watchdog: Add interface to config timeout and pretimeout in sysfs

ascend inclusion
category: feature
bugzilla: NA
CVE: NA

Those interfaces exist already in sysfs of watchdog driver core, but
they are readonly. This patch add write hook so we can config timeout
and pretimeout by writing those files.

Use Kconfig ASCEND_WATCHDOG_SYSFS_CONFIGURE to select this feature.
Signed-off-by: NWang Wensheng <wangwensheng4@huawei.com>
Acked-by: NWeilong Chen <chenweilong@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

arch/arm64/Kconfig

@@ -1370,6 +1370,16 @@ config ASCEND_CHARGE_MIGRATE_HUGEPAGES
 	  This option enable the feature to charge migrate hugepages to memory
 	  cgroup.
 
+config ASCEND_WATCHDOG_SYSFS_CONFIGURE
+	bool "Configure watchdog timeout and pretimeout via sysfs"
+	depends on WATCHDOG_SYSFS
+	help
+	  Add interface for user to configure timeout and pretimeout through
+	  sysfs. Enable this config carefully since a user could change the
+	  timeout value without notifying the userspace process that pings the
+	  watchdog. The kernel thread could be notified so it's ok to make that
+	  change when the watchdog is pinged by kernel thread.
+
 endif
 
 endmenu

drivers/watchdog/watchdog_dev.c

@@ -485,7 +485,41 @@ static ssize_t timeout_show(struct device *dev, struct device_attribute *attr,
 
 	return sprintf(buf, "%u\n", wdd->timeout);
 }
+
+#ifdef CONFIG_ASCEND_WATCHDOG_SYSFS_CONFIGURE
+static int sysfs_write;
+module_param(sysfs_write, int, 0);
+MODULE_PARM_DESC(sysfs_write,
+		 "enable configuring timeout and pretimeout via sysfs");
+
+static ssize_t timeout_store(struct device *dev, struct device_attribute *attr,
+				const char *buf, size_t count)
+{
+	int ret;
+	unsigned int val;
+	struct watchdog_device *wdd = dev_get_drvdata(dev);
+	struct watchdog_core_data *wd_data = wdd->wd_data;
+
+	if (!sysfs_write)
+		return -EOPNOTSUPP;
+
+	ret = kstrtouint(buf, 0, &val);
+	if (ret)
+		return ret;
+
+	mutex_lock(&wd_data->lock);
+	ret = watchdog_set_timeout(wdd, val);
+	mutex_unlock(&wd_data->lock);
+
+	if (!ret)
+		ret = count;
+
+	return ret;
+}
+static DEVICE_ATTR_RW(timeout);
+#else
 static DEVICE_ATTR_RO(timeout);
+#endif
 
 static ssize_t pretimeout_show(struct device *dev,
 			       struct device_attribute *attr, char *buf)
@@ -494,7 +528,36 @@ static ssize_t pretimeout_show(struct device *dev,
 
 	return sprintf(buf, "%u\n", wdd->pretimeout);
 }
+
+#ifdef CONFIG_ASCEND_WATCHDOG_SYSFS_CONFIGURE
+static ssize_t pretimeout_store(struct device *dev,
+		struct device_attribute *attr, const char *buf, size_t count)
+{
+	int ret;
+	unsigned int val;
+	struct watchdog_device *wdd = dev_get_drvdata(dev);
+	struct watchdog_core_data *wd_data = wdd->wd_data;
+
+	if (!sysfs_write)
+		return -EOPNOTSUPP;
+
+	ret = kstrtouint(buf, 0, &val);
+	if (ret)
+		return ret;
+
+	mutex_lock(&wd_data->lock);
+	ret = watchdog_set_pretimeout(wdd, val);
+	mutex_unlock(&wd_data->lock);
+
+	if (!ret)
+		ret = count;
+
+	return ret;
+}
+static DEVICE_ATTR_RW(pretimeout);
+#else
 static DEVICE_ATTR_RO(pretimeout);
+#endif
 
 static ssize_t identity_show(struct device *dev, struct device_attribute *attr,
 				char *buf)