1// SPDX-License-Identifier: GPL-2.0
2#include <linux/types.h>
3#include <linux/errno.h>
4#include <linux/tty.h>
5#include <linux/module.h>
6
7/*
8 * n_null.c - Null line discipline used in the failure path
9 *
10 * Copyright (C) Intel 2017
11 */
12
13static ssize_t n_null_read(struct tty_struct *tty, struct file *file, u8 *buf,
14 size_t nr, void **cookie, unsigned long offset)
15{
16 return -EOPNOTSUPP;
17}
18
19static ssize_t n_null_write(struct tty_struct *tty, struct file *file,
20 const u8 *buf, size_t nr)
21{
22 return -EOPNOTSUPP;
23}
24
25static struct tty_ldisc_ops null_ldisc = {
26 .owner = THIS_MODULE,
27 .num = N_NULL,
28 .name = "n_null",
29 .read = n_null_read,
30 .write = n_null_write,
31};
32
33static int __init n_null_init(void)
34{
35 BUG_ON(tty_register_ldisc(&null_ldisc));
36 return 0;
37}
38
39static void __exit n_null_exit(void)
40{
41 tty_unregister_ldisc(ldisc: &null_ldisc);
42}
43
44module_init(n_null_init);
45module_exit(n_null_exit);
46
47MODULE_LICENSE("GPL");
48MODULE_AUTHOR("Alan Cox");
49MODULE_ALIAS_LDISC(N_NULL);
50MODULE_DESCRIPTION("Null ldisc driver");
51