drm: Introduce pixel_source DRM plane property

Add support for pixel_source property to drm_plane and related
documentation. In addition, force pixel_source to
DRM_PLANE_PIXEL_SOURCE_FB in DRM_IOCTL_MODE_SETPLANE as to not break
legacy userspace.

This enum property will allow user to specify a pixel source for the
plane. Possible pixel sources will be defined in the
drm_plane_pixel_source enum.

Currently, the only pixel sources are DRM_PLANE_PIXEL_SOURCE_FB (the
default value) and DRM_PLANE_PIXEL_SOURCE_NONE.

Acked-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Acked-by: Pekka Paalanen <pekka.paalanen@collabora.com>
Acked-by: Harry Wentland <harry.wentland@amd.com>
Acked-by: Sebastian Wick <sebastian@sebastianwick.net>
Acked-by: Simon Ser <contact@emersion.fr>
Signed-off-by: Jessica Zhang <quic_jesszhan@quicinc.com>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20231027-solid-fill-v7-1-780188bfa7b2@quicinc.com

drivers/gpu/drm/drm_atomic_state_helper.c

@@ -252,6 +252,7 @@ void __drm_atomic_helper_plane_state_reset(struct drm_plane_state *plane_state,
 
 	plane_state->alpha = DRM_BLEND_ALPHA_OPAQUE;
 	plane_state->pixel_blend_mode = DRM_MODE_BLEND_PREMULTI;
+	plane_state->pixel_source = DRM_PLANE_PIXEL_SOURCE_FB;
 
 	if (plane->color_encoding_property) {
 		if (!drm_object_property_get_default_value(&plane->base,

drivers/gpu/drm/drm_atomic_uapi.c

@@ -562,6 +562,8 @@ 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->pixel_source_property) {
+		state->pixel_source = val;
 	} else if (property == plane->alpha_property) {
 		state->alpha = val;
 	} else if (property == plane->blend_mode_property) {
@@ -650,6 +652,8 @@ 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->pixel_source_property) {
+		*val = state->pixel_source;
 	} else if (property == plane->alpha_property) {
 		*val = state->alpha;
 	} else if (property == plane->blend_mode_property) {

drivers/gpu/drm/drm_blend.c

@@ -185,6 +185,25 @@
  *		 plane does not expose the "alpha" property, then this is
  *		 assumed to be 1.0
  *
+ * pixel_source:
+ *	pixel_source is set up with drm_plane_create_pixel_source_property().
+ *	It is used to toggle the active source of pixel data for the plane.
+ *	The plane will only display data from the set pixel_source -- any
+ *	data from other sources will be ignored.
+ *
+ *	For non-framebuffer sources, if pixel_source is set to a non-framebuffer
+ *	and non-NONE source, and the corresponding source property is NULL, then
+ *	the atomic commit should return an error.
+ *
+ *	Possible values:
+ *
+ *	"NONE":
+ *		No active pixel source.
+ *		Committing with a NONE pixel source will disable the plane.
+ *
+ *	"FB":
+ *		Framebuffer source set by the "FB_ID" property.
+ *
  * 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).
@@ -615,3 +634,78 @@ int drm_plane_create_blend_mode_property(struct drm_plane *plane,
 	return 0;
 }
 EXPORT_SYMBOL(drm_plane_create_blend_mode_property);
+
+static const struct drm_prop_enum_list drm_pixel_source_enum_list[] = {
+	{ DRM_PLANE_PIXEL_SOURCE_NONE, "NONE" },
+	{ DRM_PLANE_PIXEL_SOURCE_FB, "FB" },
+};
+
+/**
+ * drm_plane_create_pixel_source_property - create a new pixel source property
+ * @plane: DRM plane
+ * @extra_sources: Bitmask of additional supported pixel_sources for the driver.
+ *		   DRM_PLANE_PIXEL_SOURCE_FB and DRM_PLANE_PIXEL_SOURCE_NONE will
+ *		   always be enabled as supported sources.
+ *
+ * This creates a new property describing the current source of pixel data for the
+ * plane. The pixel_source will be initialized as DRM_PLANE_PIXEL_SOURCE_FB by default.
+ *
+ * Drivers can set a custom default source by overriding the pixel_source value in
+ * drm_plane_funcs.reset()
+ *
+ * The property is exposed to userspace as an enumeration property called
+ * "pixel_source" and has the following enumeration values:
+ *
+ * "NONE":
+ *	No active pixel source
+ *
+ * "FB":
+ *	Framebuffer pixel source
+ *
+ * Returns:
+ * Zero on success, negative errno on failure.
+ */
+int drm_plane_create_pixel_source_property(struct drm_plane *plane,
+					   unsigned long extra_sources)
+{
+	struct drm_device *dev = plane->dev;
+	struct drm_property *prop;
+	static const unsigned int valid_source_mask = BIT(DRM_PLANE_PIXEL_SOURCE_FB) |
+						      BIT(DRM_PLANE_PIXEL_SOURCE_NONE);
+	int i;
+
+	/* FB is supported by default */
+	unsigned long supported_sources = extra_sources |
+					  BIT(DRM_PLANE_PIXEL_SOURCE_FB) |
+					  BIT(DRM_PLANE_PIXEL_SOURCE_NONE);
+
+	if (WARN_ON(supported_sources & ~valid_source_mask))
+		return -EINVAL;
+
+	prop = drm_property_create(dev, DRM_MODE_PROP_ENUM | DRM_MODE_PROP_ATOMIC, "pixel_source",
+			hweight32(supported_sources));
+
+	if (!prop)
+		return -ENOMEM;
+
+	for (i = 0; i < ARRAY_SIZE(drm_pixel_source_enum_list); i++) {
+		int ret;
+
+		if (!test_bit(drm_pixel_source_enum_list[i].type, &supported_sources))
+			continue;
+
+		ret = drm_property_add_enum(prop, drm_pixel_source_enum_list[i].type,
+				drm_pixel_source_enum_list[i].name);
+		if (ret) {
+			drm_property_destroy(dev, prop);
+
+			return ret;
+		}
+	}
+
+	drm_object_attach_property(&plane->base, prop, DRM_PLANE_PIXEL_SOURCE_FB);
+	plane->pixel_source_property = prop;
+
+	return 0;
+}
+EXPORT_SYMBOL(drm_plane_create_pixel_source_property);

drivers/gpu/drm/drm_plane.c

@@ -953,6 +953,14 @@ bool drm_any_plane_has_format(struct drm_device *dev,
 }
 EXPORT_SYMBOL(drm_any_plane_has_format);
 
+static bool drm_plane_needs_disable(struct drm_plane_state *state, struct drm_framebuffer *fb)
+{
+	if (state->pixel_source == DRM_PLANE_PIXEL_SOURCE_NONE)
+		return true;
+
+	return state->pixel_source == DRM_PLANE_PIXEL_SOURCE_FB && fb == NULL;
+}
+
 /*
  * __setplane_internal - setplane handler for internal callers
  *
@@ -975,8 +983,8 @@ static int __setplane_internal(struct drm_plane *plane,
 
 	WARN_ON(drm_drv_uses_atomic_modeset(plane->dev));
 
-	/* No fb means shut it down */
+	/* No visible data means shut it down */
-	if (!fb) {
+	if (drm_plane_needs_disable(plane->state, fb)) {
 		plane->old_fb = plane->fb;
 		ret = plane->funcs->disable_plane(plane, ctx);
 		if (!ret) {
@@ -1027,8 +1035,8 @@ static int __setplane_atomic(struct drm_plane *plane,
 
 	WARN_ON(!drm_drv_uses_atomic_modeset(plane->dev));
 
-	/* No fb means shut it down */
+	/* No visible data means shut it down */
-	if (!fb)
+	if (drm_plane_needs_disable(plane->state, fb))
 		return plane->funcs->disable_plane(plane, ctx);
 
 	/*
@@ -1101,6 +1109,9 @@ int drm_mode_setplane(struct drm_device *dev, void *data,
 		return -ENOENT;
 	}
 
+	if (plane->state)
+		plane->state->pixel_source = DRM_PLANE_PIXEL_SOURCE_FB;
+
 	if (plane_req->fb_id) {
 		fb = drm_framebuffer_lookup(dev, file_priv, plane_req->fb_id);
 		if (!fb) {

include/drm/drm_blend.h

@@ -58,4 +58,6 @@ 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);
+int drm_plane_create_pixel_source_property(struct drm_plane *plane,
+					   unsigned long extra_sources);
 #endif

include/drm/drm_plane.h

@@ -40,6 +40,12 @@ enum drm_scaling_filter {
 	DRM_SCALING_FILTER_NEAREST_NEIGHBOR,
 };
 
+enum drm_plane_pixel_source {
+	DRM_PLANE_PIXEL_SOURCE_NONE,
+	DRM_PLANE_PIXEL_SOURCE_FB,
+	DRM_PLANE_PIXEL_SOURCE_MAX
+};
+
 /**
  * struct drm_plane_state - mutable plane state
  *
@@ -120,6 +126,14 @@ struct drm_plane_state {
 	/** @hotspot_y: y offset to mouse cursor hotspot */
 	int32_t hotspot_x, hotspot_y;
 
+	/**
+	 * @pixel_source:
+	 *
+	 * Source of pixel information for the plane. See
+	 * drm_plane_create_pixel_source_property() for more details.
+	 */
+	enum drm_plane_pixel_source pixel_source;
+
 	/**
 	 * @alpha:
 	 * Opacity of the plane with 0 as completely transparent and 0xffff as
@@ -713,6 +727,13 @@ struct drm_plane {
 	 */
 	struct drm_plane_state *state;
 
+	/*
+	 * @pixel_source_property:
+	 * Optional pixel_source property for this plane. See
+	 * drm_plane_create_pixel_source_property().
+	 */
+	struct drm_property *pixel_source_property;
+
 	/**
 	 * @alpha_property:
 	 * Optional alpha property for this plane. See