Re: PROBLEM: Apple external Trackpad event timestamps are jittery (regression)

On Mon, May 11, 2020 at 01:11:18PM -0700, Dmitry Torokhov wrote:

Hi,

On Mon, May 11, 2020 at 09:18:15AM +0300, Yariv wrote:

quoted

Using a vanilla installation of Ubuntu 20.04 (kernel v5.4), the
timestamps of input events from my Apple "Magic Trackpad" - 1st
generation, connected over Bluetooth - are jittery.
This is a kernel regression. I bisected the bug.

Do you see the same jitter when connected over USB? Can you also see if
there is similar jitter when you parse timestamps of SYN_RPEORT events
from "evtest"?

Could you post a sample of events generated by device (via evtest)?

unrelated, but I really recommend using 'libinput record' these days since
it can be replayed (libinput replay) or analysed easier (it's YAML).
Also, it prints delta times into the recording so you can immediately check
those without having to parse them, e.g.:

  - evdev:
    - [  0, 375974,   2,   0,       5] # EV_REL / REL_X                     5
    - [  0, 375974,   2,   1,      -2] # EV_REL / REL_Y                    -2
    - [  0, 375974,   0,   0,       0] # ------------ SYN_REPORT (0) ---------- +8ms

Cheers,
   Peter