Adding upstream version 6.1.76.upstream/6.1.76

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1306 insertions, 0 deletions

diff --git a/drivers/watchdog/watchdog_dev.c b/drivers/watchdog/watchdog_dev.c
new file mode 100644
index 000000000..81684d89d
--- /dev/null
+++ b/drivers/watchdog/watchdog_dev.c
@@ -0,0 +1,1306 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ *	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>.
+ *
+ *	(c) Copyright 2021 Hewlett Packard Enterprise Development LP.
+ *
+ *	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>
+ *
+ *	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/cdev.h>		/* For character device */
+#include <linux/errno.h>	/* For the -ENODEV/... values */
+#include <linux/fs.h>		/* For file operations */
+#include <linux/init.h>		/* For __init/__exit/... */
+#include <linux/hrtimer.h>	/* For hrtimers */
+#include <linux/kernel.h>	/* For printk/panic/... */
+#include <linux/kthread.h>	/* For kthread_work */
+#include <linux/miscdevice.h>	/* For handling misc devices */
+#include <linux/module.h>	/* For module stuff/... */
+#include <linux/mutex.h>	/* For mutexes */
+#include <linux/slab.h>		/* For memory functions */
+#include <linux/types.h>	/* For standard types (like size_t) */
+#include <linux/watchdog.h>	/* For watchdog specific items */
+#include <linux/uaccess.h>	/* For copy_to_user/put_user/... */
+
+#include "watchdog_core.h"
+#include "watchdog_pretimeout.h"
+
+#include <trace/events/watchdog.h>
+
+/* the dev_t structure to store the dynamically allocated watchdog devices */
+static dev_t watchdog_devt;
+/* Reference to watchdog device behind /dev/watchdog */
+static struct watchdog_core_data *old_wd_data;
+
+static struct kthread_worker *watchdog_kworker;
+
+static bool handle_boot_enabled =
+	IS_ENABLED(CONFIG_WATCHDOG_HANDLE_BOOT_ENABLED);
+
+static unsigned open_timeout = CONFIG_WATCHDOG_OPEN_TIMEOUT;
+
+static bool watchdog_past_open_deadline(struct watchdog_core_data *data)
+{
+	return ktime_after(ktime_get(), data->open_deadline);
+}
+
+static void watchdog_set_open_deadline(struct watchdog_core_data *data)
+{
+	data->open_deadline = open_timeout ?
+		ktime_get() + ktime_set(open_timeout, 0) : KTIME_MAX;
+}
+
+static inline bool watchdog_need_worker(struct watchdog_device *wdd)
+{
+	/* All variables in milli-seconds */
+	unsigned int hm = wdd->max_hw_heartbeat_ms;
+	unsigned int t = wdd->timeout * 1000;
+
+	/*
+	 * A worker to generate heartbeat requests is needed if all of the
+	 * following conditions are true.
+	 * - Userspace activated the watchdog.
+	 * - The driver provided a value for the maximum hardware timeout, and
+	 *   thus is aware that the framework supports generating heartbeat
+	 *   requests.
+	 * - Userspace requests a longer timeout than the hardware can handle.
+	 *
+	 * Alternatively, if userspace has not opened the watchdog
+	 * device, we take care of feeding the watchdog if it is
+	 * running.
+	 */
+	return (hm && watchdog_active(wdd) && t > hm) ||
+		(t && !watchdog_active(wdd) && watchdog_hw_running(wdd));
+}
+
+static ktime_t watchdog_next_keepalive(struct watchdog_device *wdd)
+{
+	struct watchdog_core_data *wd_data = wdd->wd_data;
+	unsigned int timeout_ms = wdd->timeout * 1000;
+	ktime_t keepalive_interval;
+	ktime_t last_heartbeat, latest_heartbeat;
+	ktime_t virt_timeout;
+	unsigned int hw_heartbeat_ms;
+
+	if (watchdog_active(wdd))
+		virt_timeout = ktime_add(wd_data->last_keepalive,
+					 ms_to_ktime(timeout_ms));
+	else
+		virt_timeout = wd_data->open_deadline;
+
+	hw_heartbeat_ms = min_not_zero(timeout_ms, wdd->max_hw_heartbeat_ms);
+	keepalive_interval = ms_to_ktime(hw_heartbeat_ms / 2);
+
+	/*
+	 * To ensure that the watchdog times out wdd->timeout seconds
+	 * after the most recent ping from userspace, the last
+	 * worker ping has to come in hw_heartbeat_ms before this timeout.
+	 */
+	last_heartbeat = ktime_sub(virt_timeout, ms_to_ktime(hw_heartbeat_ms));
+	latest_heartbeat = ktime_sub(last_heartbeat, ktime_get());
+	if (ktime_before(latest_heartbeat, keepalive_interval))
+		return latest_heartbeat;
+	return keepalive_interval;
+}
+
+static inline void watchdog_update_worker(struct watchdog_device *wdd)
+{
+	struct watchdog_core_data *wd_data = wdd->wd_data;
+
+	if (watchdog_need_worker(wdd)) {
+		ktime_t t = watchdog_next_keepalive(wdd);
+
+		if (t > 0)
+			hrtimer_start(&wd_data->timer, t,
+				      HRTIMER_MODE_REL_HARD);
+	} else {
+		hrtimer_cancel(&wd_data->timer);
+	}
+}
+
+static int __watchdog_ping(struct watchdog_device *wdd)
+{
+	struct watchdog_core_data *wd_data = wdd->wd_data;
+	ktime_t earliest_keepalive, now;
+	int err;
+
+	earliest_keepalive = ktime_add(wd_data->last_hw_keepalive,
+				       ms_to_ktime(wdd->min_hw_heartbeat_ms));
+	now = ktime_get();
+
+	if (ktime_after(earliest_keepalive, now)) {
+		hrtimer_start(&wd_data->timer,
+			      ktime_sub(earliest_keepalive, now),
+			      HRTIMER_MODE_REL_HARD);
+		return 0;
+	}
+
+	wd_data->last_hw_keepalive = now;
+
+	if (wdd->ops->ping) {
+		err = wdd->ops->ping(wdd);  /* ping the watchdog */
+		trace_watchdog_ping(wdd, err);
+	} else {
+		err = wdd->ops->start(wdd); /* restart watchdog */
+		trace_watchdog_start(wdd, err);
+	}
+
+	if (err == 0)
+		watchdog_hrtimer_pretimeout_start(wdd);
+
+	watchdog_update_worker(wdd);
+
+	return err;
+}
+
+/*
+ * watchdog_ping - ping the watchdog
+ * @wdd: 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.
+ * The caller must hold wd_data->lock.
+ *
+ * Return: 0 on success, error otherwise.
+ */
+static int watchdog_ping(struct watchdog_device *wdd)
+{
+	struct watchdog_core_data *wd_data = wdd->wd_data;
+
+	if (!watchdog_active(wdd) && !watchdog_hw_running(wdd))
+		return 0;
+
+	set_bit(_WDOG_KEEPALIVE, &wd_data->status);
+
+	wd_data->last_keepalive = ktime_get();
+	return __watchdog_ping(wdd);
+}
+
+static bool watchdog_worker_should_ping(struct watchdog_core_data *wd_data)
+{
+	struct watchdog_device *wdd = wd_data->wdd;
+
+	if (!wdd)
+		return false;
+
+	if (watchdog_active(wdd))
+		return true;
+
+	return watchdog_hw_running(wdd) && !watchdog_past_open_deadline(wd_data);
+}
+
+static void watchdog_ping_work(struct kthread_work *work)
+{
+	struct watchdog_core_data *wd_data;
+
+	wd_data = container_of(work, struct watchdog_core_data, work);
+
+	mutex_lock(&wd_data->lock);
+	if (watchdog_worker_should_ping(wd_data))
+		__watchdog_ping(wd_data->wdd);
+	mutex_unlock(&wd_data->lock);
+}
+
+static enum hrtimer_restart watchdog_timer_expired(struct hrtimer *timer)
+{
+	struct watchdog_core_data *wd_data;
+
+	wd_data = container_of(timer, struct watchdog_core_data, timer);
+
+	kthread_queue_work(watchdog_kworker, &wd_data->work);
+	return HRTIMER_NORESTART;
+}
+
+/*
+ * watchdog_start - wrapper to start the watchdog
+ * @wdd: The watchdog device to start
+ *
+ * Start the watchdog if it is not active and mark it active.
+ * The caller must hold wd_data->lock.
+ *
+ * Return: 0 on success or a negative errno code for failure.
+ */
+static int watchdog_start(struct watchdog_device *wdd)
+{
+	struct watchdog_core_data *wd_data = wdd->wd_data;
+	ktime_t started_at;
+	int err;
+
+	if (watchdog_active(wdd))
+		return 0;
+
+	set_bit(_WDOG_KEEPALIVE, &wd_data->status);
+
+	started_at = ktime_get();
+	if (watchdog_hw_running(wdd) && wdd->ops->ping) {
+		err = __watchdog_ping(wdd);
+		if (err == 0) {
+			set_bit(WDOG_ACTIVE, &wdd->status);
+			watchdog_hrtimer_pretimeout_start(wdd);
+		}
+	} else {
+		err = wdd->ops->start(wdd);
+		trace_watchdog_start(wdd, err);
+		if (err == 0) {
+			set_bit(WDOG_ACTIVE, &wdd->status);
+			wd_data->last_keepalive = started_at;
+			wd_data->last_hw_keepalive = started_at;
+			watchdog_update_worker(wdd);
+			watchdog_hrtimer_pretimeout_start(wdd);
+		}
+	}
+
+	return err;
+}
+
+/*
+ * watchdog_stop - wrapper to stop the watchdog
+ * @wdd: The watchdog device to stop
+ *
+ * Stop the watchdog if it is still active and unmark it active.
+ * If the 'nowayout' feature was set, the watchdog cannot be stopped.
+ * The caller must hold wd_data->lock.
+ *
+ * Return: 0 on success or a negative errno code for failure.
+ */
+static int watchdog_stop(struct watchdog_device *wdd)
+{
+	int err = 0;
+
+	if (!watchdog_active(wdd))
+		return 0;
+
+	if (test_bit(WDOG_NO_WAY_OUT, &wdd->status)) {
+		pr_info("watchdog%d: nowayout prevents watchdog being stopped!\n",
+			wdd->id);
+		return -EBUSY;
+	}
+
+	if (wdd->ops->stop) {
+		clear_bit(WDOG_HW_RUNNING, &wdd->status);
+		err = wdd->ops->stop(wdd);
+		trace_watchdog_stop(wdd, err);
+	} else {
+		set_bit(WDOG_HW_RUNNING, &wdd->status);
+	}
+
+	if (err == 0) {
+		clear_bit(WDOG_ACTIVE, &wdd->status);
+		watchdog_update_worker(wdd);
+		watchdog_hrtimer_pretimeout_stop(wdd);
+	}
+
+	return err;
+}
+
+/*
+ * watchdog_get_status - wrapper to get the watchdog status
+ * @wdd: The watchdog device to get the status from
+ *
+ * Get the watchdog's status flags.
+ * The caller must hold wd_data->lock.
+ *
+ * Return: watchdog's status flags.
+ */
+static unsigned int watchdog_get_status(struct watchdog_device *wdd)
+{
+	struct watchdog_core_data *wd_data = wdd->wd_data;
+	unsigned int status;
+
+	if (wdd->ops->status)
+		status = wdd->ops->status(wdd);
+	else
+		status = wdd->bootstatus & (WDIOF_CARDRESET |
+					    WDIOF_OVERHEAT |
+					    WDIOF_FANFAULT |
+					    WDIOF_EXTERN1 |
+					    WDIOF_EXTERN2 |
+					    WDIOF_POWERUNDER |
+					    WDIOF_POWEROVER);
+
+	if (test_bit(_WDOG_ALLOW_RELEASE, &wd_data->status))
+		status |= WDIOF_MAGICCLOSE;
+
+	if (test_and_clear_bit(_WDOG_KEEPALIVE, &wd_data->status))
+		status |= WDIOF_KEEPALIVEPING;
+
+	if (IS_ENABLED(CONFIG_WATCHDOG_HRTIMER_PRETIMEOUT))
+		status |= WDIOF_PRETIMEOUT;
+
+	return status;
+}
+
+/*
+ * watchdog_set_timeout - set the watchdog timer timeout
+ * @wdd:	The watchdog device to set the timeout for
+ * @timeout:	Timeout to set in seconds
+ *
+ * The caller must hold wd_data->lock.
+ *
+ * Return: 0 if successful, error otherwise.
+ */
+static int watchdog_set_timeout(struct watchdog_device *wdd,
+							unsigned int timeout)
+{
+	int err = 0;
+
+	if (!(wdd->info->options & WDIOF_SETTIMEOUT))
+		return -EOPNOTSUPP;
+
+	if (watchdog_timeout_invalid(wdd, timeout))
+		return -EINVAL;
+
+	if (wdd->ops->set_timeout) {
+		err = wdd->ops->set_timeout(wdd, timeout);
+		trace_watchdog_set_timeout(wdd, timeout, err);
+	} else {
+		wdd->timeout = timeout;
+		/* Disable pretimeout if it doesn't fit the new timeout */
+		if (wdd->pretimeout >= wdd->timeout)
+			wdd->pretimeout = 0;
+	}
+
+	watchdog_update_worker(wdd);
+
+	return err;
+}
+
+/*
+ * watchdog_set_pretimeout - set the watchdog timer pretimeout
+ * @wdd:	The watchdog device to set the timeout for
+ * @timeout:	pretimeout to set in seconds
+ *
+ * Return: 0 if successful, error otherwise.
+ */
+static int watchdog_set_pretimeout(struct watchdog_device *wdd,
+				   unsigned int timeout)
+{
+	int err = 0;
+
+	if (!watchdog_have_pretimeout(wdd))
+		return -EOPNOTSUPP;
+
+	if (watchdog_pretimeout_invalid(wdd, timeout))
+		return -EINVAL;
+
+	if (wdd->ops->set_pretimeout && (wdd->info->options & WDIOF_PRETIMEOUT))
+		err = wdd->ops->set_pretimeout(wdd, timeout);
+	else
+		wdd->pretimeout = timeout;
+
+	return err;
+}
+
+/*
+ * watchdog_get_timeleft - wrapper to get the time left before a reboot
+ * @wdd:	The watchdog device to get the remaining time from
+ * @timeleft:	The time that's left
+ *
+ * Get the time before a watchdog will reboot (if not pinged).
+ * The caller must hold wd_data->lock.
+ *
+ * Return: 0 if successful, error otherwise.
+ */
+static int watchdog_get_timeleft(struct watchdog_device *wdd,
+							unsigned int *timeleft)
+{
+	*timeleft = 0;
+
+	if (!wdd->ops->get_timeleft)
+		return -EOPNOTSUPP;
+
+	*timeleft = wdd->ops->get_timeleft(wdd);
+
+	return 0;
+}
+
+#ifdef CONFIG_WATCHDOG_SYSFS
+static ssize_t nowayout_show(struct device *dev, struct device_attribute *attr,
+				char *buf)
+{
+	struct watchdog_device *wdd = dev_get_drvdata(dev);
+
+	return sysfs_emit(buf, "%d\n", !!test_bit(WDOG_NO_WAY_OUT,
+						  &wdd->status));
+}
+
+static ssize_t nowayout_store(struct device *dev, struct device_attribute *attr,
+				const char *buf, size_t len)
+{
+	struct watchdog_device *wdd = dev_get_drvdata(dev);
+	unsigned int value;
+	int ret;
+
+	ret = kstrtouint(buf, 0, &value);
+	if (ret)
+		return ret;
+	if (value > 1)
+		return -EINVAL;
+	/* nowayout cannot be disabled once set */
+	if (test_bit(WDOG_NO_WAY_OUT, &wdd->status) && !value)
+		return -EPERM;
+	watchdog_set_nowayout(wdd, value);
+	return len;
+}
+static DEVICE_ATTR_RW(nowayout);
+
+static ssize_t status_show(struct device *dev, struct device_attribute *attr,
+				char *buf)
+{
+	struct watchdog_device *wdd = dev_get_drvdata(dev);
+	struct watchdog_core_data *wd_data = wdd->wd_data;
+	unsigned int status;
+
+	mutex_lock(&wd_data->lock);
+	status = watchdog_get_status(wdd);
+	mutex_unlock(&wd_data->lock);
+
+	return sysfs_emit(buf, "0x%x\n", status);
+}
+static DEVICE_ATTR_RO(status);
+
+static ssize_t bootstatus_show(struct device *dev,
+				struct device_attribute *attr, char *buf)
+{
+	struct watchdog_device *wdd = dev_get_drvdata(dev);
+
+	return sysfs_emit(buf, "%u\n", wdd->bootstatus);
+}
+static DEVICE_ATTR_RO(bootstatus);
+
+static ssize_t timeleft_show(struct device *dev, struct device_attribute *attr,
+				char *buf)
+{
+	struct watchdog_device *wdd = dev_get_drvdata(dev);
+	struct watchdog_core_data *wd_data = wdd->wd_data;
+	ssize_t status;
+	unsigned int val;
+
+	mutex_lock(&wd_data->lock);
+	status = watchdog_get_timeleft(wdd, &val);
+	mutex_unlock(&wd_data->lock);
+	if (!status)
+		status = sysfs_emit(buf, "%u\n", val);
+
+	return status;
+}
+static DEVICE_ATTR_RO(timeleft);
+
+static ssize_t timeout_show(struct device *dev, struct device_attribute *attr,
+				char *buf)
+{
+	struct watchdog_device *wdd = dev_get_drvdata(dev);
+
+	return sysfs_emit(buf, "%u\n", wdd->timeout);
+}
+static DEVICE_ATTR_RO(timeout);
+
+static ssize_t min_timeout_show(struct device *dev,
+				struct device_attribute *attr, char *buf)
+{
+	struct watchdog_device *wdd = dev_get_drvdata(dev);
+
+	return sysfs_emit(buf, "%u\n", wdd->min_timeout);
+}
+static DEVICE_ATTR_RO(min_timeout);
+
+static ssize_t max_timeout_show(struct device *dev,
+				struct device_attribute *attr, char *buf)
+{
+	struct watchdog_device *wdd = dev_get_drvdata(dev);
+
+	return sysfs_emit(buf, "%u\n", wdd->max_timeout);
+}
+static DEVICE_ATTR_RO(max_timeout);
+
+static ssize_t pretimeout_show(struct device *dev,
+			       struct device_attribute *attr, char *buf)
+{
+	struct watchdog_device *wdd = dev_get_drvdata(dev);
+
+	return sysfs_emit(buf, "%u\n", wdd->pretimeout);
+}
+static DEVICE_ATTR_RO(pretimeout);
+
+static ssize_t identity_show(struct device *dev, struct device_attribute *attr,
+				char *buf)
+{
+	struct watchdog_device *wdd = dev_get_drvdata(dev);
+
+	return sysfs_emit(buf, "%s\n", wdd->info->identity);
+}
+static DEVICE_ATTR_RO(identity);
+
+static ssize_t state_show(struct device *dev, struct device_attribute *attr,
+				char *buf)
+{
+	struct watchdog_device *wdd = dev_get_drvdata(dev);
+
+	if (watchdog_active(wdd))
+		return sysfs_emit(buf, "active\n");
+
+	return sysfs_emit(buf, "inactive\n");
+}
+static DEVICE_ATTR_RO(state);
+
+static ssize_t pretimeout_available_governors_show(struct device *dev,
+				   struct device_attribute *attr, char *buf)
+{
+	return watchdog_pretimeout_available_governors_get(buf);
+}
+static DEVICE_ATTR_RO(pretimeout_available_governors);
+
+static ssize_t pretimeout_governor_show(struct device *dev,
+					struct device_attribute *attr,
+					char *buf)
+{
+	struct watchdog_device *wdd = dev_get_drvdata(dev);
+
+	return watchdog_pretimeout_governor_get(wdd, buf);
+}
+
+static ssize_t pretimeout_governor_store(struct device *dev,
+					 struct device_attribute *attr,
+					 const char *buf, size_t count)
+{
+	struct watchdog_device *wdd = dev_get_drvdata(dev);
+	int ret = watchdog_pretimeout_governor_set(wdd, buf);
+
+	if (!ret)
+		ret = count;
+
+	return ret;
+}
+static DEVICE_ATTR_RW(pretimeout_governor);
+
+static umode_t wdt_is_visible(struct kobject *kobj, struct attribute *attr,
+				int n)
+{
+	struct device *dev = kobj_to_dev(kobj);
+	struct watchdog_device *wdd = dev_get_drvdata(dev);
+	umode_t mode = attr->mode;
+
+	if (attr == &dev_attr_timeleft.attr && !wdd->ops->get_timeleft)
+		mode = 0;
+	else if (attr == &dev_attr_pretimeout.attr && !watchdog_have_pretimeout(wdd))
+		mode = 0;
+	else if ((attr == &dev_attr_pretimeout_governor.attr ||
+		  attr == &dev_attr_pretimeout_available_governors.attr) &&
+		 (!watchdog_have_pretimeout(wdd) || !IS_ENABLED(CONFIG_WATCHDOG_PRETIMEOUT_GOV)))
+		mode = 0;
+
+	return mode;
+}
+static struct attribute *wdt_attrs[] = {
+	&dev_attr_state.attr,
+	&dev_attr_identity.attr,
+	&dev_attr_timeout.attr,
+	&dev_attr_min_timeout.attr,
+	&dev_attr_max_timeout.attr,
+	&dev_attr_pretimeout.attr,
+	&dev_attr_timeleft.attr,
+	&dev_attr_bootstatus.attr,
+	&dev_attr_status.attr,
+	&dev_attr_nowayout.attr,
+	&dev_attr_pretimeout_governor.attr,
+	&dev_attr_pretimeout_available_governors.attr,
+	NULL,
+};
+
+static const struct attribute_group wdt_group = {
+	.attrs = wdt_attrs,
+	.is_visible = wdt_is_visible,
+};
+__ATTRIBUTE_GROUPS(wdt);
+#else
+#define wdt_groups	NULL
+#endif
+
+/*
+ * watchdog_ioctl_op - call the watchdog drivers ioctl op if defined
+ * @wdd: The watchdog device to do the ioctl on
+ * @cmd: Watchdog command
+ * @arg: Argument pointer
+ *
+ * The caller must hold wd_data->lock.
+ *
+ * Return: 0 if successful, error otherwise.
+ */
+static int watchdog_ioctl_op(struct watchdog_device *wdd, unsigned int cmd,
+							unsigned long arg)
+{
+	if (!wdd->ops->ioctl)
+		return -ENOIOCTLCMD;
+
+	return wdd->ops->ioctl(wdd, cmd, arg);
+}
+
+/*
+ * 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).
+ *
+ * Return: @len if successful, error otherwise.
+ */
+static ssize_t watchdog_write(struct file *file, const char __user *data,
+						size_t len, loff_t *ppos)
+{
+	struct watchdog_core_data *wd_data = file->private_data;
+	struct watchdog_device *wdd;
+	int err;
+	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, &wd_data->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, &wd_data->status);
+	}
+
+	/* someone wrote to us, so we send the watchdog a keepalive ping */
+
+	err = -ENODEV;
+	mutex_lock(&wd_data->lock);
+	wdd = wd_data->wdd;
+	if (wdd)
+		err = watchdog_ping(wdd);
+	mutex_unlock(&wd_data->lock);
+
+	if (err < 0)
+		return err;
+
+	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.
+ *
+ * Return: 0 if successful, error otherwise.
+ */
+
+static long watchdog_ioctl(struct file *file, unsigned int cmd,
+							unsigned long arg)
+{
+	struct watchdog_core_data *wd_data = file->private_data;
+	void __user *argp = (void __user *)arg;
+	struct watchdog_device *wdd;
+	int __user *p = argp;
+	unsigned int val;
+	int err;
+
+	mutex_lock(&wd_data->lock);
+
+	wdd = wd_data->wdd;
+	if (!wdd) {
+		err = -ENODEV;
+		goto out_ioctl;
+	}
+
+	err = watchdog_ioctl_op(wdd, cmd, arg);
+	if (err != -ENOIOCTLCMD)
+		goto out_ioctl;
+
+	switch (cmd) {
+	case WDIOC_GETSUPPORT:
+		err = copy_to_user(argp, wdd->info,
+			sizeof(struct watchdog_info)) ? -EFAULT : 0;
+		break;
+	case WDIOC_GETSTATUS:
+		val = watchdog_get_status(wdd);
+		err = put_user(val, p);
+		break;
+	case WDIOC_GETBOOTSTATUS:
+		err = put_user(wdd->bootstatus, p);
+		break;
+	case WDIOC_SETOPTIONS:
+		if (get_user(val, p)) {
+			err = -EFAULT;
+			break;
+		}
+		if (val & WDIOS_DISABLECARD) {
+			err = watchdog_stop(wdd);
+			if (err < 0)
+				break;
+		}
+		if (val & WDIOS_ENABLECARD)
+			err = watchdog_start(wdd);
+		break;
+	case WDIOC_KEEPALIVE:
+		if (!(wdd->info->options & WDIOF_KEEPALIVEPING)) {
+			err = -EOPNOTSUPP;
+			break;
+		}
+		err = watchdog_ping(wdd);
+		break;
+	case WDIOC_SETTIMEOUT:
+		if (get_user(val, p)) {
+			err = -EFAULT;
+			break;
+		}
+		err = watchdog_set_timeout(wdd, val);
+		if (err < 0)
+			break;
+		/* 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) */
+		err = watchdog_ping(wdd);
+		if (err < 0)
+			break;
+		fallthrough;
+	case WDIOC_GETTIMEOUT:
+		/* timeout == 0 means that we don't know the timeout */
+		if (wdd->timeout == 0) {
+			err = -EOPNOTSUPP;
+			break;
+		}
+		err = put_user(wdd->timeout, p);
+		break;
+	case WDIOC_GETTIMELEFT:
+		err = watchdog_get_timeleft(wdd, &val);
+		if (err < 0)
+			break;
+		err = put_user(val, p);
+		break;
+	case WDIOC_SETPRETIMEOUT:
+		if (get_user(val, p)) {
+			err = -EFAULT;
+			break;
+		}
+		err = watchdog_set_pretimeout(wdd, val);
+		break;
+	case WDIOC_GETPRETIMEOUT:
+		err = put_user(wdd->pretimeout, p);
+		break;
+	default:
+		err = -ENOTTY;
+		break;
+	}
+
+out_ioctl:
+	mutex_unlock(&wd_data->lock);
+	return err;
+}
+
+/*
+ * 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.
+ *
+ * Return: 0 if successful, error otherwise.
+ */
+static int watchdog_open(struct inode *inode, struct file *file)
+{
+	struct watchdog_core_data *wd_data;
+	struct watchdog_device *wdd;
+	bool hw_running;
+	int err;
+
+	/* Get the corresponding watchdog device */
+	if (imajor(inode) == MISC_MAJOR)
+		wd_data = old_wd_data;
+	else
+		wd_data = container_of(inode->i_cdev, struct watchdog_core_data,
+				       cdev);
+
+	/* the watchdog is single open! */
+	if (test_and_set_bit(_WDOG_DEV_OPEN, &wd_data->status))
+		return -EBUSY;
+
+	wdd = wd_data->wdd;
+
+	/*
+	 * If the /dev/watchdog device is open, we don't want the module
+	 * to be unloaded.
+	 */
+	hw_running = watchdog_hw_running(wdd);
+	if (!hw_running && !try_module_get(wdd->ops->owner)) {
+		err = -EBUSY;
+		goto out_clear;
+	}
+
+	err = watchdog_start(wdd);
+	if (err < 0)
+		goto out_mod;
+
+	file->private_data = wd_data;
+
+	if (!hw_running)
+		get_device(&wd_data->dev);
+
+	/*
+	 * open_timeout only applies for the first open from
+	 * userspace. Set open_deadline to infinity so that the kernel
+	 * will take care of an always-running hardware watchdog in
+	 * case the device gets magic-closed or WDIOS_DISABLECARD is
+	 * applied.
+	 */
+	wd_data->open_deadline = KTIME_MAX;
+
+	/* dev/watchdog is a virtual (and thus non-seekable) filesystem */
+	return stream_open(inode, file);
+
+out_mod:
+	module_put(wd_data->wdd->ops->owner);
+out_clear:
+	clear_bit(_WDOG_DEV_OPEN, &wd_data->status);
+	return err;
+}
+
+static void watchdog_core_data_release(struct device *dev)
+{
+	struct watchdog_core_data *wd_data;
+
+	wd_data = container_of(dev, struct watchdog_core_data, dev);
+
+	kfree(wd_data);
+}
+
+/*
+ * 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.
+ *
+ * Always returns 0.
+ */
+static int watchdog_release(struct inode *inode, struct file *file)
+{
+	struct watchdog_core_data *wd_data = file->private_data;
+	struct watchdog_device *wdd;
+	int err = -EBUSY;
+	bool running;
+
+	mutex_lock(&wd_data->lock);
+
+	wdd = wd_data->wdd;
+	if (!wdd)
+		goto done;
+
+	/*
+	 * 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 (!watchdog_active(wdd))
+		err = 0;
+	else if (test_and_clear_bit(_WDOG_ALLOW_RELEASE, &wd_data->status) ||
+		 !(wdd->info->options & WDIOF_MAGICCLOSE))
+		err = watchdog_stop(wdd);
+
+	/* If the watchdog was not stopped, send a keepalive ping */
+	if (err < 0) {
+		pr_crit("watchdog%d: watchdog did not stop!\n", wdd->id);
+		watchdog_ping(wdd);
+	}
+
+	watchdog_update_worker(wdd);
+
+	/* make sure that /dev/watchdog can be re-opened */
+	clear_bit(_WDOG_DEV_OPEN, &wd_data->status);
+
+done:
+	running = wdd && watchdog_hw_running(wdd);
+	mutex_unlock(&wd_data->lock);
+	/*
+	 * Allow the owner module to be unloaded again unless the watchdog
+	 * is still running. If the watchdog is still running, it can not
+	 * be stopped, and its driver must not be unloaded.
+	 */
+	if (!running) {
+		module_put(wd_data->cdev.owner);
+		put_device(&wd_data->dev);
+	}
+	return 0;
+}
+
+static const struct file_operations watchdog_fops = {
+	.owner		= THIS_MODULE,
+	.write		= watchdog_write,
+	.unlocked_ioctl	= watchdog_ioctl,
+	.compat_ioctl	= compat_ptr_ioctl,
+	.open		= watchdog_open,
+	.release	= watchdog_release,
+};
+
+static struct miscdevice watchdog_miscdev = {
+	.minor		= WATCHDOG_MINOR,
+	.name		= "watchdog",
+	.fops		= &watchdog_fops,
+};
+
+static struct class watchdog_class = {
+	.name =		"watchdog",
+	.owner =	THIS_MODULE,
+	.dev_groups =	wdt_groups,
+};
+
+/*
+ * watchdog_cdev_register - register watchdog character device
+ * @wdd: Watchdog device
+ *
+ * Register a watchdog character device including handling the legacy
+ * /dev/watchdog node. /dev/watchdog is actually a miscdevice and
+ * thus we set it up like that.
+ *
+ * Return: 0 if successful, error otherwise.
+ */
+static int watchdog_cdev_register(struct watchdog_device *wdd)
+{
+	struct watchdog_core_data *wd_data;
+	int err;
+
+	wd_data = kzalloc(sizeof(struct watchdog_core_data), GFP_KERNEL);
+	if (!wd_data)
+		return -ENOMEM;
+	mutex_init(&wd_data->lock);
+
+	wd_data->wdd = wdd;
+	wdd->wd_data = wd_data;
+
+	if (IS_ERR_OR_NULL(watchdog_kworker)) {
+		kfree(wd_data);
+		return -ENODEV;
+	}
+
+	device_initialize(&wd_data->dev);
+	wd_data->dev.devt = MKDEV(MAJOR(watchdog_devt), wdd->id);
+	wd_data->dev.class = &watchdog_class;
+	wd_data->dev.parent = wdd->parent;
+	wd_data->dev.groups = wdd->groups;
+	wd_data->dev.release = watchdog_core_data_release;
+	dev_set_drvdata(&wd_data->dev, wdd);
+	err = dev_set_name(&wd_data->dev, "watchdog%d", wdd->id);
+	if (err) {
+		put_device(&wd_data->dev);
+		return err;
+	}
+
+	kthread_init_work(&wd_data->work, watchdog_ping_work);
+	hrtimer_init(&wd_data->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_HARD);
+	wd_data->timer.function = watchdog_timer_expired;
+	watchdog_hrtimer_pretimeout_init(wdd);
+
+	if (wdd->id == 0) {
+		old_wd_data = wd_data;
+		watchdog_miscdev.parent = wdd->parent;
+		err = misc_register(&watchdog_miscdev);
+		if (err != 0) {
+			pr_err("%s: cannot register miscdev on minor=%d (err=%d).\n",
+				wdd->info->identity, WATCHDOG_MINOR, err);
+			if (err == -EBUSY)
+				pr_err("%s: a legacy watchdog module is probably present.\n",
+					wdd->info->identity);
+			old_wd_data = NULL;
+			put_device(&wd_data->dev);
+			return err;
+		}
+	}
+
+	/* Fill in the data structures */
+	cdev_init(&wd_data->cdev, &watchdog_fops);
+	wd_data->cdev.owner = wdd->ops->owner;
+
+	/* Add the device */
+	err = cdev_device_add(&wd_data->cdev, &wd_data->dev);
+	if (err) {
+		pr_err("watchdog%d unable to add device %d:%d\n",
+			wdd->id,  MAJOR(watchdog_devt), wdd->id);
+		if (wdd->id == 0) {
+			misc_deregister(&watchdog_miscdev);
+			old_wd_data = NULL;
+		}
+		put_device(&wd_data->dev);
+		return err;
+	}
+
+	/* Record time of most recent heartbeat as 'just before now'. */
+	wd_data->last_hw_keepalive = ktime_sub(ktime_get(), 1);
+	watchdog_set_open_deadline(wd_data);
+
+	/*
+	 * If the watchdog is running, prevent its driver from being unloaded,
+	 * and schedule an immediate ping.
+	 */
+	if (watchdog_hw_running(wdd)) {
+		__module_get(wdd->ops->owner);
+		get_device(&wd_data->dev);
+		if (handle_boot_enabled)
+			hrtimer_start(&wd_data->timer, 0,
+				      HRTIMER_MODE_REL_HARD);
+		else
+			pr_info("watchdog%d running and kernel based pre-userspace handler disabled\n",
+				wdd->id);
+	}
+
+	return 0;
+}
+
+/*
+ * watchdog_cdev_unregister - unregister watchdog character device
+ * @wdd: Watchdog device
+ *
+ * Unregister watchdog character device and if needed the legacy
+ * /dev/watchdog device.
+ */
+static void watchdog_cdev_unregister(struct watchdog_device *wdd)
+{
+	struct watchdog_core_data *wd_data = wdd->wd_data;
+
+	cdev_device_del(&wd_data->cdev, &wd_data->dev);
+	if (wdd->id == 0) {
+		misc_deregister(&watchdog_miscdev);
+		old_wd_data = NULL;
+	}
+
+	if (watchdog_active(wdd) &&
+	    test_bit(WDOG_STOP_ON_UNREGISTER, &wdd->status)) {
+		watchdog_stop(wdd);
+	}
+
+	watchdog_hrtimer_pretimeout_stop(wdd);
+
+	mutex_lock(&wd_data->lock);
+	wd_data->wdd = NULL;
+	wdd->wd_data = NULL;
+	mutex_unlock(&wd_data->lock);
+
+	hrtimer_cancel(&wd_data->timer);
+	kthread_cancel_work_sync(&wd_data->work);
+
+	put_device(&wd_data->dev);
+}
+
+/**
+ * watchdog_dev_register - register a watchdog device
+ * @wdd: 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.
+ *
+ * Return: 0 if successful, error otherwise.
+ */
+int watchdog_dev_register(struct watchdog_device *wdd)
+{
+	int ret;
+
+	ret = watchdog_cdev_register(wdd);
+	if (ret)
+		return ret;
+
+	ret = watchdog_register_pretimeout(wdd);
+	if (ret)
+		watchdog_cdev_unregister(wdd);
+
+	return ret;
+}
+
+/**
+ * watchdog_dev_unregister - unregister a watchdog device
+ * @wdd: watchdog device
+ *
+ * Unregister watchdog device and if needed the legacy
+ * /dev/watchdog device.
+ */
+void watchdog_dev_unregister(struct watchdog_device *wdd)
+{
+	watchdog_unregister_pretimeout(wdd);
+	watchdog_cdev_unregister(wdd);
+}
+
+/**
+ * watchdog_set_last_hw_keepalive - set last HW keepalive time for watchdog
+ * @wdd:		Watchdog device
+ * @last_ping_ms:	Time since last HW heartbeat
+ *
+ * Adjusts the last known HW keepalive time for a watchdog timer.
+ * This is needed if the watchdog is already running when the probe
+ * function is called, and it can't be pinged immediately. This
+ * function must be called immediately after watchdog registration,
+ * and min_hw_heartbeat_ms must be set for this to be useful.
+ *
+ * Return: 0 if successful, error otherwise.
+ */
+int watchdog_set_last_hw_keepalive(struct watchdog_device *wdd,
+				   unsigned int last_ping_ms)
+{
+	struct watchdog_core_data *wd_data;
+	ktime_t now;
+
+	if (!wdd)
+		return -EINVAL;
+
+	wd_data = wdd->wd_data;
+
+	now = ktime_get();
+
+	wd_data->last_hw_keepalive = ktime_sub(now, ms_to_ktime(last_ping_ms));
+
+	if (watchdog_hw_running(wdd) && handle_boot_enabled)
+		return __watchdog_ping(wdd);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(watchdog_set_last_hw_keepalive);
+
+/**
+ * watchdog_dev_init - init dev part of watchdog core
+ *
+ * Allocate a range of chardev nodes to use for watchdog devices.
+ *
+ * Return: 0 if successful, error otherwise.
+ */
+int __init watchdog_dev_init(void)
+{
+	int err;
+
+	watchdog_kworker = kthread_create_worker(0, "watchdogd");
+	if (IS_ERR(watchdog_kworker)) {
+		pr_err("Failed to create watchdog kworker\n");
+		return PTR_ERR(watchdog_kworker);
+	}
+	sched_set_fifo(watchdog_kworker->task);
+
+	err = class_register(&watchdog_class);
+	if (err < 0) {
+		pr_err("couldn't register class\n");
+		goto err_register;
+	}
+
+	err = alloc_chrdev_region(&watchdog_devt, 0, MAX_DOGS, "watchdog");
+	if (err < 0) {
+		pr_err("watchdog: unable to allocate char dev region\n");
+		goto err_alloc;
+	}
+
+	return 0;
+
+err_alloc:
+	class_unregister(&watchdog_class);
+err_register:
+	kthread_destroy_worker(watchdog_kworker);
+	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);
+	class_unregister(&watchdog_class);
+	kthread_destroy_worker(watchdog_kworker);
+}
+
+int watchdog_dev_suspend(struct watchdog_device *wdd)
+{
+	struct watchdog_core_data *wd_data = wdd->wd_data;
+	int ret = 0;
+
+	if (!wdd->wd_data)
+		return -ENODEV;
+
+	/* ping for the last time before suspend */
+	mutex_lock(&wd_data->lock);
+	if (watchdog_worker_should_ping(wd_data))
+		ret = __watchdog_ping(wd_data->wdd);
+	mutex_unlock(&wd_data->lock);
+
+	if (ret)
+		return ret;
+
+	/*
+	 * make sure that watchdog worker will not kick in when the wdog is
+	 * suspended
+	 */
+	hrtimer_cancel(&wd_data->timer);
+	kthread_cancel_work_sync(&wd_data->work);
+
+	return 0;
+}
+
+int watchdog_dev_resume(struct watchdog_device *wdd)
+{
+	struct watchdog_core_data *wd_data = wdd->wd_data;
+	int ret = 0;
+
+	if (!wdd->wd_data)
+		return -ENODEV;
+
+	/*
+	 * __watchdog_ping will also retrigger hrtimer and therefore restore the
+	 * ping worker if needed.
+	 */
+	mutex_lock(&wd_data->lock);
+	if (watchdog_worker_should_ping(wd_data))
+		ret = __watchdog_ping(wd_data->wdd);
+	mutex_unlock(&wd_data->lock);
+
+	return ret;
+}
+
+module_param(handle_boot_enabled, bool, 0444);
+MODULE_PARM_DESC(handle_boot_enabled,
+	"Watchdog core auto-updates boot enabled watchdogs before userspace takes over (default="
+	__MODULE_STRING(IS_ENABLED(CONFIG_WATCHDOG_HANDLE_BOOT_ENABLED)) ")");
+
+module_param(open_timeout, uint, 0644);
+MODULE_PARM_DESC(open_timeout,
+	"Maximum time (in seconds, 0 means infinity) for userspace to take over a running watchdog (default="
+	__MODULE_STRING(CONFIG_WATCHDOG_OPEN_TIMEOUT) ")");