Pixel blend modes represent the alpha blending equation
selection, describing how the pixels from the current
plane are composited with the background.
Add 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.
Signed-off-by: Lowry Li <lowry.li@xxxxxxx>
---
drivers/gpu/drm/drm_atomic.c | 4 ++
drivers/gpu/drm/drm_atomic_helper.c | 1 +
drivers/gpu/drm/drm_blend.c | 126 ++++++++++++++++++++++++++++++++++++
include/drm/drm_blend.h | 6 ++
include/drm/drm_plane.h | 5 ++
5 files changed, 142 insertions(+)
diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
index 07fef42..1d18389 100644
--- a/drivers/gpu/drm/drm_atomic.c
+++ b/drivers/gpu/drm/drm_atomic.c
@@ -785,6 +785,8 @@ 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))
return -EINVAL;
@@ -852,6 +854,8 @@ static int drm_atomic_plane_set_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) {
diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
index 130da51..7f5d463 100644
--- a/drivers/gpu/drm/drm_atomic_helper.c
+++ b/drivers/gpu/drm/drm_atomic_helper.c
@@ -3515,6 +3515,7 @@ void drm_atomic_helper_plane_reset(struct drm_plane *plane)
/* Reset the alpha value to fully opaque if it matters */
if (plane->alpha_property)
plane->state->alpha = plane->alpha_property->values[1];
+ plane->state->pixel_blend_mode = DRM_MODE_BLEND_PREMULTI;
}
}
EXPORT_SYMBOL(drm_atomic_helper_plane_reset);
diff --git a/drivers/gpu/drm/drm_blend.c b/drivers/gpu/drm/drm_blend.c
index a16a74d..ac6f19c 100644
--- a/drivers/gpu/drm/drm_blend.c
+++ b/drivers/gpu/drm/drm_blend.c
@@ -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 +494,83 @@ 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 coverage.
+ *
+ * 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, j = 0;
+
+ 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, j++, 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;
+
+ if (plane->state)
+ plane->state->pixel_blend_mode = DRM_MODE_BLEND_PREMULTI;
+
+ return 0;
+}
+EXPORT_SYMBOL(drm_plane_create_blend_mode_property);
diff --git a/include/drm/drm_blend.h b/include/drm/drm_blend.h
index 330c561..28c5076 100644
--- a/include/drm/drm_blend.h
+++ b/include/drm/drm_blend.h
@@ -27,6 +27,10 @@
#include <linux/ctype.h>
#include <drm/drm_mode.h>
+#define DRM_MODE_BLEND_PIXEL_NONE 0
+#define DRM_MODE_BLEND_PREMULTI 1
+#define DRM_MODE_BLEND_COVERAGE 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
diff --git a/include/drm/drm_plane.h b/include/drm/drm_plane.h
index 14b1607..6e2c045 100644
--- a/include/drm/drm_plane.h
+++ b/include/drm/drm_plane.h
@@ -44,6 +44,8 @@
* @src_w: width of visible portion of plane (in 16.16)
* @src_h: height of visible portion of plane (in 16.16)
* @alpha: opacity of the plane
+ * @pixel_blend_mode: how the plane's framebuffer alpha channel is used when
+ * blending with the background colour.
* @rotation: rotation of the plane
* @zpos: priority of the given plane on crtc (optional)
* Note that multiple active planes on the same crtc can have an identical
@@ -116,6 +118,7 @@ struct drm_plane_state {
/* Plane opacity */
u16 alpha;
+ uint16_t pixel_blend_mode;
/* Plane rotation */
unsigned int rotation;
@@ -513,6 +516,7 @@ enum drm_plane_type {
* @alpha_property: alpha property for this plane
* @zpos_property: zpos property for this plane
* @rotation_property: rotation property for this plane
+ * @blend_mode_property: blend mode property for this plane
* @helper_private: mid-layer private data
*/
struct drm_plane {
@@ -589,6 +593,7 @@ struct drm_plane {
struct drm_property *alpha_property;
struct drm_property *zpos_property;
struct drm_property *rotation_property;
+ struct drm_property *blend_mode_property;
/**
* @color_encoding_property:
--
1.9.1
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