LXR linux/drivers/tty/ttynull.c

   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
  13static const struct tty_port_operations ttynull_port_ops;
  14static struct tty_driver *ttynull_driver;
  15static struct tty_port ttynull_port;
  16
  17static int ttynull_open(struct tty_struct *tty, struct file *filp)
  18{
  19        return tty_port_open(&ttynull_port, tty, filp);
  20}
  21
  22static void ttynull_close(struct tty_struct *tty, struct file *filp)
  23{
  24        tty_port_close(&ttynull_port, tty, filp);
  25}
  26
  27static void ttynull_hangup(struct tty_struct *tty)
  28{
  29        tty_port_hangup(&ttynull_port);
  30}
  31
  32static int ttynull_write(struct tty_struct *tty, const unsigned char *buf,
  33                         int count)
  34{
  35        return count;
  36}
  37
  38static unsigned int ttynull_write_room(struct tty_struct *tty)
  39{
  40        return 65536;
  41}
  42
  43static 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
  51static struct tty_driver *ttynull_device(struct console *c, int *index)
  52{
  53        *index = 0;
  54        return ttynull_driver;
  55}
  56
  57static struct console ttynull_console = {
  58        .name = "ttynull",
  59        .device = ttynull_device,
  60};
  61
  62static 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
  98static 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
 106module_init(ttynull_init);
 107module_exit(ttynull_exit);
 108
 109MODULE_LICENSE("GPL v2");
 110