Joystick hat buttons not properly working since upgrade to 19.04 / 5.0.0 kernel

[pivert]

Hi,

The Puma Pro flight trainer joystick has a "hat" button and a 3 positions "register selection" that multiply all the available buttons by 3.
In Kubuntu 18.04, this joystick is detected as 15 axis & 30 buttons joystick, but on Kubuntu 19.04, it only detects 10 axis, instead of 16 axis in 18.04.
This seems mainly a joydev module issue in the new kernel 5.0.0

jstest in 18.04:

Axes:  0: -6118  1:-19848  2: 32767  3: -2695  4: 32767  5:     0  6:     0  7:     0  8:     0  9:     0 10:     0 11:     0 12:     0 13:     0 14:     0 Buttons:  0:off  1:off  2:off  3:off  4:off  5:off  6:off  7:off  8:off  9:off 10:off 11:off 12:off 13:off 14:off 15:off 16:off 17:off 18:off 19:off 20:off 21:off 22:off 23:off 24:off 25:off 26:off 27:off 28:off 29:off

The "hat button" is mapped on axis (8,9) or (10,11) or (11,12) depending on the "register" selector, which is very helpful for helicopter flying in X-Plane.

jstest in 19.04:

pivert@pivert-Z390:~/X-Plane 11$ jstest /dev/input/js0
Driver version is 2.1.0.
Joystick ([url]www.pro-flight-trainer.com[/url] powered by Atmel® Pro-Flight-Trainer) has 11 axes (X, Y, Z, Rx, Ry, Rz, Throttle, Rudder, Hat0X, Hat0Y, (null))
and 30 buttons (Trigger, ThumbBtn, ThumbBtn2, TopBtn, TopBtn2, PinkieBtn, BaseBtn, BaseBtn2, BaseBtn3, BaseBtn4, BaseBtn5, BaseBtn6, ?, ?, ?, BtnDead, (null), (null), (null), (null), (null), (null), (null), (null), (null), (null), (null), (null), (null), (null)).
Testing ... (interrupt to exit)
Axes:  0:-12896  1:  4468  2: 32767  3:  1290  4: 32060  5:     0  6:     0  7:     0  8:     0  9:     0 10:     0 Buttons:  0:off  1:off  2:off  3:off  4:off  5:off  6:off  7:off  8:off  9:off 10:off 11:off 12:off 13:off 14:off 15:off 16:off 17:off 18:off 19:off 20:off 21:off 22:off 23:off 24:off 25:off 26:off 27:off 28:off 29:off

I did not find explanation, nor options to the joydev module.

How can I get back the same behavior as in 4.15 ? How to get back the extra 4 channels that were used by the hat buttons in register 2 & 3 configuration ?
Would someone have some recommendations I could check ?

Thanks,