/*
* 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"
/* the dev_t structure to store the dynamically allocated watchdog devices */
static dev_t watchdog_devt;
/* the watchdog device behind /dev/watchdog */
static struct watchdog_device *old_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)) {
dev_info(wddev->dev, "nowayout prevents watchdog being stopped!\n");
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)
{
struct watchdog_device *wdd = file->private_data;
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)
{
struct watchdog_device *wdd = file->private_data;
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* devices.
* @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;
struct watchdog_device *wdd;
/* Get the corresponding watchdog device */
if (imajor(inode) == MISC_MAJOR)
wdd = old_wdd;
else
wdd = container_of(inode->i_cdev, struct watchdog_device, cdev);
/* 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;
file->private_data = wdd;
/* 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 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)
{
struct watchdog_device *wdd = file->private_data;
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) {
dev_crit(wdd->dev, "watchdog did not stop!\n");
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: register a watchdog device
* @watchdog: watchdog device
*
* Register a watchdog device including handling the legacy
* /dev/watchdog node. /dev/watchdog is actually a miscdevice and
* thus we set it up like that.
*/
int watchdog_dev_register(struct watchdog_device *watchdog)
{
int err, devno;
if (watchdog->id == 0) {
watchdog_miscdev.parent = watchdog->parent;
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);
if (err == -EBUSY)
pr_err("%s: a legacy watchdog module is probably present.\n",
watchdog->info->identity);
return err;
}
old_wdd = watchdog;
}
/* Fill in the data structures */
devno = MKDEV(MAJOR(watchdog_devt), watchdog->id);
cdev_init(&watchdog->cdev, &watchdog_fops);
watchdog->cdev.owner = watchdog->ops->owner;
/* Add the device */
err = cdev_add(&watchdog->cdev, devno, 1);
if (err) {
pr_err("watchdog%d unable to add device %d:%d\n",
watchdog->id, MAJOR(watchdog_devt), watchdog->id);
if (watchdog->id == 0) {
misc_deregister(&watchdog_miscdev);
old_wdd = NULL;
}
}
return err;
}
/*
* watchdog_dev_unregister: unregister a watchdog device
* @watchdog: watchdog device
*
* Unregister the watchdog and if needed the legacy /dev/watchdog device.
*/
int watchdog_dev_unregister(struct watchdog_device *watchdog)
{
cdev_del(&watchdog->cdev);
if (watchdog->id == 0) {
misc_deregister(&watchdog_miscdev);
old_wdd = NULL;
}
return 0;
}
/*
* watchdog_dev_init: init dev part of watchdog core
*
* Allocate a range of chardev nodes to use for watchdog devices
*/
int __init watchdog_dev_init(void)
{
int err = alloc_chrdev_region(&watchdog_devt, 0, MAX_DOGS, "watchdog");
if (err < 0)
pr_err("watchdog: unable to allocate char dev region\n");
return err;
}
/*
* watchdog_dev_exit: exit dev part of watchdog core
*
* Release the range of chardev nodes used for watchdog devices
*/
void __exit watchdog_dev_exit(void)
{
unregister_chrdev_region(watchdog_devt, MAX_DOGS);
}
