Input: add input_device_enabled()

A helper function for drivers to decide if the device is used or not.
A lockdep check is introduced as inspecting ->users should be done under
input device's mutex.
Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@collabora.com>
Link: https://lore.kernel.org/r/20200608112211.12125-2-andrzej.p@collabora.comSigned-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

drivers/input/input.c

@@ -2127,6 +2127,14 @@ void input_enable_softrepeat(struct input_dev *dev, int delay, int period)
 }
 EXPORT_SYMBOL(input_enable_softrepeat);
 
+bool input_device_enabled(struct input_dev *dev)
+{
+	lockdep_assert_held(&dev->mutex);
+
+	return dev->users > 0;
+}
+EXPORT_SYMBOL_GPL(input_device_enabled);
+
 /**
  * input_register_device - register device with input core
  * @dev: device to be registered

include/linux/input.h

@@ -502,6 +502,8 @@ bool input_match_device_id(const struct input_dev *dev,
 
 void input_enable_softrepeat(struct input_dev *dev, int delay, int period);
 
+bool input_device_enabled(struct input_dev *dev);
+
 extern struct class input_class;
 
 /**