4 * (c) Copyright 2008-2011 Alan Cox <alan@lxorguk.ukuu.org.uk>,
7 * (c) Copyright 2008-2011 Wim Van Sebroeck <wim@iguana.be>.
10 * This source code is part of the generic code that can be used
11 * by all the watchdog timer drivers.
13 * This part of the generic code takes care of the following
14 * misc device: /dev/watchdog.
16 * Based on source code of the following authors:
17 * Matt Domsch <Matt_Domsch@dell.com>,
18 * Rob Radez <rob@osinvestor.com>,
19 * Rusty Lynch <rusty@linux.co.intel.com>
20 * Satyam Sharma <satyam@infradead.org>
21 * Randy Dunlap <randy.dunlap@oracle.com>
23 * This program is free software; you can redistribute it and/or
24 * modify it under the terms of the GNU General Public License
25 * as published by the Free Software Foundation; either version
26 * 2 of the License, or (at your option) any later version.
28 * Neither Alan Cox, CymruNet Ltd., Wim Van Sebroeck nor Iguana vzw.
29 * admit liability nor provide warranty for any of this software.
30 * This material is provided "AS-IS" and at no charge.
33 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
35 #include <linux/module.h> /* For module stuff/... */
36 #include <linux/types.h> /* For standard types (like size_t) */
37 #include <linux/errno.h> /* For the -ENODEV/... values */
38 #include <linux/kernel.h> /* For printk/panic/... */
39 #include <linux/fs.h> /* For file operations */
40 #include <linux/watchdog.h> /* For watchdog specific items */
41 #include <linux/miscdevice.h> /* For handling misc devices */
42 #include <linux/init.h> /* For __init/__exit/... */
43 #include <linux/uaccess.h> /* For copy_to_user/put_user/... */
45 /* make sure we only register one /dev/watchdog device */
46 static unsigned long watchdog_dev_busy
;
47 /* the watchdog device behind /dev/watchdog */
48 static struct watchdog_device
*wdd
;
51 * watchdog_ping: ping the watchdog.
52 * @wddev: the watchdog device to ping
54 * If the watchdog has no own ping operation then it needs to be
55 * restarted via the start operation. This wrapper function does
57 * We only ping when the watchdog device is running.
60 static int watchdog_ping(struct watchdog_device
*wddev
)
62 if (test_bit(WDOG_ACTIVE
, &wdd
->status
)) {
64 return wddev
->ops
->ping(wddev
); /* ping the watchdog */
66 return wddev
->ops
->start(wddev
); /* restart watchdog */
72 * watchdog_start: wrapper to start the watchdog.
73 * @wddev: the watchdog device to start
75 * Start the watchdog if it is not active and mark it active.
76 * This function returns zero on success or a negative errno code for
80 static int watchdog_start(struct watchdog_device
*wddev
)
84 if (!test_bit(WDOG_ACTIVE
, &wdd
->status
)) {
85 err
= wddev
->ops
->start(wddev
);
89 set_bit(WDOG_ACTIVE
, &wdd
->status
);
95 * watchdog_stop: wrapper to stop the watchdog.
96 * @wddev: the watchdog device to stop
98 * Stop the watchdog if it is still active and unmark it active.
99 * This function returns zero on success or a negative errno code for
103 static int watchdog_stop(struct watchdog_device
*wddev
)
107 if (test_bit(WDOG_ACTIVE
, &wdd
->status
)) {
108 err
= wddev
->ops
->stop(wddev
);
112 clear_bit(WDOG_ACTIVE
, &wdd
->status
);
118 * watchdog_write: writes to the watchdog.
119 * @file: file from VFS
120 * @data: user address of data
121 * @len: length of data
122 * @ppos: pointer to the file offset
124 * A write to a watchdog device is defined as a keepalive ping.
125 * Writing the magic 'V' sequence allows the next close to turn
129 static ssize_t
watchdog_write(struct file
*file
, const char __user
*data
,
130 size_t len
, loff_t
*ppos
)
139 * Note: just in case someone wrote the magic character
142 clear_bit(WDOG_ALLOW_RELEASE
, &wdd
->status
);
144 /* scan to see whether or not we got the magic character */
145 for (i
= 0; i
!= len
; i
++) {
146 if (get_user(c
, data
+ i
))
149 set_bit(WDOG_ALLOW_RELEASE
, &wdd
->status
);
152 /* someone wrote to us, so we send the watchdog a keepalive ping */
159 * watchdog_ioctl: handle the different ioctl's for the watchdog device.
160 * @file: file handle to the device
161 * @cmd: watchdog command
162 * @arg: argument pointer
164 * The watchdog API defines a common set of functions for all watchdogs
165 * according to their available features.
168 static long watchdog_ioctl(struct file
*file
, unsigned int cmd
,
171 void __user
*argp
= (void __user
*)arg
;
172 int __user
*p
= argp
;
177 case WDIOC_GETSUPPORT
:
178 return copy_to_user(argp
, wdd
->info
,
179 sizeof(struct watchdog_info
)) ? -EFAULT
: 0;
180 case WDIOC_GETSTATUS
:
181 val
= wdd
->ops
->status
? wdd
->ops
->status(wdd
) : 0;
182 return put_user(val
, p
);
183 case WDIOC_GETBOOTSTATUS
:
184 return put_user(wdd
->bootstatus
, p
);
185 case WDIOC_SETOPTIONS
:
186 if (get_user(val
, p
))
188 if (val
& WDIOS_DISABLECARD
) {
189 err
= watchdog_stop(wdd
);
193 if (val
& WDIOS_ENABLECARD
) {
194 err
= watchdog_start(wdd
);
199 case WDIOC_KEEPALIVE
:
200 if (!(wdd
->info
->options
& WDIOF_KEEPALIVEPING
))
204 case WDIOC_SETTIMEOUT
:
205 if ((wdd
->ops
->set_timeout
== NULL
) ||
206 !(wdd
->info
->options
& WDIOF_SETTIMEOUT
))
208 if (get_user(val
, p
))
210 err
= wdd
->ops
->set_timeout(wdd
, val
);
214 /* If the watchdog is active then we send a keepalive ping
215 * to make sure that the watchdog keep's running (and if
216 * possible that it takes the new timeout) */
219 case WDIOC_GETTIMEOUT
:
220 /* timeout == 0 means that we don't know the timeout */
221 if (wdd
->timeout
== 0)
223 return put_user(wdd
->timeout
, p
);
230 * watchdog_open: open the /dev/watchdog device.
231 * @inode: inode of device
232 * @file: file handle to device
234 * When the /dev/watchdog device gets opened, we start the watchdog.
235 * Watch out: the /dev/watchdog device is single open, so we make sure
236 * it can only be opened once.
239 static int watchdog_open(struct inode
*inode
, struct file
*file
)
243 /* the watchdog is single open! */
244 if (test_and_set_bit(WDOG_DEV_OPEN
, &wdd
->status
))
248 * If the /dev/watchdog device is open, we don't want the module
251 if (!try_module_get(wdd
->ops
->owner
))
254 err
= watchdog_start(wdd
);
258 /* dev/watchdog is a virtual (and thus non-seekable) filesystem */
259 return nonseekable_open(inode
, file
);
262 module_put(wdd
->ops
->owner
);
264 clear_bit(WDOG_DEV_OPEN
, &wdd
->status
);
269 * watchdog_release: release the /dev/watchdog device.
270 * @inode: inode of device
271 * @file: file handle to device
273 * This is the code for when /dev/watchdog gets closed. We will only
274 * stop the watchdog when we have received the magic char, else the
275 * watchdog will keep running.
278 static int watchdog_release(struct inode
*inode
, struct file
*file
)
283 * We only stop the watchdog if we received the magic character
284 * or if WDIOF_MAGICCLOSE is not set
286 if (test_and_clear_bit(WDOG_ALLOW_RELEASE
, &wdd
->status
) ||
287 !(wdd
->info
->options
& WDIOF_MAGICCLOSE
))
288 err
= watchdog_stop(wdd
);
290 /* If the watchdog was not stopped, send a keepalive ping */
292 pr_crit("%s: watchdog did not stop!\n", wdd
->info
->identity
);
296 /* Allow the owner module to be unloaded again */
297 module_put(wdd
->ops
->owner
);
299 /* make sure that /dev/watchdog can be re-opened */
300 clear_bit(WDOG_DEV_OPEN
, &wdd
->status
);
305 static const struct file_operations watchdog_fops
= {
306 .owner
= THIS_MODULE
,
307 .write
= watchdog_write
,
308 .unlocked_ioctl
= watchdog_ioctl
,
309 .open
= watchdog_open
,
310 .release
= watchdog_release
,
313 static struct miscdevice watchdog_miscdev
= {
314 .minor
= WATCHDOG_MINOR
,
316 .fops
= &watchdog_fops
,
320 * watchdog_dev_register:
321 * @watchdog: watchdog device
323 * Register a watchdog device as /dev/watchdog. /dev/watchdog
324 * is actually a miscdevice and thus we set it up like that.
327 int watchdog_dev_register(struct watchdog_device
*watchdog
)
331 /* Only one device can register for /dev/watchdog */
332 if (test_and_set_bit(0, &watchdog_dev_busy
)) {
333 pr_err("only one watchdog can use /dev/watchdog.\n");
339 err
= misc_register(&watchdog_miscdev
);
341 pr_err("%s: cannot register miscdev on minor=%d (err=%d).\n",
342 watchdog
->info
->identity
, WATCHDOG_MINOR
, err
);
350 clear_bit(0, &watchdog_dev_busy
);
355 * watchdog_dev_unregister:
356 * @watchdog: watchdog device
358 * Deregister the /dev/watchdog device.
361 int watchdog_dev_unregister(struct watchdog_device
*watchdog
)
363 /* Check that a watchdog device was registered in the past */
364 if (!test_bit(0, &watchdog_dev_busy
) || !wdd
)
367 /* We can only unregister the watchdog device that was registered */
368 if (watchdog
!= wdd
) {
369 pr_err("%s: watchdog was not registered as /dev/watchdog.\n",
370 watchdog
->info
->identity
);
374 misc_deregister(&watchdog_miscdev
);
376 clear_bit(0, &watchdog_dev_busy
);