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

Peter Hutterer
2023-05-02T02:13:24Z

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@who-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@google.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