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 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 ((i + 1) < count && 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 */
148static int tpk_ioctl(struct tty_struct *tty,
149			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
174static struct tty_port_operations null_ops = { };
175
176static struct tty_driver *ttyprintk_driver;
177
178static int __init ttyprintk_init(void)
179{
180	int ret = -ENOMEM;
181
182	mutex_init(&tpk_port.port_write_mutex);
183
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);
190
191	tty_port_init(&tpk_port.port);
192	tpk_port.port.ops = &null_ops;
193
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);
203
204	ret = tty_register_driver(ttyprintk_driver);
205	if (ret < 0) {
206		printk(KERN_ERR "Couldn't register ttyprintk driver\n");
207		goto error;
208	}
209
210	return 0;
211
212error:
213	put_tty_driver(ttyprintk_driver);
214	tty_port_destroy(&tpk_port.port);
215	return ret;
216}
217
218static void __exit ttyprintk_exit(void)
219{
220	tty_unregister_driver(ttyprintk_driver);
221	put_tty_driver(ttyprintk_driver);
222	tty_port_destroy(&tpk_port.port);
223}
224
225device_initcall(ttyprintk_init);
226module_exit(ttyprintk_exit);
227
228MODULE_LICENSE("GPL");
229