2 * linux/drivers/char/ttyprintk.c
4 * Copyright (C) 2010 Samo Pogacnik
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.
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.
17 #include <linux/device.h>
18 #include <linux/serial.h>
19 #include <linux/tty.h>
20 #include <linux/module.h>
22 struct ttyprintk_port
{
24 struct mutex port_write_mutex
;
27 static struct ttyprintk_port tpk_port
;
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 fragmented, with '\'nl between fragments
35 * - TPK_STR_SIZE isn't really the write_room limiting factor, because
36 * it is emptied on the fly during preformatting.
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 #define TPK_PREFIX KERN_SOH __stringify(CONFIG_TTY_PRINTK_LEVEL)
44 static char tpk_buffer
[TPK_STR_SIZE
+ 4];
46 static void tpk_flush(void)
49 tpk_buffer
[tpk_curr
] = '\0';
50 printk(TPK_PREFIX
"[U] %s\n", tpk_buffer
);
55 static int tpk_printk(const unsigned char *buf
, int count
)
64 for (i
= 0; i
< count
; i
++) {
65 if (tpk_curr
>= TPK_STR_SIZE
) {
66 /* end of tmp buffer reached: cut the message in two */
67 tpk_buffer
[tpk_curr
++] = '\\';
74 if ((i
+ 1) < count
&& buf
[i
+ 1] == '\n')
81 tpk_buffer
[tpk_curr
++] = buf
[i
];
90 * TTY operations open function.
92 static int tpk_open(struct tty_struct
*tty
, struct file
*filp
)
94 tty
->driver_data
= &tpk_port
;
96 return tty_port_open(&tpk_port
.port
, tty
, filp
);
100 * TTY operations close function.
102 static void tpk_close(struct tty_struct
*tty
, struct file
*filp
)
104 struct ttyprintk_port
*tpkp
= tty
->driver_data
;
106 mutex_lock(&tpkp
->port_write_mutex
);
107 /* flush tpk_printk buffer */
109 mutex_unlock(&tpkp
->port_write_mutex
);
111 tty_port_close(&tpkp
->port
, tty
, filp
);
115 * TTY operations write function.
117 static int tpk_write(struct tty_struct
*tty
,
118 const unsigned char *buf
, int count
)
120 struct ttyprintk_port
*tpkp
= tty
->driver_data
;
124 /* exclusive use of tpk_printk within this tty */
125 mutex_lock(&tpkp
->port_write_mutex
);
126 ret
= tpk_printk(buf
, count
);
127 mutex_unlock(&tpkp
->port_write_mutex
);
133 * TTY operations write_room function.
135 static int tpk_write_room(struct tty_struct
*tty
)
141 * TTY operations ioctl function.
143 static int tpk_ioctl(struct tty_struct
*tty
,
144 unsigned int cmd
, unsigned long arg
)
146 struct ttyprintk_port
*tpkp
= tty
->driver_data
;
161 static const struct tty_operations ttyprintk_ops
= {
165 .write_room
= tpk_write_room
,
169 static const struct tty_port_operations null_ops
= { };
171 static struct tty_driver
*ttyprintk_driver
;
173 static int __init
ttyprintk_init(void)
177 mutex_init(&tpk_port
.port_write_mutex
);
179 ttyprintk_driver
= tty_alloc_driver(1,
180 TTY_DRIVER_RESET_TERMIOS
|
181 TTY_DRIVER_REAL_RAW
|
182 TTY_DRIVER_UNNUMBERED_NODE
);
183 if (IS_ERR(ttyprintk_driver
))
184 return PTR_ERR(ttyprintk_driver
);
186 tty_port_init(&tpk_port
.port
);
187 tpk_port
.port
.ops
= &null_ops
;
189 ttyprintk_driver
->driver_name
= "ttyprintk";
190 ttyprintk_driver
->name
= "ttyprintk";
191 ttyprintk_driver
->major
= TTYAUX_MAJOR
;
192 ttyprintk_driver
->minor_start
= 3;
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 tty_set_operations(ttyprintk_driver
, &ttyprintk_ops
);
197 tty_port_link_device(&tpk_port
.port
, ttyprintk_driver
, 0);
199 ret
= tty_register_driver(ttyprintk_driver
);
201 printk(KERN_ERR
"Couldn't register ttyprintk driver\n");
208 put_tty_driver(ttyprintk_driver
);
209 tty_port_destroy(&tpk_port
.port
);
213 static void __exit
ttyprintk_exit(void)
215 tty_unregister_driver(ttyprintk_driver
);
216 put_tty_driver(ttyprintk_driver
);
217 tty_port_destroy(&tpk_port
.port
);
220 device_initcall(ttyprintk_init
);
221 module_exit(ttyprintk_exit
);
223 MODULE_LICENSE("GPL");