Explicitly state the expected CTM equations in the kerneldoc for the CTM
property, and the form of the matrix on struct drm_color_ctm.
Cc: Ville Syrjälä <ville.syrj...@linux.intel.com>
Cc: Lionel Landwerlin <lionel.g.landwer...@intel.com>
Cc: Daniel Vetter <daniel.vet...@ffwll.ch>
Signed-off-by: Brian Starkey <brian.star...@arm.com>
---
drivers/gpu/drm/drm_color_mgmt.c | 13 +++++++++++++
include/uapi/drm/drm_mode.h | 14 +++++++++++++-
2 files changed, 26 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/drm_color_mgmt.c b/drivers/gpu/drm/drm_color_mgmt.c
index 789b4c65cd69..307f7b0545b6 100644
--- a/drivers/gpu/drm/drm_color_mgmt.c
+++ b/drivers/gpu/drm/drm_color_mgmt.c
@@ -62,6 +62,19 @@
* unit/pass-thru matrix should be used. This is generally the driver
* boot-up state too.
*
+ * The output vector is related to the input vector as below::
+ *
+ * out[0] = matrix[0] * in[0] + matrix[1] * in[1] + matrix[2] *
in[2];
+ * out[1] = matrix[3] * in[0] + matrix[4] * in[1] + matrix[5] *
in[2];
+ * out[2] = matrix[6] * in[0] + matrix[7] * in[1] + matrix[8] *
in[2];
+ *
+ * The component order in the input/output vectors is assumed to be
+ * { R, G, B }.
+ *
+ * The color-space of the input vector must not be confused with the
+ * color-space implied by a framebuffer pixel format, which may be the same
+ * or different.
+ *
* “GAMMA_LUT”:
* Blob property to set the gamma lookup table (LUT) mapping pixel data
* after the transformation matrix to data sent to the connector. The
diff --git a/include/uapi/drm/drm_mode.h b/include/uapi/drm/drm_mode.h
index ce7efe2e8a5e..3f179b8867e5 100644
--- a/include/uapi/drm/drm_mode.h
+++ b/include/uapi/drm/drm_mode.h
@@ -525,7 +525,19 @@ struct drm_mode_crtc_lut {
};
struct drm_color_ctm {
- /* Conversion matrix in S31.32 format. */
+ /*
+ * Conversion matrix in row-major form:
+ *
+ * | matrix[0] matrix[1] matrix[2] |
+ * | matrix[3] matrix[4] matrix[5] |
+ * | matrix[6] matrix[7] matrix[8] |
+ *
+ * Each element is in a sign + magnitude format: S31.32, with the sign
+ * in bit 63, and the magnitude represented as fixed-point 31.32.
+ *
+ * i.e. +1.25 = 0x00000001.40000000
+ * -1.25 = 0x80000001.40000000
+ */
__s64 matrix[9];
};
--
1.7.9.5
