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![Vincent Whitchurch](/assets/img/avatar_default.png)
Register a console in the ttyprintk driver so that it can be selected for /dev/console with console=ttyprintk on the kernel command line, similar to other console drivers. Signed-off-by: Vincent Whitchurch <vincent.whitchurch@axis.com> Link: https://lore.kernel.org/r/20220215141750.92808-1-vincent.whitchurch@axis.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
232 lines
5.1 KiB
C
232 lines
5.1 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* linux/drivers/char/ttyprintk.c
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*
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* Copyright (C) 2010 Samo Pogacnik
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*/
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/*
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* This pseudo device allows user to make printk messages. It is possible
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* to store "console" messages inline with kernel messages for better analyses
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* of the boot process, for example.
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*/
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#include <linux/console.h>
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#include <linux/device.h>
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#include <linux/serial.h>
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#include <linux/tty.h>
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#include <linux/module.h>
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#include <linux/spinlock.h>
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struct ttyprintk_port {
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struct tty_port port;
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spinlock_t spinlock;
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};
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static struct ttyprintk_port tpk_port;
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/*
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* Our simple preformatting supports transparent output of (time-stamped)
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* printk messages (also suitable for logging service):
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* - any cr is replaced by nl
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* - adds a ttyprintk source tag in front of each line
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* - too long message is fragmented, with '\'nl between fragments
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* - TPK_STR_SIZE isn't really the write_room limiting factor, because
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* it is emptied on the fly during preformatting.
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*/
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#define TPK_STR_SIZE 508 /* should be bigger then max expected line length */
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#define TPK_MAX_ROOM 4096 /* we could assume 4K for instance */
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#define TPK_PREFIX KERN_SOH __stringify(CONFIG_TTY_PRINTK_LEVEL)
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static int tpk_curr;
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static char tpk_buffer[TPK_STR_SIZE + 4];
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static void tpk_flush(void)
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{
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if (tpk_curr > 0) {
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tpk_buffer[tpk_curr] = '\0';
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printk(TPK_PREFIX "[U] %s\n", tpk_buffer);
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tpk_curr = 0;
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}
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}
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static int tpk_printk(const unsigned char *buf, int count)
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{
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int i;
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for (i = 0; i < count; i++) {
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if (tpk_curr >= TPK_STR_SIZE) {
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/* end of tmp buffer reached: cut the message in two */
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tpk_buffer[tpk_curr++] = '\\';
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tpk_flush();
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}
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switch (buf[i]) {
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case '\r':
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tpk_flush();
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if ((i + 1) < count && buf[i + 1] == '\n')
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i++;
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break;
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case '\n':
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tpk_flush();
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break;
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default:
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tpk_buffer[tpk_curr++] = buf[i];
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break;
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}
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}
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return count;
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}
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/*
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* TTY operations open function.
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*/
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static int tpk_open(struct tty_struct *tty, struct file *filp)
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{
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tty->driver_data = &tpk_port;
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return tty_port_open(&tpk_port.port, tty, filp);
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}
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/*
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* TTY operations close function.
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*/
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static void tpk_close(struct tty_struct *tty, struct file *filp)
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{
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struct ttyprintk_port *tpkp = tty->driver_data;
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tty_port_close(&tpkp->port, tty, filp);
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}
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/*
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* TTY operations write function.
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*/
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static int tpk_write(struct tty_struct *tty,
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const unsigned char *buf, int count)
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{
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struct ttyprintk_port *tpkp = tty->driver_data;
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unsigned long flags;
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int ret;
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/* exclusive use of tpk_printk within this tty */
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spin_lock_irqsave(&tpkp->spinlock, flags);
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ret = tpk_printk(buf, count);
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spin_unlock_irqrestore(&tpkp->spinlock, flags);
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return ret;
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}
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/*
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* TTY operations write_room function.
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*/
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static unsigned int tpk_write_room(struct tty_struct *tty)
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{
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return TPK_MAX_ROOM;
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}
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/*
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* TTY operations hangup function.
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*/
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static void tpk_hangup(struct tty_struct *tty)
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{
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struct ttyprintk_port *tpkp = tty->driver_data;
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tty_port_hangup(&tpkp->port);
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}
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/*
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* TTY port operations shutdown function.
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*/
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static void tpk_port_shutdown(struct tty_port *tport)
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{
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struct ttyprintk_port *tpkp =
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container_of(tport, struct ttyprintk_port, port);
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unsigned long flags;
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spin_lock_irqsave(&tpkp->spinlock, flags);
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tpk_flush();
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spin_unlock_irqrestore(&tpkp->spinlock, flags);
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}
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static const struct tty_operations ttyprintk_ops = {
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.open = tpk_open,
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.close = tpk_close,
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.write = tpk_write,
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.write_room = tpk_write_room,
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.hangup = tpk_hangup,
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};
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static const struct tty_port_operations tpk_port_ops = {
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.shutdown = tpk_port_shutdown,
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};
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static struct tty_driver *ttyprintk_driver;
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static struct tty_driver *ttyprintk_console_device(struct console *c,
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int *index)
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{
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*index = 0;
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return ttyprintk_driver;
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}
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static struct console ttyprintk_console = {
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.name = "ttyprintk",
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.device = ttyprintk_console_device,
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};
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static int __init ttyprintk_init(void)
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{
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int ret;
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spin_lock_init(&tpk_port.spinlock);
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ttyprintk_driver = tty_alloc_driver(1,
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TTY_DRIVER_RESET_TERMIOS |
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TTY_DRIVER_REAL_RAW |
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TTY_DRIVER_UNNUMBERED_NODE);
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if (IS_ERR(ttyprintk_driver))
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return PTR_ERR(ttyprintk_driver);
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tty_port_init(&tpk_port.port);
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tpk_port.port.ops = &tpk_port_ops;
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ttyprintk_driver->driver_name = "ttyprintk";
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ttyprintk_driver->name = "ttyprintk";
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ttyprintk_driver->major = TTYAUX_MAJOR;
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ttyprintk_driver->minor_start = 3;
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ttyprintk_driver->type = TTY_DRIVER_TYPE_CONSOLE;
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ttyprintk_driver->init_termios = tty_std_termios;
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ttyprintk_driver->init_termios.c_oflag = OPOST | OCRNL | ONOCR | ONLRET;
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tty_set_operations(ttyprintk_driver, &ttyprintk_ops);
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tty_port_link_device(&tpk_port.port, ttyprintk_driver, 0);
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ret = tty_register_driver(ttyprintk_driver);
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if (ret < 0) {
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printk(KERN_ERR "Couldn't register ttyprintk driver\n");
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goto error;
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}
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register_console(&ttyprintk_console);
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return 0;
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error:
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tty_driver_kref_put(ttyprintk_driver);
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tty_port_destroy(&tpk_port.port);
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return ret;
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}
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static void __exit ttyprintk_exit(void)
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{
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unregister_console(&ttyprintk_console);
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tty_unregister_driver(ttyprintk_driver);
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tty_driver_kref_put(ttyprintk_driver);
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tty_port_destroy(&tpk_port.port);
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}
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device_initcall(ttyprintk_init);
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module_exit(ttyprintk_exit);
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MODULE_LICENSE("GPL");
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