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/export.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 fragmeted, with '\'nl between fragments
35 * - TPK_STR_SIZE isn't really the write_room limiting factor, bcause
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 static const char *tpk_tag = "[U] "; /* U for User */
43 static int tpk_printk(const unsigned char *buf, int count)
45 static char tmp[TPK_STR_SIZE + 4];
51 /* non nl or cr terminated message - add nl */
52 tmp[tpk_curr + 0] = '\n';
53 tmp[tpk_curr + 1] = '\0';
54 printk(KERN_INFO "%s%s", tpk_tag, tmp);
60 for (i = 0; i < count; i++) {
61 tmp[tpk_curr] = buf[i];
62 if (tpk_curr < TPK_STR_SIZE) {
65 /* replace cr with nl */
66 tmp[tpk_curr + 0] = '\n';
67 tmp[tpk_curr + 1] = '\0';
68 printk(KERN_INFO "%s%s", tpk_tag, tmp);
70 if ((i + 1) < count && buf[i + 1] == '\n')
74 tmp[tpk_curr + 1] = '\0';
75 printk(KERN_INFO "%s%s", tpk_tag, tmp);
82 /* end of tmp buffer reached: cut the message in two */
83 tmp[tpk_curr + 1] = '\\';
84 tmp[tpk_curr + 2] = '\n';
85 tmp[tpk_curr + 3] = '\0';
86 printk(KERN_INFO "%s%s", tpk_tag, tmp);
95 * TTY operations open function.
97 static int tpk_open(struct tty_struct *tty, struct file *filp)
99 tty->driver_data = &tpk_port;
101 return tty_port_open(&tpk_port.port, tty, filp);
105 * TTY operations close function.
107 static void tpk_close(struct tty_struct *tty, struct file *filp)
109 struct ttyprintk_port *tpkp = tty->driver_data;
111 mutex_lock(&tpkp->port_write_mutex);
112 /* flush tpk_printk buffer */
114 mutex_unlock(&tpkp->port_write_mutex);
116 tty_port_close(&tpkp->port, tty, filp);
120 * TTY operations write function.
122 static int tpk_write(struct tty_struct *tty,
123 const unsigned char *buf, int count)
125 struct ttyprintk_port *tpkp = tty->driver_data;
129 /* exclusive use of tpk_printk within this tty */
130 mutex_lock(&tpkp->port_write_mutex);
131 ret = tpk_printk(buf, count);
132 mutex_unlock(&tpkp->port_write_mutex);
138 * TTY operations write_room function.
140 static int tpk_write_room(struct tty_struct *tty)
146 * TTY operations ioctl function.
148 static int tpk_ioctl(struct tty_struct *tty,
149 unsigned int cmd, unsigned long arg)
151 struct ttyprintk_port *tpkp = tty->driver_data;
166 static const struct tty_operations ttyprintk_ops = {
170 .write_room = tpk_write_room,
174 static struct tty_port_operations null_ops = { };
176 static struct tty_driver *ttyprintk_driver;
178 static int __init ttyprintk_init(void)
182 mutex_init(&tpk_port.port_write_mutex);
184 ttyprintk_driver = tty_alloc_driver(1,
185 TTY_DRIVER_RESET_TERMIOS |
186 TTY_DRIVER_REAL_RAW |
187 TTY_DRIVER_UNNUMBERED_NODE);
188 if (IS_ERR(ttyprintk_driver))
189 return PTR_ERR(ttyprintk_driver);
191 tty_port_init(&tpk_port.port);
192 tpk_port.port.ops = &null_ops;
194 ttyprintk_driver->driver_name = "ttyprintk";
195 ttyprintk_driver->name = "ttyprintk";
196 ttyprintk_driver->major = TTYAUX_MAJOR;
197 ttyprintk_driver->minor_start = 3;
198 ttyprintk_driver->type = TTY_DRIVER_TYPE_CONSOLE;
199 ttyprintk_driver->init_termios = tty_std_termios;
200 ttyprintk_driver->init_termios.c_oflag = OPOST | OCRNL | ONOCR | ONLRET;
201 tty_set_operations(ttyprintk_driver, &ttyprintk_ops);
202 tty_port_link_device(&tpk_port.port, ttyprintk_driver, 0);
204 ret = tty_register_driver(ttyprintk_driver);
206 printk(KERN_ERR "Couldn't register ttyprintk driver\n");
213 tty_unregister_driver(ttyprintk_driver);
214 put_tty_driver(ttyprintk_driver);
215 tty_port_destroy(&tpk_port.port);
216 ttyprintk_driver = NULL;
219 device_initcall(ttyprintk_init);