MYMAJOR
pcr.pm_regdev = makedev(MYMAJOR, 0);
rv = mknod("rumpttyU0", S_IFCHR | 0666, makedev(MYMAJOR, 0));
rv = mknod("rumpttyU1", S_IFCHR | 0666, makedev(MYMAJOR, 1));
pcr.pm_regdev = makedev(MYMAJOR, 0);
makedev(MYMAJOR, minnum));