[mirror_ubuntu-artful-kernel.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.
 *	We only ping when the watchdog device is running.
 */

static int watchdog_ping(struct watchdog_device *wddev)
{
	if (test_bit(WDOG_ACTIVE, &wdd->status)) {
		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 (!test_bit(WDOG_ACTIVE, &wdd->status)) {
		err = wddev->ops->start(wddev);
		if (err < 0)
			return err;

		set_bit(WDOG_ACTIVE, &wdd->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.
 */

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

	if (test_bit(WDOG_ACTIVE, &wdd->status)) {
		err = wddev->ops->stop(wddev);
		if (err < 0)
			return err;

		clear_bit(WDOG_ACTIVE, &wdd->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.
 */

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;
	int 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;
	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.
 */

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

	err = watchdog_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.
234445b4	57	* We only ping when the watchdog device is running.
43316044 WVS	58	*/
	59
	60	static int watchdog_ping(struct watchdog_device *wddev)
	61	{
234445b4 WVS	62	if (test_bit(WDOG_ACTIVE, &wdd->status)) {
	63	if (wddev->ops->ping)
	64	return wddev->ops->ping(wddev); /* ping the watchdog */
	65	else
	66	return wddev->ops->start(wddev); /* restart watchdog */
	67	}
	68	return 0;
	69	}
	70
	71	/*
	72	* watchdog_start: wrapper to start the watchdog.
	73	* @wddev: the watchdog device to start
	74	*
	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
	77	* failure.
	78	*/
	79
	80	static int watchdog_start(struct watchdog_device *wddev)
	81	{
	82	int err;
	83
	84	if (!test_bit(WDOG_ACTIVE, &wdd->status)) {
	85	err = wddev->ops->start(wddev);
	86	if (err < 0)
	87	return err;
	88
	89	set_bit(WDOG_ACTIVE, &wdd->status);
	90	}
	91	return 0;
	92	}
	93
	94	/*
	95	* watchdog_stop: wrapper to stop the watchdog.
	96	* @wddev: the watchdog device to stop
	97	*
	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
	100	* failure.
	101	*/
	102
	103	static int watchdog_stop(struct watchdog_device *wddev)
	104	{
	105	int err;
	106
	107	if (test_bit(WDOG_ACTIVE, &wdd->status)) {
	108	err = wddev->ops->stop(wddev);
	109	if (err < 0)
	110	return err;
	111
	112	clear_bit(WDOG_ACTIVE, &wdd->status);
	113	}
	114	return 0;
43316044 WVS	115	}
	116
	117	/*
	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
	123	*
	124	* A write to a watchdog device is defined as a keepalive ping.
	125	*/
	126
	127	static ssize_t watchdog_write(struct file file, const char __user data,
	128	size_t len, loff_t *ppos)
	129	{
	130	size_t i;
	131	char c;
	132
	133	if (len == 0)
	134	return 0;
	135
	136	for (i = 0; i != len; i++) {
	137	if (get_user(c, data + i))
	138	return -EFAULT;
	139	}
	140
	141	/* someone wrote to us, so we send the watchdog a keepalive ping */
	142	watchdog_ping(wdd);
	143
	144	return len;
	145	}
	146
2fa03560 WVS	147	/*
	148	* watchdog_ioctl: handle the different ioctl's for the watchdog device.
	149	* @file: file handle to the device
	150	* @cmd: watchdog command
	151	* @arg: argument pointer
	152	*
	153	* The watchdog API defines a common set of functions for all watchdogs
	154	* according to their available features.
	155	*/
	156
	157	static long watchdog_ioctl(struct file *file, unsigned int cmd,
	158	unsigned long arg)
	159	{
	160	void __user argp = (void __user )arg;
	161	int __user *p = argp;
	162	unsigned int val;
234445b4	163	int err;
2fa03560 WVS	164
	165	switch (cmd) {
	166	case WDIOC_GETSUPPORT:
	167	return copy_to_user(argp, wdd->info,
	168	sizeof(struct watchdog_info)) ? -EFAULT : 0;
	169	case WDIOC_GETSTATUS:
	170	val = wdd->ops->status ? wdd->ops->status(wdd) : 0;
	171	return put_user(val, p);
	172	case WDIOC_GETBOOTSTATUS:
	173	return put_user(wdd->bootstatus, p);
234445b4 WVS	174	case WDIOC_SETOPTIONS:
	175	if (get_user(val, p))
	176	return -EFAULT;
	177	if (val & WDIOS_DISABLECARD) {
	178	err = watchdog_stop(wdd);
	179	if (err < 0)
	180	return err;
	181	}
	182	if (val & WDIOS_ENABLECARD) {
	183	err = watchdog_start(wdd);
	184	if (err < 0)
	185	return err;
	186	}
	187	return 0;
c2dc00e4 WVS	188	case WDIOC_KEEPALIVE:
	189	if (!(wdd->info->options & WDIOF_KEEPALIVEPING))
	190	return -EOPNOTSUPP;
	191	watchdog_ping(wdd);
	192	return 0;
2fa03560 WVS	193	default:
	194	return -ENOTTY;
	195	}
	196	}
	197
43316044 WVS	198	/*
	199	* watchdog_open: open the /dev/watchdog device.
	200	* @inode: inode of device
	201	* @file: file handle to device
	202	*
	203	* When the /dev/watchdog device gets opened, we start the watchdog.
	204	* Watch out: the /dev/watchdog device is single open, so we make sure
	205	* it can only be opened once.
	206	*/
	207
	208	static int watchdog_open(struct inode inode, struct file file)
	209	{
	210	int err = -EBUSY;
	211
	212	/* the watchdog is single open! */
	213	if (test_and_set_bit(WDOG_DEV_OPEN, &wdd->status))
	214	return -EBUSY;
	215
	216	/*
	217	* If the /dev/watchdog device is open, we don't want the module
	218	* to be unloaded.
	219	*/
	220	if (!try_module_get(wdd->ops->owner))
	221	goto out;
	222
234445b4	223	err = watchdog_start(wdd);
43316044 WVS	224	if (err < 0)
	225	goto out_mod;
	226
	227	/* dev/watchdog is a virtual (and thus non-seekable) filesystem */
	228	return nonseekable_open(inode, file);
	229
	230	out_mod:
	231	module_put(wdd->ops->owner);
	232	out:
	233	clear_bit(WDOG_DEV_OPEN, &wdd->status);
	234	return err;
	235	}
	236
	237	/*
	238	* watchdog_release: release the /dev/watchdog device.
	239	* @inode: inode of device
	240	* @file: file handle to device
	241	*
	242	* This is the code for when /dev/watchdog gets closed.
	243	*/
	244
	245	static int watchdog_release(struct inode inode, struct file file)
	246	{
	247	int err;
	248
234445b4 WVS	249	err = watchdog_stop(wdd);
234445b4 WVS	250	if (err < 0) {
43316044 WVS	251	pr_crit("%s: watchdog did not stop!\n", wdd->info->identity);
	252	watchdog_ping(wdd);
	253	}
	254
	255	/* Allow the owner module to be unloaded again */
	256	module_put(wdd->ops->owner);
	257
	258	/* make sure that /dev/watchdog can be re-opened */
	259	clear_bit(WDOG_DEV_OPEN, &wdd->status);
	260
	261	return 0;
	262	}
	263
	264	static const struct file_operations watchdog_fops = {
	265	.owner = THIS_MODULE,
	266	.write = watchdog_write,
2fa03560	267	.unlocked_ioctl = watchdog_ioctl,
43316044 WVS	268	.open = watchdog_open,
	269	.release = watchdog_release,
	270	};
	271
	272	static struct miscdevice watchdog_miscdev = {
	273	.minor = WATCHDOG_MINOR,
	274	.name = "watchdog",
	275	.fops = &watchdog_fops,
	276	};
	277
	278	/*
	279	* watchdog_dev_register:
	280	* @watchdog: watchdog device
	281	*
	282	* Register a watchdog device as /dev/watchdog. /dev/watchdog
	283	* is actually a miscdevice and thus we set it up like that.
	284	*/
	285
	286	int watchdog_dev_register(struct watchdog_device *watchdog)
	287	{
	288	int err;
	289
	290	/* Only one device can register for /dev/watchdog */
	291	if (test_and_set_bit(0, &watchdog_dev_busy)) {
	292	pr_err("only one watchdog can use /dev/watchdog.\n");
	293	return -EBUSY;
	294	}
	295
	296	wdd = watchdog;
	297
	298	err = misc_register(&watchdog_miscdev);
	299	if (err != 0) {
	300	pr_err("%s: cannot register miscdev on minor=%d (err=%d).\n",
	301	watchdog->info->identity, WATCHDOG_MINOR, err);
	302	goto out;
	303	}
	304
	305	return 0;
	306
	307	out:
	308	wdd = NULL;
	309	clear_bit(0, &watchdog_dev_busy);
	310	return err;
	311	}
	312
	313	/*
	314	* watchdog_dev_unregister:
	315	* @watchdog: watchdog device
	316	*
	317	* Deregister the /dev/watchdog device.
	318	*/
	319
	320	int watchdog_dev_unregister(struct watchdog_device *watchdog)
	321	{
	322	/* Check that a watchdog device was registered in the past */
	323	if (!test_bit(0, &watchdog_dev_busy) \|\| !wdd)
	324	return -ENODEV;
	325
	326	/* We can only unregister the watchdog device that was registered */
	327	if (watchdog != wdd) {
	328	pr_err("%s: watchdog was not registered as /dev/watchdog.\n",
	329	watchdog->info->identity);
	330	return -ENODEV;
	331	}
332
333	misc_deregister(&watchdog_miscdev);
334	wdd = NULL;
335	clear_bit(0, &watchdog_dev_busy);
336	return 0;
337	}