[SOLVED] How to make Asus UX302LG / UX303UX brightness Fn keys work

[flyingrhino]

Setup:

Clean install LM17.3 xfce
Asus UX302LG laptop (but will probably also work on other similar generation Asus laptops)

Problem:

Fn F5 and F6 keys to control brightness do not work.
By default brightness is at 100% (stays this way after reboot).
Right click the battery icon and changing brightness value remains until reboot.
Note: It is controlled in this file: /sys/class/backlight/intel_backlight/brightness (or actual_brightness)
And the max_brightness value is as high as it can go

BTW, keyboard backlight (Fn F3 and F4) work properly.

Solution:

To make the Fn F5+F6 (display brightness) work, I edited the following file:
sudo vim /etc/default/grub

and modified the line to look like:
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_backlight=vendor acpi_osi= "
*** That's a SPACE after the acpi_osi= ***

Then save and exit vim.

sudo update-grub
And rebooted. Now Fn F5+F6 keys work, and also the brightness control in the tray battery icon.

Brightness value survives a reboot.

Note: Now it is controlled in this file: 'cat /sys/class/backlight/asus-nb-wmi/brightness'

BTW, keyboard backlight (Fn F3 and F4) still work properly.

I found that "GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_backlight=vendor" without the acpi part did not work.
You might succeed only with the vendor bit, but I needed both arguments for it to work.

[flyingrhino]

Today I followed this procedure on Asus UX303 UX and it works too.

[WiltshireJon]

Maybe I was lucky but all the function keys worked as expected "straight out of the box" on an Asus UX360UA

[flyingrhino]

That was the laptop I wanted to buy, but I really wanted >8Gb RAM and at the time the UX303 was the only one that satisfied this demand.

Good to know that it works properly on the UX360 because that is a much more popular machine than the UX303 that I own.
The UX303 has a GPU that I don't need. But it does have 12 Gb RAM that I wanted...