[PATCH v4 09/16] drm/vkms: Allow to attach encoders and CRTCs via configfs

[Louis Chauvet]

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

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

> Signed-off-by: Louis Chauvet <louis.chauvet at bootlin.com>
> Co-developed-by: José Expósito <jose.exposito89 at gmail.com>
> Signed-off-by: José Expósito <jose.exposito89 at gmail.com>
> ---
>   Documentation/gpu/vkms.rst           |  2 +
>   drivers/gpu/drm/vkms/vkms_configfs.c | 58 ++++++++++++++++++++++++++++
>   2 files changed, 60 insertions(+)
> 
> diff --git a/Documentation/gpu/vkms.rst b/Documentation/gpu/vkms.rst
> index e24767448775..650dbfa76f59 100644
> --- a/Documentation/gpu/vkms.rst
> +++ b/Documentation/gpu/vkms.rst
> @@ -106,6 +106,7 @@ Next, create one or more encoders::
>   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
> +  sudo ln -s /config/vkms/my-vkms/crtcs/crtc0 /config/vkms/my-vkms/encoders/encoder0/possible_crtcs
>   
>   Since at least one primary plane is required, make sure to set the right type::
>   
> @@ -122,6 +123,7 @@ 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 rm /config/vkms/my-vkms/encoders/*/possible_crtcs/*
>     sudo rmdir /config/vkms/my-vkms/planes/*
>     sudo rmdir /config/vkms/my-vkms/crtcs/*
>     sudo rmdir /config/vkms/my-vkms/encoders/*
> diff --git a/drivers/gpu/drm/vkms/vkms_configfs.c b/drivers/gpu/drm/vkms/vkms_configfs.c
> index 0df86e63570a..7de601e39d2b 100644
> --- a/drivers/gpu/drm/vkms/vkms_configfs.c
> +++ b/drivers/gpu/drm/vkms/vkms_configfs.c
> @@ -70,11 +70,13 @@ struct vkms_configfs_crtc {
>    *
>    * @group: Top level configuration group that represents a encoder.
>    * Initialized when a new directory is created under "/config/vkms/encoders"
> + * @possible_crtcs_group: Default subgroup of @group at "encoder/possible_crtcs"
>    * @dev: The vkms_configfs_device this encoder belongs to
>    * @config: Configuration of the VKMS encoder
>    */
>   struct vkms_configfs_encoder {
>   	struct config_group group;
> +	struct config_group possible_crtcs_group;
>   	struct vkms_configfs_device *dev;
>   	struct vkms_config_encoder *config;
>   };
> @@ -100,6 +102,10 @@ struct vkms_configfs_encoder {
>   	container_of(to_config_group((item)), struct vkms_configfs_encoder, \
>   		     group)
>   
> +#define encoder_possible_crtcs_item_to_vkms_configfs_encoder(item) \
> +	container_of(to_config_group((item)), struct vkms_configfs_encoder, \
> +		     possible_crtcs_group)
> +
>   static ssize_t crtc_writeback_show(struct config_item *item, char *page)
>   {
>   	struct vkms_configfs_crtc *crtc;
> @@ -364,6 +370,52 @@ static const struct config_item_type plane_group_type = {
>   	.ct_owner	= THIS_MODULE,
>   };
>   
> +static int encoder_possible_crtcs_allow_link(struct config_item *src,
> +					     struct config_item *target)
> +{
> +	struct vkms_configfs_encoder *encoder;
> +	struct vkms_configfs_crtc *crtc;
> +	int ret;
> +
> +	if (target->ci_type != &crtc_item_type)
> +		return -EINVAL;
> +
> +	encoder = encoder_possible_crtcs_item_to_vkms_configfs_encoder(src);
> +	crtc = crtc_item_to_vkms_configfs_crtc(target);
> +
> +	scoped_guard(mutex, &encoder->dev->lock) {
> +		if (encoder->dev->enabled)
> +			return -EBUSY;
> +
> +		ret = vkms_config_encoder_attach_crtc(encoder->config, crtc->config);
> +	}
> +
> +	return ret;
> +}
> +
> +static void encoder_possible_crtcs_drop_link(struct config_item *src,
> +					     struct config_item *target)
> +{
> +	struct vkms_configfs_encoder *encoder;
> +	struct vkms_configfs_crtc *crtc;
> +
> +	encoder = encoder_possible_crtcs_item_to_vkms_configfs_encoder(src);
> +	crtc = crtc_item_to_vkms_configfs_crtc(target);
> +
> +	scoped_guard(mutex, &encoder->dev->lock)
> +		vkms_config_encoder_detach_crtc(encoder->config, crtc->config);
> +}
> +
> +static struct configfs_item_operations encoder_possible_crtcs_item_operations = {
> +	.allow_link	= encoder_possible_crtcs_allow_link,
> +	.drop_link	= encoder_possible_crtcs_drop_link,
> +};
> +
> +static const struct config_item_type encoder_possible_crtcs_group_type = {
> +	.ct_item_ops	= &encoder_possible_crtcs_item_operations,
> +	.ct_owner	= THIS_MODULE,
> +};
> +
>   static void encoder_release(struct config_item *item)
>   {
>   	struct vkms_configfs_encoder *encoder;
> @@ -413,6 +465,12 @@ static struct config_group *make_encoder_group(struct config_group *group,
>   
>   		config_group_init_type_name(&encoder->group, name,
>   					    &encoder_item_type);
> +
> +		config_group_init_type_name(&encoder->possible_crtcs_group,
> +					    "possible_crtcs",
> +					    &encoder_possible_crtcs_group_type);
> +		configfs_add_default_group(&encoder->possible_crtcs_group,
> +					   &encoder->group);
>   	}
>   
>   	return &encoder->group;

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