Hi,

On Wed, Jun 09, 2021 at 09:23:27PM +0000, Simon Ser wrote:
> This function sends a hotplug uevent with a CONNECTOR property.
> 
> Signed-off-by: Simon Ser <contact@emersion.fr>
> ---
>  drivers/gpu/drm/drm_sysfs.c | 25 +++++++++++++++++++++++++
>  include/drm/drm_sysfs.h     |  1 +
>  2 files changed, 26 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_sysfs.c b/drivers/gpu/drm/drm_sysfs.c
> index 968a9560b4aa..8423e44c3035 100644
> --- a/drivers/gpu/drm/drm_sysfs.c
> +++ b/drivers/gpu/drm/drm_sysfs.c
> @@ -343,6 +343,31 @@ void drm_sysfs_hotplug_event(struct drm_device *dev)
>  }
>  EXPORT_SYMBOL(drm_sysfs_hotplug_event);
>  
> +/**
> + * drm_sysfs_connector_hotplug_event - generate a DRM uevent for any connector
> + * change
> + * @connector: connector which has changed
> + *
> + * Send a uevent for the DRM connector specified by @connector. This will send
> + * a uevent with the properties HOTPLUG=1 and CONNECTOR.
> + */
> +void drm_sysfs_connector_hotplug_event(struct drm_connector *connector)
> +{
> +	struct drm_device *dev = connector->dev;
> +	char hotplug_str[] = "HOTPLUG=1", conn_id[21];
> +	char *envp[] = { hotplug_str, conn_id, NULL };
> +
> +	snprintf(conn_id, sizeof(conn_id),
> +		 "CONNECTOR=%u", connector->base.id);
> +
> +	drm_dbg_kms(connector->dev,
> +		    "[CONNECTOR:%d:%s] generating connector hotplug event\n",
> +		    connector->base.id, connector->name);
> +
> +	kobject_uevent_env(&dev->primary->kdev->kobj, KOBJ_CHANGE, envp);
> +}
> +EXPORT_SYMBOL(drm_sysfs_connector_hotplug_event);

Would it make sense to call sysfs_notify on the status file?

It would allow to call poll() on the status file in sysfs and skipping
udev in simple cases?

Maxime