HL_MAX_MINORS
id = idr_alloc(&hl_devs_idr, hdev, 0, HL_MAX_MINORS, GFP_KERNEL);
rc = alloc_chrdev_region(&dev, 0, HL_MAX_MINORS, HL_NAME);
unregister_chrdev_region(MKDEV(hl_major, 0), HL_MAX_MINORS);
unregister_chrdev_region(MKDEV(hl_major, 0), HL_MAX_MINORS);