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Commit 97065e03 authored by Henrik Rydberg's avatar Henrik Rydberg Committed by Dmitry Torokhov
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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: default avatarHenrik Rydberg <rydberg@euromail.se>
Signed-off-by: default avatarDmitry Torokhov <dtor@mail.ru>
parent d90e6f6a

Documentation/input/multi-touch-protocol.txt

+16 −0
Original line number Original line Diff line number Diff line
@@ -68,6 +68,22 @@ like: 
   SYN_MT_REPORT

   SYN_MT_REPORT

   SYN_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

Event Semantics

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