1/*
2 * linux/drivers/char/ttyprintk.c
3 *
4 * Copyright (C) 2010 Samo Pogacnik
5 *
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.
9 */
10
11/*
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.
15 */
16
17#include <linux/device.h>
18#include <linux/serial.h>
19#include <linux/tty.h>
20#include <linux/module.h>
21
22struct ttyprintk_port {
23 struct tty_port port;
24 struct mutex port_write_mutex;
25};
26
27static struct ttyprintk_port tpk_port;
28
29/*
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.
37 */
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)
41
42static int tpk_curr;
43
44static char tpk_buffer[TPK_STR_SIZE + 4];
45
46static void tpk_flush(void)
47{
48 if (tpk_curr > 0) {
49 tpk_buffer[tpk_curr] = '\0';
50 printk(TPK_PREFIX "[U] %s\n", tpk_buffer);
51 tpk_curr = 0;
52 }
53}
54
55static int tpk_printk(const unsigned char *buf, int count)
56{
57 int i = tpk_curr;
58
59 if (buf == NULL) {
60 tpk_flush();
61 return i;
62 }
63
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++] = '\\';
68 tpk_flush();
69 }
70
71 switch (buf[i]) {
72 case '\r':
73 tpk_flush();
74 if ((i + 1) < count && buf[i + 1] == '\n')
75 i++;
76 break;
77 case '\n':
78 tpk_flush();
79 break;
80 default:
81 tpk_buffer[tpk_curr++] = buf[i];
82 break;
83 }
84 }
85
86 return count;
87}
88
89/*
90 * TTY operations open function.
91 */
92static int tpk_open(struct tty_struct *tty, struct file *filp)
93{
94 tty->driver_data = &tpk_port;
95
96 return tty_port_open(&tpk_port.port, tty, filp);
97}
98
99/*
100 * TTY operations close function.
101 */
102static void tpk_close(struct tty_struct *tty, struct file *filp)
103{
104 struct ttyprintk_port *tpkp = tty->driver_data;
105
106 mutex_lock(&tpkp->port_write_mutex);
107 /* flush tpk_printk buffer */
108 tpk_printk(NULL, 0);
109 mutex_unlock(&tpkp->port_write_mutex);
110
111 tty_port_close(&tpkp->port, tty, filp);
112}
113
114/*
115 * TTY operations write function.
116 */
117static int tpk_write(struct tty_struct *tty,
118 const unsigned char *buf, int count)
119{
120 struct ttyprintk_port *tpkp = tty->driver_data;
121 int ret;
122
123
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);
128
129 return ret;
130}
131
132/*
133 * TTY operations write_room function.
134 */
135static int tpk_write_room(struct tty_struct *tty)
136{
137 return TPK_MAX_ROOM;
138}
139
140/*
141 * TTY operations ioctl function.
142 */
143static int tpk_ioctl(struct tty_struct *tty,
144 unsigned int cmd, unsigned long arg)
145{
146 struct ttyprintk_port *tpkp = tty->driver_data;
147
148 if (!tpkp)
149 return -EINVAL;
150
151 switch (cmd) {
152 /* Stop TIOCCONS */
153 case TIOCCONS:
154 return -EOPNOTSUPP;
155 default:
156 return -ENOIOCTLCMD;
157 }
158 return 0;
159}
160
161static const struct tty_operations ttyprintk_ops = {
162 .open = tpk_open,
163 .close = tpk_close,
164 .write = tpk_write,
165 .write_room = tpk_write_room,
166 .ioctl = tpk_ioctl,
167};
168
169static const struct tty_port_operations null_ops = { };
170
171static struct tty_driver *ttyprintk_driver;
172
173static int __init ttyprintk_init(void)
174{
175 int ret = -ENOMEM;
176
177 mutex_init(&tpk_port.port_write_mutex);
178
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);
185
186 tty_port_init(&tpk_port.port);
187 tpk_port.port.ops = &null_ops;
188
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);
198
199 ret = tty_register_driver(ttyprintk_driver);
200 if (ret < 0) {
201 printk(KERN_ERR "Couldn't register ttyprintk driver\n");
202 goto error;
203 }
204
205 return 0;
206
207error:
208 put_tty_driver(ttyprintk_driver);
209 tty_port_destroy(&tpk_port.port);
210 return ret;
211}
212
213static void __exit ttyprintk_exit(void)
214{
215 tty_unregister_driver(ttyprintk_driver);
216 put_tty_driver(ttyprintk_driver);
217 tty_port_destroy(&tpk_port.port);
218}
219
220device_initcall(ttyprintk_init);
221module_exit(ttyprintk_exit);
222
223MODULE_LICENSE("GPL");
224