+ *
+ * The discover client holds talloc references to the devices (and the
+ * devices' boot options), so callbacks may store boot options and devices
+ * as long as the client remains allocated.
+ *
+ * The boot_status and system_info structs are allocated by the client,
+ * and will be free()ed after the callback is invoked. If the callback
+ * stores these structures for usage beyond the duration of the callback,
+ * it must talloc_steal() them.