drm/doc: Document color space handling

Again move it from the unmaintainable csv into DOC free-form overview
sections.

v2: Types Lionel&Sean spotted.

Cc: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Reviewed-by: Sean Paul <seanpaul@chromium.org>
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Link: http://patchwork.freedesktop.org/patch/msgid/1474448370-32227-6-git-send-email-daniel.vetter@ffwll.ch

Documentation/gpu/drm-kms.rst

@@ -296,6 +296,18 @@ Plane Composition Properties
 .. kernel-doc:: drivers/gpu/drm/drm_blend.c
    :export:
 
+Color Management Properties
+---------------------------
+
+.. kernel-doc:: drivers/gpu/drm/drm_color_mgmt.c
+   :doc: overview
+
+.. kernel-doc:: include/drm/drm_color_mgmt.h
+   :internal:
+
+.. kernel-doc:: drivers/gpu/drm/drm_color_mgmt.c
+   :export:
+
 Existing KMS Properties
 -----------------------
 

Documentation/gpu/kms-properties.csv

@@ -24,11 +24,6 @@ Owner Module/Drivers,Group,Property Name,Type,Property Values,Object attached,De
 ,,“suggested Y”,RANGE,"Min=0, Max=0xffffffff",Connector,property to suggest an Y offset for a connector
 ,Optional,"""aspect ratio""",ENUM,"{ ""None"", ""4:3"", ""16:9"" }",Connector,TDB
 ,,“dirty”,ENUM | IMMUTABLE,"{ ""Off"", ""On"", ""Annotate"" }",Connector,TBD
-,,“DEGAMMA_LUT”,BLOB,0,CRTC,DRM property to set the degamma lookup table (LUT) mapping pixel data from the framebuffer before it is given to the transformation matrix. The data is an interpreted as an array of struct drm_color_lut elements. Hardware might choose not to use the full precision of the LUT elements nor use all the elements of the LUT (for example the hardware might choose to interpolate between LUT[0] and LUT[4]).
-,,“DEGAMMA_LUT_SIZE”,RANGE | IMMUTABLE,"Min=0, Max=UINT_MAX",CRTC,DRM property to gives the size of the lookup table to be set on the DEGAMMA_LUT property (the size depends on the underlying hardware).
-,,“CTM”,BLOB,0,CRTC,DRM property to set the current transformation matrix (CTM) apply to pixel data after the lookup through the degamma LUT and before the lookup through the gamma LUT. The data is an interpreted as a struct drm_color_ctm.
-,,“GAMMA_LUT”,BLOB,0,CRTC,DRM property to set the gamma lookup table (LUT) mapping pixel data after to the transformation matrix to data sent to the connector. The data is an interpreted as an array of struct drm_color_lut elements. Hardware might choose not to use the full precision of the LUT elements nor use all the elements of the LUT (for example the hardware might choose to interpolate between LUT[0] and LUT[4]).
-,,“GAMMA_LUT_SIZE”,RANGE | IMMUTABLE,"Min=0, Max=UINT_MAX",CRTC,DRM property to gives the size of the lookup table to be set on the GAMMA_LUT property (the size depends on the underlying hardware).
 i915,Generic,"""Broadcast RGB""",ENUM,"{ ""Automatic"", ""Full"", ""Limited 16:235"" }",Connector,"When this property is set to Limited 16:235 and CTM is set, the hardware will be programmed with the result of the multiplication of CTM by the limited range matrix to ensure the pixels normaly in the range 0..1.0 are remapped to the range 16/255..235/255."
 ,,“audio”,ENUM,"{ ""force-dvi"", ""off"", ""auto"", ""on"" }",Connector,TBD
 ,SDVO-TV,“mode”,ENUM,"{ ""NTSC_M"", ""NTSC_J"", ""NTSC_443"", ""PAL_B"" } etc.",Connector,TBD

drivers/gpu/drm/drm_color_mgmt.c

@@ -26,6 +26,54 @@
 
 #include "drm_crtc_internal.h"
 
+/**
+ * DOC: overview
+ *
+ * Color management or color space adjustments is supported through a set of 5
+ * properties on the &drm_crtc object. They are set up by calling
+ * drm_crtc_enable_color_mgmt().
+ *
+ * "DEGAMMA_LUT”:
+ *	Blob property to set the degamma lookup table (LUT) mapping pixel data
+ *	from the framebuffer before it is given to the transformation matrix.
+ *	The data is interpreted as an array of struct &drm_color_lut elements.
+ *	Hardware might choose not to use the full precision of the LUT elements
+ *	nor use all the elements of the LUT (for example the hardware might
+ *	choose to interpolate between LUT[0] and LUT[4]).
+ *
+ * “DEGAMMA_LUT_SIZE”:
+ *	Unsinged range property to give the size of the lookup table to be set
+ *	on the DEGAMMA_LUT property (the size depends on the underlying
+ *	hardware). If drivers support multiple LUT sizes then they should
+ *	publish the largest size, and sub-sample smaller sized LUTs (e.g. for
+ *	split-gamma modes) appropriately.
+ *
+ * “CTM”:
+ *	Blob property to set the current transformation matrix (CTM) apply to
+ *	pixel data after the lookup through the degamma LUT and before the
+ *	lookup through the gamma LUT. The data is interpreted as a struct
+ *	&drm_color_ctm.
+ *
+ * “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
+ *	data is interpreted as an array of struct &drm_color_lut elements.
+ *	Hardware might choose not to use the full precision of the LUT elements
+ *	nor use all the elements of the LUT (for example the hardware might
+ *	choose to interpolate between LUT[0] and LUT[4]).
+ *
+ * “GAMMA_LUT_SIZE”:
+ *	Unsigned range property to give the size of the lookup table to be set
+ *	on the GAMMA_LUT property (the size depends on the underlying hardware).
+ *	If drivers support multiple LUT sizes then they should publish the
+ *	largest size, and sub-sample smaller sized LUTs (e.g. for split-gamma
+ *	modes) appropriately.
+ *
+ * There is also support for a legacy gamma table, which is set up by calling
+ * drm_mode_crtc_set_gamma_size(). Drivers which support both should use
+ * drm_atomic_helper_legacy_gamma_set() to alias the legacy gamma ramp with the
+ * "GAMMA_LUT" property above.
+ */
 
 /**
  * drm_crtc_enable_color_mgmt - enable color management properties

include/drm/drm_color_mgmt.h

@@ -33,9 +33,14 @@ void drm_crtc_enable_color_mgmt(struct drm_crtc *crtc,
 int drm_mode_crtc_set_gamma_size(struct drm_crtc *crtc,
 				 int gamma_size);
 
-/*
- * Extract a degamma/gamma LUT value provided by user and round it to the
- * precision supported by the hardware.
+/**
+ * drm_color_lut_extract - clamp&round LUT entries
+ * @user_input: input value
+ * @bit_precision: number of bits the hw LUT supports
+ *
+ * Extract a degamma/gamma LUT value provided by user (in the form of
+ * &drm_color_lut entries) and round it to the precision supported by the
+ * hardware.
  */
 static inline uint32_t drm_color_lut_extract(uint32_t user_input,
 					     uint32_t bit_precision)