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authorHenrik Rydberg <rydberg@euromail.se>2010-03-21 22:31:26 -0700
committerDmitry Torokhov <dmitry.torokhov@gmail.com>2010-03-21 22:38:56 -0700
commit97065e033ec5fd824d0133ecd0c614fe1e5c20bd (patch)
tree4914099f6e34c75a6994dd2f90c8236fc808118f /Documentation/input
parentd90e6f6aad0ffdc674bc3a05c85c40dcc18e604c (diff)
downloadlinux-97065e033ec5fd824d0133ecd0c614fe1e5c20bd.tar.gz
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>
Diffstat (limited to 'Documentation/input')
-rw-r--r--Documentation/input/multi-touch-protocol.txt16
1 files changed, 16 insertions, 0 deletions
diff --git a/Documentation/input/multi-touch-protocol.txt b/Documentation/input/multi-touch-protocol.txt
index 8490480ce43..eacb2260666 100644
--- a/Documentation/input/multi-touch-protocol.txt
+++ b/Documentation/input/multi-touch-protocol.txt
@@ -68,6 +68,22 @@ like:
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
---------------