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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 |
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