ASUS laptop FX503: Keyboard backlight control not work in Linux

Question

The laptop is ASUS FX503vd, I tried several versions of Linux kernels (currently running one is the 4.17.1), but still have not managed to make the keyboard backlight control keys work. After the system boot on, the backlight is always on. There are two function keys (reused the numerical keypad) which is to control the brightness of the backlight. In windows, I can adjust down its brightness until fully off. But pressing the same keys in Linux has no effect at all. My feeling is the kernel did not detected the corresponding WMI device

Below is the /sys/devices/platform/asus-nb-wmi/ contents:

~ $ ls /sys/devices/platform/asus-nb-wmi/

cpufv driver_override input/ power/ uevent

driver@ hwmon/ modalias subsystem@

And, below is the kernel message filtered by 'asus' keyword: (i.e. dmesg |grep 'asus')

[ 6.698065] asus_wmi: ASUS WMI generic driver loaded

[ 6.700669] asus_wmi: Initialization: 0x1

[ 6.700723] asus_wmi: BIOS WMI version: 8.1

[ 6.700764] asus_wmi: SFUN value: 0x4a0061

[ 6.701323] input: Asus WMI hotkeys as /devices/platform/asus-nb-wmi/input/input10

[ 6.703080] asus_wmi: Number of fans: 1

Does anyone have some clues about the laptop keyboard issue?

Does the driver depend on the layout of the keyboard?

Thanks in advance. -woody

Answer 1

Here is guid in kernel Documentation in Documentation/laptops/asus-laptop.txt.

According to that follow the steps to enable this functionality.

1. modprobe asus-laptop (check dmesg)
2. You can control lcd backlight power and brightness with /sys/class/backlight/asus-laptop/. Brightness Values are between 0 and 15.

Answer 2

I hope you did it somehow but for those who didn't managed to do it, there is a little advice

!!! This works only on ubuntu based distros !!!

You will probably have to install newer kernel (which is not in repository for everyone to install). That may help you with much more problems like backlight issues or so.

You can look at this answer. There is written how to update your current kernel. kernel versions are not up to date so you'll have to choose some higher version.

I hope this helps :)