Input: clarify the no-finger event in multitouch protocol
The current documentation does not explicitly specify how to report
zero fingers, leaving a potential problem in the driver implementations
and giving no parsing directive to userland. This patch defines two
equally valid ways.
Signed-off-by: Henrik Rydberg <rydberg@euromail.se>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>
diff --git a/Documentation/input/multi-touch-protocol.txt b/Documentation/input/multi-touch-protocol.txt
index 8490480..eacb226 100644
--- a/Documentation/input/multi-touch-protocol.txt
+++ b/Documentation/input/multi-touch-protocol.txt
@@ -68,6 +68,22 @@
SYN_MT_REPORT
SYN_REPORT
+Here is the sequence after lifting one of the fingers:
+
+ ABS_MT_POSITION_X
+ ABS_MT_POSITION_Y
+ SYN_MT_REPORT
+ SYN_REPORT
+
+And here is the sequence after lifting the remaining finger:
+
+ SYN_MT_REPORT
+ SYN_REPORT
+
+If the driver reports one of BTN_TOUCH or ABS_PRESSURE in addition to the
+ABS_MT events, the last SYN_MT_REPORT event may be omitted. Otherwise, the
+last SYN_REPORT will be dropped by the input core, resulting in no
+zero-finger event reaching userland.
Event Semantics
---------------