Re: [RFC PATCH 07/11] drm: Add writeback-connector pixel format properties

[Daniel Vetter <daniel@ffwll.ch>]

On Tue, Oct 11, 2016 at 03:54:04PM +0100, Brian Starkey wrote:
> So that userspace can determine what pixel formats are supported for a
> writeback connector's framebuffer, add a pixel format list to writeback
> connectors. This is in the form of an immutable blob containing an array
> of formats, and an immutable uint holding the array size.
> 
> Signed-off-by: Brian Starkey <brian.starkey@arm.com>

I think we should have a dedicated writeback property registration
function, e.g. drm_writeback_connector_init(). That would then take the
pixel format list and everything else and make sure it's set up correctly.
For safety we might want to put a WARN_ON(type == WRITEBACK) into
drm_connector_init, to make sure no one botches this up.

Maybe even put all that into a new drm_writeback.c file, that then also
gives you a nice place to group all the documentation (including the DOC:
overview comment).

> ---
>  drivers/gpu/drm/drm_connector.c |   73 ++++++++++++++++++++++++++++++++++++++-
>  include/drm/drm_connector.h     |   12 +++++++
>  include/drm/drm_crtc.h          |   12 +++++++
>  3 files changed, 96 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
> index fb83870..2f1f61d 100644
> --- a/drivers/gpu/drm/drm_connector.c
> +++ b/drivers/gpu/drm/drm_connector.c
> @@ -249,9 +249,14 @@ int drm_connector_init(struct drm_device *dev,
>  		drm_object_attach_property(&connector->base, config->prop_crtc_id, 0);
>  	}
>  
> -	if (connector_type == DRM_MODE_CONNECTOR_WRITEBACK)
> +	if (connector_type == DRM_MODE_CONNECTOR_WRITEBACK) {
>  		drm_object_attach_property(&connector->base,
>  					   config->prop_fb_id, 0);
> +		drm_object_attach_property(&connector->base,
> +					   config->pixel_formats_property, 0);
> +		drm_object_attach_property(&connector->base,
> +					   config->pixel_formats_size_property, 0);
> +	}
>  
>  	connector->debugfs_entry = NULL;
>  out_put_type_id:
> @@ -851,6 +856,45 @@ int drm_mode_create_suggested_offset_properties(struct drm_device *dev)
>  EXPORT_SYMBOL(drm_mode_create_suggested_offset_properties);
>  
>  /**
> + * drm_mode_create_writeback_connector_properties - create writeback connector properties
> + * @dev: DRM device
> + *
> + * Create the properties specific to writeback connectors. These will be attached
> + * to writeback connectors by drm_connector_init. Drivers can set these
> + * properties using drm_mode_connector_set_writeback_formats().
> + *
> + *  "PIXEL_FORMATS":
> + *	Immutable blob property to store the supported pixel formats table. The
> + *	data is an array of u32 DRM_FORMAT_* fourcc values.
> + *	Userspace can use this blob to find out what pixel formats are supported
> + *	by the connector's writeback engine.
> + *
> + *  "PIXEL_FORMATS_SIZE":
> + *      Immutable unsigned range property storing the number of entries in the
> + *      PIXEL_FORMATS array.
> + */
> +int drm_mode_create_writeback_connector_properties(struct drm_device *dev)
> +{
> +	if (dev->mode_config.pixel_formats_property &&
> +	    dev->mode_config.pixel_formats_size_property)
> +		return 0;
> +
> +	dev->mode_config.pixel_formats_property =
> +		drm_property_create(dev, DRM_MODE_PROP_BLOB | DRM_MODE_PROP_IMMUTABLE,
> +			"PIXEL_FORMATS", 0);
> +
> +	dev->mode_config.pixel_formats_size_property =
> +		drm_property_create_range(dev, DRM_MODE_PROP_IMMUTABLE,
> +			"PIXEL_FORMATS_SIZE", 0, UINT_MAX);
> +
> +	if (dev->mode_config.pixel_formats_property == NULL ||
> +	    dev->mode_config.pixel_formats_size_property == NULL)
> +		return -ENOMEM;
> +	return 0;
> +}
> +EXPORT_SYMBOL(drm_mode_create_writeback_connector_properties);
> +
> +/**
>   * drm_mode_connector_set_path_property - set tile property on connector
>   * @connector: connector to set property on.
>   * @path: path to use for property; must not be NULL.
> @@ -957,6 +1001,33 @@ int drm_mode_connector_update_edid_property(struct drm_connector *connector,
>  }
>  EXPORT_SYMBOL(drm_mode_connector_update_edid_property);
>  
> +int drm_mode_connector_set_writeback_formats(struct drm_connector *connector,
> +					     u32 *formats,
> +					     unsigned int n_formats)
> +{
> +	struct drm_device *dev = connector->dev;
> +	size_t size = n_formats * sizeof(*formats);
> +	int ret;
> +
> +	if (connector->connector_type != DRM_MODE_CONNECTOR_WRITEBACK)
> +		return -EINVAL;
> +
> +	ret = drm_property_replace_global_blob(dev,
> +					       &connector->pixel_formats_blob_ptr,
> +					       size,
> +					       formats,
> +					       &connector->base,
> +					       dev->mode_config.pixel_formats_property);
> +
> +	if (!ret)
> +		drm_object_property_set_value(&connector->base,
> +					      dev->mode_config.pixel_formats_size_property,
> +					      n_formats);
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL(drm_mode_connector_set_writeback_formats);
> +
>  int drm_mode_connector_set_obj_prop(struct drm_mode_object *obj,
>  				    struct drm_property *property,
>  				    uint64_t value)
> diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
> index 30a766a..e77ae5c 100644
> --- a/include/drm/drm_connector.h
> +++ b/include/drm/drm_connector.h
> @@ -615,6 +615,14 @@ struct drm_connector {
>  	 */
>  	struct drm_property_blob *tile_blob_ptr;
>  
> +	/**
> +	 * @pixel_formats_blob_ptr
> +	 *
> +	 * DRM blob property data for the pixel formats list on writeback
> +	 * connectors
> +	 */
> +	struct drm_property_blob *pixel_formats_blob_ptr;
> +
>  /* should we poll this connector for connects and disconnects */
>  /* hot plug detectable */
>  #define DRM_CONNECTOR_POLL_HPD (1 << 0)
> @@ -757,12 +765,16 @@ int drm_mode_create_tv_properties(struct drm_device *dev,
>  int drm_mode_create_scaling_mode_property(struct drm_device *dev);
>  int drm_mode_create_aspect_ratio_property(struct drm_device *dev);
>  int drm_mode_create_suggested_offset_properties(struct drm_device *dev);
> +int drm_mode_create_writeback_connector_properties(struct drm_device *dev);
>  
>  int drm_mode_connector_set_path_property(struct drm_connector *connector,
>  					 const char *path);
>  int drm_mode_connector_set_tile_property(struct drm_connector *connector);
>  int drm_mode_connector_update_edid_property(struct drm_connector *connector,
>  					    const struct edid *edid);
> +int drm_mode_connector_set_writeback_formats(struct drm_connector *connector,
> +					     u32 *formats,
> +					     unsigned int n_formats);
>  
>  /**
>   * drm_for_each_connector - iterate over all connectors
> diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
> index 61932f5..c4a3164 100644
> --- a/include/drm/drm_crtc.h
> +++ b/include/drm/drm_crtc.h
> @@ -1302,6 +1302,18 @@ struct drm_mode_config {
>  	 */
>  	struct drm_property *suggested_y_property;
>  
> +	/**
> +	 * @pixel_formats_property: Property for writeback connectors, storing
> +	 * an array of the supported pixel formats for the writeback engine
> +	 * (read-only).

I love cross-references in kernel-doc. I think mentioning
drm_writeback_connector_init here would be perfect (for both of them).
-Daniel

> +	 */
> +	struct drm_property *pixel_formats_property;
> +	/**
> +	 * @pixel_formats_size_property: Property for writeback connectors,
> +	 * stating the size of the pixel formats array (read-only).
> +	 */
> +	struct drm_property *pixel_formats_size_property;
> +
>  	/* dumb ioctl parameters */
>  	uint32_t preferred_depth, prefer_shadow;
>  
> -- 
> 1.7.9.5
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch