Re: [PATCH RFC v6 01/10] drm: Introduce pixel_source DRM plane property

Dmitry Baryshkov
2023-09-24T10:06:42Z

On 29/08/2023 03:05, Jessica Zhang wrote:
> 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.
>
> Signed-off-by: Jessica Zhang <quic_jesszhan@quicinc.com>

Acked-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>

Minor question below

> ---
> drivers/gpu/drm/drm_atomic_state_helper.c | 1 +
> drivers/gpu/drm/drm_atomic_uapi.c | 4 ++
> drivers/gpu/drm/drm_blend.c | 90 +++++++++++++++++++++++++++++++
> drivers/gpu/drm/drm_plane.c | 19 +++++--
> include/drm/drm_blend.h | 2 +
> include/drm/drm_plane.h | 21 ++++++++
> 6 files changed, 133 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_atomic_state_helper.c b/drivers/gpu/drm/drm_atomic_state_helper.c
> index 784e63d70a42..01638c51ce0a 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->color_encoding_property) {
> if (!drm_object_property_get_default_value(&plane->base,
> diff --git a/drivers/gpu/drm/drm_atomic_uapi.c b/drivers/gpu/drm/drm_atomic_uapi.c
> index d867e7f9f2cd..454f980e16c9 100644
> --- a/drivers/gpu/drm/drm_atomic_uapi.c
> +++ b/drivers/gpu/drm/drm_atomic_uapi.c
> @@ -544,6 +544,8 @@ 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) {
> @@ -616,6 +618,8 @@ 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) {
> diff --git a/drivers/gpu/drm/drm_blend.c b/drivers/gpu/drm/drm_blend.c
> index 6e74de833466..c3c57bae06b7 100644
> --- a/drivers/gpu/drm/drm_blend.c
> +++ b/drivers/gpu/drm/drm_blend.c
> @@ -185,6 +185,21 @@
> * 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.
> + *
> + * 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 +630,78 @@ 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);

Nit: if valid_source_mask and supported_sources are moved towards the
top, it might look better. It doesn't warrant sending v7 just to fix
this issue though.

> + 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);

As you are going to extend planes to support non-FB sources, would it be
logical to stop declaring FB as a default one as well? I think DIM layer
planes will only support solid fill source.

> +
> + 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);
> diff --git a/drivers/gpu/drm/drm_plane.c b/drivers/gpu/drm/drm_plane.c
> index 24e7998d1731..559d101162ba 100644
> --- a/drivers/gpu/drm/drm_plane.c
> +++ b/drivers/gpu/drm/drm_plane.c
> @@ -839,6 +839,14 @@ 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
> *
> @@ -861,8 +869,8 @@ static int __setplane_internal(struct drm_plane *plane,
>
> WARN_ON(drm_drv_uses_atomic_modeset(plane->dev));
>
> - /* No fb means shut it down */
> - if (!fb) {
> + /* No visible data means shut it down */
> + if (drm_plane_needs_disable(plane->state, fb)) {
> plane->old_fb = plane->fb;
> ret = plane->funcs->disable_plane(plane, ctx);
> if (!ret) {
> @@ -913,8 +921,8 @@ static int __setplane_atomic(struct drm_plane *plane,
>
> WARN_ON(!drm_drv_uses_atomic_modeset(plane->dev));
>
> - /* No fb means shut it down */
> - if (!fb)
> + /* No visible data means shut it down */
> + if (drm_plane_needs_disable(plane->state, fb))
> return plane->funcs->disable_plane(plane, ctx);
>
> /*
> @@ -987,6 +995,9 @@ 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) {
> diff --git a/include/drm/drm_blend.h b/include/drm/drm_blend.h
> index 88bdfec3bd88..122bbfbaae33 100644
> --- a/include/drm/drm_blend.h
> +++ b/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
> diff --git a/include/drm/drm_plane.h b/include/drm/drm_plane.h
> index 51291983ea44..89508b4dea4a 100644
> --- a/include/drm/drm_plane.h
> +++ b/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
> *
> @@ -116,6 +122,14 @@ struct drm_plane_state {
> /** @src_h: height of visible portion of plane (in 16.16) */
> uint32_t src_h, src_w;
>
> + /**
> + * @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
> @@ -699,6 +713,13 @@ 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
>

--
With best wishes
Dmitry