Input: make sure input handlers define only one processing method

Input core expects input handlers to be either filters, or regular
handlers, but not both. Additionally, for regular handlers it does
not make sense to define both single event method and batch method.

Refuse registering handler if it defines more than one method.

Reviewed-by: Jeff LaBundy <jeff@labundy.com>
Reviewed-by: Benjamin Tissoires <bentiss@kernel.org>
Link: https://lore.kernel.org/r/20240703213756.3375978-3-dmitry.torokhov@gmail.com
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

1 files changed, 24 insertions, 0 deletions

diff --git a/drivers/input/input.c b/drivers/input/input.c
index fd4997ba263c..7e4f8824f4fd 100644
--- a/drivers/input/input.c
+++ b/drivers/input/input.c
@@ -2517,6 +2517,26 @@ void input_unregister_device(struct input_dev *dev)
 }
 EXPORT_SYMBOL(input_unregister_device);
 
+static int input_handler_check_methods(const struct input_handler *handler)
+{
+	int count = 0;
+
+	if (handler->filter)
+		count++;
+	if (handler->events)
+		count++;
+	if (handler->event)
+		count++;
+
+	if (count > 1) {
+		pr_err("%s: only one event processing method can be defined (%s)\n",
+		       __func__, handler->name);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
 /**
  * input_register_handler - register a new input handler
  * @handler: handler to be registered
@@ -2530,6 +2550,10 @@ int input_register_handler(struct input_handler *handler)
 	struct input_dev *dev;
 	int error;
 
+	error = input_handler_check_methods(handler);
+	if (error)
+		return error;
+
 	error = mutex_lock_interruptible(&input_mutex);
 	if (error)
 		return error;