I've tried following the Ubuntu hotkeys/media keys troubleshooting guide and /usr/share/doc/udev/README.keymap.txt.gz to make the Fn keys work. After copying the map file and modifying /lib/udev/rules.d/95-keymap.rules I get the correct key names from sudo /lib/udev/keymap -i input/event4, but none of them do anything at all.
How do I make sure that at least wlan and kbdillumup/kbdillumdown work?
$ /lib/udev/findkeyboards
AT keyboard: input/event4
$ cat /sys/class/dmi/id/sys_vendor
SAMSUNG ELECTRONICS CO., LTD.
$ cat /sys/class/dmi/id/product_name
90X3A
samsung-90x3a map file:
0xCE prog1 # Fn+F1 Unknown
0x8D prog3 # Fn+F6 Economy mode
0x97 kbdillumdown # Fn+F7 Keyboard background light down
0x96 kbdillumup # Fn+F8 Keyboard background light up
0xD5 wlan # Fn+F12 Wifi on/off
Update: The information below will be from Arch Linux since I no longer have Ubuntu.
xdotool key XF86KbdBrightnessUp prints nothing, but returns with exit code 0. I'm not sure if that means anything.
acpi_listen prints nothing when pressing Fn+F7/Fn+F8.