I have an Asus fx553vd laptop with the very recent mainline kernel(4.13.9), bios: GL553VD.302 and ubuntu 16.04
All the hotkeys on the keyboard work and also show On-Screen-Notification. But on pressing fn + f3/f4 (keyboard backlight imllumination), only On-Screen_Notification is shown and nothing happens.
I've also tried checking through acpi_listen. But acpi_listen gives no output when fn + f3/f4 are pressed. Also tried the different grub cmd options, eg: "acpi_osi=", "acpi_backlight=", but nothing is working.
Please can someone point me in the right direction, as to how to make these two keys work.
Edit: I have checked the /sys/class/leds directory, and there is no directory named kbd_backlight. There is a phy0-led directory though. But all the files in it are blank. eg: brightness, max_brightness.