Unable to have wired Xbox 360 style controllers recognized by Android 5 (Samsung Galaxy Note Pro 12.2)

I've got the Samsung Note Pro tablet on the latest android 5.0.2

I've got 2 gamepads which work on the Xbox 360 and when I try to use them on the tablet none of them are recognized.

I've followed all guides I've found around in this and other sites talking about the subject and:

• I've got a root device
• I've been able to find the Vendor and ProdID of both by looking into `/sys/kernel/debug/usb/devices'
  • both of the USB wired controllers appear there
    • gamepad 1 = vendor 0738, prodID 4738
    • gamepad 2 = vendor 1bad, prodID f025
• So I've created the following files with the config of an Xbox 360 controller:
  • /system/usr/keylayout/Vendor_0738_Product_4738.kl
  • /system/usr/keylayout/Vendor_1bad_Product_f025.kl
• Just in case, I tried with and without the following too:
  • /system/usr/keychars/Vendor_0738_Product_4738.kcm
  • /system/usr/keychars/Vendor_1bad_Product_f025.kcm
• All of those have the right 644 rw-r--r-- permissions

After all changes, rebooting and reconnecting... still, none of the 2 controllers are recognized by this Android tablet.

I checked the following with each of them plugged in, and they were not appearing as connected:

• /proc/bus/input/devices

Any idea what the problem could be? Or what else could I try? Most guides talk about the .kl files above and they say it should work, but in this case, it doesn't... any other suggestion?

Ta