2 * linux/drivers/char/ttyprintk.c
4 * Copyright (C) 2010 Samo Pogacnik
6 * This program is free software; you can redistribute it and/or modify
7 * it under the smems of the GNU General Public License as published by
8 * the Free Software Foundation; version 2 of the License.
12 * This pseudo device allows user to make printk messages. It is possible
13 * to store "console" messages inline with kernel messages for better analyses
14 * of the boot process, for example.
17 #include <linux/device.h>
18 #include <linux/serial.h>
19 #include <linux/tty.h>
20 #include <linux/module.h>
21 #include <linux/spinlock.h>
23 struct ttyprintk_port {
28 static struct ttyprintk_port tpk_port;
31 * Our simple preformatting supports transparent output of (time-stamped)
32 * printk messages (also suitable for logging service):
33 * - any cr is replaced by nl
34 * - adds a ttyprintk source tag in front of each line
35 * - too long message is fragmented, with '\'nl between fragments
36 * - TPK_STR_SIZE isn't really the write_room limiting factor, because
37 * it is emptied on the fly during preformatting.
39 #define TPK_STR_SIZE 508 /* should be bigger then max expected line length */
40 #define TPK_MAX_ROOM 4096 /* we could assume 4K for instance */
43 static char tpk_buffer[TPK_STR_SIZE + 4];
45 static void tpk_flush(void)
48 tpk_buffer[tpk_curr] = '\0';
49 pr_info("[U] %s\n", tpk_buffer);
54 static int tpk_printk(const unsigned char *buf, int count)
63 for (i = 0; i < count; i++) {
64 if (tpk_curr >= TPK_STR_SIZE) {
65 /* end of tmp buffer reached: cut the message in two */
66 tpk_buffer[tpk_curr++] = '\\';
73 if ((i + 1) < count && buf[i + 1] == '\n')
80 tpk_buffer[tpk_curr++] = buf[i];
89 * TTY operations open function.
91 static int tpk_open(struct tty_struct *tty, struct file *filp)
93 tty->driver_data = &tpk_port;
95 return tty_port_open(&tpk_port.port, tty, filp);
99 * TTY operations close function.
101 static void tpk_close(struct tty_struct *tty, struct file *filp)
103 struct ttyprintk_port *tpkp = tty->driver_data;
106 spin_lock_irqsave(&tpkp->spinlock, flags);
107 /* flush tpk_printk buffer */
109 spin_unlock_irqrestore(&tpkp->spinlock, flags);
111 tty_port_close(&tpkp->port, tty, filp);
115 * TTY operations write function.
117 static int tpk_write(struct tty_struct *tty,
118 const unsigned char *buf, int count)
120 struct ttyprintk_port *tpkp = tty->driver_data;
125 /* exclusive use of tpk_printk within this tty */
126 spin_lock_irqsave(&tpkp->spinlock, flags);
127 ret = tpk_printk(buf, count);
128 spin_unlock_irqrestore(&tpkp->spinlock, flags);
134 * TTY operations write_room function.
136 static int tpk_write_room(struct tty_struct *tty)
142 * TTY operations ioctl function.
144 static int tpk_ioctl(struct tty_struct *tty,
145 unsigned int cmd, unsigned long arg)
147 struct ttyprintk_port *tpkp = tty->driver_data;
163 * TTY operations hangup function.
165 static void tpk_hangup(struct tty_struct *tty)
167 struct ttyprintk_port *tpkp = tty->driver_data;
169 tty_port_hangup(&tpkp->port);
172 static const struct tty_operations ttyprintk_ops = {
176 .write_room = tpk_write_room,
178 .hangup = tpk_hangup,
181 static const struct tty_port_operations null_ops = { };
183 static struct tty_driver *ttyprintk_driver;
185 static int __init ttyprintk_init(void)
189 spin_lock_init(&tpk_port.spinlock);
191 ttyprintk_driver = tty_alloc_driver(1,
192 TTY_DRIVER_RESET_TERMIOS |
193 TTY_DRIVER_REAL_RAW |
194 TTY_DRIVER_UNNUMBERED_NODE);
195 if (IS_ERR(ttyprintk_driver))
196 return PTR_ERR(ttyprintk_driver);
198 tty_port_init(&tpk_port.port);
199 tpk_port.port.ops = &null_ops;
201 ttyprintk_driver->driver_name = "ttyprintk";
202 ttyprintk_driver->name = "ttyprintk";
203 ttyprintk_driver->major = TTYAUX_MAJOR;
204 ttyprintk_driver->minor_start = 3;
205 ttyprintk_driver->type = TTY_DRIVER_TYPE_CONSOLE;
206 ttyprintk_driver->init_termios = tty_std_termios;
207 ttyprintk_driver->init_termios.c_oflag = OPOST | OCRNL | ONOCR | ONLRET;
208 tty_set_operations(ttyprintk_driver, &ttyprintk_ops);
209 tty_port_link_device(&tpk_port.port, ttyprintk_driver, 0);
211 ret = tty_register_driver(ttyprintk_driver);
213 printk(KERN_ERR "Couldn't register ttyprintk driver\n");
220 put_tty_driver(ttyprintk_driver);
221 tty_port_destroy(&tpk_port.port);
225 static void __exit ttyprintk_exit(void)
227 tty_unregister_driver(ttyprintk_driver);
228 put_tty_driver(ttyprintk_driver);
229 tty_port_destroy(&tpk_port.port);
232 device_initcall(ttyprintk_init);
233 module_exit(ttyprintk_exit);
235 MODULE_LICENSE("GPL");