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>
21 struct ttyprintk_port {
23 struct mutex port_write_mutex;
26 static struct ttyprintk_port tpk_port;
29 * Our simple preformatting supports transparent output of (time-stamped)
30 * printk messages (also suitable for logging service):
31 * - any cr is replaced by nl
32 * - adds a ttyprintk source tag in front of each line
33 * - too long message is fragmeted, with '\'nl between fragments
34 * - TPK_STR_SIZE isn't really the write_room limiting factor, bcause
35 * it is emptied on the fly during preformatting.
37 #define TPK_STR_SIZE 508 /* should be bigger then max expected line length */
38 #define TPK_MAX_ROOM 4096 /* we could assume 4K for instance */
39 static const char *tpk_tag = "[U] "; /* U for User */
42 static int tpk_printk(const unsigned char *buf, int count)
44 static char tmp[TPK_STR_SIZE + 4];
50 /* non nl or cr terminated message - add nl */
51 tmp[tpk_curr + 0] = '\n';
52 tmp[tpk_curr + 1] = '\0';
53 printk(KERN_INFO "%s%s", tpk_tag, tmp);
59 for (i = 0; i < count; i++) {
60 tmp[tpk_curr] = buf[i];
61 if (tpk_curr < TPK_STR_SIZE) {
64 /* replace cr with nl */
65 tmp[tpk_curr + 0] = '\n';
66 tmp[tpk_curr + 1] = '\0';
67 printk(KERN_INFO "%s%s", tpk_tag, tmp);
69 if (buf[i + 1] == '\n')
73 tmp[tpk_curr + 1] = '\0';
74 printk(KERN_INFO "%s%s", tpk_tag, tmp);
81 /* end of tmp buffer reached: cut the message in two */
82 tmp[tpk_curr + 1] = '\\';
83 tmp[tpk_curr + 2] = '\n';
84 tmp[tpk_curr + 3] = '\0';
85 printk(KERN_INFO "%s%s", tpk_tag, tmp);
94 * TTY operations open function.
96 static int tpk_open(struct tty_struct *tty, struct file *filp)
98 tty->driver_data = &tpk_port;
100 return tty_port_open(&tpk_port.port, tty, filp);
104 * TTY operations close function.
106 static void tpk_close(struct tty_struct *tty, struct file *filp)
108 struct ttyprintk_port *tpkp = tty->driver_data;
110 mutex_lock(&tpkp->port_write_mutex);
111 /* flush tpk_printk buffer */
113 mutex_unlock(&tpkp->port_write_mutex);
115 tty_port_close(&tpkp->port, tty, filp);
119 * TTY operations write function.
121 static int tpk_write(struct tty_struct *tty,
122 const unsigned char *buf, int count)
124 struct ttyprintk_port *tpkp = tty->driver_data;
128 /* exclusive use of tpk_printk within this tty */
129 mutex_lock(&tpkp->port_write_mutex);
130 ret = tpk_printk(buf, count);
131 mutex_unlock(&tpkp->port_write_mutex);
137 * TTY operations write_room function.
139 static int tpk_write_room(struct tty_struct *tty)
145 * TTY operations ioctl function.
147 static int tpk_ioctl(struct tty_struct *tty,
148 unsigned int cmd, unsigned long arg)
150 struct ttyprintk_port *tpkp = tty->driver_data;
165 static const struct tty_operations ttyprintk_ops = {
169 .write_room = tpk_write_room,
173 struct tty_port_operations null_ops = { };
175 static struct tty_driver *ttyprintk_driver;
177 static int __init ttyprintk_init(void)
182 ttyprintk_driver = alloc_tty_driver(1);
183 if (!ttyprintk_driver)
186 ttyprintk_driver->owner = THIS_MODULE;
187 ttyprintk_driver->driver_name = "ttyprintk";
188 ttyprintk_driver->name = "ttyprintk";
189 ttyprintk_driver->major = TTYAUX_MAJOR;
190 ttyprintk_driver->minor_start = 3;
191 ttyprintk_driver->num = 1;
192 ttyprintk_driver->type = TTY_DRIVER_TYPE_CONSOLE;
193 ttyprintk_driver->init_termios = tty_std_termios;
194 ttyprintk_driver->init_termios.c_oflag = OPOST | OCRNL | ONOCR | ONLRET;
195 ttyprintk_driver->flags = TTY_DRIVER_RESET_TERMIOS |
196 TTY_DRIVER_REAL_RAW | TTY_DRIVER_DYNAMIC_DEV;
197 tty_set_operations(ttyprintk_driver, &ttyprintk_ops);
199 ret = tty_register_driver(ttyprintk_driver);
201 printk(KERN_ERR "Couldn't register ttyprintk driver\n");
205 /* create our unnumbered device */
206 rp = device_create(tty_class, NULL, MKDEV(TTYAUX_MAJOR, 3), NULL,
207 ttyprintk_driver->name);
209 printk(KERN_ERR "Couldn't create ttyprintk device\n");
214 tty_port_init(&tpk_port.port);
215 tpk_port.port.ops = &null_ops;
216 mutex_init(&tpk_port.port_write_mutex);
221 put_tty_driver(ttyprintk_driver);
222 ttyprintk_driver = NULL;
225 module_init(ttyprintk_init);