CODEWITHSUNDEEP
pythonlinuxlinux-kernelkeyboardevdev
jth
jth

Reputation: 409

Why does timestamp wrap around for `libevdev` events?

I've been playing around with python-libevdev and noticed that event timestamps seem to wrap around. For example, when I ran the following script:

import libevdev as ev

with open('/dev/input/by-path/my-event-kbd', 'rb') as fd: 
    device = ev.Device(fd)
    device.grab()
    for e in device.events():
        if e.matches(ev.EV_KEY):
            if e.value == 0:                                                                                                                      
                print('release', e.usec)
            elif e.value == 1:
                print('press  ', e.usec)

I got:

press   285047
release 898527
press   383116
release 828000
press   164149
release 295935
press   929637
release 65158
press   593924
release 750227
press   81770
release 210363
press   533884
release 652184
press   949230
release 81242

and so on. The docs for InputEvent.usec just say:

The timestamp, microseconds

Can anyone explain why/how the values wrap around? How would I use these values to calculate the time elapsed between a key being pressed and then released?

Upvotes: 0

Views: 63

Answers (1)

jth
jth

Reputation: 409

Ah, I was confused. The full timestamp is given by InputEvent.sec (seconds) plus InputEvent.usec (microseconds).

Upvotes: 0

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