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

/*
 *	watchdog_core.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.
 *
 *	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 EXPORT_SYMBOL/module stuff/... */
#include <linux/types.h>	/* For standard types */
#include <linux/errno.h>	/* For the -ENODEV/... values */
#include <linux/kernel.h>	/* For printk/panic/... */
#include <linux/reboot.h>	/* For restart handler */
#include <linux/watchdog.h>	/* For watchdog specific items */
#include <linux/init.h>		/* For __init/__exit/... */
#include <linux/idr.h>		/* For ida_* macros */
#include <linux/err.h>		/* For IS_ERR macros */
#include <linux/of.h>		/* For of_get_timeout_sec */

#include "watchdog_core.h"	/* For watchdog_dev_register/... */

static DEFINE_IDA(watchdog_ida);
static struct class *watchdog_class;

/*
 * Deferred Registration infrastructure.
 *
 * Sometimes watchdog drivers needs to be loaded as soon as possible,
 * for example when it's impossible to disable it. To do so,
 * raising the initcall level of the watchdog driver is a solution.
 * But in such case, the miscdev is maybe not ready (subsys_initcall), and
 * watchdog_core need miscdev to register the watchdog as a char device.
 *
 * The deferred registration infrastructure offer a way for the watchdog
 * subsystem to register a watchdog properly, even before miscdev is ready.
 */

static DEFINE_MUTEX(wtd_deferred_reg_mutex);
static LIST_HEAD(wtd_deferred_reg_list);
static bool wtd_deferred_reg_done;

static int watchdog_deferred_registration_add(struct watchdog_device *wdd)
{
	list_add_tail(&wdd->deferred,
		      &wtd_deferred_reg_list);
	return 0;
}

static void watchdog_deferred_registration_del(struct watchdog_device *wdd)
{
	struct list_head *p, *n;
	struct watchdog_device *wdd_tmp;

	list_for_each_safe(p, n, &wtd_deferred_reg_list) {
		wdd_tmp = list_entry(p, struct watchdog_device,
				     deferred);
		if (wdd_tmp == wdd) {
			list_del(&wdd_tmp->deferred);
			break;
		}
	}
}

static void watchdog_check_min_max_timeout(struct watchdog_device *wdd)
{
	/*
	 * Check that we have valid min and max timeout values, if
	 * not reset them both to 0 (=not used or unknown)
	 */
	if (wdd->min_timeout > wdd->max_timeout) {
		pr_info("Invalid min and max timeout values, resetting to 0!\n");
		wdd->min_timeout = 0;
		wdd->max_timeout = 0;
	}
}

/**
 * watchdog_init_timeout() - initialize the timeout field
 * @timeout_parm: timeout module parameter
 * @dev: Device that stores the timeout-sec property
 *
 * Initialize the timeout field of the watchdog_device struct with either the
 * timeout module parameter (if it is valid value) or the timeout-sec property
 * (only if it is a valid value and the timeout_parm is out of bounds).
 * If none of them are valid then we keep the old value (which should normally
 * be the default timeout value.
 *
 * A zero is returned on success and -EINVAL for failure.
 */
int watchdog_init_timeout(struct watchdog_device *wdd,
				unsigned int timeout_parm, struct device *dev)
{
	unsigned int t = 0;
	int ret = 0;

	watchdog_check_min_max_timeout(wdd);

	/* try to get the timeout module parameter first */
	if (!watchdog_timeout_invalid(wdd, timeout_parm) && timeout_parm) {
		wdd->timeout = timeout_parm;
		return ret;
	}
	if (timeout_parm)
		ret = -EINVAL;

	/* try to get the timeout_sec property */
	if (dev == NULL || dev->of_node == NULL)
		return ret;
	of_property_read_u32(dev->of_node, "timeout-sec", &t);
	if (!watchdog_timeout_invalid(wdd, t) && t)
		wdd->timeout = t;
	else
		ret = -EINVAL;

	return ret;
}
EXPORT_SYMBOL_GPL(watchdog_init_timeout);

static int watchdog_reboot_notifier(struct notifier_block *nb,
				    unsigned long code, void *data)
{
	struct watchdog_device *wdd = container_of(nb, struct watchdog_device,
						   reboot_nb);

	if (code == SYS_DOWN || code == SYS_HALT) {
		if (watchdog_active(wdd)) {
			int ret;

			ret = wdd->ops->stop(wdd);
			if (ret)
				return NOTIFY_BAD;
		}
	}

	return NOTIFY_DONE;
}

static int watchdog_restart_notifier(struct notifier_block *nb,
				     unsigned long action, void *data)
{
	struct watchdog_device *wdd = container_of(nb, struct watchdog_device,
						   restart_nb);

	int ret;

	ret = wdd->ops->restart(wdd);
	if (ret)
		return NOTIFY_BAD;

	return NOTIFY_DONE;
}

/**
 * watchdog_set_restart_priority - Change priority of restart handler
 * @wdd: watchdog device
 * @priority: priority of the restart handler, should follow these guidelines:
 *   0:   use watchdog's restart function as last resort, has limited restart
 *        capabilies
 *   128: default restart handler, use if no other handler is expected to be
 *        available and/or if restart is sufficient to restart the entire system
 *   255: preempt all other handlers
 *
 * If a wdd->ops->restart function is provided when watchdog_register_device is
 * called, it will be registered as a restart handler with the priority given
 * here.
 */
void watchdog_set_restart_priority(struct watchdog_device *wdd, int priority)
{
	wdd->restart_nb.priority = priority;
}
EXPORT_SYMBOL_GPL(watchdog_set_restart_priority);

static int __watchdog_register_device(struct watchdog_device *wdd)
{
	int ret, id = -1, devno;

	if (wdd == NULL || wdd->info == NULL || wdd->ops == NULL)
		return -EINVAL;

	/* Mandatory operations need to be supported */
	if (wdd->ops->start == NULL || wdd->ops->stop == NULL)
		return -EINVAL;

	watchdog_check_min_max_timeout(wdd);

	/*
	 * Note: now that all watchdog_device data has been verified, we
	 * will not check this anymore in other functions. If data gets
	 * corrupted in a later stage then we expect a kernel panic!
	 */

	mutex_init(&wdd->lock);

	/* Use alias for watchdog id if possible */
	if (wdd->parent) {
		ret = of_alias_get_id(wdd->parent->of_node, "watchdog");
		if (ret >= 0)
			id = ida_simple_get(&watchdog_ida, ret,
					    ret + 1, GFP_KERNEL);
	}

	if (id < 0)
		id = ida_simple_get(&watchdog_ida, 0, MAX_DOGS, GFP_KERNEL);

	if (id < 0)
		return id;
	wdd->id = id;

	ret = watchdog_dev_register(wdd);
	if (ret) {
		ida_simple_remove(&watchdog_ida, id);
		if (!(id == 0 && ret == -EBUSY))
			return ret;

		/* Retry in case a legacy watchdog module exists */
		id = ida_simple_get(&watchdog_ida, 1, MAX_DOGS, GFP_KERNEL);
		if (id < 0)
			return id;
		wdd->id = id;

		ret = watchdog_dev_register(wdd);
		if (ret) {
			ida_simple_remove(&watchdog_ida, id);
			return ret;
		}
	}

	devno = wdd->cdev.dev;
	wdd->dev = device_create(watchdog_class, wdd->parent, devno,
					wdd, "watchdog%d", wdd->id);
	if (IS_ERR(wdd->dev)) {
		watchdog_dev_unregister(wdd);
		ida_simple_remove(&watchdog_ida, id);
		ret = PTR_ERR(wdd->dev);
		return ret;
	}

	if (test_bit(WDOG_STOP_ON_REBOOT, &wdd->status)) {
		wdd->reboot_nb.notifier_call = watchdog_reboot_notifier;

		ret = register_reboot_notifier(&wdd->reboot_nb);
		if (ret) {
			dev_err(wdd->dev, "Cannot register reboot notifier (%d)\n",
				ret);
			watchdog_dev_unregister(wdd);
			device_destroy(watchdog_class, devno);
			ida_simple_remove(&watchdog_ida, wdd->id);
			wdd->dev = NULL;
			return ret;
		}
	}

	if (wdd->ops->restart) {
		wdd->restart_nb.notifier_call = watchdog_restart_notifier;

		ret = register_restart_handler(&wdd->restart_nb);
		if (ret)
			dev_warn(wdd->dev, "Cannot register restart handler (%d)\n",
				 ret);
	}

	return 0;
}

/**
 * watchdog_register_device() - register a watchdog device
 * @wdd: watchdog device
 *
 * Register a watchdog device with the kernel so that the
 * watchdog timer can be accessed from userspace.
 *
 * A zero is returned on success and a negative errno code for
 * failure.
 */

int watchdog_register_device(struct watchdog_device *wdd)
{
	int ret;

	mutex_lock(&wtd_deferred_reg_mutex);
	if (wtd_deferred_reg_done)
		ret = __watchdog_register_device(wdd);
	else
		ret = watchdog_deferred_registration_add(wdd);
	mutex_unlock(&wtd_deferred_reg_mutex);
	return ret;
}
EXPORT_SYMBOL_GPL(watchdog_register_device);

static void __watchdog_unregister_device(struct watchdog_device *wdd)
{
	int ret;
	int devno;

	if (wdd == NULL)
		return;

	if (wdd->ops->restart)
		unregister_restart_handler(&wdd->restart_nb);

	if (test_bit(WDOG_STOP_ON_REBOOT, &wdd->status))
		unregister_reboot_notifier(&wdd->reboot_nb);

	devno = wdd->cdev.dev;
	ret = watchdog_dev_unregister(wdd);
	if (ret)
		pr_err("error unregistering /dev/watchdog (err=%d)\n", ret);
	device_destroy(watchdog_class, devno);
	ida_simple_remove(&watchdog_ida, wdd->id);
	wdd->dev = NULL;
}

/**
 * watchdog_unregister_device() - unregister a watchdog device
 * @wdd: watchdog device to unregister
 *
 * Unregister a watchdog device that was previously successfully
 * registered with watchdog_register_device().
 */

void watchdog_unregister_device(struct watchdog_device *wdd)
{
	mutex_lock(&wtd_deferred_reg_mutex);
	if (wtd_deferred_reg_done)
		__watchdog_unregister_device(wdd);
	else
		watchdog_deferred_registration_del(wdd);
	mutex_unlock(&wtd_deferred_reg_mutex);
}

EXPORT_SYMBOL_GPL(watchdog_unregister_device);

static int __init watchdog_deferred_registration(void)
{
	mutex_lock(&wtd_deferred_reg_mutex);
	wtd_deferred_reg_done = true;
	while (!list_empty(&wtd_deferred_reg_list)) {
		struct watchdog_device *wdd;

		wdd = list_first_entry(&wtd_deferred_reg_list,
				       struct watchdog_device, deferred);
		list_del(&wdd->deferred);
		__watchdog_register_device(wdd);
	}
	mutex_unlock(&wtd_deferred_reg_mutex);
	return 0;
}

static int __init watchdog_init(void)
{
	watchdog_class = watchdog_dev_init();
	if (IS_ERR(watchdog_class))
		return PTR_ERR(watchdog_class);

	watchdog_deferred_registration();
	return 0;
}

static void __exit watchdog_exit(void)
{
	watchdog_dev_exit();
	ida_destroy(&watchdog_ida);
}

subsys_initcall_sync(watchdog_init);
module_exit(watchdog_exit);

MODULE_AUTHOR("Alan Cox <alan@lxorguk.ukuu.org.uk>");
MODULE_AUTHOR("Wim Van Sebroeck <wim@iguana.be>");
MODULE_DESCRIPTION("WatchDog Timer Driver Core");
MODULE_LICENSE("GPL");
Commit	Line	Data
43316044 WVS	1	/*
	2	* watchdog_core.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	* This source code is part of the generic code that can be used
	10	* by all the watchdog timer drivers.
	11	*
	12	* Based on source code of the following authors:
	13	* Matt Domsch <Matt_Domsch@dell.com>,
	14	* Rob Radez <rob@osinvestor.com>,
	15	* Rusty Lynch <rusty@linux.co.intel.com>
	16	* Satyam Sharma <satyam@infradead.org>
	17	* Randy Dunlap <randy.dunlap@oracle.com>
	18	*
	19	* This program is free software; you can redistribute it and/or
	20	* modify it under the terms of the GNU General Public License
	21	* as published by the Free Software Foundation; either version
	22	* 2 of the License, or (at your option) any later version.
	23	*
	24	* Neither Alan Cox, CymruNet Ltd., Wim Van Sebroeck nor Iguana vzw.
	25	* admit liability nor provide warranty for any of this software.
	26	* This material is provided "AS-IS" and at no charge.
	27	*/
	28
	29	#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
	30
	31	#include <linux/module.h> /* For EXPORT_SYMBOL/module stuff/... */
	32	#include <linux/types.h> /* For standard types */
	33	#include <linux/errno.h> /* For the -ENODEV/... values */
	34	#include <linux/kernel.h> /* For printk/panic/... */
2165bf52	35	#include <linux/reboot.h> /* For restart handler */
43316044 WVS	36	#include <linux/watchdog.h> /* For watchdog specific items */
43316044 WVS	37	#include <linux/init.h> /* For __init/__exit/... */
45f5fed3	38	#include <linux/idr.h> /* For ida_* macros */
d6b469d9	39	#include <linux/err.h> /* For IS_ERR macros */
3048253e	40	#include <linux/of.h> /* For of_get_timeout_sec */
43316044	41
6cfb5aa8	42	#include "watchdog_core.h" /* For watchdog_dev_register/... */
43316044	43
45f5fed3	44	static DEFINE_IDA(watchdog_ida);
d6b469d9	45	static struct class *watchdog_class;
45f5fed3	46
ef90174f JBT	47	/*
	48	* Deferred Registration infrastructure.
	49	*
	50	* Sometimes watchdog drivers needs to be loaded as soon as possible,
	51	* for example when it's impossible to disable it. To do so,
	52	* raising the initcall level of the watchdog driver is a solution.
	53	* But in such case, the miscdev is maybe not ready (subsys_initcall), and
	54	* watchdog_core need miscdev to register the watchdog as a char device.
	55	*
	56	* The deferred registration infrastructure offer a way for the watchdog
	57	* subsystem to register a watchdog properly, even before miscdev is ready.
	58	*/
	59
	60	static DEFINE_MUTEX(wtd_deferred_reg_mutex);
	61	static LIST_HEAD(wtd_deferred_reg_list);
	62	static bool wtd_deferred_reg_done;
	63
	64	static int watchdog_deferred_registration_add(struct watchdog_device *wdd)
	65	{
	66	list_add_tail(&wdd->deferred,
	67	&wtd_deferred_reg_list);
	68	return 0;
	69	}
	70
	71	static void watchdog_deferred_registration_del(struct watchdog_device *wdd)
	72	{
	73	struct list_head p, n;
	74	struct watchdog_device *wdd_tmp;
	75
	76	list_for_each_safe(p, n, &wtd_deferred_reg_list) {
	77	wdd_tmp = list_entry(p, struct watchdog_device,
	78	deferred);
	79	if (wdd_tmp == wdd) {
	80	list_del(&wdd_tmp->deferred);
	81	break;
	82	}
	83	}
	84	}
	85
3048253e FP	86	static void watchdog_check_min_max_timeout(struct watchdog_device *wdd)
	87	{
	88	/*
	89	* Check that we have valid min and max timeout values, if
	90	* not reset them both to 0 (=not used or unknown)
	91	*/
	92	if (wdd->min_timeout > wdd->max_timeout) {
	93	pr_info("Invalid min and max timeout values, resetting to 0!\n");
	94	wdd->min_timeout = 0;
	95	wdd->max_timeout = 0;
	96	}
	97	}
	98
	99	/**
	100	* watchdog_init_timeout() - initialize the timeout field
	101	* @timeout_parm: timeout module parameter
	102	* @dev: Device that stores the timeout-sec property
	103	*
	104	* Initialize the timeout field of the watchdog_device struct with either the
	105	* timeout module parameter (if it is valid value) or the timeout-sec property
	106	* (only if it is a valid value and the timeout_parm is out of bounds).
	107	* If none of them are valid then we keep the old value (which should normally
	108	* be the default timeout value.
	109	*
	110	* A zero is returned on success and -EINVAL for failure.
	111	*/
	112	int watchdog_init_timeout(struct watchdog_device *wdd,
	113	unsigned int timeout_parm, struct device *dev)
	114	{
	115	unsigned int t = 0;
	116	int ret = 0;
	117
	118	watchdog_check_min_max_timeout(wdd);
	119
6ffcff93	120	/* try to get the timeout module parameter first */
2c34d599	121	if (!watchdog_timeout_invalid(wdd, timeout_parm) && timeout_parm) {
3048253e FP	122	wdd->timeout = timeout_parm;
	123	return ret;
	124	}
	125	if (timeout_parm)
	126	ret = -EINVAL;
	127
	128	/* try to get the timeout_sec property */
	129	if (dev == NULL \|\| dev->of_node == NULL)
	130	return ret;
	131	of_property_read_u32(dev->of_node, "timeout-sec", &t);
2c34d599	132	if (!watchdog_timeout_invalid(wdd, t) && t)
3048253e FP	133	wdd->timeout = t;
	134	else
	135	ret = -EINVAL;
	136
	137	return ret;
	138	}
	139	EXPORT_SYMBOL_GPL(watchdog_init_timeout);
	140
e1313196 DR	141	static int watchdog_reboot_notifier(struct notifier_block *nb,
	142	unsigned long code, void *data)
	143	{
	144	struct watchdog_device *wdd = container_of(nb, struct watchdog_device,
	145	reboot_nb);
	146
	147	if (code == SYS_DOWN \|\| code == SYS_HALT) {
	148	if (watchdog_active(wdd)) {
	149	int ret;
	150
	151	ret = wdd->ops->stop(wdd);
	152	if (ret)
	153	return NOTIFY_BAD;
	154	}
	155	}
	156
	157	return NOTIFY_DONE;
	158	}
	159
2165bf52 DR	160	static int watchdog_restart_notifier(struct notifier_block *nb,
	161	unsigned long action, void *data)
	162	{
	163	struct watchdog_device *wdd = container_of(nb, struct watchdog_device,
	164	restart_nb);
	165
	166	int ret;
	167
	168	ret = wdd->ops->restart(wdd);
	169	if (ret)
	170	return NOTIFY_BAD;
	171
	172	return NOTIFY_DONE;
	173	}
	174
	175	/**
	176	* watchdog_set_restart_priority - Change priority of restart handler
	177	* @wdd: watchdog device
	178	* @priority: priority of the restart handler, should follow these guidelines:
	179	* 0: use watchdog's restart function as last resort, has limited restart
	180	* capabilies
	181	* 128: default restart handler, use if no other handler is expected to be
	182	* available and/or if restart is sufficient to restart the entire system
	183	* 255: preempt all other handlers
	184	*
	185	* If a wdd->ops->restart function is provided when watchdog_register_device is
	186	* called, it will be registered as a restart handler with the priority given
	187	* here.
	188	*/
	189	void watchdog_set_restart_priority(struct watchdog_device *wdd, int priority)
	190	{
	191	wdd->restart_nb.priority = priority;
	192	}
	193	EXPORT_SYMBOL_GPL(watchdog_set_restart_priority);
	194
ef90174f	195	static int __watchdog_register_device(struct watchdog_device *wdd)
43316044	196	{
9dd4e173	197	int ret, id = -1, devno;
43316044 WVS	198
	199	if (wdd == NULL \|\| wdd->info == NULL \|\| wdd->ops == NULL)
	200	return -EINVAL;
	201
	202	/* Mandatory operations need to be supported */
	203	if (wdd->ops->start == NULL \|\| wdd->ops->stop == NULL)
	204	return -EINVAL;
	205
3048253e	206	watchdog_check_min_max_timeout(wdd);
3f43f68e	207
43316044 WVS	208	/*
	209	* Note: now that all watchdog_device data has been verified, we
	210	* will not check this anymore in other functions. If data gets
	211	* corrupted in a later stage then we expect a kernel panic!
	212	*/
	213
f4e9c82f	214	mutex_init(&wdd->lock);
9dd4e173 JC	215
	216	/* Use alias for watchdog id if possible */
	217	if (wdd->parent) {
	218	ret = of_alias_get_id(wdd->parent->of_node, "watchdog");
	219	if (ret >= 0)
	220	id = ida_simple_get(&watchdog_ida, ret,
	221	ret + 1, GFP_KERNEL);
	222	}
	223
	224	if (id < 0)
	225	id = ida_simple_get(&watchdog_ida, 0, MAX_DOGS, GFP_KERNEL);
	226
45f5fed3 AC	227	if (id < 0)
	228	return id;
	229	wdd->id = id;
	230
43316044 WVS	231	ret = watchdog_dev_register(wdd);
43316044 WVS	232	if (ret) {
45f5fed3 AC	233	ida_simple_remove(&watchdog_ida, id);
	234	if (!(id == 0 && ret == -EBUSY))
	235	return ret;
	236
	237	/* Retry in case a legacy watchdog module exists */
	238	id = ida_simple_get(&watchdog_ida, 1, MAX_DOGS, GFP_KERNEL);
	239	if (id < 0)
	240	return id;
	241	wdd->id = id;
	242
	243	ret = watchdog_dev_register(wdd);
	244	if (ret) {
	245	ida_simple_remove(&watchdog_ida, id);
	246	return ret;
	247	}
43316044 WVS	248	}
43316044 WVS	249
d6b469d9 AC	250	devno = wdd->cdev.dev;
d6b469d9 AC	251	wdd->dev = device_create(watchdog_class, wdd->parent, devno,
33b71126	252	wdd, "watchdog%d", wdd->id);
d6b469d9 AC	253	if (IS_ERR(wdd->dev)) {
	254	watchdog_dev_unregister(wdd);
	255	ida_simple_remove(&watchdog_ida, id);
	256	ret = PTR_ERR(wdd->dev);
	257	return ret;
	258	}
	259
e1313196 DR	260	if (test_bit(WDOG_STOP_ON_REBOOT, &wdd->status)) {
	261	wdd->reboot_nb.notifier_call = watchdog_reboot_notifier;
	262
	263	ret = register_reboot_notifier(&wdd->reboot_nb);
	264	if (ret) {
	265	dev_err(wdd->dev, "Cannot register reboot notifier (%d)\n",
	266	ret);
	267	watchdog_dev_unregister(wdd);
	268	device_destroy(watchdog_class, devno);
	269	ida_simple_remove(&watchdog_ida, wdd->id);
	270	wdd->dev = NULL;
	271	return ret;
	272	}
	273	}
	274
2165bf52 DR	275	if (wdd->ops->restart) {
	276	wdd->restart_nb.notifier_call = watchdog_restart_notifier;
	277
	278	ret = register_restart_handler(&wdd->restart_nb);
	279	if (ret)
	280	dev_warn(wdd->dev, "Cannot register restart handler (%d)\n",
	281	ret);
	282	}
	283
43316044 WVS	284	return 0;
43316044 WVS	285	}
43316044 WVS	286
43316044 WVS	287	/**
ef90174f JBT	288	* watchdog_register_device() - register a watchdog device
ef90174f JBT	289	* @wdd: watchdog device
43316044	290	*
ef90174f JBT	291	* Register a watchdog device with the kernel so that the
	292	* watchdog timer can be accessed from userspace.
	293	*
	294	* A zero is returned on success and a negative errno code for
	295	* failure.
43316044	296	*/
ef90174f JBT	297
	298	int watchdog_register_device(struct watchdog_device *wdd)
	299	{
	300	int ret;
	301
	302	mutex_lock(&wtd_deferred_reg_mutex);
	303	if (wtd_deferred_reg_done)
	304	ret = __watchdog_register_device(wdd);
	305	else
	306	ret = watchdog_deferred_registration_add(wdd);
	307	mutex_unlock(&wtd_deferred_reg_mutex);
	308	return ret;
	309	}
	310	EXPORT_SYMBOL_GPL(watchdog_register_device);
	311
	312	static void __watchdog_unregister_device(struct watchdog_device *wdd)
43316044 WVS	313	{
43316044 WVS	314	int ret;
b232a70a	315	int devno;
43316044 WVS	316
	317	if (wdd == NULL)
	318	return;
	319
2165bf52 DR	320	if (wdd->ops->restart)
	321	unregister_restart_handler(&wdd->restart_nb);
	322
e1313196 DR	323	if (test_bit(WDOG_STOP_ON_REBOOT, &wdd->status))
	324	unregister_reboot_notifier(&wdd->reboot_nb);
	325
b232a70a	326	devno = wdd->cdev.dev;
43316044 WVS	327	ret = watchdog_dev_unregister(wdd);
43316044 WVS	328	if (ret)
27c766aa	329	pr_err("error unregistering /dev/watchdog (err=%d)\n", ret);
d6b469d9	330	device_destroy(watchdog_class, devno);
45f5fed3	331	ida_simple_remove(&watchdog_ida, wdd->id);
d6b469d9	332	wdd->dev = NULL;
43316044	333	}
ef90174f JBT	334
	335	/**
	336	* watchdog_unregister_device() - unregister a watchdog device
	337	* @wdd: watchdog device to unregister
	338	*
	339	* Unregister a watchdog device that was previously successfully
	340	* registered with watchdog_register_device().
	341	*/
	342
	343	void watchdog_unregister_device(struct watchdog_device *wdd)
	344	{
	345	mutex_lock(&wtd_deferred_reg_mutex);
	346	if (wtd_deferred_reg_done)
	347	__watchdog_unregister_device(wdd);
	348	else
	349	watchdog_deferred_registration_del(wdd);
	350	mutex_unlock(&wtd_deferred_reg_mutex);
	351	}
	352
43316044 WVS	353	EXPORT_SYMBOL_GPL(watchdog_unregister_device);
43316044 WVS	354
ef90174f JBT	355	static int __init watchdog_deferred_registration(void)
	356	{
	357	mutex_lock(&wtd_deferred_reg_mutex);
	358	wtd_deferred_reg_done = true;
	359	while (!list_empty(&wtd_deferred_reg_list)) {
	360	struct watchdog_device *wdd;
	361
	362	wdd = list_first_entry(&wtd_deferred_reg_list,
	363	struct watchdog_device, deferred);
	364	list_del(&wdd->deferred);
	365	__watchdog_register_device(wdd);
	366	}
	367	mutex_unlock(&wtd_deferred_reg_mutex);
	368	return 0;
	369	}
	370
45f5fed3 AC	371	static int __init watchdog_init(void)
45f5fed3 AC	372	{
906d7a5c PA	373	watchdog_class = watchdog_dev_init();
906d7a5c PA	374	if (IS_ERR(watchdog_class))
d6b469d9	375	return PTR_ERR(watchdog_class);
d6b469d9	376
ef90174f	377	watchdog_deferred_registration();
d6b469d9	378	return 0;
45f5fed3 AC	379	}
	380
	381	static void __exit watchdog_exit(void)
	382	{
	383	watchdog_dev_exit();
	384	ida_destroy(&watchdog_ida);
	385	}
	386
ef90174f	387	subsys_initcall_sync(watchdog_init);
45f5fed3 AC	388	module_exit(watchdog_exit);
45f5fed3 AC	389
43316044 WVS	390	MODULE_AUTHOR("Alan Cox <alan@lxorguk.ukuu.org.uk>");
	391	MODULE_AUTHOR("Wim Van Sebroeck <wim@iguana.be>");
	392	MODULE_DESCRIPTION("WatchDog Timer Driver Core");
	393	MODULE_LICENSE("GPL");