Kieran's solution doesn't work for Samsung NP940X3L. I tried to set it for the following value:
xxd -p /sys/firmware/efi/efivars/KBDBacklitLvl-5af56f53-985c-47d5-920c-f1c531d06852
0700000005
Backlight goes on briefly during early boot stages but then shuts off.
Kieran's solution doesn't work for Samsung NP940X3L. I tried to set it for the following value: efi/efivars/ KBDBacklitLvl- 5af56f53- 985c-47d5- 920c-f1c531d068 52
xxd -p /sys/firmware/
0700000005
Backlight goes on briefly during early boot stages but then shuts off.