Re: [PATCH RFC v4 2/7] drm: Introduce pixel_source DRM plane property

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On 6/30/2023 7:43 AM, Sebastian Wick wrote:
On Fri, Jun 30, 2023 at 2:26 AM Jessica Zhang <quic_jesszhan@xxxxxxxxxxx> wrote:

Add support for pixel_source property to drm_plane and related
documentation.

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.

The current possible pixel sources are DRM_PLANE_PIXEL_SOURCE_FB and
DRM_PLANE_PIXEL_SOURCE_COLOR. The default value is *_SOURCE_FB.

Signed-off-by: Jessica Zhang <quic_jesszhan@xxxxxxxxxxx>
---
  drivers/gpu/drm/drm_atomic_state_helper.c |  1 +
  drivers/gpu/drm/drm_atomic_uapi.c         |  4 ++
  drivers/gpu/drm/drm_blend.c               | 81 +++++++++++++++++++++++++++++++
  include/drm/drm_blend.h                   |  2 +
  include/drm/drm_plane.h                   | 21 ++++++++
  5 files changed, 109 insertions(+)

diff --git a/drivers/gpu/drm/drm_atomic_state_helper.c b/drivers/gpu/drm/drm_atomic_state_helper.c
index fe14be2bd2b2..86fb876efbe6 100644
--- a/drivers/gpu/drm/drm_atomic_state_helper.c
+++ b/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_state->solid_fill_blob) {
                 drm_property_blob_put(plane_state->solid_fill_blob);
diff --git a/drivers/gpu/drm/drm_atomic_uapi.c b/drivers/gpu/drm/drm_atomic_uapi.c
index a28b4ee79444..6e59c21af66b 100644
--- a/drivers/gpu/drm/drm_atomic_uapi.c
+++ b/drivers/gpu/drm/drm_atomic_uapi.c
@@ -596,6 +596,8 @@ static int drm_atomic_plane_set_property(struct drm_plane *plane,
                 drm_property_blob_put(solid_fill);

                 return ret;
+       } 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) {
@@ -671,6 +673,8 @@ drm_atomic_plane_get_property(struct drm_plane *plane,
         } else if (property == plane->solid_fill_property) {
                 *val = state->solid_fill_blob ?
                         state->solid_fill_blob->base.id : 0;
+       } 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) {
diff --git a/drivers/gpu/drm/drm_blend.c b/drivers/gpu/drm/drm_blend.c
index 38c3c5d6453a..8c100a957ee2 100644
--- a/drivers/gpu/drm/drm_blend.c
+++ b/drivers/gpu/drm/drm_blend.c
@@ -189,6 +189,18 @@
   *     solid_fill is set up with drm_plane_create_solid_fill_property(). It
   *     contains pixel data that drivers can use to fill a plane.
   *
+ * pixel_source:
+ *     pixel_source is set up with drm_plane_create_pixel_source_property().
+ *     It is used to toggle the source of pixel data for the plane.
+ *
+ *     Possible values:
+ *
+ *     "FB":
+ *             Framebuffer source
+ *
+ *     "COLOR":
+ *             solid_fill source
+ *
   * 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).
@@ -648,3 +660,72 @@ int drm_plane_create_solid_fill_property(struct drm_plane *plane)
         return 0;
  }
  EXPORT_SYMBOL(drm_plane_create_solid_fill_property);
+
+/**
+ * drm_plane_create_pixel_source_property - create a new pixel source property
+ * @plane: drm plane
+ * @supported_sources: bitmask of supported pixel_sources for the driver (NOT
+ *                     including DRM_PLANE_PIXEL_SOURCE_FB, as it will be supported
+ *                     by default).
+ *
+ * This creates a new property describing the current source of pixel data for the
+ * plane.
+ *
+ * The property is exposed to userspace as an enumeration property called
+ * "pixel_source" and has the following enumeration values:
+ *
+ * "FB":
+ *     Framebuffer pixel source
+ *
+ * "COLOR":
+ *     Solid fill color pixel source

Can we add a "NONE" value?

I know it has been discussed earlier if we *need*  this and I don't
think we do. I just think it would be better API design to disable
planes this way than having to know that a framebuffer pixel source
with a NULL framebuffer disables the plane. Obviously also keep the
old behavior for backwards compatibility.

Hi Sebastian,

Sounds good.

So if pixel_source == NONE disables the planes, would that mean cases where pixel_source == COLOR && solid_fill_blob == NULL, the atomic commit should throw an error?

Thanks,

Jessica Zhang


+ *
+ * Returns:
+ * Zero on success, negative errno on failure.
+ */
+int drm_plane_create_pixel_source_property(struct drm_plane *plane,
+                                          unsigned int supported_sources)
+{
+       struct drm_device *dev = plane->dev;
+       struct drm_property *prop;
+       const struct drm_prop_enum_list enum_list[] = {
+               { DRM_PLANE_PIXEL_SOURCE_FB, "FB" },
+               { DRM_PLANE_PIXEL_SOURCE_COLOR, "COLOR" },
+       };
+       unsigned int valid_source_mask = BIT(DRM_PLANE_PIXEL_SOURCE_FB) |
+                                      BIT(DRM_PLANE_PIXEL_SOURCE_COLOR);
+       int i;
+
+       /* FB is supported by default */
+       supported_sources |= BIT(DRM_PLANE_PIXEL_SOURCE_FB);
+
+       if (WARN_ON(supported_sources & ~valid_source_mask))
+               return -EINVAL;
+
+       prop = drm_property_create(dev, DRM_MODE_PROP_ENUM, "pixel_source",
+                       hweight32(supported_sources));
+
+       if (!prop)
+               return -ENOMEM;
+
+       for (i = 0; i < ARRAY_SIZE(enum_list); i++) {
+               int ret;
+
+               if (!(BIT(enum_list[i].type) & supported_sources))
+                       continue;
+
+               ret = drm_property_add_enum(prop, enum_list[i].type, 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);
diff --git a/include/drm/drm_blend.h b/include/drm/drm_blend.h
index 0338a860b9c8..31af7cfa5b1b 100644
--- a/include/drm/drm_blend.h
+++ b/include/drm/drm_blend.h
@@ -59,4 +59,6 @@ int drm_atomic_normalize_zpos(struct drm_device *dev,
  int drm_plane_create_blend_mode_property(struct drm_plane *plane,
                                          unsigned int supported_modes);
  int drm_plane_create_solid_fill_property(struct drm_plane *plane);
+int drm_plane_create_pixel_source_property(struct drm_plane *plane,
+                                          unsigned int supported_sources);
  #endif
diff --git a/include/drm/drm_plane.h b/include/drm/drm_plane.h
index f6ab313cb83e..73fb6cf8a5d9 100644
--- a/include/drm/drm_plane.h
+++ b/include/drm/drm_plane.h
@@ -59,6 +59,12 @@ struct drm_solid_fill {
         uint32_t b;
  };

+enum drm_plane_pixel_source {
+       DRM_PLANE_PIXEL_SOURCE_FB,
+       DRM_PLANE_PIXEL_SOURCE_COLOR,
+       DRM_PLANE_PIXEL_SOURCE_MAX
+};
+
  /**
   * struct drm_plane_state - mutable plane state
   *
@@ -152,6 +158,14 @@ struct drm_plane_state {
          */
         struct drm_solid_fill solid_fill;

+       /*
+        * @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
@@ -742,6 +756,13 @@ struct drm_plane {
          */
         struct drm_property *solid_fill_property;

+       /*
+        * @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

--
2.41.0





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