Input: fix regression when re-registering input handlers

Commit d469647bafd9 ("Input: simplify event handling logic") introduced
code that would set handler->events() method to either
input_handler_events_filter() or input_handler_events_default() or
input_handler_events_null(), depending on the kind of input handler
(a filter or a regular one) we are dealing with. Unfortunately this
breaks cases when we try to re-register the same filter (as is the case
with sysrq handler): after initial registration the handler will have 2
event handling methods defined, and will run afoul of the check in
input_handler_check_methods():

	input: input_handler_check_methods: only one event processing method can be defined (sysrq)
	sysrq: Failed to register input handler, error -22

Fix this by adding handle_events() method to input_handle structure and
setting it up when registering a new input handle according to event
handling methods defined in associated input_handler structure, thus
avoiding modifying the input_handler structure.

Reported-by: "Ned T. Crigler" <crigler@gmail.com>
Reported-by: Christian Heusel <christian@heusel.eu>
Tested-by: "Ned T. Crigler" <crigler@gmail.com>
Tested-by: Peter Seiderer <ps.report@gmx.net>
Fixes: d469647bafd9 ("Input: simplify event handling logic")
Link: https://lore.kernel.org/r/Zx2iQp6csn42PJA7@xavtug
Cc: stable@vger.kernel.org
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

1 files changed, 9 insertions, 1 deletions

diff --git a/include/linux/input.h b/include/linux/input.h
index 89a0be6ee0e2..cd866b020a01 100644
--- a/include/linux/input.h
+++ b/include/linux/input.h
@@ -339,12 +339,16 @@ struct input_handler {
  * @name: name given to the handle by handler that created it
  * @dev: input device the handle is attached to
  * @handler: handler that works with the device through this handle
+ * @handle_events: event sequence handler. It is set up by the input core
+ *	according to event handling method specified in the @handler. See
+ *	input_handle_setup_event_handler().
+ *	This method is being called by the input core with interrupts disabled
+ *	and dev->event_lock spinlock held and so it may not sleep.
  * @d_node: used to put the handle on device's list of attached handles
  * @h_node: used to put the handle on handler's list of handles from which
  *	it gets events
  */
 struct input_handle {
-
 	void *private;
 
 	int open;
@@ -353,6 +357,10 @@ struct input_handle {
 	struct input_dev *dev;
 	struct input_handler *handler;
 
+	unsigned int (*handle_events)(struct input_handle *handle,
+				      struct input_value *vals,
+				      unsigned int count);
+
 	struct list_head	d_node;
 	struct list_head	h_node;
 };