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 fragmeted, with '\'nl between fragments
36 * - TPK_STR_SIZE isn't really the write_room limiting factor, bcause
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 */
41 static const char *tpk_tag = "[U] "; /* U for User */
44 static int tpk_printk(const unsigned char *buf, int count)
46 static char tmp[TPK_STR_SIZE + 4];
52 /* non nl or cr terminated message - add nl */
53 tmp[tpk_curr + 0] = '\n';
54 tmp[tpk_curr + 1] = '\0';
55 printk(KERN_INFO "%s%s", tpk_tag, tmp);
61 for (i = 0; i < count; i++) {
62 tmp[tpk_curr] = buf[i];
63 if (tpk_curr < TPK_STR_SIZE) {
66 /* replace cr with nl */
67 tmp[tpk_curr + 0] = '\n';
68 tmp[tpk_curr + 1] = '\0';
69 printk(KERN_INFO "%s%s", tpk_tag, tmp);
71 if ((i + 1) < count && buf[i + 1] == '\n')
75 tmp[tpk_curr + 1] = '\0';
76 printk(KERN_INFO "%s%s", tpk_tag, tmp);
83 /* end of tmp buffer reached: cut the message in two */
84 tmp[tpk_curr + 1] = '\\';
85 tmp[tpk_curr + 2] = '\n';
86 tmp[tpk_curr + 3] = '\0';
87 printk(KERN_INFO "%s%s", tpk_tag, tmp);
96 * TTY operations open function.
98 static int tpk_open(struct tty_struct *tty, struct file *filp)
100 tty->driver_data = &tpk_port;
102 return tty_port_open(&tpk_port.port, tty, filp);
106 * TTY operations close function.
108 static void tpk_close(struct tty_struct *tty, struct file *filp)
110 struct ttyprintk_port *tpkp = tty->driver_data;
113 spin_lock_irqsave(&tpkp->spinlock, flags);
114 /* flush tpk_printk buffer */
116 spin_unlock_irqrestore(&tpkp->spinlock, flags);
118 tty_port_close(&tpkp->port, tty, filp);
122 * TTY operations write function.
124 static int tpk_write(struct tty_struct *tty,
125 const unsigned char *buf, int count)
127 struct ttyprintk_port *tpkp = tty->driver_data;
132 /* exclusive use of tpk_printk within this tty */
133 spin_lock_irqsave(&tpkp->spinlock, flags);
134 ret = tpk_printk(buf, count);
135 spin_unlock_irqrestore(&tpkp->spinlock, flags);
141 * TTY operations write_room function.
143 static int tpk_write_room(struct tty_struct *tty)
149 * TTY operations ioctl function.
151 static int tpk_ioctl(struct tty_struct *tty,
152 unsigned int cmd, unsigned long arg)
154 struct ttyprintk_port *tpkp = tty->driver_data;
170 * TTY operations hangup function.
172 static void tpk_hangup(struct tty_struct *tty)
174 struct ttyprintk_port *tpkp = tty->driver_data;
176 tty_port_hangup(&tpkp->port);
179 static const struct tty_operations ttyprintk_ops = {
183 .write_room = tpk_write_room,
185 .hangup = tpk_hangup,
188 static struct tty_port_operations null_ops = { };
190 static struct tty_driver *ttyprintk_driver;
192 static int __init ttyprintk_init(void)
196 spin_lock_init(&tpk_port.spinlock);
198 ttyprintk_driver = tty_alloc_driver(1,
199 TTY_DRIVER_RESET_TERMIOS |
200 TTY_DRIVER_REAL_RAW |
201 TTY_DRIVER_UNNUMBERED_NODE);
202 if (IS_ERR(ttyprintk_driver))
203 return PTR_ERR(ttyprintk_driver);
205 tty_port_init(&tpk_port.port);
206 tpk_port.port.ops = &null_ops;
208 ttyprintk_driver->driver_name = "ttyprintk";
209 ttyprintk_driver->name = "ttyprintk";
210 ttyprintk_driver->major = TTYAUX_MAJOR;
211 ttyprintk_driver->minor_start = 3;
212 ttyprintk_driver->type = TTY_DRIVER_TYPE_CONSOLE;
213 ttyprintk_driver->init_termios = tty_std_termios;
214 ttyprintk_driver->init_termios.c_oflag = OPOST | OCRNL | ONOCR | ONLRET;
215 tty_set_operations(ttyprintk_driver, &ttyprintk_ops);
216 tty_port_link_device(&tpk_port.port, ttyprintk_driver, 0);
218 ret = tty_register_driver(ttyprintk_driver);
220 printk(KERN_ERR "Couldn't register ttyprintk driver\n");
227 put_tty_driver(ttyprintk_driver);
228 tty_port_destroy(&tpk_port.port);
232 static void __exit ttyprintk_exit(void)
234 tty_unregister_driver(ttyprintk_driver);
235 put_tty_driver(ttyprintk_driver);
236 tty_port_destroy(&tpk_port.port);
239 device_initcall(ttyprintk_init);
240 module_exit(ttyprintk_exit);
242 MODULE_LICENSE("GPL");