ST_NBR_MODE_BITS
#define TAPE_NR(x) ( ((iminor(x) & ~255) >> (ST_NBR_MODE_BITS + 1)) | \
#define TAPE_MINOR(d, m, n) (((d & ~(255 >> (ST_NBR_MODE_BITS + 1))) << (ST_NBR_MODE_BITS + 1)) | \
(d & (255 >> (ST_NBR_MODE_BITS + 1))) | (m << ST_MODE_SHIFT) | ((n != 0) << 7) )
i = mode << (4 - ST_NBR_MODE_BITS);
#define ST_NBR_MODES (1 << ST_NBR_MODE_BITS)
#define ST_MODE_SHIFT (7 - ST_NBR_MODE_BITS)
#define ST_MAX_TAPES (1 << (20 - (ST_NBR_MODE_BITS + 1)))
#define ST_MAX_TAPE_ENTRIES (ST_MAX_TAPES << (ST_NBR_MODE_BITS + 1))