Re: [PATCH 21/22] drm/vkms: Allow to hot-add connectors

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

On Sat, Oct 18, 2025 at 04:01:21AM +0200, Louis Chauvet wrote:
> In order to allow creating dynamic connector, add the required
> infrastructure in vkms_connector.
> 
> Co-developed-by: José Expósito <jose.exposito89@gmail.com>
> Signed-off-by: José Expósito <jose.exposito89@gmail.com>
> [Louis Chauvet: use drm_atomic_helper_connector_reset instead of
> drm_mode_config_reset because connector is not yet registered]

Aha! That was why, thanks a lot for figuring this out :)

> Signed-off-by: Louis Chauvet <louis.chauvet@bootlin.com>
> ---
>  drivers/gpu/drm/vkms/vkms_connector.c | 69 ++++++++++++++++++++++++++++++++++-
>  drivers/gpu/drm/vkms/vkms_connector.h | 33 +++++++++++++++++
>  drivers/gpu/drm/vkms/vkms_output.c    | 11 +++++-
>  3 files changed, 111 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/vkms/vkms_connector.c b/drivers/gpu/drm/vkms/vkms_connector.c
> index 339d747e729e..77a544728721 100644
> --- a/drivers/gpu/drm/vkms/vkms_connector.c
> +++ b/drivers/gpu/drm/vkms/vkms_connector.c
> @@ -1,5 +1,4 @@
>  // SPDX-License-Identifier: GPL-2.0+
> -
>  #include <drm/drm_atomic_helper.h>
>  #include <drm/drm_edid.h>
>  #include <drm/drm_managed.h>
> @@ -144,9 +143,77 @@ struct vkms_connector *vkms_connector_init(struct vkms_device *vkmsdev,
>  	return connector;
>  }
>  
> +static const struct drm_connector_funcs vkms_dynamic_connector_funcs = {
> +	.fill_modes = drm_helper_probe_single_connector_modes,
> +	.reset = drm_atomic_helper_connector_reset,
> +	.atomic_duplicate_state = drm_atomic_helper_connector_duplicate_state,
> +	.atomic_destroy_state = drm_atomic_helper_connector_destroy_state,
> +	.destroy = drm_connector_cleanup,
> +	.detect = vkms_connector_detect,
> +};
> +
>  void vkms_trigger_connector_hotplug(struct vkms_device *vkmsdev)
>  {
>  	struct drm_device *dev = &vkmsdev->drm;
>  
>  	drm_kms_helper_hotplug_event(dev);
>  }
> +
> +struct vkms_connector *vkms_connector_hot_add(struct vkms_device *vkmsdev,
> +					      struct vkms_config_connector *connector_cfg)
> +{
> +	struct vkms_config_encoder *encoder_cfg;
> +	struct vkms_connector *connector;
> +	int ret;
> +	unsigned long idx = 0;
> +
> +	connector = kzalloc(sizeof(*connector), GFP_KERNEL);

Could we use drmm_kzalloc instead?

> +	if (IS_ERR(connector))
> +		return connector;
> +	ret = drm_connector_dynamic_init(&vkmsdev->drm,
> +					 &connector->base,
> +					 &vkms_dynamic_connector_funcs,
> +					 connector_cfg->type,
> +					 NULL);
> +	if (ret)
> +		return ERR_PTR(ret);
> +	drm_connector_helper_add(&connector->base, &vkms_conn_helper_funcs);
> +
> +	vkms_config_connector_for_each_possible_encoder(connector_cfg, idx, encoder_cfg) {
> +		ret = drm_connector_attach_encoder(&connector->base,
> +						   encoder_cfg->encoder);
> +		if (ret)
> +			return ERR_PTR(ret);
> +	}
> +
> +	drm_atomic_helper_connector_reset(&connector->base);
> +
> +	ret = drm_connector_dynamic_register(&connector->base);
> +	if (ret)
> +		return ERR_PTR(ret);
> +
> +	return connector;
> +}
> +
> +void vkms_connector_hot_remove(struct vkms_device *vkmsdev,
> +			       struct vkms_connector *connector)
> +{
> +	drm_connector_unregister(&connector->base);
> +	drm_mode_config_reset(&vkmsdev->drm);
> +	drm_connector_put(&connector->base);
> +}
> +
> +int vkms_connector_hot_attach_encoder(struct vkms_device *vkmsdev,
> +				      struct vkms_connector *connector,
> +				      struct drm_encoder *encoder)
> +{
> +	int ret;
> +
> +	ret = drm_connector_attach_encoder(&connector->base, encoder);
> +	if (ret)
> +		return ret;
> +
> +	drm_mode_config_reset(&vkmsdev->drm);
> +
> +	return ret;
> +}
> diff --git a/drivers/gpu/drm/vkms/vkms_connector.h b/drivers/gpu/drm/vkms/vkms_connector.h
> index a124c5403697..224950c13a93 100644
> --- a/drivers/gpu/drm/vkms/vkms_connector.h
> +++ b/drivers/gpu/drm/vkms/vkms_connector.h
> @@ -7,6 +7,7 @@
>  
>  #define drm_connector_to_vkms_connector(target) \
>  	container_of(target, struct vkms_connector, base)
> +struct vkms_config_connector;
>  
>  /**
>   * struct vkms_connector - VKMS custom type wrapping around the DRM connector
> @@ -33,4 +34,36 @@ struct vkms_connector *vkms_connector_init(struct vkms_device *vkmsdev,
>   */
>  void vkms_trigger_connector_hotplug(struct vkms_device *vkmsdev);
>  
> +/**
> + * vkms_connector_hot_add() - Create a connector after the device is created
> + * @vkmsdev: Device to hot-add the connector to
> + * @connector_cfg: Connector's configuration
> + *
> + * Returns:
> + * The connector or an error on failure.
> + */
> +struct vkms_connector *vkms_connector_hot_add(struct vkms_device *vkmsdev,
> +					      struct vkms_config_connector *connector_cfg);
> +
> +/**
> + * vkms_connector_hot_remove() - Remove a connector after a device is created
> + * @connector: The connector to hot-remove
> + */
> +void vkms_connector_hot_remove(struct vkms_device *vkmsdev,
> +			       struct vkms_connector *connector);
> +
> +/**
> + * vkms_connector_hot_attach_encoder() - Attach a connector to a encoder after
> + * the device is created.
> + * @vkmsdev: Device containing the connector and the encoder
> + * @connector: Connector to attach to @encoder
> + * @encoder: Target encoder
> + *
> + * Returns:
> + * 0 on success or an error on failure.
> + */
> +int vkms_connector_hot_attach_encoder(struct vkms_device *vkmsdev,
> +				      struct vkms_connector *connector,
> +				      struct drm_encoder *encoder);
> +
>  #endif /* _VKMS_CONNECTOR_H_ */
> diff --git a/drivers/gpu/drm/vkms/vkms_output.c b/drivers/gpu/drm/vkms/vkms_output.c
> index 217f054d9598..aba2f9ab243d 100644
> --- a/drivers/gpu/drm/vkms/vkms_output.c
> +++ b/drivers/gpu/drm/vkms/vkms_output.c
> @@ -92,7 +92,7 @@ int vkms_output_init(struct vkms_device *vkmsdev)
>  		}
>  	}
>  
> -	vkms_config_for_each_connector(vkmsdev->config, connector_cfg) {
> +	vkms_config_for_each_connector_static(vkmsdev->config, connector_cfg) {
>  		struct vkms_config_encoder *possible_encoder;
>  		unsigned long idx = 0;
>  
> @@ -116,5 +116,14 @@ int vkms_output_init(struct vkms_device *vkmsdev)
>  
>  	drm_mode_config_reset(dev);
>  
> +	vkms_config_for_each_connector_dynamic(vkmsdev->config, connector_cfg) {
> +		if (connector_cfg->enabled) {
> +			connector_cfg->connector = vkms_connector_hot_add(vkmsdev, connector_cfg);
> +
> +			if (IS_ERR(connector_cfg->connector))
> +				return PTR_ERR(connector_cfg->connector);
> +		}
> +	}
> +
>  	return 0;
>  }
> 
> -- 
> 2.51.0
>