[PATCH 1/2] drm: Introduce plane SIZE_HINTS property

[Harry Wentland]

On 2/7/23 23:09, Ville Syrjala wrote:
> From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> 
> Add a new immutable plane property by which a plane can advertise
> a handful of recommended plane sizes. This would be mostly exposed
> by cursor planes as a slightly more capable replacement for
> the DRM_CAP_CURSOR_WIDTH/HEIGHT caps, which can only declare
> a one size fits all limit for the whole device.
> 
> Currently eg. amdgpu/i915/nouveau just advertize the max cursor
> size via the cursor size caps. But always using the max sized
> cursor can waste a surprising amount of power, so a better
> stragey is desirable.
> 
> Most other drivers don't specify any cursor size at all, in
> which case the ioctl code just claims that 64x64 is a great
> choice. Whether that is actually true is debatable.
> 
> A poll of various compositor developers informs us that
> blindly probing with setcursor/atomic ioctl to determine
> suitable cursor sizes is not acceptable, thus the
> introduction of the new property to supplant the cursor
> size caps. The compositor will now be free to select a
> more optimal cursor size from the short list of options.
> 
> Note that the reported sizes (either via the property or the
> caps) make no claims about things such as plane scaling. So
> these things should only really be consulted for simple
> "cursor like" use cases.
> 
> Cc: Simon Ser <contact at emersion.fr>
> Cc: Jonas Ådahl <jadahl at redhat.com>
> Cc: Daniel Stone <daniel at fooishbar.org>
> Cc: Pekka Paalanen <pekka.paalanen at collabora.com>
> Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>

This would be great to have. amdgpu could take advantage of it as
well. I didn't have a thorough look at the details of this
implementation but like what it does, so this is
Acked-by: Harry Wentland <harry.wentland at amd.com>

Harry

> ---
>   drivers/gpu/drm/drm_mode_config.c |  7 +++++++
>   drivers/gpu/drm/drm_plane.c       | 33 +++++++++++++++++++++++++++++++
>   include/drm/drm_mode_config.h     |  5 +++++
>   include/drm/drm_plane.h           |  4 ++++
>   include/uapi/drm/drm_mode.h       |  5 +++++
>   5 files changed, 54 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_mode_config.c b/drivers/gpu/drm/drm_mode_config.c
> index 87eb591fe9b5..21860f94a18c 100644
> --- a/drivers/gpu/drm/drm_mode_config.c
> +++ b/drivers/gpu/drm/drm_mode_config.c
> @@ -374,6 +374,13 @@ static int drm_mode_create_standard_properties(struct drm_device *dev)
>   		return -ENOMEM;
>   	dev->mode_config.modifiers_property = prop;
>   
> +	prop = drm_property_create(dev,
> +				   DRM_MODE_PROP_IMMUTABLE | DRM_MODE_PROP_BLOB,
> +				   "SIZE_HINTS", 0);
> +	if (!prop)
> +		return -ENOMEM;
> +	dev->mode_config.size_hints_property = prop;
> +
>   	return 0;
>   }
>   
> diff --git a/drivers/gpu/drm/drm_plane.c b/drivers/gpu/drm/drm_plane.c
> index 24e7998d1731..d0a277f4be1f 100644
> --- a/drivers/gpu/drm/drm_plane.c
> +++ b/drivers/gpu/drm/drm_plane.c
> @@ -1582,3 +1582,36 @@ int drm_plane_create_scaling_filter_property(struct drm_plane *plane,
>   	return 0;
>   }
>   EXPORT_SYMBOL(drm_plane_create_scaling_filter_property);
> +
> +/**
> + * drm_plane_add_size_hint_property - create a size hint property
> + *
> + * @plane: drm plane
> + * @hints: size hints
> + * @num_hints: number of size hints
> + *
> + * Create a size hints property for the plane.
> + *
> + * RETURNS:
> + * Zero for success or -errno
> + */
> +int drm_plane_add_size_hints_property(struct drm_plane *plane,
> +				      const struct drm_plane_size_hint *hints,
> +				      int num_hints)
> +{
> +	struct drm_device *dev = plane->dev;
> +	struct drm_mode_config *config = &dev->mode_config;
> +	struct drm_property_blob *blob;
> +
> +	blob = drm_property_create_blob(dev,
> +					array_size(sizeof(hints[0]), num_hints),
> +					hints);
> +	if (IS_ERR(blob))
> +		return PTR_ERR(blob);
> +
> +	drm_object_attach_property(&plane->base, config->size_hints_property,
> +				   blob->base.id);
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL(drm_plane_add_size_hints_property);
> diff --git a/include/drm/drm_mode_config.h b/include/drm/drm_mode_config.h
> index e5b053001d22..ed9f6938dca1 100644
> --- a/include/drm/drm_mode_config.h
> +++ b/include/drm/drm_mode_config.h
> @@ -949,6 +949,11 @@ struct drm_mode_config {
>   	 */
>   	struct drm_property *modifiers_property;
>   
> +	/**
> +	 * @size_hints_property: Plane SIZE_HINTS property.
> +	 */
> +	struct drm_property *size_hints_property;
> +
>   	/* cursor size */
>   	uint32_t cursor_width, cursor_height;
>   
> diff --git a/include/drm/drm_plane.h b/include/drm/drm_plane.h
> index 51291983ea44..1997d7d64b69 100644
> --- a/include/drm/drm_plane.h
> +++ b/include/drm/drm_plane.h
> @@ -32,6 +32,7 @@
>   #include <drm/drm_util.h>
>   
>   struct drm_crtc;
> +struct drm_plane_size_hint;
>   struct drm_printer;
>   struct drm_modeset_acquire_ctx;
>   
> @@ -945,5 +946,8 @@ drm_plane_get_damage_clips(const struct drm_plane_state *state);
>   
>   int drm_plane_create_scaling_filter_property(struct drm_plane *plane,
>   					     unsigned int supported_filters);
> +int drm_plane_add_size_hints_property(struct drm_plane *plane,
> +				      const struct drm_plane_size_hint *hints,
> +				      int num_hints);
>   
>   #endif
> diff --git a/include/uapi/drm/drm_mode.h b/include/uapi/drm/drm_mode.h
> index 46becedf5b2f..4f0551d7f481 100644
> --- a/include/uapi/drm/drm_mode.h
> +++ b/include/uapi/drm/drm_mode.h
> @@ -849,6 +849,11 @@ struct drm_color_lut {
>   	__u16 reserved;
>   };
>   
> +struct drm_plane_size_hint {
> +	__u16 width;
> +	__u16 height;
> +};
> +
>   /**
>    * struct hdr_metadata_infoframe - HDR Metadata Infoframe Data.
>    *