[RFC][PATCH] Input: Use monotonic time for event time stamps.

[john stultz <johnstul@us.ibm.com>]

Hi
	In reviewing the Android patch set, I noticed the following patch from
Arve which looks like it resolves a reasonable issue (events using
CLOCK_REALTIME timestamps, which can jump forwards or backwards via
settimeofday()).

I'm not very familiar with the evdev interface, so I'm not sure if
changing the timestamps to CLOCK_MONOTONIC could cause an ABI problem
with legacy apps. Even so, I wanted to send the patch out for review and
consideration as it seems like a reasonable fix.

thanks
-john



From 20950b728f120cd808965c1a20b024aa79706d8d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=3D=3FUTF-8=3Fq=3FArve=3D20Hj=3DC3=3DB8nnev=3DC3=3DA5g=3F=3D?= <arve@android.com>
Date: Fri, 2 Dec 2011 13:59:05 +0800
Subject: [PATCH] Input: Use monotonic time for event time stamps.
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Since wall time can jump backwards, it cannot be used to determine if one
event occured before another or for how long a key was pressed.

CC: Dmitry Torokhov <dmitry.torokhov@gmail.com>
CC: linux-input@vger.kernel.org
Signed-off-by: Arve Hjønnevåg <arve@android.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>
---
 drivers/input/evdev.c |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)

diff --git a/drivers/input/evdev.c b/drivers/input/evdev.c
index 4cf2534..ec329b4 100644
--- a/drivers/input/evdev.c
+++ b/drivers/input/evdev.c
@@ -94,8 +94,11 @@ static void evdev_event(struct input_handle *handle,
 	struct evdev *evdev = handle->private;
 	struct evdev_client *client;
 	struct input_event event;
+	struct timespec ts;
 
-	do_gettimeofday(&event.time);
+	ktime_get_ts(&ts);
+	event.time.tv_sec = ts.tv_sec;
+	event.time.tv_usec = ts.tv_nsec / NSEC_PER_USEC;
 	event.type = type;
 	event.code = code;
 	event.value = value;
-- 
1.7.3.2.146.gca209



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