Re: [PATCH 06/19] drm/blend: Add a generic alpha property

From: Daniel Vetter <daniel@ffwll.ch>
To: Maxime Ripard <maxime.ripard@free-electrons.com>
Cc: Chen-Yu Tsai <wens@csie.org>,
	Daniel Vetter <daniel.vetter@intel.com>,
	Jani Nikula <jani.nikula@linux.intel.com>,
	Sean Paul <seanpaul@chromium.org>,
	Thomas Petazzoni <thomas.petazzoni@free-electrons.com>,
	Boris Brezillon <boris.brezillon@free-electrons.com>,
	linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org,
	Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
	linux-arm-kernel@lists.infradead.org, thomas@vitsch.nl
Subject: Re: [PATCH 06/19] drm/blend: Add a generic alpha property
Date: Tue, 9 Jan 2018 13:32:41 +0100	[thread overview]
Message-ID: <20180109123241.GU26573@phenom.ffwll.local> (raw)
In-Reply-To: <5c765fc730d75cb362dc37bcdb3b3aeacc7bdb30.1515494838.git-series.maxime.ripard@free-electrons.com>

On Tue, Jan 09, 2018 at 11:56:25AM +0100, Maxime Ripard wrote:
> Some drivers duplicate the logic to create a property to store a per-plane
> alpha.
> 
> Let's create a helper in order to move that to the core.
> 
> Cc: Boris Brezillon <boris.brezillon@free-electrons.com>
> Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>

Do we have userspace for this? Is encoding a fixed 0-255 range really the
best idea?

I know other drivers have skimped on the rules here a bit ... But at least
internally (i.e. within the drm_plane_state) we probably should restrict
ourselves to u8. And this needs real docs (i.e. the full blend equation
drivers are supposed to implement).
-Daniel

> ---
>  Documentation/gpu/kms-properties.csv |  2 +-
>  drivers/gpu/drm/drm_atomic.c         |  4 ++++-
>  drivers/gpu/drm/drm_atomic_helper.c  |  1 +-
>  drivers/gpu/drm/drm_blend.c          | 32 +++++++++++++++++++++++++++++-
>  include/drm/drm_blend.h              |  1 +-
>  include/drm/drm_plane.h              |  6 +++++-
>  6 files changed, 45 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/gpu/kms-properties.csv b/Documentation/gpu/kms-properties.csv
> index 927b65e14219..a3c3969c1992 100644
> --- a/Documentation/gpu/kms-properties.csv
> +++ b/Documentation/gpu/kms-properties.csv
> @@ -99,5 +99,5 @@ radeon,DVI-I,“coherent”,RANGE,"Min=0, Max=1",Connector,TBD
>  ,,"""underscan vborder""",RANGE,"Min=0, Max=128",Connector,TBD
>  ,Audio,“audio”,ENUM,"{ ""off"", ""on"", ""auto"" }",Connector,TBD
>  ,FMT Dithering,“dither”,ENUM,"{ ""off"", ""on"" }",Connector,TBD
> -rcar-du,Generic,"""alpha""",RANGE,"Min=0, Max=255",Plane,TBD
> +,,"""alpha""",RANGE,"Min=0, Max=255",Plane,Opacity of the plane from transparent (0) to opaque (255)
>  ,,"""colorkey""",RANGE,"Min=0, Max=0x01ffffff",Plane,TBD
> diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
> index c2da5585e201..ade18cf62c89 100644
> --- a/drivers/gpu/drm/drm_atomic.c
> +++ b/drivers/gpu/drm/drm_atomic.c
> @@ -749,6 +749,8 @@ static int drm_atomic_plane_set_property(struct drm_plane *plane,
>  		state->src_w = val;
>  	} else if (property == config->prop_src_h) {
>  		state->src_h = val;
> +	} else if (property == plane->alpha_property) {
> +		state->alpha = val;
>  	} else if (property == plane->rotation_property) {
>  		if (!is_power_of_2(val & DRM_MODE_ROTATE_MASK))
>  			return -EINVAL;
> @@ -810,6 +812,8 @@ drm_atomic_plane_get_property(struct drm_plane *plane,
>  		*val = state->src_w;
>  	} else if (property == config->prop_src_h) {
>  		*val = state->src_h;
> +	} else if (property == plane->alpha_property) {
> +		*val = state->alpha;
>  	} 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 71d712f1b56a..018993df4c18 100644
> --- a/drivers/gpu/drm/drm_atomic_helper.c
> +++ b/drivers/gpu/drm/drm_atomic_helper.c
> @@ -3372,6 +3372,7 @@ void drm_atomic_helper_plane_reset(struct drm_plane *plane)
>  
>  	if (plane->state) {
>  		plane->state->plane = plane;
> +		plane->state->alpha = 255;
>  		plane->state->rotation = DRM_MODE_ROTATE_0;
>  	}
>  }
> diff --git a/drivers/gpu/drm/drm_blend.c b/drivers/gpu/drm/drm_blend.c
> index 2e5e089dd912..8eea2a8af458 100644
> --- a/drivers/gpu/drm/drm_blend.c
> +++ b/drivers/gpu/drm/drm_blend.c
> @@ -104,6 +104,38 @@
>   */
>  
>  /**
> + * drm_plane_create_alpha_property - create a new alpha property
> + * @plane: drm plane
> + * @alpha: initial value of alpha, from 0 (transparent) to 255 (opaque)
> + *
> + * This function initializes a generic, mutable, alpha property and
> + * enables support for it in the DRM core.
> + *
> + * Drivers can then attach this property to their plane to enable
> + * support for configurable plane alpha.
> + *
> + * Returns:
> + * 0 on success, negative error code on failure.
> + */
> +int drm_plane_create_alpha_property(struct drm_plane *plane, u8 alpha)
> +{
> +	struct drm_property *prop;
> +
> +	prop = drm_property_create_range(plane->dev, 0, "alpha", 0, 255);
> +	if (!prop)
> +		return -ENOMEM;
> +
> +	drm_object_attach_property(&plane->base, prop, alpha);
> +	plane->alpha_property = prop;
> +
> +	if (plane->state)
> +		plane->state->alpha = alpha;
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL(drm_plane_create_alpha_property);
> +
> +/**
>   * drm_plane_create_rotation_property - create a new rotation property
>   * @plane: drm plane
>   * @rotation: initial value of the rotation property
> diff --git a/include/drm/drm_blend.h b/include/drm/drm_blend.h
> index 17606026590b..5979a8fce453 100644
> --- a/include/drm/drm_blend.h
> +++ b/include/drm/drm_blend.h
> @@ -36,6 +36,7 @@ static inline bool drm_rotation_90_or_270(unsigned int rotation)
>  	return rotation & (DRM_MODE_ROTATE_90 | DRM_MODE_ROTATE_270);
>  }
>  
> +int drm_plane_create_alpha_property(struct drm_plane *plane, u8 alpha);
>  int drm_plane_create_rotation_property(struct drm_plane *plane,
>  				       unsigned int rotation,
>  				       unsigned int supported_rotations);
> diff --git a/include/drm/drm_plane.h b/include/drm/drm_plane.h
> index 571615079230..a5e26064b132 100644
> --- a/include/drm/drm_plane.h
> +++ b/include/drm/drm_plane.h
> @@ -42,6 +42,7 @@ struct drm_modeset_acquire_ctx;
>   *	plane (in 16.16)
>   * @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
>   * @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
> @@ -105,6 +106,9 @@ struct drm_plane_state {
>  	uint32_t src_x, src_y;
>  	uint32_t src_h, src_w;
>  
> +	/* Plane opacity */
> +	u8 alpha;
> +
>  	/* Plane rotation */
>  	unsigned int rotation;
>  
> @@ -481,6 +485,7 @@ enum drm_plane_type {
>   * @funcs: helper functions
>   * @properties: property tracking for this plane
>   * @type: type of plane (overlay, primary, cursor)
> + * @alpha_property: alpha property for this plane
>   * @zpos_property: zpos property for this plane
>   * @rotation_property: rotation property for this plane
>   * @helper_private: mid-layer private data
> @@ -546,6 +551,7 @@ struct drm_plane {
>  	 */
>  	struct drm_plane_state *state;
>  
> +	struct drm_property *alpha_property;
>  	struct drm_property *zpos_property;
>  	struct drm_property *rotation_property;
>  };
> -- 
> git-series 0.9.1
> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch