[PATCH] Input: Add MT_TOOL_PALM

[Charlie Mooney <charliemooney@chromium.org>]

Currently there are only two "tools" that can be specified by a
multi-touch driver: MT_TOOL_FINGER and MT_TOOL_PEN.  In working with
Elan (The touch vendor) and discussing their next-gen devices it
seems that it will be useful to have more tools so that their devices
can give the upper layers of the stack hints as to what is touching
the sensor.

In particular they have new experimental firmware that can better
differentiate between palms vs fingertips and would like to plumb a
patch so that we can use their hints in higher-level gesture soft-
ware.  The firmware on the device can reasonably do a better job of
palm detection because it has access to all of the raw sensor readings
as opposed to just the width/pressure/etc that are exposed by the
driver.  As such, the firmware can characterize what a palm looks like
in much finer-grained detail and this change would allow such a
device to share its findings with the kernel.

Signed-off-by: Charlie Mooney <charliemooney@chromium.org>
---
 Documentation/input/multi-touch-protocol.txt | 9 ++++++---
 include/uapi/linux/input.h                   | 3 ++-
 2 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/Documentation/input/multi-touch-protocol.txt b/Documentation/input/multi-touch-protocol.txt
index 7b4f59c..b85d000 100644
--- a/Documentation/input/multi-touch-protocol.txt
+++ b/Documentation/input/multi-touch-protocol.txt
@@ -312,9 +312,12 @@ ABS_MT_TOOL_TYPE
 
 The type of approaching tool. A lot of kernel drivers cannot distinguish
 between different tool types, such as a finger or a pen. In such cases, the
-event should be omitted. The protocol currently supports MT_TOOL_FINGER and
-MT_TOOL_PEN [2]. For type B devices, this event is handled by input core;
-drivers should instead use input_mt_report_slot_state().
+event should be omitted. The protocol currently supports MT_TOOL_FINGER,
+MT_TOOL_PEN, and MT_TOOL_PALM [2]. For type B devices, this event is handled
+by input core; drivers should instead use input_mt_report_slot_state().
+A contact's ABS_MT_TOOL_TYPE may change over time while still touching the
+device, because the firmware may not be able to determine which tool is being
+used when it first appears.
 
 ABS_MT_BLOB_ID
 
diff --git a/include/uapi/linux/input.h b/include/uapi/linux/input.h
index b0a8130..2f62ab2 100644
--- a/include/uapi/linux/input.h
+++ b/include/uapi/linux/input.h
@@ -973,7 +973,8 @@ struct input_keymap_entry {
  */
 #define MT_TOOL_FINGER		0
 #define MT_TOOL_PEN		1
-#define MT_TOOL_MAX		1
+#define MT_TOOL_PALM		2
+#define MT_TOOL_MAX		2
 
 /*
  * Values describing the status of a force-feedback effect
-- 
2.1.2