Re: [PATCH v3 02/11] drm/connector: Add FIXME for GETRESOURCES ioctl wrt. uninited connectors

[Jani Nikula <jani.nikula@linux.intel.com>]

On Thu, 12 Dec 2024, Imre Deak <imre.deak@intel.com> wrote:
> The connectors enumerated by the GETRESOURCES ioctl may not be fully
> initialized yet wrt. to the state set up during connector registration
> (for instance the connector's debugfs/sysfs interfaces may not exist
> yet). This can happen in two ways:
>
> 1. Connectors initialized and added to the
>    drm_mode_config::connector_list during driver loading will be visible
>    to the GETRESOURCES ioctl caller once the driver is registered via
>    drm_dev_register()->drm_minor_register(DRM_MINOR_PRIMARY) and before
>    the connectors are registered via drm_dev_register()->
>    drm_modeset_register_all().
>
> 2. Dynamic connectors (MST) - after being initialized - may be added to
>    the connector_list after the driver is loaded and registered and before
>    the connector's userspace interfaces (debugfs, sysfs etc.) are added
>    in drm_connector_dynamic_register().
>
> A solution for 1. would be to register the driver only after the
> connectors are registered, for 2. to add the connector to connector_list
> only after the userspace interfaces are registered.
>
> The fix would require a bigger change, not the topic of this patchset,
> so adding only a FIXME comment here.

References to "this patchset" become meaningless after this has been
committed.

Reviewed-by: Jani Nikula <jani.nikula@intel.com>

>
> Suggested-by: Simona Vetter <simona.vetter@ffwll.ch>
> Signed-off-by: Imre Deak <imre.deak@intel.com>
> ---
>  drivers/gpu/drm/drm_mode_config.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_mode_config.c b/drivers/gpu/drm/drm_mode_config.c
> index 37d2e0a4ef4be..8642a2fb25a90 100644
> --- a/drivers/gpu/drm/drm_mode_config.c
> +++ b/drivers/gpu/drm/drm_mode_config.c
> @@ -150,6 +150,15 @@ int drm_mode_getresources(struct drm_device *dev, void *data,
>  	drm_connector_list_iter_begin(dev, &conn_iter);
>  	count = 0;
>  	connector_id = u64_to_user_ptr(card_res->connector_id_ptr);
> +	/*
> +	 * FIXME: the connectors on the list may not be fully initialized yet,
> +	 * if the ioctl is called before the connectors are registered. (See
> +	 * drm_dev_register()->drm_modeset_register_all() for static and
> +	 * drm_connector_dynamic_register() for dynamic connectors.)
> +	 * The driver should only get registered after static connectors are
> +	 * fully initialized and dynamic connectors should be added to the
> +	 * connector list only after fully initializing them.
> +	 */
>  	drm_for_each_connector_iter(connector, &conn_iter) {
>  		/* only expose writeback connectors if userspace understands them */
>  		if (!file_priv->writeback_connectors &&

-- 
Jani Nikula, Intel