[PATCH 3/3] input: reintroduce filtering of mt axis when the device is not multitouch

[Benjamin Tissoires <benjamin.tissoires@redhat.com>]

Some devices (like the PS3 Sixaxis) have a lot of absolute axis which
are mapped by hid-input on ABS_MISC and beyond. These axis interfere
with the multitouch protocol.
The kernel considers those device to be following the multitouch protocol
A, and removes the filtering of such events.

We can rely on INPUT_PROP_MT to know if the device is multitouch or not,
and then rely on mt to know if the device uses the protocol B.

Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
---
 Documentation/input/multi-touch-protocol.txt | 3 ++-
 drivers/input/input.c                        | 3 ++-
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/Documentation/input/multi-touch-protocol.txt b/Documentation/input/multi-touch-protocol.txt
index 420444f..b476845 100644
--- a/Documentation/input/multi-touch-protocol.txt
+++ b/Documentation/input/multi-touch-protocol.txt
@@ -55,7 +55,8 @@ surface. The order in which the packets appear in the event stream is not
 important.  Event filtering and finger tracking is left to user space [3].
 
 Note that type A device are requested to manually set the property
-INPUT_PROP_MT.
+INPUT_PROP_MT. If this property is not set, the absolute multitouch axis
+will be statefull, so this step is now mandatory.
 Type B devices does not need to set INPUT_PROP_MT manually, as this is done
 by calling input_mt_init_slot().
 
diff --git a/drivers/input/input.c b/drivers/input/input.c
index 1198785..239639e 100644
--- a/drivers/input/input.c
+++ b/drivers/input/input.c
@@ -224,7 +224,8 @@ static int input_handle_abs_event(struct input_dev *dev,
 		return INPUT_IGNORE_EVENT;
 	}
 
-	is_mt_event = input_is_mt_value(code);
+	is_mt_event = test_bit(INPUT_PROP_MT, dev->propbit) &&
+			input_is_mt_value(code);
 
 	if (!is_mt_event) {
 		pold = &dev->absinfo[code].value;
-- 
1.8.3.1