Your UdevDb.txt shows that you did the hwdb mangling successfully, i. e. your input/event12 has "E: KEYBOARD_KEY_700E3=middle". However, "middle" will definitively not work, as udev only knows about "KEY_*" constants, not "BTN_* constants" (admittedly this is the first time I head that someone remaps buttons).
I assume in Ubuntu 13.04 and earlier you had an udev rule which assigned the key code (274) directly, not the key name? Please confirm this.
So I suppose what broke is that you are not able to directly specify a key code any more, only a name?
Your UdevDb.txt shows that you did the hwdb mangling successfully, i. e. your input/event12 has "E: KEYBOARD_ KEY_700E3= middle" . However, "middle" will definitively not work, as udev only knows about "KEY_*" constants, not "BTN_* constants" (admittedly this is the first time I head that someone remaps buttons).
I assume in Ubuntu 13.04 and earlier you had an udev rule which assigned the key code (274) directly, not the key name? Please confirm this.
So I suppose what broke is that you are not able to directly specify a key code any more, only a name?