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 <[email protected]> >>> >>> 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: [email protected] >>> Cc: Mihail Atanassov <[email protected]> >>> Cc: Liviu Dudau <[email protected]> >>> Cc: Brian Starkey <[email protected]> >>> Cc: Mali DP Maintainers <[email protected]> >>> Cc: Johnson Lin <[email protected]> >>> Cc: Uma Shankar <[email protected]> >>> Cc: Shashank Sharma <[email protected]> >>> Signed-off-by: Ville Syrjälä <[email protected]> >> >> 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 <[email protected]> >> >> (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 >> [email protected] >> https://lists.freedesktop.org/mailman/listinfo/dri-devel > _______________________________________________ Intel-gfx mailing list [email protected] https://lists.freedesktop.org/mailman/listinfo/intel-gfx
