On Thu, 12 Dec 2024, Imre Deak <imre.deak@xxxxxxxxx> 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@xxxxxxxxx>
>
> Suggested-by: Simona Vetter <simona.vetter@xxxxxxxx>
> Signed-off-by: Imre Deak <imre.deak@xxxxxxxxx>
> ---
> 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
