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Message-ID: <20210610111145.7fdf9a53@eldfell>
Date: Thu, 10 Jun 2021 11:11:45 +0300
From: Pekka Paalanen <ppaalanen@...il.com>
To: Werner Sembach <wse@...edocomputers.com>
Cc: harry.wentland@....com, sunpeng.li@....com,
alexander.deucher@....com, christian.koenig@....com,
airlied@...ux.ie, daniel@...ll.ch,
maarten.lankhorst@...ux.intel.com, mripard@...nel.org,
tzimmermann@...e.de, jani.nikula@...ux.intel.com,
joonas.lahtinen@...ux.intel.com, rodrigo.vivi@...el.com,
amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
linux-kernel@...r.kernel.org, intel-gfx@...ts.freedesktop.org
Subject: Re: [PATCH v2 5/7] drm/uAPI: Add "active color format" drm property
as feedback for userspace
On Tue, 8 Jun 2021 19:43:18 +0200
Werner Sembach <wse@...edocomputers.com> wrote:
> Add a new general drm property "active color format" which can be used by
> graphic drivers to report the used color format back to userspace.
>
> There was no way to check which color format got actually used on a given
> monitor. To surely predict this, one must know the exact capabilities of the
> monitor, the GPU, and the connection used and what the default behaviour of the
> used driver is (e.g. amdgpu prefers YCbCr 4:4:4 while i915 prefers RGB). This
> property helps eliminating the guessing on this point.
>
> In the future, automatic color calibration for screens might also depend on this
> information being available.
>
> Signed-off-by: Werner Sembach <wse@...edocomputers.com>
> ---
> drivers/gpu/drm/drm_atomic_uapi.c | 2 ++
> drivers/gpu/drm/drm_connector.c | 46 +++++++++++++++++++++++++++++++
> include/drm/drm_connector.h | 13 +++++++++
> 3 files changed, 61 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_atomic_uapi.c b/drivers/gpu/drm/drm_atomic_uapi.c
> index 7ae4e40936b5..bb78da2405f9 100644
> --- a/drivers/gpu/drm/drm_atomic_uapi.c
> +++ b/drivers/gpu/drm/drm_atomic_uapi.c
> @@ -875,6 +875,8 @@ drm_atomic_connector_get_property(struct drm_connector *connector,
> *val = state->max_requested_bpc;
> } else if (property == connector->active_bpc_property) {
> *val = state->active_bpc;
> + } else if (property == connector->active_color_format_property) {
> + *val = state->active_color_format;
> } 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 c0c3c09bfed0..f4f35c4117b6 100644
> --- a/drivers/gpu/drm/drm_connector.c
> +++ b/drivers/gpu/drm/drm_connector.c
> @@ -887,6 +887,14 @@ static const struct drm_prop_enum_list drm_dp_subconnector_enum_list[] = {
> { DRM_MODE_SUBCONNECTOR_Native, "Native" }, /* DP */
> };
>
> +static const struct drm_prop_enum_list drm_color_format_enum_list[] = {
> + { 0, "none" },
> + { DRM_COLOR_FORMAT_RGB444, "rgb" },
> + { DRM_COLOR_FORMAT_YCRCB444, "ycbcr444" },
> + { DRM_COLOR_FORMAT_YCRCB422, "ycbcr422" },
> + { DRM_COLOR_FORMAT_YCRCB420, "ycbcr420" },
> +};
> +
> DRM_ENUM_NAME_FN(drm_get_dp_subconnector_name,
> drm_dp_subconnector_enum_list)
>
> @@ -1202,6 +1210,14 @@ static const struct drm_prop_enum_list dp_colorspaces[] = {
> * display engine and connected monitor, and the "max bpc" property.
> * Drivers shall use drm_connector_attach_active_bpc_property() to install
> * this property.
> +
> + * active color format:
> + * This read-only property tells userspace the color format actually used
> + * by the hardware display engine on "the cable" on a connector. The chosen
> + * value depends on hardware capabilities, both display engine and
> + * connected monitor. Drivers shall use
> + * drm_connector_attach_active_color_format_property() to install this
> + * property.
Hi,
I think also the enum values should be documented in the UAPI docs. Or
listed at the very least. Otherwise userspace developers "do not know"
what strings to decode.
Thanks,
pq
> *
> * Connectors also have one standardized atomic property:
> *
> @@ -2191,6 +2207,36 @@ int drm_connector_attach_active_bpc_property(struct drm_connector *connector,
> }
> EXPORT_SYMBOL(drm_connector_attach_active_bpc_property);
>
> +/**
> + * drm_connector_attach_active_color_format_property - attach "active color format" property
> + * @connector: connector to attach active color format property on.
> + *
> + * This is used to check the applied color format on a connector.
> + *
> + * Returns:
> + * Zero on success, negative errno on failure.
> + */
> +int drm_connector_attach_active_color_format_property(struct drm_connector *connector)
> +{
> + struct drm_device *dev = connector->dev;
> + struct drm_property *prop;
> +
> + prop = connector->active_color_format_property;
> + if (!prop) {
> + prop = drm_property_create_enum(dev, 0, "active color format", drm_color_format_enum_list, ARRAY_SIZE(drm_color_format_enum_list));
> + if (!prop)
> + return -ENOMEM;
> +
> + connector->active_color_format_property = prop;
> + }
> +
> + drm_object_attach_property(&connector->base, prop, 0);
> + connector->state->active_color_format = 0;
> +
> + return 0;
> +}
> +EXPORT_SYMBOL(drm_connector_attach_active_color_format_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 c58cba2b6afe..167cd36129ae 100644
> --- a/include/drm/drm_connector.h
> +++ b/include/drm/drm_connector.h
> @@ -788,6 +788,12 @@ struct drm_connector_state {
> */
> u8 active_bpc;
>
> + /**
> + * active_color_format: Read only property set by the GPU driver to the
> + * actually used color format after evaluating all hardware limitations.
> + */
> + u32 active_color_format;
> +
> /**
> * @hdr_output_metadata:
> * DRM blob property for HDR output metadata
> @@ -1393,6 +1399,12 @@ struct drm_connector {
> */
> struct drm_property *active_bpc_property;
>
> + /**
> + * @active_color_format_property: Default connector property for the
> + * active color format to be driven out of the connector.
> + */
> + struct drm_property *active_color_format_property;
> +
> #define DRM_CONNECTOR_POLL_HPD (1 << 0)
> #define DRM_CONNECTOR_POLL_CONNECT (1 << 1)
> #define DRM_CONNECTOR_POLL_DISCONNECT (1 << 2)
> @@ -1713,6 +1725,7 @@ 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);
> +int drm_connector_attach_active_color_format_property(struct drm_connector *connector);
>
> /**
> * struct drm_tile_group - Tile group metadata
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