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

[Wanlong Gao <gaowanlong@cn.fujitsu.com>]

On 12/21/2011 09:01 AM, john stultz wrote:

> 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.


seems reasonable.

> 
> 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;


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