Re: [PATCH v4 07/16] drm/vkms: Allow to attach planes and CRTCs via configfs

[Louis Chauvet <louis.chauvet@bootlin.com>]

Le 07/04/2025 à 10:14, José Expósito a écrit :
> From: Louis Chauvet <louis.chauvet@bootlin.com>
> 
> Create a default subgroup at /config/vkms/planes/plane/possible_crtcs
> that will contain symbolic links to the possible CRTCs for the plane.

Reviewed-by: Louis Chauvet <louis.chauvet@bootlin.com>

> Signed-off-by: Louis Chauvet <louis.chauvet@bootlin.com>
> Co-developed-by: José Expósito <jose.exposito89@gmail.com>
> Signed-off-by: José Expósito <jose.exposito89@gmail.com>
> ---
>   Documentation/gpu/vkms.rst           |  9 +++++
>   drivers/gpu/drm/vkms/vkms_configfs.c | 58 ++++++++++++++++++++++++++++
>   2 files changed, 67 insertions(+)
> 
> diff --git a/Documentation/gpu/vkms.rst b/Documentation/gpu/vkms.rst
> index abe7a0f5a4ab..13b96837a266 100644
> --- a/Documentation/gpu/vkms.rst
> +++ b/Documentation/gpu/vkms.rst
> @@ -98,6 +98,14 @@ CRTCs have 1 configurable attribute:
>   
>   - writeback: Enable or disable writeback connector support by writing 1 or 0
>   
> +To finish the configuration, link the different pipeline items::
> +
> +  sudo ln -s /config/vkms/my-vkms/crtcs/crtc0 /config/vkms/my-vkms/planes/plane0/possible_crtcs
> +
> +Since at least one primary plane is required, make sure to set the right type::
> +
> +  echo "1" | sudo tee /config/vkms/my-vkms/planes/plane0/type
> +
>   Once you are done configuring the VKMS instance, enable it::
>   
>     echo "1" | sudo tee /config/vkms/my-vkms/enabled
> @@ -108,6 +116,7 @@ Finally, you can remove the VKMS instance disabling it::
>   
>   And removing the top level directory and its subdirectories::
>   
> +  sudo rm /config/vkms/my-vkms/planes/*/possible_crtcs/*
>     sudo rmdir /config/vkms/my-vkms/planes/*
>     sudo rmdir /config/vkms/my-vkms/crtcs/*
>     sudo rmdir /config/vkms/my-vkms
> diff --git a/drivers/gpu/drm/vkms/vkms_configfs.c b/drivers/gpu/drm/vkms/vkms_configfs.c
> index e9f445043268..2cf97c2b6203 100644
> --- a/drivers/gpu/drm/vkms/vkms_configfs.c
> +++ b/drivers/gpu/drm/vkms/vkms_configfs.c
> @@ -38,11 +38,13 @@ struct vkms_configfs_device {
>    *
>    * @group: Top level configuration group that represents a plane.
>    * Initialized when a new directory is created under "/config/vkms/planes"
> + * @possible_crtcs_group: Default subgroup of @group at "plane/possible_crtcs"
>    * @dev: The vkms_configfs_device this plane belongs to
>    * @config: Configuration of the VKMS plane
>    */
>   struct vkms_configfs_plane {
>   	struct config_group group;
> +	struct config_group possible_crtcs_group;
>   	struct vkms_configfs_device *dev;
>   	struct vkms_config_plane *config;
>   };
> @@ -71,6 +73,10 @@ struct vkms_configfs_crtc {
>   #define plane_item_to_vkms_configfs_plane(item) \
>   	container_of(to_config_group((item)), struct vkms_configfs_plane, group)
>   
> +#define plane_possible_crtcs_item_to_vkms_configfs_plane(item) \
> +	container_of(to_config_group((item)), struct vkms_configfs_plane, \
> +		     possible_crtcs_group)
> +
>   #define crtc_item_to_vkms_configfs_crtc(item) \
>   	container_of(to_config_group((item)), struct vkms_configfs_crtc, group)
>   
> @@ -178,6 +184,52 @@ static const struct config_item_type crtc_group_type = {
>   	.ct_owner	= THIS_MODULE,
>   };
>   
> +static int plane_possible_crtcs_allow_link(struct config_item *src,
> +					   struct config_item *target)
> +{
> +	struct vkms_configfs_plane *plane;
> +	struct vkms_configfs_crtc *crtc;
> +	int ret;
> +
> +	if (target->ci_type != &crtc_item_type)
> +		return -EINVAL;
> +
> +	plane = plane_possible_crtcs_item_to_vkms_configfs_plane(src);
> +	crtc = crtc_item_to_vkms_configfs_crtc(target);
> +
> +	scoped_guard(mutex, &plane->dev->lock) {
> +		if (plane->dev->enabled)
> +			return -EBUSY;
> +
> +		ret = vkms_config_plane_attach_crtc(plane->config, crtc->config);
> +	}
> +
> +	return ret;
> +}
> +
> +static void plane_possible_crtcs_drop_link(struct config_item *src,
> +					   struct config_item *target)
> +{
> +	struct vkms_configfs_plane *plane;
> +	struct vkms_configfs_crtc *crtc;
> +
> +	plane = plane_possible_crtcs_item_to_vkms_configfs_plane(src);
> +	crtc = crtc_item_to_vkms_configfs_crtc(target);
> +
> +	scoped_guard(mutex, &plane->dev->lock)
> +		vkms_config_plane_detach_crtc(plane->config, crtc->config);
> +}
> +
> +static struct configfs_item_operations plane_possible_crtcs_item_operations = {
> +	.allow_link	= plane_possible_crtcs_allow_link,
> +	.drop_link	= plane_possible_crtcs_drop_link,
> +};
> +
> +static const struct config_item_type plane_possible_crtcs_group_type = {
> +	.ct_item_ops	= &plane_possible_crtcs_item_operations,
> +	.ct_owner	= THIS_MODULE,
> +};
> +
>   static ssize_t plane_type_show(struct config_item *item, char *page)
>   {
>   	struct vkms_configfs_plane *plane;
> @@ -272,6 +324,12 @@ static struct config_group *make_plane_group(struct config_group *group,
>   		}
>   
>   		config_group_init_type_name(&plane->group, name, &plane_item_type);
> +
> +		config_group_init_type_name(&plane->possible_crtcs_group,
> +					    "possible_crtcs",
> +					    &plane_possible_crtcs_group_type);
> +		configfs_add_default_group(&plane->possible_crtcs_group,
> +					   &plane->group);
>   	}
>   
>   	return &plane->group;

-- 
Louis Chauvet, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com