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>
22 struct ttyprintk_port {
24 struct mutex port_write_mutex;
27 static struct ttyprintk_port tpk_port;
30 * Our simple preformatting supports transparent output of (time-stamped)
31 * printk messages (also suitable for logging service):
32 * - any cr is replaced by nl
33 * - adds a ttyprintk source tag in front of each line
34 * - too long message is fragmented, with '\'nl between fragments
35 * - TPK_STR_SIZE isn't really the write_room limiting factor, because
36 * it is emptied on the fly during preformatting.
38 #define TPK_STR_SIZE 508 /* should be bigger then max expected line length */
39 #define TPK_MAX_ROOM 4096 /* we could assume 4K for instance */
40 #define TPK_PREFIX KERN_SOH __stringify(CONFIG_TTY_PRINTK_LEVEL)
44 static char tpk_buffer[TPK_STR_SIZE + 4];
46 static void tpk_flush(void)
49 tpk_buffer[tpk_curr] = '\0';
50 printk(TPK_PREFIX "[U] %s\n", tpk_buffer);
55 static int tpk_printk(const unsigned char *buf, int count)
64 for (i = 0; i < count; i++) {
65 if (tpk_curr >= TPK_STR_SIZE) {
66 /* end of tmp buffer reached: cut the message in two */
67 tpk_buffer[tpk_curr++] = '\\';
74 if ((i + 1) < count && buf[i + 1] == '\n')
81 tpk_buffer[tpk_curr++] = buf[i];
90 * TTY operations open function.
92 static int tpk_open(struct tty_struct *tty, struct file *filp)
94 tty->driver_data = &tpk_port;
96 return tty_port_open(&tpk_port.port, tty, filp);
100 * TTY operations close function.
102 static void tpk_close(struct tty_struct *tty, struct file *filp)
104 struct ttyprintk_port *tpkp = tty->driver_data;
106 mutex_lock(&tpkp->port_write_mutex);
107 /* flush tpk_printk buffer */
109 mutex_unlock(&tpkp->port_write_mutex);
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;
124 /* exclusive use of tpk_printk within this tty */
125 mutex_lock(&tpkp->port_write_mutex);
126 ret = tpk_printk(buf, count);
127 mutex_unlock(&tpkp->port_write_mutex);
133 * TTY operations write_room function.
135 static int tpk_write_room(struct tty_struct *tty)
141 * TTY operations ioctl function.
143 static int tpk_ioctl(struct tty_struct *tty,
144 unsigned int cmd, unsigned long arg)
146 struct ttyprintk_port *tpkp = tty->driver_data;
161 static const struct tty_operations ttyprintk_ops = {
165 .write_room = tpk_write_room,
169 static const struct tty_port_operations null_ops = { };
171 static struct tty_driver *ttyprintk_driver;
173 static int __init ttyprintk_init(void)
177 mutex_init(&tpk_port.port_write_mutex);
179 ttyprintk_driver = tty_alloc_driver(1,
180 TTY_DRIVER_RESET_TERMIOS |
181 TTY_DRIVER_REAL_RAW |
182 TTY_DRIVER_UNNUMBERED_NODE);
183 if (IS_ERR(ttyprintk_driver))
184 return PTR_ERR(ttyprintk_driver);
186 tty_port_init(&tpk_port.port);
187 tpk_port.port.ops = &null_ops;
189 ttyprintk_driver->driver_name = "ttyprintk";
190 ttyprintk_driver->name = "ttyprintk";
191 ttyprintk_driver->major = TTYAUX_MAJOR;
192 ttyprintk_driver->minor_start = 3;
193 ttyprintk_driver->type = TTY_DRIVER_TYPE_CONSOLE;
194 ttyprintk_driver->init_termios = tty_std_termios;
195 ttyprintk_driver->init_termios.c_oflag = OPOST | OCRNL | ONOCR | ONLRET;
196 tty_set_operations(ttyprintk_driver, &ttyprintk_ops);
197 tty_port_link_device(&tpk_port.port, ttyprintk_driver, 0);
199 ret = tty_register_driver(ttyprintk_driver);
201 printk(KERN_ERR "Couldn't register ttyprintk driver\n");
208 put_tty_driver(ttyprintk_driver);
209 tty_port_destroy(&tpk_port.port);
213 static void __exit ttyprintk_exit(void)
215 tty_unregister_driver(ttyprintk_driver);
216 put_tty_driver(ttyprintk_driver);
217 tty_port_destroy(&tpk_port.port);
220 device_initcall(ttyprintk_init);
221 module_exit(ttyprintk_exit);
223 MODULE_LICENSE("GPL");