MSR_MAJOR
dev = device_create(&msr_class, NULL, MKDEV(MSR_MAJOR, cpu), NULL,
device_destroy(&msr_class, MKDEV(MSR_MAJOR, cpu));
if (__register_chrdev(MSR_MAJOR, 0, NR_CPUS, "cpu/msr", &msr_fops)) {
pr_err("unable to get major %d for msr\n", MSR_MAJOR);
__unregister_chrdev(MSR_MAJOR, 0, NR_CPUS, "cpu/msr");
__unregister_chrdev(MSR_MAJOR, 0, NR_CPUS, "cpu/msr");