mtlocate
struct mtlocate locate_info;
error = sasetpos(periph, /*hard*/ 0, (struct mtlocate *)arg);
sasetpos(struct cam_periph *periph, int hard, struct mtlocate *locate_info)
struct mtlocate *);
#define MTIOCEXTLOCATE _IOW('m', 10, struct mtlocate) /* seek to position */
struct mtlocate mtl;