Comment 26 for bug 6628

I saw those comments, but they don't provide the actually interesting information. As long as the scancodes aren't recognized and it doesn't produce correct key codes, then xev can't receive anything. You have to use the keymap tool to figure out the missing scan codes. acpi_listen is rather uninteresting here as well, it's only relevant on some models which have broken kernel drivers (usually the kernel translates hotkey related ACPI events into input events).