Input: multitouch - add tracking ID to the protocol

There are a few multi-touch devices that support finger tracking
well in hardware, Stantum being the prime example. By exposing the
tracking ID in the MT protocol, evdev bandwidth and cpu usage in
user space can be reduced.

This patch adds the ABS_MT_TRACKING_ID to the MT protocol.

Signed-off-by: Henrik Rydberg <rydberg@euromail.se>
Tested-by: Stéphane Chatty <chatty@enac.fr>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>

2 files changed, 2 insertions, 0 deletions

diff --git a/drivers/input/input.c b/drivers/input/input.c
index e54e002665b0..5d445f48789b 100644
--- a/drivers/input/input.c
+++ b/drivers/input/input.c
@@ -42,6 +42,7 @@ static unsigned int input_abs_bypass_init_data[] __initdata = {
         ABS_MT_POSITION_Y,
         ABS_MT_TOOL_TYPE,
         ABS_MT_BLOB_ID,
+        ABS_MT_TRACKING_ID,
         0
 };
 static unsigned long input_abs_bypass[BITS_TO_LONGS(ABS_CNT)];
diff --git a/include/linux/input.h b/include/linux/input.h
index 0e6ff5de3588..6fed4f6a9c9e 100644
--- a/include/linux/input.h
+++ b/include/linux/input.h
@@ -656,6 +656,7 @@ struct input_absinfo {
 #define ABS_MT_POSITION_Y       0x36    /* Center Y ellipse position */
 #define ABS_MT_TOOL_TYPE        0x37    /* Type of touching device */
 #define ABS_MT_BLOB_ID          0x38    /* Group a set of packets as a blob */
+#define ABS_MT_TRACKING_ID      0x39    /* Unique ID of initiated contact */
 
 #define ABS_MAX                 0x3f
 #define ABS_CNT                 (ABS_MAX+1)