Unity screen brightness fix for Ubuntu 18.04
Updated: May 25, 2019
Just recently, I upgraded my
Asus Vivobook to Bionic. After five great years, Trusty
had come to the end of its supported life, and I had to make a choice. So I did. I made two choices. I
upgraded the system, and then decided to test and eventually use both
Unity and
Plasma desktops, sort of in tandem. In both cases, the
results are quite good. Especially with the former, this is rather encouraging, because Unity
is no longer an official thing.
The one really outstanding problem that I’ve discovered in this setup is that my laptop Fn
brightness and volume keys had stopped working. Not a major thing, but it does mar the overall feel,
plus on laptops, you sort of expect to be able to use them. The rest of the keys work fine (including,
for instance, screen off), and there are no such issues in either the Ubuntu (Gnome) or Plasma
environments. I spent a bit of time reading, tweaking, and I do have a fix.
All roads lead to Rome – problem
If you search for any combo of words brightness, unity and not working, you will get a lot of
results. But this is true for pretty much everything in Linux, and even other operating systems.
Apparently, the problems I was facing aren’t new, they had not affected me on Trusty. Specifically,
there’s this
volume bug, and then for the
screen brightness,
this
one covers it well.
Here, I will just focus on the brightness part. First, the symptoms. The brightness keys do nothing,
even after a long delay. There are no visible errors anywhere. Even the slider is missing in the
brightness section of the power management facility in the Unity settings.
Please note that I have
Intel graphics on this ultrabook, and therefore the proposed solution is
only relevant to that hardware configuration. However, as you’ve seen in the linked bug for a specific
Nvidia-graphics use case, the first part of the listed solution should help, regardless of your
graphics card choice.
Solution, step 1: GRUB update
The
solution seems to be a combination of changing the boot parameters and
adding a configuration file for how X11 handles PCI devices. This is
not that different from how I fixed a similar
set of problems on my old eeePC netbook, both a decade ago and indeed just a few weeks back. You need
to edit the default
GRUB2 configuration by appending a different implementation.
sudo nano /etc/default/grub
And then inside this file, change the line:
GRUB_CMDLINE_LINUX_DEFAULT=”quiet splash”
To the following:
GRUB_CMDLINE_LINUX_DEFAULT=”quiet splash acpi_osi=”
After that you need to update the GRUB configuration by running an update:
sudo update-grub
The change above tells the kernel to actually NOT use the default (Linux) OS interface, as
apparently, it is not working correctly. Now, for your own convenience, if the above does not work for,
once you’ve fully implemented the solution, you can also try one of the the following:
GRUB_CMDLINE_LINUX_DEFAULT=”quiet splash acpi_backlight=vendor”
GRUB_CMDLINE_LINUX_DEFAULT=”quiet splash acpi_backlight=native”
Reboot. When the system comes up, verify that you have the right parameters by inspecting the kernel
command line via:
cat /proc/cmdline. The ACPI string you’ve appended should be there. Check
the brightness keys. If they work, great. If not, then there’s also the second (optional) step for
systems with Intel graphics.
Solution, step 2: X11 configuration (Intel only)
Here, we will create a tweak for the Intel graphics card, specifically the backlight option. You
also need to check the BUS ID for your graphics card. You can do this with the
lspci command, which will give you the desired output. Then, create the
following file:
sudo nano /usr/share/X11/xorg.conf.d/XX-intel.conf
And add the following block of text:
Section “Device”
Identifier “card0”
Driver “intel”
Option “Backlight”
“intel_backlight”
BusID “PCI:X:Y:Z”
EndSection
Replace XX-intel.conf with a number, e.g. 20-intel.conf, 30-intel.conf. The number simply tell the
system when to load the particular configuration, as it parses the contents of the directory in
sequential numerical order. Replace PCI:X:Y:Z with the right bus ID number, like PCI:0:2:0. Once again,
reboot and check whether your problem is solved. For me, this had done the trick, I had the brightness
control, and the slider shows correctly. The one “downside” is that the boot splash screen looks darker
than before. That’s the only thing.
Conclusion
I am never happy when I need to tweak system configurations, and until recently, the Vivobook &
Trusty have had a perfect record. This is no longer true with Unity, then again, this is also an
unsupported scenario. But I do feel it’s important to resolve, because it gives me a better
understanding of what I can do and expect to achieve with Unity, especially since this is a production
system.
We still have the Fn volume keys issues to fix. The idea is to do this without having to resort to
using PPA or any external, third-party packages. I’ll explore this in a follow-up article, even if the
results may not have a happy ending like here. True, worst case, I can simply use Plasma, which works
splendidly, looks the part even in its tweaked Unity-like guise, and it’s already proven its worth on
my Slimbook. Anyway, I hope this little hack tutorial was useful. Happy Linuxing and see you
around.