[linux-block.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/... */

/* 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.
 */

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

/*
 *	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.
 */

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;

	for (i = 0; i != len; i++) {
		if (get_user(c, data + i))
			return -EFAULT;
	}

	/* 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;

	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);
	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 = wdd->ops->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.
 */

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

	err = wdd->ops->stop(wdd);
	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
	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;
	49
	50	/*
	51	* watchdog_ping: ping the watchdog.
	52	* @wddev: the watchdog device to ping
	53	*
	54	* If the watchdog has no own ping operation then it needs to be
	55	* restarted via the start operation. This wrapper function does
	56	* exactly that.
	57	*/
	58
	59	static int watchdog_ping(struct watchdog_device *wddev)
	60	{
	61	if (wddev->ops->ping)
	62	return wddev->ops->ping(wddev); /* ping the watchdog */
	63	else
	64	return wddev->ops->start(wddev); /* restart the watchdog */
65	}
66
67	/*
68	* watchdog_write: writes to the watchdog.
69	* @file: file from VFS
70	* @data: user address of data
71	* @len: length of data
72	* @ppos: pointer to the file offset
73	*
74	* A write to a watchdog device is defined as a keepalive ping.
75	*/
76
77	static ssize_t watchdog_write(struct file file, const char __user data,
78	size_t len, loff_t *ppos)
79	{
80	size_t i;
81	char c;
82
83	if (len == 0)
84	return 0;
85
86	for (i = 0; i != len; i++) {
87	if (get_user(c, data + i))
88	return -EFAULT;
89	}
90
91	/* someone wrote to us, so we send the watchdog a keepalive ping */
92	watchdog_ping(wdd);
93
94	return len;
95	}
96
2fa03560 WVS	97	/*
	98	* watchdog_ioctl: handle the different ioctl's for the watchdog device.
	99	* @file: file handle to the device
	100	* @cmd: watchdog command
	101	* @arg: argument pointer
	102	*
	103	* The watchdog API defines a common set of functions for all watchdogs
	104	* according to their available features.
	105	*/
	106
	107	static long watchdog_ioctl(struct file *file, unsigned int cmd,
	108	unsigned long arg)
	109	{
	110	void __user argp = (void __user )arg;
	111	int __user *p = argp;
	112	unsigned int val;
	113
	114	switch (cmd) {
	115	case WDIOC_GETSUPPORT:
	116	return copy_to_user(argp, wdd->info,
	117	sizeof(struct watchdog_info)) ? -EFAULT : 0;
	118	case WDIOC_GETSTATUS:
	119	val = wdd->ops->status ? wdd->ops->status(wdd) : 0;
	120	return put_user(val, p);
	121	case WDIOC_GETBOOTSTATUS:
	122	return put_user(wdd->bootstatus, p);
	123	default:
	124	return -ENOTTY;
	125	}
	126	}
	127
43316044 WVS	128	/*
	129	* watchdog_open: open the /dev/watchdog device.
	130	* @inode: inode of device
	131	* @file: file handle to device
	132	*
	133	* When the /dev/watchdog device gets opened, we start the watchdog.
	134	* Watch out: the /dev/watchdog device is single open, so we make sure
	135	* it can only be opened once.
	136	*/
	137
	138	static int watchdog_open(struct inode inode, struct file file)
	139	{
	140	int err = -EBUSY;
	141
	142	/* the watchdog is single open! */
	143	if (test_and_set_bit(WDOG_DEV_OPEN, &wdd->status))
	144	return -EBUSY;
	145
	146	/*
	147	* If the /dev/watchdog device is open, we don't want the module
	148	* to be unloaded.
	149	*/
	150	if (!try_module_get(wdd->ops->owner))
	151	goto out;
	152
	153	err = wdd->ops->start(wdd);
	154	if (err < 0)
	155	goto out_mod;
	156
	157	/* dev/watchdog is a virtual (and thus non-seekable) filesystem */
	158	return nonseekable_open(inode, file);
	159
	160	out_mod:
	161	module_put(wdd->ops->owner);
	162	out:
	163	clear_bit(WDOG_DEV_OPEN, &wdd->status);
	164	return err;
	165	}
	166
	167	/*
	168	* watchdog_release: release the /dev/watchdog device.
	169	* @inode: inode of device
	170	* @file: file handle to device
	171	*
	172	* This is the code for when /dev/watchdog gets closed.
	173	*/
	174
	175	static int watchdog_release(struct inode inode, struct file file)
	176	{
	177	int err;
	178
	179	err = wdd->ops->stop(wdd);
	180	if (err != 0) {
	181	pr_crit("%s: watchdog did not stop!\n", wdd->info->identity);
	182	watchdog_ping(wdd);
	183	}
	184
	185	/* Allow the owner module to be unloaded again */
	186	module_put(wdd->ops->owner);
	187
	188	/* make sure that /dev/watchdog can be re-opened */
	189	clear_bit(WDOG_DEV_OPEN, &wdd->status);
	190
	191	return 0;
192	}
193
194	static const struct file_operations watchdog_fops = {
195	.owner = THIS_MODULE,
196	.write = watchdog_write,
2fa03560	197	.unlocked_ioctl = watchdog_ioctl,
43316044 WVS	198	.open = watchdog_open,
	199	.release = watchdog_release,
	200	};
	201
	202	static struct miscdevice watchdog_miscdev = {
	203	.minor = WATCHDOG_MINOR,
	204	.name = "watchdog",
	205	.fops = &watchdog_fops,
	206	};
	207
	208	/*
	209	* watchdog_dev_register:
	210	* @watchdog: watchdog device
	211	*
	212	* Register a watchdog device as /dev/watchdog. /dev/watchdog
	213	* is actually a miscdevice and thus we set it up like that.
	214	*/
	215
	216	int watchdog_dev_register(struct watchdog_device *watchdog)
	217	{
	218	int err;
	219
	220	/* Only one device can register for /dev/watchdog */
	221	if (test_and_set_bit(0, &watchdog_dev_busy)) {
	222	pr_err("only one watchdog can use /dev/watchdog.\n");
	223	return -EBUSY;
	224	}
	225
	226	wdd = watchdog;
	227
	228	err = misc_register(&watchdog_miscdev);
	229	if (err != 0) {
	230	pr_err("%s: cannot register miscdev on minor=%d (err=%d).\n",
	231	watchdog->info->identity, WATCHDOG_MINOR, err);
	232	goto out;
	233	}
	234
	235	return 0;
	236
	237	out:
	238	wdd = NULL;
	239	clear_bit(0, &watchdog_dev_busy);
	240	return err;
	241	}
	242
	243	/*
	244	* watchdog_dev_unregister:
	245	* @watchdog: watchdog device
	246	*
	247	* Deregister the /dev/watchdog device.
	248	*/
	249
	250	int watchdog_dev_unregister(struct watchdog_device *watchdog)
	251	{
	252	/* Check that a watchdog device was registered in the past */
	253	if (!test_bit(0, &watchdog_dev_busy) \|\| !wdd)
	254	return -ENODEV;
	255
	256	/* We can only unregister the watchdog device that was registered */
	257	if (watchdog != wdd) {
	258	pr_err("%s: watchdog was not registered as /dev/watchdog.\n",
	259	watchdog->info->identity);
	260	return -ENODEV;
	261	}
262
263	misc_deregister(&watchdog_miscdev);
264	wdd = NULL;
265	clear_bit(0, &watchdog_dev_busy);
266	return 0;
267	}