linux-kernel - [PATCH 1/4] Input: make sure input handlers define only one processing method

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Date: Sun, 30 Jun 2024 23:05:49 -0700
From: Dmitry Torokhov <dmitry.torokhov@...il.com>
To: linux-input@...r.kernel.org
Cc: Benjamin Tissoires <bentiss@...nel.org>,
	Jeff LaBundy <jeff@...undy.com>,
	linux-kernel@...r.kernel.org
Subject: [PATCH 1/4] 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.

Signed-off-by: Dmitry Torokhov <dmitry.torokhov@...il.com>
---
 drivers/input/input.c | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/drivers/input/input.c b/drivers/input/input.c
index fd4997ba263c..8434348faeac 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 should 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;
-- 
2.45.2.803.g4e1b14247a-goog