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Commit a5ec8332 authored by Lowry Li's avatar Lowry Li Committed by Ayan Kumar Halder
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drm: Add per-plane pixel blend mode property 



Pixel blend modes represent the alpha blending equation
selection, describing how the pixels from the current
plane are composited with the background.

Adds a pixel_blend_mode to drm_plane_state and a
blend_mode_property to drm_plane, and related support
functions.

Defines three blend modes in drm_blend.h.

Changes since v1:
 - Moves the blending equation into the DOC comment
 - Refines the comments of drm_plane_create_blend_mode_property to not
   enumerate the #defines, but instead the string values
 - Uses fg.* instead of pixel.* and plane_alpha instead of plane.alpha
Changes since v2:
 - Refines the comments of drm_plane_create_blend_mode_property:
      1) Puts the descriptions (after the ":") on a new line
      2) Adds explaining why @supported_modes need PREMUL as default
Changes since v3:
 - Refines drm_plane_create_blend_mode_property(). drm_property_add_enum()
   can calculate the index itself just fine, so no point in having the
   caller pass it in.
 - Since the current DRM assumption is that alpha is premultiplied
   as default, define DRM_MODE_BLEND_PREMULTI as 0 will be better.
 - Refines some comments.
Changes since v4:
 - Adds comments in drm_blend.h.
 - Removes setting default value in drm_plane_create_blend_mode_property()
   as it is already in __drm_atomic_helper_plane_reset().
 - Fixes to use state->pixel_blend_mode instead of using
   plane->state->pixel_blend_mode in reset function.
 - Rebases on drm-misc-next.

Reviewed-by: default avatarLiviu Dudau <liviu.dudau@arm.com>
Signed-off-by: default avatarLowry Li <lowry.li@arm.com>
Signed-off-by: default avatarAyan Kumar Halder <ayan.halder@arm.com>
Reviewed-by: default avatarSean Paul <seanpaul@chromium.org>
Link: https://patchwork.freedesktop.org/patch/245734/
parent 06e3c297

drivers/gpu/drm/drm_atomic.c

+4 −0
Original line number Diff line number Diff line
@@ -895,6 +895,8 @@ static int drm_atomic_plane_set_property(struct drm_plane *plane, 
		state->src_h = val;

	} else if (property == plane->alpha_property) {

		state->alpha = val;

	} else if (property == plane->blend_mode_property) {

		state->pixel_blend_mode = val;

	} else if (property == plane->rotation_property) {

		if (!is_power_of_2(val & DRM_MODE_ROTATE_MASK)) {

			DRM_DEBUG_ATOMIC("[PLANE:%d:%s] bad rotation bitmask: 0x%llx\n",
@@ -968,6 +970,8 @@ drm_atomic_plane_get_property(struct drm_plane *plane, 
		*val = state->src_h;

	} else if (property == plane->alpha_property) {

		*val = state->alpha;

	} else if (property == plane->blend_mode_property) {

		*val = state->pixel_blend_mode;

	} else if (property == plane->rotation_property) {

		*val = state->rotation;

	} else if (property == plane->zpos_property) {

drivers/gpu/drm/drm_atomic_helper.c

+1 −0
Original line number Diff line number Diff line
@@ -3569,6 +3569,7 @@ void __drm_atomic_helper_plane_reset(struct drm_plane *plane, 
	/* Reset the alpha value to fully opaque if it matters */

	if (plane->alpha_property)

		state->alpha = plane->alpha_property->values[1];

	state->pixel_blend_mode = DRM_MODE_BLEND_PREMULTI;



	plane->state = state;

}

drivers/gpu/drm/drm_blend.c

+123 −0
Original line number Diff line number Diff line
@@ -107,6 +107,52 @@ 
 *	planes. Without this property the primary plane is always below the cursor

 *	plane, and ordering between all other planes is undefined.

 *

 * pixel blend mode:

 *	Pixel blend mode is set up with drm_plane_create_blend_mode_property().

 *	It adds a blend mode for alpha blending equation selection, describing

 *	how the pixels from the current plane are composited with the

 *	background.

 *

 *	 Three alpha blending equations are defined:

 *

 *	 "None":

 *		 Blend formula that ignores the pixel alpha::

 *

 *			 out.rgb = plane_alpha * fg.rgb +

 *				 (1 - plane_alpha) * bg.rgb

 *

 *	 "Pre-multiplied":

 *		 Blend formula that assumes the pixel color values

 *		 have been already pre-multiplied with the alpha

 *		 channel values::

 *

 *			 out.rgb = plane_alpha * fg.rgb +

 *				 (1 - (plane_alpha * fg.alpha)) * bg.rgb

 *

 *	 "Coverage":

 *		 Blend formula that assumes the pixel color values have not

 *		 been pre-multiplied and will do so when blending them to the

 *		 background color values::

 *

 *			 out.rgb = plane_alpha * fg.alpha * fg.rgb +

 *				 (1 - (plane_alpha * fg.alpha)) * bg.rgb

 *

 *	 Using the following symbols:

 *

 *	 "fg.rgb":

 *		 Each of the RGB component values from the plane's pixel

 *	 "fg.alpha":

 *		 Alpha component value from the plane's pixel. If the plane's

 *		 pixel format has no alpha component, then this is assumed to be

 *		 1.0. In these cases, this property has no effect, as all three

 *		 equations become equivalent.

 *	 "bg.rgb":

 *		 Each of the RGB component values from the background

 *	 "plane_alpha":

 *		 Plane alpha value set by the plane "alpha" property. If the

 *		 plane does not expose the "alpha" property, then this is

 *		 assumed to be 1.0

 *

 * Note that all the property extensions described here apply either to the

 * plane or the CRTC (e.g. for the background color, which currently is not

 * exposed and assumed to be black).
@@ -448,3 +494,80 @@ int drm_atomic_normalize_zpos(struct drm_device *dev, 
	return 0;

}

EXPORT_SYMBOL(drm_atomic_normalize_zpos);



/**

 * drm_plane_create_blend_mode_property - create a new blend mode property

 * @plane: drm plane

 * @supported_modes: bitmask of supported modes, must include

 *		     BIT(DRM_MODE_BLEND_PREMULTI). Current DRM assumption is

 *		     that alpha is premultiplied, and old userspace can break if

 *		     the property defaults to anything else.

 *

 * This creates a new property describing the blend mode.

 *

 * The property exposed to userspace is an enumeration property (see

 * drm_property_create_enum()) called "pixel blend mode" and has the

 * following enumeration values:

 *

 * "None":

 *	Blend formula that ignores the pixel alpha.

 *

 * "Pre-multiplied":

 *	Blend formula that assumes the pixel color values have been already

 *	pre-multiplied with the alpha channel values.

 *

 * "Coverage":

 *	Blend formula that assumes the pixel color values have not been

 *	pre-multiplied and will do so when blending them to the background color

 *	values.

 *

 * RETURNS:

 * Zero for success or -errno

 */

int drm_plane_create_blend_mode_property(struct drm_plane *plane,

					 unsigned int supported_modes)

{

	struct drm_device *dev = plane->dev;

	struct drm_property *prop;

	static const struct drm_prop_enum_list props[] = {

		{ DRM_MODE_BLEND_PIXEL_NONE, "None" },

		{ DRM_MODE_BLEND_PREMULTI, "Pre-multiplied" },

		{ DRM_MODE_BLEND_COVERAGE, "Coverage" },

	};

	unsigned int valid_mode_mask = BIT(DRM_MODE_BLEND_PIXEL_NONE) |

				       BIT(DRM_MODE_BLEND_PREMULTI)   |

				       BIT(DRM_MODE_BLEND_COVERAGE);

	int i;



	if (WARN_ON((supported_modes & ~valid_mode_mask) ||

		    ((supported_modes & BIT(DRM_MODE_BLEND_PREMULTI)) == 0)))

		return -EINVAL;



	prop = drm_property_create(dev, DRM_MODE_PROP_ENUM,

				   "pixel blend mode",

				   hweight32(supported_modes));

	if (!prop)

		return -ENOMEM;



	for (i = 0; i < ARRAY_SIZE(props); i++) {

		int ret;



		if (!(BIT(props[i].type) & supported_modes))

			continue;



		ret = drm_property_add_enum(prop, props[i].type,

					    props[i].name);



		if (ret) {

			drm_property_destroy(dev, prop);



			return ret;

		}

	}



	drm_object_attach_property(&plane->base, prop, DRM_MODE_BLEND_PREMULTI);

	plane->blend_mode_property = prop;



	return 0;

}

EXPORT_SYMBOL(drm_plane_create_blend_mode_property);

include/drm/drm_blend.h

+6 −0
Original line number Diff line number Diff line
@@ -27,6 +27,10 @@ 
#include <linux/ctype.h>

#include <drm/drm_mode.h>



#define DRM_MODE_BLEND_PREMULTI		0

#define DRM_MODE_BLEND_COVERAGE		1

#define DRM_MODE_BLEND_PIXEL_NONE	2



struct drm_device;

struct drm_atomic_state;

struct drm_plane;
@@ -52,4 +56,6 @@ int drm_plane_create_zpos_immutable_property(struct drm_plane *plane, 
					     unsigned int zpos);

int drm_atomic_normalize_zpos(struct drm_device *dev,

			      struct drm_atomic_state *state);

int drm_plane_create_blend_mode_property(struct drm_plane *plane,

					 unsigned int supported_modes);

#endif

include/drm/drm_plane.h

+9 −0
Original line number Diff line number Diff line
@@ -117,6 +117,7 @@ struct drm_plane_state { 
	 * details.

	 */

	u16 alpha;

	uint16_t pixel_blend_mode;



	/**

	 * @rotation:
@@ -659,6 +660,14 @@ struct drm_plane { 
	 * drm_plane_create_rotation_property().

	 */

	struct drm_property *rotation_property;

	/**

	 * @blend_mode_property:

	 * Optional "pixel blend mode" enum property for this plane.

	 * Blend mode property represents the alpha blending equation selection,

	 * describing how the pixels from the current plane are composited with

	 * the background.

	 */

	struct drm_property *blend_mode_property;



	/**

	 * @color_encoding_property: