TTY: remove re-assignments to tty_driver members
[linux-2.6.git] / drivers / char / ttyprintk.c
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/export.h>
21
22 struct ttyprintk_port {
23         struct tty_port port;
24         struct mutex port_write_mutex;
25 };
26
27 static 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 */
40 static const char *tpk_tag = "[U] "; /* U for User */
41 static int tpk_curr;
42
43 static 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  */
97 static 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  */
107 static 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  */
122 static 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  */
140 static int tpk_write_room(struct tty_struct *tty)
141 {
142         return TPK_MAX_ROOM;
143 }
144
145 /*
146  * TTY operations ioctl function.
147  */
148 static 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
166 static 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
174 static struct tty_port_operations null_ops = { };
175
176 static struct tty_driver *ttyprintk_driver;
177
178 static 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->driver_name = "ttyprintk";
188         ttyprintk_driver->name = "ttyprintk";
189         ttyprintk_driver->major = TTYAUX_MAJOR;
190         ttyprintk_driver->minor_start = 3;
191         ttyprintk_driver->type = TTY_DRIVER_TYPE_CONSOLE;
192         ttyprintk_driver->init_termios = tty_std_termios;
193         ttyprintk_driver->init_termios.c_oflag = OPOST | OCRNL | ONOCR | ONLRET;
194         ttyprintk_driver->flags = TTY_DRIVER_RESET_TERMIOS |
195                 TTY_DRIVER_REAL_RAW | TTY_DRIVER_DYNAMIC_DEV;
196         tty_set_operations(ttyprintk_driver, &ttyprintk_ops);
197
198         ret = tty_register_driver(ttyprintk_driver);
199         if (ret < 0) {
200                 printk(KERN_ERR "Couldn't register ttyprintk driver\n");
201                 goto error;
202         }
203
204         /* create our unnumbered device */
205         rp = device_create(tty_class, NULL, MKDEV(TTYAUX_MAJOR, 3), NULL,
206                                 ttyprintk_driver->name);
207         if (IS_ERR(rp)) {
208                 printk(KERN_ERR "Couldn't create ttyprintk device\n");
209                 ret = PTR_ERR(rp);
210                 goto error;
211         }
212
213         tty_port_init(&tpk_port.port);
214         tpk_port.port.ops = &null_ops;
215         mutex_init(&tpk_port.port_write_mutex);
216
217         return 0;
218
219 error:
220         put_tty_driver(ttyprintk_driver);
221         ttyprintk_driver = NULL;
222         return ret;
223 }
224 module_init(ttyprintk_init);