On Fri, Jun 04, 2021 at 07:17:21PM +0200, Werner Sembach wrote:
> Add a new general drm property "active bpc" which can be used by graphic drivers
> to report the applied bit depth per pixel back to userspace.
>
> While "max bpc" can be used to change the color depth, there was no way to check
> which one actually got used. While in theory the driver chooses the best/highest
> color depth within the max bpc setting a user might not be fully aware what his
> hardware is or isn't capable off. This is meant as a quick way to double check
> the setup.
>
> In the future, automatic color calibration for screens might also depend on this
> information available.
>
> Signed-off-by: Werner Sembach <wse@xxxxxxxxxxxxxxxxxxx>
> ---
> drivers/gpu/drm/drm_atomic_uapi.c | 2 ++
> drivers/gpu/drm/drm_connector.c | 40 +++++++++++++++++++++++++++++++
> include/drm/drm_connector.h | 15 ++++++++++++
> 3 files changed, 57 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_atomic_uapi.c b/drivers/gpu/drm/drm_atomic_uapi.c
> index 268bb69c2e2f..7ae4e40936b5 100644
> --- a/drivers/gpu/drm/drm_atomic_uapi.c
> +++ b/drivers/gpu/drm/drm_atomic_uapi.c
> @@ -873,6 +873,8 @@ drm_atomic_connector_get_property(struct drm_connector *connector,
> *val = 0;
> } else if (property == connector->max_bpc_property) {
> *val = state->max_requested_bpc;
> + } else if (property == connector->active_bpc_property) {
> + *val = state->active_bpc;
> } else if (connector->funcs->atomic_get_property) {
> return connector->funcs->atomic_get_property(connector,
> state, property, val);
> diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
> index 7631f76e7f34..5f42a5be5822 100644
> --- a/drivers/gpu/drm/drm_connector.c
> +++ b/drivers/gpu/drm/drm_connector.c
> @@ -1195,6 +1195,13 @@ static const struct drm_prop_enum_list dp_colorspaces[] = {
> * drm_connector_attach_max_bpc_property() to create and attach the
> * property to the connector during initialization.
> *
> + * active bpc:
> + * This read-only range property is used by userspace check the bit depth
> + * actually applied by the GPU driver after evaluation all hardware
> + * capabilities and max bpc. Drivers to use the function
> + * drm_connector_attach_active_bpc_property() to create and attach the
> + * property to the connector during initialization.
> + *
> * Connectors also have one standardized atomic property:
> *
> * CRTC_ID:
> @@ -2150,6 +2157,39 @@ int drm_connector_attach_max_bpc_property(struct drm_connector *connector,
> }
> EXPORT_SYMBOL(drm_connector_attach_max_bpc_property);
>
> +/**
> + * drm_connector_attach_active_bpc_property - attach "active bpc" property
> + * @connector: connector to attach active bpc property on.
> + * @min: The minimum bit depth supported by the connector.
> + * @max: The maximum bit depth supported by the connector.
> + *
> + * This is used to check the applied bit depth on a connector.
> + *
> + * Returns:
> + * Zero on success, negative errno on failure.
> + */
> +int drm_connector_attach_active_bpc_property(struct drm_connector *connector,
> + int min, int max)
> +{
> + struct drm_device *dev = connector->dev;
> + struct drm_property *prop;
> +
> + prop = connector->active_bpc_property;
> + if (!prop) {
> + prop = drm_property_create_range(dev, 0, "active bpc", min, max);
Should be immutable.
Also wondering what the semantics of this should be when eg. DSC
is active?
> + if (!prop)
> + return -ENOMEM;
> +
> + connector->active_bpc_property = prop;
> + }
> +
> + drm_object_attach_property(&connector->base, prop, 0);
> + connector->state->active_bpc = 0;
> +
> + return 0;
> +}
> +EXPORT_SYMBOL(drm_connector_attach_active_bpc_property);
> +
> /**
> * drm_connector_set_vrr_capable_property - sets the variable refresh rate
> * capable property for a connector
> diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
> index 1922b278ffad..c58cba2b6afe 100644
> --- a/include/drm/drm_connector.h
> +++ b/include/drm/drm_connector.h
> @@ -781,6 +781,13 @@ struct drm_connector_state {
> */
> u8 max_bpc;
>
> + /**
> + * @active_bpc: Read only property set by the GPU driver to the actually
> + * applied bit depth of the pixels after evaluating all hardware
> + * limitations.
> + */
> + u8 active_bpc;
> +
> /**
> * @hdr_output_metadata:
> * DRM blob property for HDR output metadata
> @@ -1380,6 +1387,12 @@ struct drm_connector {
> */
> struct drm_property *max_bpc_property;
>
> + /**
> + * @active_bpc_property: Default connector property for the active bpc
> + * to be driven out of the connector.
> + */
> + struct drm_property *active_bpc_property;
> +
> #define DRM_CONNECTOR_POLL_HPD (1 << 0)
> #define DRM_CONNECTOR_POLL_CONNECT (1 << 1)
> #define DRM_CONNECTOR_POLL_DISCONNECT (1 << 2)
> @@ -1698,6 +1711,8 @@ int drm_connector_set_panel_orientation_with_quirk(
> int width, int height);
> int drm_connector_attach_max_bpc_property(struct drm_connector *connector,
> int min, int max);
> +int drm_connector_attach_active_bpc_property(struct drm_connector *connector,
> + int min, int max);
>
> /**
> * struct drm_tile_group - Tile group metadata
> --
> 2.25.1
--
Ville Syrjälä
Intel
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