iopgd_index
unsigned long offset = iopgd_index(da) * sizeof(da);
unsigned long offset = iopgd_index(da) * sizeof(da);
unsigned long offset = iopgd_index(da) * sizeof(da);
unsigned long pd_offset = iopgd_index(da) * sizeof(da);
offset = iopgd_index(da) * sizeof(da);
#define iopgd_offset(obj, da) ((obj)->iopgd + iopgd_index(da))