fdisk_get_disk_geom
int sectsize = fdisk_get_disk_geom(epp, PHYSGEOM, SSIZE);
int numcyl = fdisk_get_disk_geom(epp, PHYSGEOM, NCYL);
int sec_sz = fdisk_get_disk_geom(epp, PHYSGEOM, SSIZE);
extern int fdisk_get_disk_geom(ext_part_t *epp, int type, int what);