DRF_HW_LO
#define DRF_HW_BITS(o,drf) (DRF_HW_HI((o),drf) - DRF_HW_LO((o),drf) + 1)
#define DRF_HW_SMASK(o,drf) (DRF_HW_MASK((o),drf) << DRF_HW_LO((o),drf))