Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
tjh.dev
kernel
os
linux
1#include <linux/types.h>
2#include <linux/errno.h>
3#include <linux/tty.h>
4#include <linux/module.h>
5
6/*
7 * n_null.c - Null line discipline used in the failure path
8 *
9 * Copyright (C) Intel 2017
10 *
11 * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
12 *
13 * This program is free software; you can redistribute it and/or modify
14 * it under the terms of the GNU General Public License version 2
15 * as published by the Free Software Foundation.
16 *
17 * This program is distributed in the hope that it will be useful,
18 * but WITHOUT ANY WARRANTY; without even the implied warranty of
19 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
20 * GNU General Public License for more details.
21 *
22 * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
23 */
24
25static int n_null_open(struct tty_struct *tty)
26{
27 return 0;
28}
29
30static void n_null_close(struct tty_struct *tty)
31{
32}
33
34static ssize_t n_null_read(struct tty_struct *tty, struct file *file,
35 unsigned char __user * buf, size_t nr)
36{
37 return -EOPNOTSUPP;
38}
39
40static ssize_t n_null_write(struct tty_struct *tty, struct file *file,
41 const unsigned char *buf, size_t nr)
42{
43 return -EOPNOTSUPP;
44}
45
46static void n_null_receivebuf(struct tty_struct *tty,
47 const unsigned char *cp, char *fp,
48 int cnt)
49{
50}
51
52static struct tty_ldisc_ops null_ldisc = {
53 .owner = THIS_MODULE,
54 .magic = TTY_LDISC_MAGIC,
55 .name = "n_null",
56 .open = n_null_open,
57 .close = n_null_close,
58 .read = n_null_read,
59 .write = n_null_write,
60 .receive_buf = n_null_receivebuf
61};
62
63static int __init n_null_init(void)
64{
65 BUG_ON(tty_register_ldisc(N_NULL, &null_ldisc));
66 return 0;
67}
68
69static void __exit n_null_exit(void)
70{
71 tty_unregister_ldisc(N_NULL);
72}
73
74module_init(n_null_init);
75module_exit(n_null_exit);
76
77MODULE_LICENSE("GPL");
78MODULE_AUTHOR("Alan Cox");
79MODULE_ALIAS_LDISC(N_NULL);
80MODULE_DESCRIPTION("Null ldisc driver");