typedef int (*plugin_read_cb) (user_data_t *);
typedef int (*plugin_write_cb) (const data_set_t *, const value_list_t *,
user_data_t *);
typedef int (*plugin_read_cb) (user_data_t *);
typedef int (*plugin_write_cb) (const data_set_t *, const value_list_t *,
user_data_t *);