxxxxx> >>> Cc: Mali DP Maintainers <malidp@xxxxxxxxxxxx> >>> Cc: Johnson Lin <johnson.lin@xxxxxxxxx> >>> Cc: Uma Shankar <uma.shankar@xxxxxxxxx> >>> Cc: Shashank Sharma <shashank.sharma@xxxxxxxxx> >>> Signed-off-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> >> >> Good clarification. Our new CTM implementation (1) actually assumed >> two's complement but nobody's using it yet, so we'll patch it to >> convert. > > Another reason to start looking into igt and the tests there? That would > have caught this too ... There need to be new IGT tests that can actually test for signed-magnitude vs two's compliment differences, which would have to be tests of the CTM in some non-RGB colorspace where negative numbers are actually meaningful. The existing tests will test a negative matrix but in RGB colorspace any negative number will simply map to zero/black, no matter the magnitude. I'll put such a test on our team's backlog but not sure when we'll actually get to it. We'd have to check if we could have a meaningful test for this with the current capabilities of DC. Harry > -Daniel > >> >> Reviewed-by: Harry Wentland <harry.wentland@xxxxxxx> >> >> (1) https://patchwork.freedesktop.org/patch/204005/ >> >> Harry >> >>> --- >>> 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 { >>> >> _______________________________________________ >> dri-devel mailing list >> dri-devel@xxxxxxxxxxxxxxxxxxxxx >> https://lists.freedesktop.org/mailman/listinfo/dri-devel > _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
