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

[Sebastian Wick]

On Fri, Jun 30, 2023 at 11:27 PM Jessica Zhang
<quic_jesszhan@xxxxxxxxxxx> wrote:
>
>
>
> 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?

I would say so, yes.

> 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
> >>
> >
>