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

Jessica Zhang
2023-06-30T21:28:07Z

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