- struct bt_field *packet_context = NULL, *writer_packet_context = NULL;
- struct bt_field_class *struct_class = NULL, *field_class = NULL;
- struct bt_field *field = NULL, *writer_field = NULL;
+ const struct bt_field *packet_context = NULL, *writer_packet_context = NULL;
+ const struct bt_field_class *struct_class = NULL, *field_class = NULL;
+ const struct bt_field *field = NULL, *writer_field = NULL;