Commit 4fd5e720 authored by Daniel Vetter's avatar Daniel Vetter
Browse files

drm/docs: Document where the C8 color lut is stored 



Also add notes that for atomic drivers it's really somewhere else and
no longer in struct drm_crtc.

Maybe we should put a bigger warning here that this is confusing,
since the pixel format is a plane property, but the GAMMA_LUT property
is on the crtc. But I think we can fix this if/when someone finds a
need for a per-plane CLUT, since I'm not sure such hw even exists. I'm
also not sure whether even hardware with a CLUT and a full color
correction pipeline with degamm/cgm/gamma exists.

Motivated by comments from Geert that we have a gap here.

v2: More names for color luts (Laurent).

Reviewed-by: default avatarAlex Deucher <alexander.deucher@amd.com>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: default avatarLaurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Signed-off-by: default avatarDaniel Vetter <daniel.vetter@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220124221633.952374-1-daniel.vetter@ffwll.ch
parent 8b250cd3

drivers/gpu/drm/drm_color_mgmt.c

+4 −0
Original line number Diff line number Diff line
@@ -82,6 +82,10 @@ 
 *	driver boot-up state too. Drivers can access this blob through

 *	&drm_crtc_state.gamma_lut.

 *

 *	Note that for mostly historical reasons stemming from Xorg heritage,

 *	this is also used to store the color map (also sometimes color lut, CLUT

 *	or color palette) for indexed formats like DRM_FORMAT_C8.

 *

 * “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).

include/drm/drm_crtc.h

+10 −0
Original line number Diff line number Diff line
@@ -285,6 +285,10 @@ struct drm_crtc_state { 
	 * Lookup table for converting pixel data after the color conversion

	 * matrix @ctm.  See drm_crtc_enable_color_mgmt(). The blob (if not

	 * NULL) is an array of &struct drm_color_lut.

	 *

	 * Note that for mostly historical reasons stemming from Xorg heritage,

	 * this is also used to store the color map (also sometimes color lut,

	 * CLUT or color palette) for indexed formats like DRM_FORMAT_C8.

	 */

	struct drm_property_blob *gamma_lut;
@@ -1075,12 +1079,18 @@ struct drm_crtc { 
	/**

	 * @gamma_size: Size of legacy gamma ramp reported to userspace. Set up

	 * by calling drm_mode_crtc_set_gamma_size().

	 *

	 * Note that atomic drivers need to instead use

	 * &drm_crtc_state.gamma_lut. See drm_crtc_enable_color_mgmt().

	 */

	uint32_t gamma_size;



	/**

	 * @gamma_store: Gamma ramp values used by the legacy SETGAMMA and

	 * GETGAMMA IOCTls. Set up by calling drm_mode_crtc_set_gamma_size().

	 *

	 * Note that atomic drivers need to instead use

	 * &drm_crtc_state.gamma_lut. See drm_crtc_enable_color_mgmt().

	 */

	uint16_t *gamma_store;