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// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (C) 2019 Axis Communications AB
*
* The console is useful for userspace applications which expect a console
* device to work without modifications even when no console is available
* or desired.
*
* In order to use this driver, you should redirect the console to this
* TTY, or boot the kernel with console=ttynull.
*
* Based on ttyprintk.c:
* Copyright (C) 2010 Samo Pogacnik
*/
#include <linux/console.h>
#include <linux/module.h>
#include <linux/tty.h>
static const struct tty_port_operations ttynull_port_ops;
static struct tty_driver *ttynull_driver;
static struct tty_port ttynull_port;
static int ttynull_open(struct tty_struct *tty, struct file *filp)
{
return tty_port_open(&ttynull_port, tty, filp);
}
static void ttynull_close(struct tty_struct *tty, struct file *filp)
{
tty_port_close(&ttynull_port, tty, filp);
}
static void ttynull_hangup(struct tty_struct *tty)
{
tty_port_hangup(&ttynull_port);
}
static int ttynull_write(struct tty_struct *tty, const unsigned char *buf,
int count)
{
return count;
}
static int ttynull_write_room(struct tty_struct *tty)
{
return 65536;
}
static const struct tty_operations ttynull_ops = {
.open = ttynull_open,
.close = ttynull_close,
.hangup = ttynull_hangup,
.write = ttynull_write,
.write_room = ttynull_write_room,
};
static struct tty_driver *ttynull_device(struct console *c, int *index)
{
*index = 0;
return ttynull_driver;
}
static struct console ttynull_console = {
.name = "ttynull",
.device = ttynull_device,
};
void __init register_ttynull_console(void)
{
if (!ttynull_driver)
return;
if (add_preferred_console(ttynull_console.name, 0, NULL))
return;
register_console(&ttynull_console);
}
static int __init ttynull_init(void)
{
struct tty_driver *driver;
int ret;
driver = tty_alloc_driver(1,
TTY_DRIVER_RESET_TERMIOS |
TTY_DRIVER_REAL_RAW |
TTY_DRIVER_UNNUMBERED_NODE);
if (IS_ERR(driver))
return PTR_ERR(driver);
tty_port_init(&ttynull_port);
ttynull_port.ops = &ttynull_port_ops;
driver->driver_name = "ttynull";
driver->name = "ttynull";
driver->type = TTY_DRIVER_TYPE_CONSOLE;
driver->init_termios = tty_std_termios;
driver->init_termios.c_oflag = OPOST | OCRNL | ONOCR | ONLRET;
tty_set_operations(driver, &ttynull_ops);
tty_port_link_device(&ttynull_port, driver, 0);
ret = tty_register_driver(driver);
if (ret < 0) {
put_tty_driver(driver);
tty_port_destroy(&ttynull_port);
return ret;
}
ttynull_driver = driver;
register_console(&ttynull_console);
return 0;
}
static void __exit ttynull_exit(void)
{
unregister_console(&ttynull_console);
tty_unregister_driver(ttynull_driver);
put_tty_driver(ttynull_driver);
tty_port_destroy(&ttynull_port);
}
module_init(ttynull_init);
module_exit(ttynull_exit);
MODULE_LICENSE("GPL v2");
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