The mysterious XF86AudioPlay issue

Summary

I was getting “<XF86AudioPlay> is undefined” in the status bar of Emacs displayed every 2-3 seconds. Nowhere else I noticed any misbehavior or problems, and also couldn’t find any related log entries. It didn’t stop, though didn’t want to reboot my system to see whether that would fix the problem, but it was driving me nuts. Now, as a starting point I adjusted my sway configuration, to react to the XF86AudioPlay key press event: bindsym XF86AudioPlay exec playerctl play-pause After reloading sway, my music player started to play for 2-3 seconds, stopped playing, started again, etc. It wasn’t a Emacs bug, but something indeed seemed to send the XF86AudioPlay key event every 2-3 seconds. It wasn’t my USB keyboard or any stuck key on it, as verified also by unplugging it. So which device was causing this? libinput from libinput-tools to the rescue: % sudo libinput debug-events [...] -event12 KEYBOARD_KEY +0.000s KEY_PLAYPAUSE (164) pressed event12 KEYBOARD_KEY +0.000s KEY_PLAYPAUSE (164) released event12 KEYBOARD_KEY +2.887s KEY_PLAYPAUSE (164) pressed event12 KEYBOARD_KEY +2.887s KEY_PLAYPAUSE (164) released event12 KEYBOARD_KEY +5.773s KEY_PLAYPAUSE (164) pressed event12 KEYBOARD_KEY +5.774s KEY_PLAYPAUSE (164) released [...] The `event12` device was sending this event, what’s behind this? % sudo udevadm info /dev/input/event12 P: /devices/pci0000:00/0000:00:1f.3/skl_hda_dsp_generic/sound/card0/input17/event12 M: event12 R: 12 J: c13:76 U: input D: c 13:76 N: input/event12 L: 0 S: input/by-path/pci-0000:00:1f.3-platform-skl_hda_dsp_generic-event E: DEVPATH=/devices/pci0000:00/0000:00:1f.3/skl_hda_dsp_generic/sound/card0/input17/event12 E: DEVNAME=/dev/input/event12 E: MAJOR=13 E: MINOR=76 E: SUBSYSTEM=input E: USEC_INITIALIZED=12468722 E: ID_INPUT=1 E: ID_INPUT_KEY=1 E: ID_INPUT_SWITCH=1 E: ID_PATH=pci-0000:00:1f.3-platform-skl_hda_dsp_generic E: ID_PATH_TAG=pci-0000_00_1f_3-platform-skl_hda_dsp_generic E: XKBMODEL=pc105 E: XKBLAYOUT=us E: XKBOPTIONS=lv3:ralt_switch,...