watchdog: WatchDog Timer Driver Core - Add minimum and max timeout

Add min_timeout (minimum timeout) and max_timeout
values so that the framework can check if the new
timeout value is between the minimum and maximum
timeout values. If both values are 0, then the
framework will leave the check for the watchdog
device driver itself.
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>

Documentation/watchdog/watchdog-kernel-api.txt

@@ -43,6 +43,8 @@ struct watchdog_device {
 	const struct watchdog_ops *ops;
 	unsigned int bootstatus;
 	unsigned int timeout;
+	unsigned int min_timeout;
+	unsigned int max_timeout;
 	void *driver_data;
 	unsigned long status;
 };
@@ -52,6 +54,8 @@ It contains following fields:
   additional information about the watchdog timer itself. (Like it's unique name)
 * ops: a pointer to the list of watchdog operations that the watchdog supports.
 * timeout: the watchdog timer's timeout value (in seconds).
+* min_timeout: the watchdog timer's minimum timeout value (in seconds).
+* max_timeout: the watchdog timer's maximum timeout value (in seconds).
 * bootstatus: status of the device after booting (reported with watchdog
   WDIOF_* status bits).
 * driver_data: a pointer to the drivers private data of a watchdog device.

drivers/watchdog/watchdog_core.c

@@ -58,6 +58,16 @@ int watchdog_register_device(struct watchdog_device *wdd)
 	if (wdd->ops->start == NULL || wdd->ops->stop == NULL)
 		return -EINVAL;
 
+	/*
+	 * Check that we have valid min and max timeout values, if
+	 * not reset them both to 0 (=not used or unknown)
+	 */
+	if (wdd->min_timeout > wdd->max_timeout) {
+		pr_info("Invalid min and max timeout values, resetting to 0!\n");
+		wdd->min_timeout = 0;
+		wdd->max_timeout = 0;
+	}
+
 	/*
 	 * Note: now that all watchdog_device data has been verified, we
 	 * will not check this anymore in other functions. If data gets

drivers/watchdog/watchdog_dev.c

@@ -220,6 +220,9 @@ static long watchdog_ioctl(struct file *file, unsigned int cmd,
 			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;

include/linux/watchdog.h

@@ -95,6 +95,8 @@ struct watchdog_ops {
  * @ops:	Pointer to the list of watchdog operations.
  * @bootstatus:	Status of the watchdog device at boot.
  * @timeout:	The watchdog devices timeout value.
+ * @min_timeout:The watchdog devices minimum timeout value.
+ * @max_timeout:The watchdog devices maximum timeout value.
  * @driver-data:Pointer to the drivers private data.
  * @status:	Field that contains the devices internal status bits.
  *
@@ -109,6 +111,8 @@ struct watchdog_device {
 	const struct watchdog_ops *ops;
 	unsigned int bootstatus;
 	unsigned int timeout;
+	unsigned int min_timeout;
+	unsigned int max_timeout;
 	void *driver_data;
 	unsigned long status;
 /* Bit numbers for status flags */