1. 根目录:
2. drivers
3. watchdog
4. 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/watchdog.h>	/* For watchdog specific items */
#include <linux/init.h>		/* For __init/__exit/... */

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

/**
 * 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;

	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;

	/*
	 * 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;
	}

	/*
	 * 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!
	 */

	/* We only support 1 watchdog device via the /dev/watchdog interface */
	ret = watchdog_dev_register(wdd);
	if (ret) {
		pr_err("error registering /dev/watchdog (err=%d)\n", ret);
		return ret;
	}

	return 0;
}
EXPORT_SYMBOL_GPL(watchdog_register_device);

/**
 * 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)
{
	int ret;

	if (wdd == NULL)
		return;

	ret = watchdog_dev_unregister(wdd);
	if (ret)
		pr_err("error unregistering /dev/watchdog (err=%d)\n", ret);
}
EXPORT_SYMBOL_GPL(watchdog_unregister_device);

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");