// SPDX-License-Identifier: GPL-2.0#include <linux/types.h>#include <linux/errno.h>#include <linux/tty.h>#include <linux/module.h> /* *  n_null.c - Null line discipline used in the failure path * *  Copyright (C) Intel 2017 */ static ssize_t n_null_read(struct tty_struct *tty, struct file *file, u8 *buf,			   size_t nr, void **cookie, unsigned long offset){	return -EOPNOTSUPP;} static ssize_t n_null_write(struct tty_struct *tty, struct file *file,			    const u8 *buf, size_t nr){	return -EOPNOTSUPP;} static struct tty_ldisc_ops null_ldisc = {	.owner		=	THIS_MODULE,	.num		=	N_NULL,	.name		=	"n_null",	.read		=	n_null_read,	.write		=	n_null_write,}; static int __init n_null_init(void){	BUG_ON(tty_register_ldisc(&null_ldisc));	return 0;} static void __exit n_null_exit(void){	tty_unregister_ldisc(&null_ldisc);} module_init(n_null_init);module_exit(n_null_exit); MODULE_LICENSE("GPL");MODULE_AUTHOR("Alan Cox");MODULE_ALIAS_LDISC(N_NULL);MODULE_DESCRIPTION("Null ldisc driver");