On 1 June 2018 at 13:41, Lowry Li <lowry.li@xxxxxxx> wrote:
> 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.
> + *
Thanks for the explanation Lowry.
Sigh, old userspace :-\
One pedantic suggestion s/defaults to coverage/defaults to anything else/
Since defaulting to "none" or any future blend mode is also a no-go.
I wouldn't bother resending solely for ^^. Perhaps squash locally
before merging?
With that, the patch is
Reviewed-by: Emil Velikov <emil.velikov@xxxxxxxxxxxxx>
-Emil
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