1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Copyright (C) 2019 Axis Communications AB
4 *
5 * Based on ttyprintk.c:
6 * Copyright (C) 2010 Samo Pogacnik
7 */
8
9 #include <linux/console.h>
10 #include <linux/module.h>
11 #include <linux/tty.h>
12
13 static const struct tty_port_operations ttynull_port_ops;
14 static struct tty_driver *ttynull_driver;
15 static struct tty_port ttynull_port;
16
ttynull_open(struct tty_struct * tty,struct file * filp)17 static int ttynull_open(struct tty_struct *tty, struct file *filp)
18 {
19 return tty_port_open(&ttynull_port, tty, filp);
20 }
21
ttynull_close(struct tty_struct * tty,struct file * filp)22 static void ttynull_close(struct tty_struct *tty, struct file *filp)
23 {
24 tty_port_close(&ttynull_port, tty, filp);
25 }
26
ttynull_hangup(struct tty_struct * tty)27 static void ttynull_hangup(struct tty_struct *tty)
28 {
29 tty_port_hangup(&ttynull_port);
30 }
31
ttynull_write(struct tty_struct * tty,const u8 * buf,size_t count)32 static ssize_t ttynull_write(struct tty_struct *tty, const u8 *buf,
33 size_t count)
34 {
35 return count;
36 }
37
ttynull_write_room(struct tty_struct * tty)38 static unsigned int ttynull_write_room(struct tty_struct *tty)
39 {
40 return 65536;
41 }
42
43 static const struct tty_operations ttynull_ops = {
44 .open = ttynull_open,
45 .close = ttynull_close,
46 .hangup = ttynull_hangup,
47 .write = ttynull_write,
48 .write_room = ttynull_write_room,
49 };
50
ttynull_device(struct console * c,int * index)51 static struct tty_driver *ttynull_device(struct console *c, int *index)
52 {
53 *index = 0;
54 return ttynull_driver;
55 }
56
57 static struct console ttynull_console = {
58 .name = "ttynull",
59 .device = ttynull_device,
60 };
61
ttynull_init(void)62 static int __init ttynull_init(void)
63 {
64 struct tty_driver *driver;
65 int ret;
66
67 driver = tty_alloc_driver(1,
68 TTY_DRIVER_RESET_TERMIOS |
69 TTY_DRIVER_REAL_RAW |
70 TTY_DRIVER_UNNUMBERED_NODE);
71 if (IS_ERR(driver))
72 return PTR_ERR(driver);
73
74 tty_port_init(&ttynull_port);
75 ttynull_port.ops = &ttynull_port_ops;
76
77 driver->driver_name = "ttynull";
78 driver->name = "ttynull";
79 driver->type = TTY_DRIVER_TYPE_CONSOLE;
80 driver->init_termios = tty_std_termios;
81 driver->init_termios.c_oflag = OPOST | OCRNL | ONOCR | ONLRET;
82 tty_set_operations(driver, &ttynull_ops);
83 tty_port_link_device(&ttynull_port, driver, 0);
84
85 ret = tty_register_driver(driver);
86 if (ret < 0) {
87 tty_driver_kref_put(driver);
88 tty_port_destroy(&ttynull_port);
89 return ret;
90 }
91
92 ttynull_driver = driver;
93 register_console(&ttynull_console);
94
95 return 0;
96 }
97
ttynull_exit(void)98 static void __exit ttynull_exit(void)
99 {
100 unregister_console(&ttynull_console);
101 tty_unregister_driver(ttynull_driver);
102 tty_driver_kref_put(ttynull_driver);
103 tty_port_destroy(&ttynull_port);
104 }
105
106 module_init(ttynull_init);
107 module_exit(ttynull_exit);
108
109 MODULE_DESCRIPTION("NULL TTY driver");
110 MODULE_LICENSE("GPL v2");
111