Re: [PATCH 06/22] drm/vkms: Introduce configfs for plane color encoding

["José Expósito" <jose.exposito89@gmail.com>]

On Sat, Oct 18, 2025 at 04:01:06AM +0200, Louis Chauvet wrote:
> To allows the userspace to test many hardware configuration, introduce a
> new interface to configure the available color encoding per planes. VKMS
> supports multiple color encoding, so the userspace can choose any
> combination.
> 
> The supported color encoding are configured by writing a color encoding
> bitmask to the file `supported_color_encoding` and the default color
> encoding is chosen by writing a color encoding bitmask to
> `default_color_encoding`.
> 
> Signed-off-by: Louis Chauvet <louis.chauvet@bootlin.com>
> ---
>  Documentation/gpu/vkms.rst           |   7 ++-
>  drivers/gpu/drm/vkms/vkms_configfs.c | 102 +++++++++++++++++++++++++++++++++++
>  2 files changed, 108 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/gpu/vkms.rst b/Documentation/gpu/vkms.rst
> index a432968cc711..4ff75b53a386 100644
> --- a/Documentation/gpu/vkms.rst
> +++ b/Documentation/gpu/vkms.rst
> @@ -87,7 +87,7 @@ Start by creating one or more planes::
>  
>    sudo mkdir /config/vkms/my-vkms/planes/plane0
>  
> -Planes have 3 configurable attribute:
> +Planes have 5 configurable attribute:
>  
>  - type: Plane type: 0 overlay, 1 primary, 2 cursor (same values as those
>    exposed by the "type" property of a plane)
> @@ -96,6 +96,11 @@ Planes have 3 configurable attribute:
>    (same values as those exposed by the "rotation" property of a plane)
>  - default_rotation: Default rotation presented to the userspace, same values as
>    possible_rotations.
> +- supported_color_encoding: Available encoding for a plane, as a bitmask:
> +  0x01 YCBCR_BT601, 0x02: YCBCR_BT709, 0x04 YCBCR_BT2020 (same values as those exposed
> +  by the COLOR_ENCODING property of a plane)
> +- default_color_encoding: Default color encoding presented to the userspace, same
> +  values as supported_color_encoding
>  
>  Continue by creating one or more CRTCs::
>  
> diff --git a/drivers/gpu/drm/vkms/vkms_configfs.c b/drivers/gpu/drm/vkms/vkms_configfs.c
> index 450e45e66a45..a4e0e054cf2d 100644
> --- a/drivers/gpu/drm/vkms/vkms_configfs.c
> +++ b/drivers/gpu/drm/vkms/vkms_configfs.c
> @@ -412,14 +412,116 @@ static ssize_t plane_default_rotation_store(struct config_item *item,
>  	return count;
>  }
>  
> +static ssize_t plane_supported_color_encoding_show(struct config_item *item, char *page)
> +{
> +	struct vkms_configfs_plane *plane;
> +	unsigned int supported_color_encoding;
> +
> +	plane = plane_item_to_vkms_configfs_plane(item);
> +
> +	scoped_guard(mutex, &plane->dev->lock) {
> +		supported_color_encoding = vkms_config_plane_get_supported_color_encoding(plane->config);
> +	}
> +
> +	return sprintf(page, "%u", supported_color_encoding);
> +}
> +
> +static ssize_t plane_supported_color_encoding_store(struct config_item *item,
> +						    const char *page, size_t count)
> +{
> +	struct vkms_configfs_plane *plane = plane_item_to_vkms_configfs_plane(item);
> +	int ret, val = 0;
> +
> +	ret = kstrtouint(page, 10, &val);
> +	if (ret)
> +		return ret;
> +
> +	/* Should be a supported value */
> +	if (val & ~(BIT(DRM_COLOR_YCBCR_BT601) |
> +		    BIT(DRM_COLOR_YCBCR_BT709) |
> +		    BIT(DRM_COLOR_YCBCR_BT2020)))
> +		return -EINVAL;
> +	/* Should at least provide one color range */
> +	if ((val & (BIT(DRM_COLOR_YCBCR_BT601) |
> +		    BIT(DRM_COLOR_YCBCR_BT709) |
> +		    BIT(DRM_COLOR_YCBCR_BT2020))) == 0)
> +		return -EINVAL;
> +
> +	scoped_guard(mutex, &plane->dev->lock) {
> +		/* Ensures that the default rotation is included in supported rotation */
> +		if (plane->dev->enabled ||
> +		    (val & vkms_config_plane_get_default_color_encoding(plane->config)) !=
> +		     vkms_config_plane_get_default_color_encoding(plane->config))
> +			return -EINVAL;

I think that the same problem that I mention having to configure
plane rotation in 2 steps applies for color encoding.

> +		vkms_config_plane_set_supported_color_encoding(plane->config, val);
> +	}
> +
> +	return count;
> +}
> +
> +/* Plane default_color_encoding : vkms/<device>/planes/<plane>/default_color_encoding */
> +
> +static ssize_t plane_default_color_encoding_show(struct config_item *item, char *page)
> +{
> +	struct vkms_configfs_plane *plane;
> +	unsigned int default_color_encoding;
> +
> +	plane = plane_item_to_vkms_configfs_plane(item);
> +
> +	scoped_guard(mutex, &plane->dev->lock) {
> +		default_color_encoding = vkms_config_plane_get_default_color_encoding(plane->config);
> +	}
> +
> +	return sprintf(page, "%u", default_color_encoding);
> +}
> +
> +static ssize_t plane_default_color_encoding_store(struct config_item *item,
> +						  const char *page, size_t count)
> +{
> +	struct vkms_configfs_plane *plane = plane_item_to_vkms_configfs_plane(item);
> +	int ret, val = 0;
> +
> +	ret = kstrtouint(page, 10, &val);
> +	if (ret)
> +		return ret;
> +
> +	/* Should be a supported value */
> +	if (val & ~(BIT(DRM_COLOR_YCBCR_BT601) |
> +		    BIT(DRM_COLOR_YCBCR_BT709) |
> +		    BIT(DRM_COLOR_YCBCR_BT2020)))
> +		return -EINVAL;
> +	/* Should at least provide one color range */
> +	if ((val & (BIT(DRM_COLOR_YCBCR_BT601) |
> +		    BIT(DRM_COLOR_YCBCR_BT709) |
> +		    BIT(DRM_COLOR_YCBCR_BT2020))) == 0)
> +		return -EINVAL;
> +
> +	scoped_guard(mutex, &plane->dev->lock) {
> +		/* Ensures that the default rotation is included in supported rotation */
> +		if (plane->dev->enabled ||
> +		    (val & vkms_config_plane_get_supported_color_encoding(plane->config)) !=
> +		     val)
> +			return -EINVAL;
> +
> +		vkms_config_plane_set_default_color_encoding(plane->config, val);

As I mentioned in the previous patch, I think that default color encoding
is sometimes a bitmask and sometimes the actual color?

> +	}
> +
> +	return count;
> +}
> +
>  CONFIGFS_ATTR(plane_, type);
>  CONFIGFS_ATTR(plane_, supported_rotations);
>  CONFIGFS_ATTR(plane_, default_rotation);
> +CONFIGFS_ATTR(plane_, supported_color_encoding);
> +CONFIGFS_ATTR(plane_, default_color_encoding);
>  
>  static struct configfs_attribute *plane_item_attrs[] = {
>  	&plane_attr_type,
>  	&plane_attr_supported_rotations,
>  	&plane_attr_default_rotation,
> +	&plane_attr_supported_color_encoding,
> +	&plane_attr_default_color_encoding,
>  	NULL,
>  };
>  
> 
> -- 
> 2.51.0
>