+/**
+ * io_out_wait - leave the output plan idle until something wakes us.
+ * @conn: the connection that plan is for.
+ * @waitaddr: the address to wait on.
+ * @next: function to call after waiting.
+ * @arg: @next argument
+ *
+ * io_wait() makes the input plan idle: if you're not using io_duplex it
+ * doesn't matter which plan is waiting. Otherwise, you may need to use
+ * io_out_wait() instead, to specify explicitly that the output plan is
+ * waiting.
+ */
+#define io_out_wait(conn, waitaddr, next, arg) \
+ io_out_wait_((conn), (waitaddr), \
+ typesafe_cb_preargs(struct io_plan *, void *, \
+ (next), (arg), \
+ struct io_conn *), \
+ (arg))
+
+struct io_plan *io_out_wait_(struct io_conn *conn,
+ const void *wait,
+ struct io_plan *(*next)(struct io_conn *, void *),
+ void *arg);
+