int (*source_add)(struct sr_session *session, void *priv, int events,
int timeout, sr_receive_data_callback cb, void *cb_data);
int (*source_remove)(struct sr_session *session, void *priv);
int (*source_add)(struct sr_session *session, void *priv, int events,
int timeout, sr_receive_data_callback cb, void *cb_data);
int (*source_remove)(struct sr_session *session, void *priv);