IOPGD_SHIFT
da = i << IOPGD_SHIFT;
da = (i << IOPGD_SHIFT) + (j << IOPTE_SHIFT);
da = i << IOPGD_SHIFT;
#define IOPGD_SIZE BIT(IOPGD_SHIFT)
#define PTRS_PER_IOPGD (1UL << (32 - IOPGD_SHIFT))
#define PTRS_PER_IOPTE (1UL << (IOPGD_SHIFT - IOPTE_SHIFT))
#define iopgd_index(da) (((da) >> IOPGD_SHIFT) & (PTRS_PER_IOPGD - 1))