mtio_state
enum mtio_state state;
static int st_check_media(dev_t dev, enum mtio_state state);
st_check_media(dev_t dev, enum mtio_state state)
enum mtio_state prev_state;
enum mtio_state state = MTIO_NONE;
enum mtio_state un_mediastate; /* current media state */
enum mtio_state un_specified_mediastate; /* expected state */