[deliverable/linux.git] / drivers / watchdog / watchdog_dev.c

/*
 *	watchdog_dev.c
 *
 *	(c) Copyright 2008-2011 Alan Cox <alan@lxorguk.ukuu.org.uk>,
 *						All Rights Reserved.
 *
 *	(c) Copyright 2008-2011 Wim Van Sebroeck <wim@iguana.be>.
 *
 *
 *	This source code is part of the generic code that can be used
 *	by all the watchdog timer drivers.
 *
 *	This part of the generic code takes care of the following
 *	misc device: /dev/watchdog.
 *
 *	Based on source code of the following authors:
 *	  Matt Domsch <Matt_Domsch@dell.com>,
 *	  Rob Radez <rob@osinvestor.com>,
 *	  Rusty Lynch <rusty@linux.co.intel.com>
 *	  Satyam Sharma <satyam@infradead.org>
 *	  Randy Dunlap <randy.dunlap@oracle.com>
 *
 *	This program is free software; you can redistribute it and/or
 *	modify it under the terms of the GNU General Public License
 *	as published by the Free Software Foundation; either version
 *	2 of the License, or (at your option) any later version.
 *
 *	Neither Alan Cox, CymruNet Ltd., Wim Van Sebroeck nor Iguana vzw.
 *	admit liability nor provide warranty for any of this software.
 *	This material is provided "AS-IS" and at no charge.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>	/* For module stuff/... */
#include <linux/types.h>	/* For standard types (like size_t) */
#include <linux/errno.h>	/* For the -ENODEV/... values */
#include <linux/kernel.h>	/* For printk/panic/... */
#include <linux/fs.h>		/* For file operations */
#include <linux/watchdog.h>	/* For watchdog specific items */
#include <linux/miscdevice.h>	/* For handling misc devices */
#include <linux/init.h>		/* For __init/__exit/... */
#include <linux/uaccess.h>	/* For copy_to_user/put_user/... */

#include "watchdog_core.h"

/* make sure we only register one /dev/watchdog device */
static unsigned long watchdog_dev_busy;
/* the watchdog device behind /dev/watchdog */
static struct watchdog_device *wdd;

/*
 *	watchdog_ping: ping the watchdog.
 *	@wddev: the watchdog device to ping
 *
 *	If the watchdog has no own ping operation then it needs to be
 *	restarted via the start operation. This wrapper function does
 *	exactly that.
 *	We only ping when the watchdog device is running.
 */

static int watchdog_ping(struct watchdog_device *wddev)
{
	if (watchdog_active(wddev)) {
		if (wddev->ops->ping)
			return wddev->ops->ping(wddev);  /* ping the watchdog */
		else
			return wddev->ops->start(wddev); /* restart watchdog */
	}
	return 0;
}

/*
 *	watchdog_start: wrapper to start the watchdog.
 *	@wddev: the watchdog device to start
 *
 *	Start the watchdog if it is not active and mark it active.
 *	This function returns zero on success or a negative errno code for
 *	failure.
 */

static int watchdog_start(struct watchdog_device *wddev)
{
	int err;

	if (!watchdog_active(wddev)) {
		err = wddev->ops->start(wddev);
		if (err < 0)
			return err;

		set_bit(WDOG_ACTIVE, &wddev->status);
	}
	return 0;
}

/*
 *	watchdog_stop: wrapper to stop the watchdog.
 *	@wddev: the watchdog device to stop
 *
 *	Stop the watchdog if it is still active and unmark it active.
 *	This function returns zero on success or a negative errno code for
 *	failure.
 *	If the 'nowayout' feature was set, the watchdog cannot be stopped.
 */

static int watchdog_stop(struct watchdog_device *wddev)
{
	int err = -EBUSY;

	if (test_bit(WDOG_NO_WAY_OUT, &wddev->status)) {
		pr_info("%s: nowayout prevents watchdog to be stopped!\n",
							wddev->info->identity);
		return err;
	}

	if (watchdog_active(wddev)) {
		err = wddev->ops->stop(wddev);
		if (err < 0)
			return err;

		clear_bit(WDOG_ACTIVE, &wddev->status);
	}
	return 0;
}

/*
 *	watchdog_write: writes to the watchdog.
 *	@file: file from VFS
 *	@data: user address of data
 *	@len: length of data
 *	@ppos: pointer to the file offset
 *
 *	A write to a watchdog device is defined as a keepalive ping.
 *	Writing the magic 'V' sequence allows the next close to turn
 *	off the watchdog (if 'nowayout' is not set).
 */

static ssize_t watchdog_write(struct file *file, const char __user *data,
						size_t len, loff_t *ppos)
{
	size_t i;
	char c;

	if (len == 0)
		return 0;

	/*
	 * Note: just in case someone wrote the magic character
	 * five months ago...
	 */
	clear_bit(WDOG_ALLOW_RELEASE, &wdd->status);

	/* scan to see whether or not we got the magic character */
	for (i = 0; i != len; i++) {
		if (get_user(c, data + i))
			return -EFAULT;
		if (c == 'V')
			set_bit(WDOG_ALLOW_RELEASE, &wdd->status);
	}

	/* someone wrote to us, so we send the watchdog a keepalive ping */
	watchdog_ping(wdd);

	return len;
}

/*
 *	watchdog_ioctl: handle the different ioctl's for the watchdog device.
 *	@file: file handle to the device
 *	@cmd: watchdog command
 *	@arg: argument pointer
 *
 *	The watchdog API defines a common set of functions for all watchdogs
 *	according to their available features.
 */

static long watchdog_ioctl(struct file *file, unsigned int cmd,
							unsigned long arg)
{
	void __user *argp = (void __user *)arg;
	int __user *p = argp;
	unsigned int val;
	int err;

	if (wdd->ops->ioctl) {
		err = wdd->ops->ioctl(wdd, cmd, arg);
		if (err != -ENOIOCTLCMD)
			return err;
	}

	switch (cmd) {
	case WDIOC_GETSUPPORT:
		return copy_to_user(argp, wdd->info,
			sizeof(struct watchdog_info)) ? -EFAULT : 0;
	case WDIOC_GETSTATUS:
		val = wdd->ops->status ? wdd->ops->status(wdd) : 0;
		return put_user(val, p);
	case WDIOC_GETBOOTSTATUS:
		return put_user(wdd->bootstatus, p);
	case WDIOC_SETOPTIONS:
		if (get_user(val, p))
			return -EFAULT;
		if (val & WDIOS_DISABLECARD) {
			err = watchdog_stop(wdd);
			if (err < 0)
				return err;
		}
		if (val & WDIOS_ENABLECARD) {
			err = watchdog_start(wdd);
			if (err < 0)
				return err;
		}
		return 0;
	case WDIOC_KEEPALIVE:
		if (!(wdd->info->options & WDIOF_KEEPALIVEPING))
			return -EOPNOTSUPP;
		watchdog_ping(wdd);
		return 0;
	case WDIOC_SETTIMEOUT:
		if ((wdd->ops->set_timeout == NULL) ||
		    !(wdd->info->options & WDIOF_SETTIMEOUT))
			return -EOPNOTSUPP;
		if (get_user(val, p))
			return -EFAULT;
		if ((wdd->max_timeout != 0) &&
		    (val < wdd->min_timeout || val > wdd->max_timeout))
				return -EINVAL;
		err = wdd->ops->set_timeout(wdd, val);
		if (err < 0)
			return err;
		/* If the watchdog is active then we send a keepalive ping
		 * to make sure that the watchdog keep's running (and if
		 * possible that it takes the new timeout) */
		watchdog_ping(wdd);
		/* Fall */
	case WDIOC_GETTIMEOUT:
		/* timeout == 0 means that we don't know the timeout */
		if (wdd->timeout == 0)
			return -EOPNOTSUPP;
		return put_user(wdd->timeout, p);
	case WDIOC_GETTIMELEFT:
		if (!wdd->ops->get_timeleft)
			return -EOPNOTSUPP;

		return put_user(wdd->ops->get_timeleft(wdd), p);
	default:
		return -ENOTTY;
	}
}

/*
 *	watchdog_open: open the /dev/watchdog device.
 *	@inode: inode of device
 *	@file: file handle to device
 *
 *	When the /dev/watchdog device gets opened, we start the watchdog.
 *	Watch out: the /dev/watchdog device is single open, so we make sure
 *	it can only be opened once.
 */

static int watchdog_open(struct inode *inode, struct file *file)
{
	int err = -EBUSY;

	/* the watchdog is single open! */
	if (test_and_set_bit(WDOG_DEV_OPEN, &wdd->status))
		return -EBUSY;

	/*
	 * If the /dev/watchdog device is open, we don't want the module
	 * to be unloaded.
	 */
	if (!try_module_get(wdd->ops->owner))
		goto out;

	err = watchdog_start(wdd);
	if (err < 0)
		goto out_mod;

	/* dev/watchdog is a virtual (and thus non-seekable) filesystem */
	return nonseekable_open(inode, file);

out_mod:
	module_put(wdd->ops->owner);
out:
	clear_bit(WDOG_DEV_OPEN, &wdd->status);
	return err;
}

/*
 *      watchdog_release: release the /dev/watchdog device.
 *      @inode: inode of device
 *      @file: file handle to device
 *
 *	This is the code for when /dev/watchdog gets closed. We will only
 *	stop the watchdog when we have received the magic char (and nowayout
 *	was not set), else the watchdog will keep running.
 */

static int watchdog_release(struct inode *inode, struct file *file)
{
	int err = -EBUSY;

	/*
	 * We only stop the watchdog if we received the magic character
	 * or if WDIOF_MAGICCLOSE is not set. If nowayout was set then
	 * watchdog_stop will fail.
	 */
	if (test_and_clear_bit(WDOG_ALLOW_RELEASE, &wdd->status) ||
	    !(wdd->info->options & WDIOF_MAGICCLOSE))
		err = watchdog_stop(wdd);

	/* If the watchdog was not stopped, send a keepalive ping */
	if (err < 0) {
		pr_crit("%s: watchdog did not stop!\n", wdd->info->identity);
		watchdog_ping(wdd);
	}

	/* Allow the owner module to be unloaded again */
	module_put(wdd->ops->owner);

	/* make sure that /dev/watchdog can be re-opened */
	clear_bit(WDOG_DEV_OPEN, &wdd->status);

	return 0;
}

static const struct file_operations watchdog_fops = {
	.owner		= THIS_MODULE,
	.write		= watchdog_write,
	.unlocked_ioctl	= watchdog_ioctl,
	.open		= watchdog_open,
	.release	= watchdog_release,
};

static struct miscdevice watchdog_miscdev = {
	.minor		= WATCHDOG_MINOR,
	.name		= "watchdog",
	.fops		= &watchdog_fops,
};

/*
 *	watchdog_dev_register:
 *	@watchdog: watchdog device
 *
 *	Register a watchdog device as /dev/watchdog. /dev/watchdog
 *	is actually a miscdevice and thus we set it up like that.
 */

int watchdog_dev_register(struct watchdog_device *watchdog)
{
	int err;

	/* Only one device can register for /dev/watchdog */
	if (test_and_set_bit(0, &watchdog_dev_busy)) {
		pr_err("only one watchdog can use /dev/watchdog\n");
		return -EBUSY;
	}

	wdd = watchdog;

	err = misc_register(&watchdog_miscdev);
	if (err != 0) {
		pr_err("%s: cannot register miscdev on minor=%d (err=%d)\n",
		       watchdog->info->identity, WATCHDOG_MINOR, err);
		goto out;
	}

	return 0;

out:
	wdd = NULL;
	clear_bit(0, &watchdog_dev_busy);
	return err;
}

/*
 *	watchdog_dev_unregister:
 *	@watchdog: watchdog device
 *
 *	Deregister the /dev/watchdog device.
 */

int watchdog_dev_unregister(struct watchdog_device *watchdog)
{
	/* Check that a watchdog device was registered in the past */
	if (!test_bit(0, &watchdog_dev_busy) || !wdd)
		return -ENODEV;

	/* We can only unregister the watchdog device that was registered */
	if (watchdog != wdd) {
		pr_err("%s: watchdog was not registered as /dev/watchdog\n",
		       watchdog->info->identity);
		return -ENODEV;
	}

	misc_deregister(&watchdog_miscdev);
	wdd = NULL;
	clear_bit(0, &watchdog_dev_busy);
	return 0;
}
Commit	Line	Data
43316044 WVS	1	/*
	2	* watchdog_dev.c
	3	*
	4	* (c) Copyright 2008-2011 Alan Cox <alan@lxorguk.ukuu.org.uk>,
	5	* All Rights Reserved.
	6	*
	7	* (c) Copyright 2008-2011 Wim Van Sebroeck <wim@iguana.be>.
	8	*
	9	*
	10	* This source code is part of the generic code that can be used
	11	* by all the watchdog timer drivers.
	12	*
	13	* This part of the generic code takes care of the following
	14	* misc device: /dev/watchdog.
	15	*
	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>
	22	*
	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.
	27	*
	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.
	31	*/
	32
	33	#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
	34
	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/... */
	44
6cfb5aa8	45	#include "watchdog_core.h"
09a46e73	46
43316044 WVS	47	/* make sure we only register one /dev/watchdog device */
	48	static unsigned long watchdog_dev_busy;
	49	/* the watchdog device behind /dev/watchdog */
	50	static struct watchdog_device *wdd;
	51
	52	/*
	53	* watchdog_ping: ping the watchdog.
	54	* @wddev: the watchdog device to ping
	55	*
	56	* If the watchdog has no own ping operation then it needs to be
	57	* restarted via the start operation. This wrapper function does
	58	* exactly that.
234445b4	59	* We only ping when the watchdog device is running.
43316044 WVS	60	*/
	61
	62	static int watchdog_ping(struct watchdog_device *wddev)
	63	{
257f8c4a	64	if (watchdog_active(wddev)) {
234445b4 WVS	65	if (wddev->ops->ping)
	66	return wddev->ops->ping(wddev); /* ping the watchdog */
	67	else
	68	return wddev->ops->start(wddev); /* restart watchdog */
	69	}
	70	return 0;
	71	}
	72
	73	/*
	74	* watchdog_start: wrapper to start the watchdog.
	75	* @wddev: the watchdog device to start
	76	*
	77	* Start the watchdog if it is not active and mark it active.
	78	* This function returns zero on success or a negative errno code for
	79	* failure.
	80	*/
	81
	82	static int watchdog_start(struct watchdog_device *wddev)
	83	{
	84	int err;
	85
257f8c4a	86	if (!watchdog_active(wddev)) {
234445b4 WVS	87	err = wddev->ops->start(wddev);
	88	if (err < 0)
	89	return err;
	90
cb7efc02	91	set_bit(WDOG_ACTIVE, &wddev->status);
234445b4 WVS	92	}
	93	return 0;
	94	}
	95
	96	/*
	97	* watchdog_stop: wrapper to stop the watchdog.
	98	* @wddev: the watchdog device to stop
	99	*
	100	* Stop the watchdog if it is still active and unmark it active.
	101	* This function returns zero on success or a negative errno code for
	102	* failure.
7e192b9c	103	* If the 'nowayout' feature was set, the watchdog cannot be stopped.
234445b4 WVS	104	*/
	105
	106	static int watchdog_stop(struct watchdog_device *wddev)
	107	{
7e192b9c WVS	108	int err = -EBUSY;
7e192b9c WVS	109
cb7efc02	110	if (test_bit(WDOG_NO_WAY_OUT, &wddev->status)) {
7e192b9c	111	pr_info("%s: nowayout prevents watchdog to be stopped!\n",
cb7efc02	112	wddev->info->identity);
7e192b9c WVS	113	return err;
7e192b9c WVS	114	}
234445b4	115
257f8c4a	116	if (watchdog_active(wddev)) {
234445b4 WVS	117	err = wddev->ops->stop(wddev);
	118	if (err < 0)
	119	return err;
	120
cb7efc02	121	clear_bit(WDOG_ACTIVE, &wddev->status);
234445b4 WVS	122	}
234445b4 WVS	123	return 0;
43316044 WVS	124	}
	125
	126	/*
	127	* watchdog_write: writes to the watchdog.
	128	* @file: file from VFS
	129	* @data: user address of data
	130	* @len: length of data
	131	* @ppos: pointer to the file offset
	132	*
	133	* A write to a watchdog device is defined as a keepalive ping.
017cf080	134	* Writing the magic 'V' sequence allows the next close to turn
7e192b9c	135	* off the watchdog (if 'nowayout' is not set).
43316044 WVS	136	*/
	137
	138	static ssize_t watchdog_write(struct file file, const char __user data,
	139	size_t len, loff_t *ppos)
	140	{
	141	size_t i;
	142	char c;
	143
	144	if (len == 0)
	145	return 0;
	146
017cf080 WVS	147	/*
	148	* Note: just in case someone wrote the magic character
	149	* five months ago...
	150	*/
	151	clear_bit(WDOG_ALLOW_RELEASE, &wdd->status);
	152
	153	/* scan to see whether or not we got the magic character */
43316044 WVS	154	for (i = 0; i != len; i++) {
	155	if (get_user(c, data + i))
	156	return -EFAULT;
017cf080 WVS	157	if (c == 'V')
017cf080 WVS	158	set_bit(WDOG_ALLOW_RELEASE, &wdd->status);
43316044 WVS	159	}
	160
	161	/* someone wrote to us, so we send the watchdog a keepalive ping */
	162	watchdog_ping(wdd);
	163
	164	return len;
	165	}
	166
2fa03560 WVS	167	/*
	168	* watchdog_ioctl: handle the different ioctl's for the watchdog device.
	169	* @file: file handle to the device
	170	* @cmd: watchdog command
	171	* @arg: argument pointer
	172	*
	173	* The watchdog API defines a common set of functions for all watchdogs
	174	* according to their available features.
	175	*/
	176
	177	static long watchdog_ioctl(struct file *file, unsigned int cmd,
	178	unsigned long arg)
	179	{
	180	void __user argp = (void __user )arg;
	181	int __user *p = argp;
	182	unsigned int val;
234445b4	183	int err;
2fa03560	184
78d88fc0 WVS	185	if (wdd->ops->ioctl) {
	186	err = wdd->ops->ioctl(wdd, cmd, arg);
	187	if (err != -ENOIOCTLCMD)
	188	return err;
	189	}
	190
2fa03560 WVS	191	switch (cmd) {
	192	case WDIOC_GETSUPPORT:
	193	return copy_to_user(argp, wdd->info,
	194	sizeof(struct watchdog_info)) ? -EFAULT : 0;
	195	case WDIOC_GETSTATUS:
	196	val = wdd->ops->status ? wdd->ops->status(wdd) : 0;
	197	return put_user(val, p);
	198	case WDIOC_GETBOOTSTATUS:
	199	return put_user(wdd->bootstatus, p);
234445b4 WVS	200	case WDIOC_SETOPTIONS:
	201	if (get_user(val, p))
	202	return -EFAULT;
	203	if (val & WDIOS_DISABLECARD) {
	204	err = watchdog_stop(wdd);
	205	if (err < 0)
	206	return err;
	207	}
	208	if (val & WDIOS_ENABLECARD) {
	209	err = watchdog_start(wdd);
	210	if (err < 0)
	211	return err;
	212	}
	213	return 0;
c2dc00e4 WVS	214	case WDIOC_KEEPALIVE:
	215	if (!(wdd->info->options & WDIOF_KEEPALIVEPING))
	216	return -EOPNOTSUPP;
	217	watchdog_ping(wdd);
	218	return 0;
014d694e WVS	219	case WDIOC_SETTIMEOUT:
	220	if ((wdd->ops->set_timeout == NULL) \|\|
	221	!(wdd->info->options & WDIOF_SETTIMEOUT))
	222	return -EOPNOTSUPP;
	223	if (get_user(val, p))
	224	return -EFAULT;
3f43f68e WVS	225	if ((wdd->max_timeout != 0) &&
	226	(val < wdd->min_timeout \|\| val > wdd->max_timeout))
	227	return -EINVAL;
014d694e WVS	228	err = wdd->ops->set_timeout(wdd, val);
	229	if (err < 0)
	230	return err;
014d694e WVS	231	/* If the watchdog is active then we send a keepalive ping
	232	* to make sure that the watchdog keep's running (and if
	233	* possible that it takes the new timeout) */
	234	watchdog_ping(wdd);
	235	/* Fall */
	236	case WDIOC_GETTIMEOUT:
	237	/* timeout == 0 means that we don't know the timeout */
	238	if (wdd->timeout == 0)
	239	return -EOPNOTSUPP;
	240	return put_user(wdd->timeout, p);
fd7b673c VK	241	case WDIOC_GETTIMELEFT:
	242	if (!wdd->ops->get_timeleft)
	243	return -EOPNOTSUPP;
	244
	245	return put_user(wdd->ops->get_timeleft(wdd), p);
2fa03560 WVS	246	default:
	247	return -ENOTTY;
	248	}
	249	}
	250
43316044 WVS	251	/*
	252	* watchdog_open: open the /dev/watchdog device.
	253	* @inode: inode of device
	254	* @file: file handle to device
	255	*
	256	* When the /dev/watchdog device gets opened, we start the watchdog.
	257	* Watch out: the /dev/watchdog device is single open, so we make sure
	258	* it can only be opened once.
	259	*/
	260
	261	static int watchdog_open(struct inode inode, struct file file)
	262	{
	263	int err = -EBUSY;
	264
	265	/* the watchdog is single open! */
	266	if (test_and_set_bit(WDOG_DEV_OPEN, &wdd->status))
	267	return -EBUSY;
	268
	269	/*
	270	* If the /dev/watchdog device is open, we don't want the module
	271	* to be unloaded.
	272	*/
	273	if (!try_module_get(wdd->ops->owner))
	274	goto out;
	275
234445b4	276	err = watchdog_start(wdd);
43316044 WVS	277	if (err < 0)
	278	goto out_mod;
	279
	280	/* dev/watchdog is a virtual (and thus non-seekable) filesystem */
	281	return nonseekable_open(inode, file);
	282
	283	out_mod:
	284	module_put(wdd->ops->owner);
	285	out:
	286	clear_bit(WDOG_DEV_OPEN, &wdd->status);
	287	return err;
	288	}
	289
	290	/*
	291	* watchdog_release: release the /dev/watchdog device.
	292	* @inode: inode of device
	293	* @file: file handle to device
	294	*
017cf080	295	* This is the code for when /dev/watchdog gets closed. We will only
7e192b9c WVS	296	* stop the watchdog when we have received the magic char (and nowayout
7e192b9c WVS	297	* was not set), else the watchdog will keep running.
43316044 WVS	298	*/
	299
	300	static int watchdog_release(struct inode inode, struct file file)
	301	{
017cf080 WVS	302	int err = -EBUSY;
	303
	304	/*
	305	* We only stop the watchdog if we received the magic character
7e192b9c WVS	306	* or if WDIOF_MAGICCLOSE is not set. If nowayout was set then
7e192b9c WVS	307	* watchdog_stop will fail.
017cf080 WVS	308	*/
	309	if (test_and_clear_bit(WDOG_ALLOW_RELEASE, &wdd->status) \|\|
	310	!(wdd->info->options & WDIOF_MAGICCLOSE))
	311	err = watchdog_stop(wdd);
43316044	312
017cf080	313	/* If the watchdog was not stopped, send a keepalive ping */
234445b4	314	if (err < 0) {
43316044 WVS	315	pr_crit("%s: watchdog did not stop!\n", wdd->info->identity);
	316	watchdog_ping(wdd);
	317	}
	318
	319	/* Allow the owner module to be unloaded again */
	320	module_put(wdd->ops->owner);
	321
	322	/* make sure that /dev/watchdog can be re-opened */
	323	clear_bit(WDOG_DEV_OPEN, &wdd->status);
	324
	325	return 0;
	326	}
	327
	328	static const struct file_operations watchdog_fops = {
	329	.owner = THIS_MODULE,
	330	.write = watchdog_write,
2fa03560	331	.unlocked_ioctl = watchdog_ioctl,
43316044 WVS	332	.open = watchdog_open,
	333	.release = watchdog_release,
	334	};
	335
	336	static struct miscdevice watchdog_miscdev = {
	337	.minor = WATCHDOG_MINOR,
	338	.name = "watchdog",
	339	.fops = &watchdog_fops,
	340	};
	341
	342	/*
	343	* watchdog_dev_register:
	344	* @watchdog: watchdog device
	345	*
	346	* Register a watchdog device as /dev/watchdog. /dev/watchdog
	347	* is actually a miscdevice and thus we set it up like that.
	348	*/
	349
	350	int watchdog_dev_register(struct watchdog_device *watchdog)
	351	{
	352	int err;
	353
	354	/* Only one device can register for /dev/watchdog */
	355	if (test_and_set_bit(0, &watchdog_dev_busy)) {
27c766aa	356	pr_err("only one watchdog can use /dev/watchdog\n");
43316044 WVS	357	return -EBUSY;
	358	}
	359
	360	wdd = watchdog;
	361
	362	err = misc_register(&watchdog_miscdev);
	363	if (err != 0) {
27c766aa JP	364	pr_err("%s: cannot register miscdev on minor=%d (err=%d)\n",
27c766aa JP	365	watchdog->info->identity, WATCHDOG_MINOR, err);
43316044 WVS	366	goto out;
	367	}
	368
	369	return 0;
	370
	371	out:
	372	wdd = NULL;
	373	clear_bit(0, &watchdog_dev_busy);
	374	return err;
	375	}
	376
	377	/*
	378	* watchdog_dev_unregister:
	379	* @watchdog: watchdog device
	380	*
	381	* Deregister the /dev/watchdog device.
	382	*/
	383
	384	int watchdog_dev_unregister(struct watchdog_device *watchdog)
	385	{
	386	/* Check that a watchdog device was registered in the past */
	387	if (!test_bit(0, &watchdog_dev_busy) \|\| !wdd)
	388	return -ENODEV;
	389
	390	/* We can only unregister the watchdog device that was registered */
	391	if (watchdog != wdd) {
27c766aa JP	392	pr_err("%s: watchdog was not registered as /dev/watchdog\n",
27c766aa JP	393	watchdog->info->identity);
43316044 WVS	394	return -ENODEV;
	395	}
	396
	397	misc_deregister(&watchdog_miscdev);
	398	wdd = NULL;
	399	clear_bit(0, &watchdog_dev_busy);
	400	return 0;
	401	}