7e192b9c42
Add support for the nowayout feature to the WatchDog Timer Driver Core framework. This feature prevents the watchdog timer from being stopped. Signed-off-by: Alan Cox <alan@lxorguk.ukuu.org.uk> Signed-off-by: Wim Van Sebroeck <wim@iguana.be> Acked-by: Arnd Bergmann <arnd@arndb.de> Acked-by: Wolfram Sang <w.sang@pengutronix.de>
387 lines
9.8 KiB
C
387 lines
9.8 KiB
C
/*
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* watchdog_dev.c
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*
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* (c) Copyright 2008-2011 Alan Cox <alan@lxorguk.ukuu.org.uk>,
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* All Rights Reserved.
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*
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* (c) Copyright 2008-2011 Wim Van Sebroeck <wim@iguana.be>.
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*
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*
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* This source code is part of the generic code that can be used
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* by all the watchdog timer drivers.
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*
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* This part of the generic code takes care of the following
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* misc device: /dev/watchdog.
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*
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* Based on source code of the following authors:
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* Matt Domsch <Matt_Domsch@dell.com>,
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* Rob Radez <rob@osinvestor.com>,
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* Rusty Lynch <rusty@linux.co.intel.com>
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* Satyam Sharma <satyam@infradead.org>
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* Randy Dunlap <randy.dunlap@oracle.com>
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*
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* Neither Alan Cox, CymruNet Ltd., Wim Van Sebroeck nor Iguana vzw.
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* admit liability nor provide warranty for any of this software.
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* This material is provided "AS-IS" and at no charge.
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*/
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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#include <linux/module.h> /* For module stuff/... */
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#include <linux/types.h> /* For standard types (like size_t) */
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#include <linux/errno.h> /* For the -ENODEV/... values */
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#include <linux/kernel.h> /* For printk/panic/... */
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#include <linux/fs.h> /* For file operations */
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#include <linux/watchdog.h> /* For watchdog specific items */
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#include <linux/miscdevice.h> /* For handling misc devices */
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#include <linux/init.h> /* For __init/__exit/... */
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#include <linux/uaccess.h> /* For copy_to_user/put_user/... */
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/* make sure we only register one /dev/watchdog device */
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static unsigned long watchdog_dev_busy;
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/* the watchdog device behind /dev/watchdog */
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static struct watchdog_device *wdd;
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/*
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* watchdog_ping: ping the watchdog.
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* @wddev: the watchdog device to ping
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*
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* If the watchdog has no own ping operation then it needs to be
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* restarted via the start operation. This wrapper function does
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* exactly that.
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* We only ping when the watchdog device is running.
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*/
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static int watchdog_ping(struct watchdog_device *wddev)
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{
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if (test_bit(WDOG_ACTIVE, &wdd->status)) {
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if (wddev->ops->ping)
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return wddev->ops->ping(wddev); /* ping the watchdog */
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else
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return wddev->ops->start(wddev); /* restart watchdog */
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}
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return 0;
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}
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/*
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* watchdog_start: wrapper to start the watchdog.
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* @wddev: the watchdog device to start
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*
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* Start the watchdog if it is not active and mark it active.
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* This function returns zero on success or a negative errno code for
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* failure.
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*/
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static int watchdog_start(struct watchdog_device *wddev)
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{
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int err;
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if (!test_bit(WDOG_ACTIVE, &wdd->status)) {
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err = wddev->ops->start(wddev);
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if (err < 0)
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return err;
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set_bit(WDOG_ACTIVE, &wdd->status);
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}
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return 0;
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}
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/*
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* watchdog_stop: wrapper to stop the watchdog.
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* @wddev: the watchdog device to stop
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*
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* Stop the watchdog if it is still active and unmark it active.
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* This function returns zero on success or a negative errno code for
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* failure.
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* If the 'nowayout' feature was set, the watchdog cannot be stopped.
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*/
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static int watchdog_stop(struct watchdog_device *wddev)
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{
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int err = -EBUSY;
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if (test_bit(WDOG_NO_WAY_OUT, &wdd->status)) {
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pr_info("%s: nowayout prevents watchdog to be stopped!\n",
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wdd->info->identity);
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return err;
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}
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if (test_bit(WDOG_ACTIVE, &wdd->status)) {
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err = wddev->ops->stop(wddev);
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if (err < 0)
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return err;
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clear_bit(WDOG_ACTIVE, &wdd->status);
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}
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return 0;
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}
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/*
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* watchdog_write: writes to the watchdog.
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* @file: file from VFS
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* @data: user address of data
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* @len: length of data
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* @ppos: pointer to the file offset
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*
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* A write to a watchdog device is defined as a keepalive ping.
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* Writing the magic 'V' sequence allows the next close to turn
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* off the watchdog (if 'nowayout' is not set).
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*/
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static ssize_t watchdog_write(struct file *file, const char __user *data,
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size_t len, loff_t *ppos)
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{
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size_t i;
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char c;
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if (len == 0)
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return 0;
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/*
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* Note: just in case someone wrote the magic character
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* five months ago...
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*/
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clear_bit(WDOG_ALLOW_RELEASE, &wdd->status);
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/* scan to see whether or not we got the magic character */
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for (i = 0; i != len; i++) {
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if (get_user(c, data + i))
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return -EFAULT;
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if (c == 'V')
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set_bit(WDOG_ALLOW_RELEASE, &wdd->status);
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}
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/* someone wrote to us, so we send the watchdog a keepalive ping */
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watchdog_ping(wdd);
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return len;
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}
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/*
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* watchdog_ioctl: handle the different ioctl's for the watchdog device.
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* @file: file handle to the device
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* @cmd: watchdog command
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* @arg: argument pointer
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*
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* The watchdog API defines a common set of functions for all watchdogs
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* according to their available features.
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*/
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static long watchdog_ioctl(struct file *file, unsigned int cmd,
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unsigned long arg)
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{
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void __user *argp = (void __user *)arg;
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int __user *p = argp;
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unsigned int val;
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int err;
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switch (cmd) {
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case WDIOC_GETSUPPORT:
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return copy_to_user(argp, wdd->info,
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sizeof(struct watchdog_info)) ? -EFAULT : 0;
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case WDIOC_GETSTATUS:
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val = wdd->ops->status ? wdd->ops->status(wdd) : 0;
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return put_user(val, p);
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case WDIOC_GETBOOTSTATUS:
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return put_user(wdd->bootstatus, p);
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case WDIOC_SETOPTIONS:
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if (get_user(val, p))
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return -EFAULT;
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if (val & WDIOS_DISABLECARD) {
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err = watchdog_stop(wdd);
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if (err < 0)
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return err;
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}
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if (val & WDIOS_ENABLECARD) {
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err = watchdog_start(wdd);
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if (err < 0)
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return err;
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}
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return 0;
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case WDIOC_KEEPALIVE:
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if (!(wdd->info->options & WDIOF_KEEPALIVEPING))
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return -EOPNOTSUPP;
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watchdog_ping(wdd);
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return 0;
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case WDIOC_SETTIMEOUT:
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if ((wdd->ops->set_timeout == NULL) ||
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!(wdd->info->options & WDIOF_SETTIMEOUT))
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return -EOPNOTSUPP;
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if (get_user(val, p))
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return -EFAULT;
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err = wdd->ops->set_timeout(wdd, val);
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if (err < 0)
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return err;
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wdd->timeout = val;
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/* If the watchdog is active then we send a keepalive ping
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* to make sure that the watchdog keep's running (and if
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* possible that it takes the new timeout) */
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watchdog_ping(wdd);
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/* Fall */
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case WDIOC_GETTIMEOUT:
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/* timeout == 0 means that we don't know the timeout */
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if (wdd->timeout == 0)
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return -EOPNOTSUPP;
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return put_user(wdd->timeout, p);
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default:
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return -ENOTTY;
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}
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}
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/*
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* watchdog_open: open the /dev/watchdog device.
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* @inode: inode of device
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* @file: file handle to device
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*
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* When the /dev/watchdog device gets opened, we start the watchdog.
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* Watch out: the /dev/watchdog device is single open, so we make sure
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* it can only be opened once.
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*/
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static int watchdog_open(struct inode *inode, struct file *file)
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{
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int err = -EBUSY;
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/* the watchdog is single open! */
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if (test_and_set_bit(WDOG_DEV_OPEN, &wdd->status))
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return -EBUSY;
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/*
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* If the /dev/watchdog device is open, we don't want the module
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* to be unloaded.
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*/
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if (!try_module_get(wdd->ops->owner))
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goto out;
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err = watchdog_start(wdd);
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if (err < 0)
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goto out_mod;
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/* dev/watchdog is a virtual (and thus non-seekable) filesystem */
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return nonseekable_open(inode, file);
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out_mod:
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module_put(wdd->ops->owner);
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out:
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clear_bit(WDOG_DEV_OPEN, &wdd->status);
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return err;
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}
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/*
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* watchdog_release: release the /dev/watchdog device.
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* @inode: inode of device
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* @file: file handle to device
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*
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* This is the code for when /dev/watchdog gets closed. We will only
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* stop the watchdog when we have received the magic char (and nowayout
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* was not set), else the watchdog will keep running.
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*/
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static int watchdog_release(struct inode *inode, struct file *file)
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{
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int err = -EBUSY;
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/*
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* We only stop the watchdog if we received the magic character
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* or if WDIOF_MAGICCLOSE is not set. If nowayout was set then
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* watchdog_stop will fail.
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*/
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if (test_and_clear_bit(WDOG_ALLOW_RELEASE, &wdd->status) ||
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!(wdd->info->options & WDIOF_MAGICCLOSE))
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err = watchdog_stop(wdd);
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/* If the watchdog was not stopped, send a keepalive ping */
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if (err < 0) {
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pr_crit("%s: watchdog did not stop!\n", wdd->info->identity);
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watchdog_ping(wdd);
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}
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/* Allow the owner module to be unloaded again */
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module_put(wdd->ops->owner);
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/* make sure that /dev/watchdog can be re-opened */
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clear_bit(WDOG_DEV_OPEN, &wdd->status);
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return 0;
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}
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static const struct file_operations watchdog_fops = {
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.owner = THIS_MODULE,
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.write = watchdog_write,
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.unlocked_ioctl = watchdog_ioctl,
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.open = watchdog_open,
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.release = watchdog_release,
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};
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static struct miscdevice watchdog_miscdev = {
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.minor = WATCHDOG_MINOR,
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.name = "watchdog",
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.fops = &watchdog_fops,
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};
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/*
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* watchdog_dev_register:
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* @watchdog: watchdog device
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*
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* Register a watchdog device as /dev/watchdog. /dev/watchdog
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* is actually a miscdevice and thus we set it up like that.
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*/
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int watchdog_dev_register(struct watchdog_device *watchdog)
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{
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int err;
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/* Only one device can register for /dev/watchdog */
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if (test_and_set_bit(0, &watchdog_dev_busy)) {
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pr_err("only one watchdog can use /dev/watchdog.\n");
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return -EBUSY;
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}
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wdd = watchdog;
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err = misc_register(&watchdog_miscdev);
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if (err != 0) {
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pr_err("%s: cannot register miscdev on minor=%d (err=%d).\n",
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watchdog->info->identity, WATCHDOG_MINOR, err);
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goto out;
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}
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return 0;
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out:
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wdd = NULL;
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clear_bit(0, &watchdog_dev_busy);
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return err;
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}
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/*
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* watchdog_dev_unregister:
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* @watchdog: watchdog device
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*
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* Deregister the /dev/watchdog device.
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*/
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int watchdog_dev_unregister(struct watchdog_device *watchdog)
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{
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/* Check that a watchdog device was registered in the past */
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if (!test_bit(0, &watchdog_dev_busy) || !wdd)
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return -ENODEV;
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/* We can only unregister the watchdog device that was registered */
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if (watchdog != wdd) {
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pr_err("%s: watchdog was not registered as /dev/watchdog.\n",
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watchdog->info->identity);
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return -ENODEV;
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}
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misc_deregister(&watchdog_miscdev);
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wdd = NULL;
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clear_bit(0, &watchdog_dev_busy);
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return 0;
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}
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