2 files changed, 8 insertions, 4 deletions

diff --git a/Documentation/input/multi-touch-protocol.txt b/Documentation/input/multi-touch-protocol.txt
index 7b4f59c09ee2..b85d000faeb4 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 a1d7e931ab72..2320b0ce7579 100644
--- a/include/uapi/linux/input.h
+++ b/include/uapi/linux/input.h
@@ -972,7 +972,8 @@ 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