xref: /openbmc/linux/drivers/char/ttyprintk.c (revision 4800cd83)
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 
21 struct ttyprintk_port {
22 	struct tty_port port;
23 	struct mutex port_write_mutex;
24 };
25 
26 static struct ttyprintk_port tpk_port;
27 
28 /*
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.
36  */
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 */
40 static int tpk_curr;
41 
42 static int tpk_printk(const unsigned char *buf, int count)
43 {
44 	static char tmp[TPK_STR_SIZE + 4];
45 	int i = tpk_curr;
46 
47 	if (buf == NULL) {
48 		/* flush tmp[] */
49 		if (tpk_curr > 0) {
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);
54 			tpk_curr = 0;
55 		}
56 		return i;
57 	}
58 
59 	for (i = 0; i < count; i++) {
60 		tmp[tpk_curr] = buf[i];
61 		if (tpk_curr < TPK_STR_SIZE) {
62 			switch (buf[i]) {
63 			case '\r':
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);
68 				tpk_curr = 0;
69 				if (buf[i + 1] == '\n')
70 					i++;
71 				break;
72 			case '\n':
73 				tmp[tpk_curr + 1] = '\0';
74 				printk(KERN_INFO "%s%s", tpk_tag, tmp);
75 				tpk_curr = 0;
76 				break;
77 			default:
78 				tpk_curr++;
79 			}
80 		} else {
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);
86 			tpk_curr = 0;
87 		}
88 	}
89 
90 	return count;
91 }
92 
93 /*
94  * TTY operations open function.
95  */
96 static int tpk_open(struct tty_struct *tty, struct file *filp)
97 {
98 	tty->driver_data = &tpk_port;
99 
100 	return tty_port_open(&tpk_port.port, tty, filp);
101 }
102 
103 /*
104  * TTY operations close function.
105  */
106 static void tpk_close(struct tty_struct *tty, struct file *filp)
107 {
108 	struct ttyprintk_port *tpkp = tty->driver_data;
109 
110 	mutex_lock(&tpkp->port_write_mutex);
111 	/* flush tpk_printk buffer */
112 	tpk_printk(NULL, 0);
113 	mutex_unlock(&tpkp->port_write_mutex);
114 
115 	tty_port_close(&tpkp->port, tty, filp);
116 }
117 
118 /*
119  * TTY operations write function.
120  */
121 static int tpk_write(struct tty_struct *tty,
122 		const unsigned char *buf, int count)
123 {
124 	struct ttyprintk_port *tpkp = tty->driver_data;
125 	int ret;
126 
127 
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);
132 
133 	return ret;
134 }
135 
136 /*
137  * TTY operations write_room function.
138  */
139 static int tpk_write_room(struct tty_struct *tty)
140 {
141 	return TPK_MAX_ROOM;
142 }
143 
144 /*
145  * TTY operations ioctl function.
146  */
147 static int tpk_ioctl(struct tty_struct *tty, struct file *file,
148 			unsigned int cmd, unsigned long arg)
149 {
150 	struct ttyprintk_port *tpkp = tty->driver_data;
151 
152 	if (!tpkp)
153 		return -EINVAL;
154 
155 	switch (cmd) {
156 	/* Stop TIOCCONS */
157 	case TIOCCONS:
158 		return -EOPNOTSUPP;
159 	default:
160 		return -ENOIOCTLCMD;
161 	}
162 	return 0;
163 }
164 
165 static const struct tty_operations ttyprintk_ops = {
166 	.open = tpk_open,
167 	.close = tpk_close,
168 	.write = tpk_write,
169 	.write_room = tpk_write_room,
170 	.ioctl = tpk_ioctl,
171 };
172 
173 struct tty_port_operations null_ops = { };
174 
175 static struct tty_driver *ttyprintk_driver;
176 
177 static int __init ttyprintk_init(void)
178 {
179 	int ret = -ENOMEM;
180 	void *rp;
181 
182 	ttyprintk_driver = alloc_tty_driver(1);
183 	if (!ttyprintk_driver)
184 		return ret;
185 
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);
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 	/* create our unnumbered device */
206 	rp = device_create(tty_class, NULL, MKDEV(TTYAUX_MAJOR, 3), NULL,
207 				ttyprintk_driver->name);
208 	if (IS_ERR(rp)) {
209 		printk(KERN_ERR "Couldn't create ttyprintk device\n");
210 		ret = PTR_ERR(rp);
211 		goto error;
212 	}
213 
214 	tty_port_init(&tpk_port.port);
215 	tpk_port.port.ops = &null_ops;
216 	mutex_init(&tpk_port.port_write_mutex);
217 
218 	return 0;
219 
220 error:
221 	put_tty_driver(ttyprintk_driver);
222 	ttyprintk_driver = NULL;
223 	return ret;
224 }
225 module_init(ttyprintk_init);
226