Our secret driver – cleanup

It's important to realize that we must free any buffers we have allocated. Here, however, as we performed a managed allocation in the init code (devm_kzalloc()), we have the benefit of not needing to worry about cleanup; the kernel handles it. Of course, in the driver's cleanup code path (invoked upon rmmod(8)), we deregister the misc driver with the kernel:

static void __exit miscdrv_rdwr_exit(void)
{
    misc_deregister(&llkd_miscdev);
    pr_info("LLKD misc (rdwr) driver deregistered, bye\n");
}

You will notice that we also, seemingly uselessly, use two global integers, ga and gb, in places in this version of the driver. Indeed, they have no real meaning here; the reason we have them at all becomes clear only in the last two chapters of this book, on kernel synchronization. Please ignore them for now.