At the side panel from my all in one monitor, there are 2 keys for raising and lowering volume (see picture).
After installing Ubuntu 16.04.03, both keys working proper but after the first system update to the kernel 4.13.0-36 (also kernel 4.15.0-29 and Ubuntu 18.04) only the upper button for raising volumen works, the other stop working. I get no output with xev and showkey command when I use the "volume -"button.
With a fresh install without any updates I tried "showkey -s" and it says, the keycode for lowering volume is: 0xe0 0x2e 0xe0 0xae and for raising volume is: 0xe0 0x30 0xe0 0xb0
Related to this issue: How do keyboard input and text output work? I think it is on the kernel versions. Is it possible to compare both kernels to see what is missing?
Summarized: Both hardware volume keys (DELL InspironOne 2310) on side Panel working with an old kernel but after updating kernel/ MATE 18.04. the button for lowering volume is dead and didn't showing off a keycode.
