samples/vfio-mdev/mtty: expand minor range when registering chrdev region

Actually, total amount of available minor number
for a single major is MINORMARK + 1. So expand
minor range when registering chrdev region.
Signed-off-by: Chengguang Xu <cgxu519@gmx.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

samples/vfio-mdev/mtty.c

@@ -1442,7 +1442,8 @@ static int __init mtty_dev_init(void)
 
 	idr_init(&mtty_dev.vd_idr);
 
-	ret = alloc_chrdev_region(&mtty_dev.vd_devt, 0, MINORMASK, MTTY_NAME);
+	ret = alloc_chrdev_region(&mtty_dev.vd_devt, 0, MINORMASK + 1,
+				  MTTY_NAME);
 
 	if (ret < 0) {
 		pr_err("Error: failed to register mtty_dev, err:%d\n", ret);
@@ -1450,7 +1451,7 @@ static int __init mtty_dev_init(void)
 	}
 
 	cdev_init(&mtty_dev.vd_cdev, &vd_fops);
-	cdev_add(&mtty_dev.vd_cdev, mtty_dev.vd_devt, MINORMASK);
+	cdev_add(&mtty_dev.vd_cdev, mtty_dev.vd_devt, MINORMASK + 1);
 
 	pr_info("major_number:%d\n", MAJOR(mtty_dev.vd_devt));
 
@@ -1487,7 +1488,7 @@ static int __init mtty_dev_init(void)
 
 failed1:
 	cdev_del(&mtty_dev.vd_cdev);
-	unregister_chrdev_region(mtty_dev.vd_devt, MINORMASK);
+	unregister_chrdev_region(mtty_dev.vd_devt, MINORMASK + 1);
 
 all_done:
 	return ret;
@@ -1501,7 +1502,7 @@ static void __exit mtty_dev_exit(void)
 	device_unregister(&mtty_dev.dev);
 	idr_destroy(&mtty_dev.vd_idr);
 	cdev_del(&mtty_dev.vd_cdev);
-	unregister_chrdev_region(mtty_dev.vd_devt, MINORMASK);
+	unregister_chrdev_region(mtty_dev.vd_devt, MINORMASK + 1);
 	class_destroy(mtty_dev.vd_class);
 	mtty_dev.vd_class = NULL;
 	pr_info("mtty_dev: Unloaded!\n");