drm/uapi: Document CTM matrix better

Document in which order the CTM matrix elements are stored.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230411222931.15127-2-ville.syrjala@linux.intel.com
Reviewed-by: Xaver Hugl <xaver.hugl@gmail.com>
Acked-by: Simon Ser <contact@emersion.fr>

diff --git a/include/uapi/drm/drm_mode.h b/include/uapi/drm/drm_mode.h
index 46beced..4369105 100644 (file)
--- a/include/uapi/drm/drm_mode.h
+++ b/include/uapi/drm/drm_mode.h
@@ -834,6 +834,11 @@ struct drm_color_ctm {
        /*
         * Conversion matrix in S31.32 sign-magnitude
         * (not two's complement!) format.
+        *
+        * out   matrix    in
+        * |R|   |0 1 2|   |R|
+        * |G| = |3 4 5| x |G|
+        * |B|   |6 7 8|   |B|
         */
        __u64 matrix[9];
 };