linux-kernel - Re: [PATCH] Call input_set_timestamp for events injected using uinput

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Message-ID: <20230502021305.GA798180@quokka>
Date:   Tue, 2 May 2023 12:13:05 +1000
From:   Peter Hutterer <peter.hutterer@...-t.net>
To:     Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:     Biswarup Pal <biswarupp@...gle.com>, kernel-team@...roid.com,
        linux-input@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Call input_set_timestamp for events injected using uinput

Thanks for the CC, I would've missed that.

On Mon, May 01, 2023 at 06:05:59PM -0700, Dmitry Torokhov wrote:
> On Thu, Apr 27, 2023 at 12:01:51AM +0000, Biswarup Pal wrote:
> > Currently, uinput doesn't use the input_set_timestamp API, so any
> > event injected using uinput is not accurately timestamped in terms of
> > measuring when the actual event happened. Hence, call the
> > input_set_timestamp API from uinput in order to provide a more
> > accurate sense of time for the event. Propagate only the timestamps
> > which are a) positive, b) within a pre-defined offset (10 secs) from
> > the current time, and c) not in the future.
> 
> This makes sense to me. Peter, do you see any issues?

nope, this looks good and has my 
Reviewed-by: Peter Hutterer <peter.hutterer@...-t.net> 

afaict any code that has compiler warnings enabled should have this on
zero anyway. It'd be really nice to pass a timestamp down to uinput but
that's obviously a lot more involved.

Cheers,
  Peter

> 
> Thanks!
> 
> > 
> > Signed-off-by: Biswarup Pal <biswarupp@...gle.com>
> > ---
> >  drivers/input/misc/uinput.c | 34 ++++++++++++++++++++++++++++++++++
> >  1 file changed, 34 insertions(+)
> > 
> > diff --git a/drivers/input/misc/uinput.c b/drivers/input/misc/uinput.c
> > index f2593133e524..d98212d55108 100644
> > --- a/drivers/input/misc/uinput.c
> > +++ b/drivers/input/misc/uinput.c
> > @@ -33,6 +33,7 @@
> >  #define UINPUT_NAME		"uinput"
> >  #define UINPUT_BUFFER_SIZE	16
> >  #define UINPUT_NUM_REQUESTS	16
> > +#define UINPUT_TIMESTAMP_ALLOWED_OFFSET_SECS 10
> >  
> >  enum uinput_state { UIST_NEW_DEVICE, UIST_SETUP_COMPLETE, UIST_CREATED };
> >  
> > @@ -569,11 +570,40 @@ static int uinput_setup_device_legacy(struct uinput_device *udev,
> >  	return retval;
> >  }
> >  
> > +/*
> > + * Returns true if the given timestamp is valid (i.e., if all the following
> > + * conditions are satisfied), false otherwise.
> > + * 1) given timestamp is positive
> > + * 2) it's within the allowed offset before the current time
> > + * 3) it's not in the future
> > + */
> > +static bool is_valid_timestamp(const ktime_t timestamp)
> > +{
> > +	ktime_t zero_time;
> > +	ktime_t current_time;
> > +	ktime_t min_time;
> > +	ktime_t offset;
> > +
> > +	zero_time = ktime_set(0, 0);
> > +	if (ktime_compare(zero_time, timestamp) >= 0)
> > +		return false;
> > +
> > +	current_time = ktime_get();
> > +	offset = ktime_set(UINPUT_TIMESTAMP_ALLOWED_OFFSET_SECS, 0);
> > +	min_time = ktime_sub(current_time, offset);
> > +
> > +	if (ktime_after(min_time, timestamp) || ktime_after(timestamp, current_time))
> > +		return false;
> > +
> > +	return true;
> > +}
> > +
> >  static ssize_t uinput_inject_events(struct uinput_device *udev,
> >  				    const char __user *buffer, size_t count)
> >  {
> >  	struct input_event ev;
> >  	size_t bytes = 0;
> > +	ktime_t timestamp;
> >  
> >  	if (count != 0 && count < input_event_size())
> >  		return -EINVAL;
> > @@ -588,6 +618,10 @@ static ssize_t uinput_inject_events(struct uinput_device *udev,
> >  		if (input_event_from_user(buffer + bytes, &ev))
> >  			return -EFAULT;
> >  
> > +		timestamp = ktime_set(ev.input_event_sec, ev.input_event_usec * NSEC_PER_USEC);
> > +		if (is_valid_timestamp(timestamp))
> > +			input_set_timestamp(udev->dev, timestamp);
> > +
> >  		input_event(udev->dev, ev.type, ev.code, ev.value);
> >  		bytes += input_event_size();
> >  		cond_resched();
> > -- 
> > 2.40.1.495.gc816e09b53d-goog
> > 
> 
> -- 
> Dmitry