door_my_data
if ((dt = door_my_data(0)) == NULL)
(void) door_my_data(1); /* create info, if necessary */
(void) door_my_data(1); /* make sure we have a door_data_t */
door_data_t *ddp = door_my_data(create_if_missing);
door_data_t *ddp = door_my_data(create_if_missing);