I am having the same problem with the newer UX305CA. Apparently it is really common since the hardware is not recognized, so I just assigned a new shortcut. Following this answer:
sudo apt-get install xbacklight
Then assign new shortcut:
- Settings > Keyboard > Shortcuts > Custom Shortcuts > +
Add those two:
- Brightness up:
xbacklight -inc 10
- Brightness down:
xbacklight -dec 10
Then click on each of the
Disabled and select the new shortcut. In my case I used Alt+F5 and Alt+F6 (since I use Ctrl+F5 for web dev).
If you want, you can also mess with the boot options to fix it:
I have the same problem. there is a workaround although.
add "acpi_osi=" at the and of the kernel boot parameters.
to permanently do this edit /etc/default/grub as root and add "acpi_osi=" at the end of GRUB_CMDLINE_LINUX_DEFAULT then run "update-grub" as root
after that brightness and all other hotkeys work but the ambient light sensor is no longer detected. But this is not a big problem since there is no standard ambient light regulation of screen brightness anyway