pinephone: play/pause on headset also triggers volume down

Describe your issue

What's the expected behaviour?

play/pause button toggles play, does not change volume.

What's the current behaviour?

Oftentimes, the button makes the volume go down. In evdev I see the following:

sometimes:

Event: time 1612902015.836954, type 1 (EV_KEY), code 164 (KEY_PLAYPAUSE), value 1
Event: time 1612902015.836954, -------------- SYN_REPORT ------------
Event: time 1612902015.961948, type 1 (EV_KEY), code 164 (KEY_PLAYPAUSE), value 0
Event: time 1612902015.961948, -------------- SYN_REPORT ------------

most of the time:

Event: time 1612902017.461935, type 1 (EV_KEY), code 114 (KEY_VOLUMEDOWN), value 1
Event: time 1612902017.461935, -------------- SYN_REPORT ------------
Event: time 1612902017.524438, type 1 (EV_KEY), code 164 (KEY_PLAYPAUSE), value 1
Event: time 1612902017.524438, type 1 (EV_KEY), code 114 (KEY_VOLUMEDOWN), value 0
Event: time 1612902017.524438, -------------- SYN_REPORT ------------
Event: time 1612902017.586913, type 1 (EV_KEY), code 164 (KEY_PLAYPAUSE), value 0
Event: time 1612902017.586913, type 1 (EV_KEY), code 114 (KEY_VOLUMEDOWN), value 1
Event: time 1612902017.586913, -------------- SYN_REPORT ------------
Event: time 1612902017.649390, type 1 (EV_KEY), code 114 (KEY_VOLUMEDOWN), value 0
Event: time 1612902017.649390, -------------- SYN_REPORT ------------

How to reproduce your issue?

Plug headset into pinephone, make sure the killswitch for headphones is off. Open evdev and press the button.

What device are you using?

pine64-pinephone

On what postmarketOS version did you encounter the issue?

  • edge (master branch)
  • stable (v20.05 branch)

On what environment did you encounter the issue?

Phone environments

  • Phosh (shouldn't matter, as it's visible in evdev)

How did you get postmarketOS image?

  • I built it using pmbootstrap

Tested pma!1943 just before it was merged.

What's the build date of the image? (in yyyy-mm-dd format)

2021-02-21

Additional information

See comment here: !1943 (comment 505476138)

This looks like a hardware issue, are other people experiencing this too? I should probably try another headset at some point and verify if it happens there too.