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Samo Pogacnik24b4b672010-08-25 20:44:07 +02001/*
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>
Paul Gortmaker66300e62011-07-10 12:14:53 -040020#include <linux/export.h>
Samo Pogacnik24b4b672010-08-25 20:44:07 +020021
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 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.
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 */
40static const char *tpk_tag = "[U] "; /* U for User */
41static int tpk_curr;
42
43static int tpk_printk(const unsigned char *buf, int count)
44{
45 static char tmp[TPK_STR_SIZE + 4];
46 int i = tpk_curr;
47
48 if (buf == NULL) {
49 /* flush tmp[] */
50 if (tpk_curr > 0) {
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);
55 tpk_curr = 0;
56 }
57 return i;
58 }
59
60 for (i = 0; i < count; i++) {
61 tmp[tpk_curr] = buf[i];
62 if (tpk_curr < TPK_STR_SIZE) {
63 switch (buf[i]) {
64 case '\r':
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);
69 tpk_curr = 0;
70 if (buf[i + 1] == '\n')
71 i++;
72 break;
73 case '\n':
74 tmp[tpk_curr + 1] = '\0';
75 printk(KERN_INFO "%s%s", tpk_tag, tmp);
76 tpk_curr = 0;
77 break;
78 default:
79 tpk_curr++;
80 }
81 } else {
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);
87 tpk_curr = 0;
88 }
89 }
90
91 return count;
92}
93
94/*
95 * TTY operations open function.
96 */
97static int tpk_open(struct tty_struct *tty, struct file *filp)
98{
99 tty->driver_data = &tpk_port;
100
101 return tty_port_open(&tpk_port.port, tty, filp);
102}
103
104/*
105 * TTY operations close function.
106 */
107static void tpk_close(struct tty_struct *tty, struct file *filp)
108{
109 struct ttyprintk_port *tpkp = tty->driver_data;
110
111 mutex_lock(&tpkp->port_write_mutex);
112 /* flush tpk_printk buffer */
113 tpk_printk(NULL, 0);
114 mutex_unlock(&tpkp->port_write_mutex);
115
116 tty_port_close(&tpkp->port, tty, filp);
117}
118
119/*
120 * TTY operations write function.
121 */
122static int tpk_write(struct tty_struct *tty,
123 const unsigned char *buf, int count)
124{
125 struct ttyprintk_port *tpkp = tty->driver_data;
126 int ret;
127
128
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);
133
134 return ret;
135}
136
137/*
138 * TTY operations write_room function.
139 */
140static int tpk_write_room(struct tty_struct *tty)
141{
142 return TPK_MAX_ROOM;
143}
144
145/*
146 * TTY operations ioctl function.
147 */
Alan Cox6caa76b2011-02-14 16:27:22 +0000148static int tpk_ioctl(struct tty_struct *tty,
Samo Pogacnik24b4b672010-08-25 20:44:07 +0200149 unsigned int cmd, unsigned long arg)
150{
151 struct ttyprintk_port *tpkp = tty->driver_data;
152
153 if (!tpkp)
154 return -EINVAL;
155
156 switch (cmd) {
157 /* Stop TIOCCONS */
158 case TIOCCONS:
159 return -EOPNOTSUPP;
160 default:
161 return -ENOIOCTLCMD;
162 }
163 return 0;
164}
165
166static const struct tty_operations ttyprintk_ops = {
167 .open = tpk_open,
168 .close = tpk_close,
169 .write = tpk_write,
170 .write_room = tpk_write_room,
171 .ioctl = tpk_ioctl,
172};
173
Al Viro33694652011-08-18 20:11:59 +0100174static struct tty_port_operations null_ops = { };
Samo Pogacnik24b4b672010-08-25 20:44:07 +0200175
176static struct tty_driver *ttyprintk_driver;
177
178static int __init ttyprintk_init(void)
179{
180 int ret = -ENOMEM;
181 void *rp;
182
183 ttyprintk_driver = alloc_tty_driver(1);
184 if (!ttyprintk_driver)
185 return ret;
186
187 ttyprintk_driver->owner = THIS_MODULE;
188 ttyprintk_driver->driver_name = "ttyprintk";
189 ttyprintk_driver->name = "ttyprintk";
190 ttyprintk_driver->major = TTYAUX_MAJOR;
191 ttyprintk_driver->minor_start = 3;
192 ttyprintk_driver->num = 1;
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 ttyprintk_driver->flags = TTY_DRIVER_RESET_TERMIOS |
197 TTY_DRIVER_REAL_RAW | TTY_DRIVER_DYNAMIC_DEV;
198 tty_set_operations(ttyprintk_driver, &ttyprintk_ops);
199
200 ret = tty_register_driver(ttyprintk_driver);
201 if (ret < 0) {
202 printk(KERN_ERR "Couldn't register ttyprintk driver\n");
203 goto error;
204 }
205
206 /* create our unnumbered device */
207 rp = device_create(tty_class, NULL, MKDEV(TTYAUX_MAJOR, 3), NULL,
208 ttyprintk_driver->name);
209 if (IS_ERR(rp)) {
210 printk(KERN_ERR "Couldn't create ttyprintk device\n");
211 ret = PTR_ERR(rp);
212 goto error;
213 }
214
215 tty_port_init(&tpk_port.port);
216 tpk_port.port.ops = &null_ops;
217 mutex_init(&tpk_port.port_write_mutex);
218
219 return 0;
220
221error:
222 put_tty_driver(ttyprintk_driver);
223 ttyprintk_driver = NULL;
224 return ret;
225}
226module_init(ttyprintk_init);