I am not able to change the screen brightness on lenovo z570.
Even the function keys for the brightness are also not working. Any idea ?
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Finally got the brightness controls to work properly!
The issue persists due to presence of two backlight modules
intel_backlight. You can cross check if both modules exists by running the below command.
If you find
acpi_video0 as one of the modules run the command:
sudo tee /sys/class/backlight/acpi_video0/brightness <<< 5
If no change is observed, it is time to remove this module. My assumption is that by default
intel_backlight is ignored and
acpi_video0 is being used by the kernel for handling backlight.
Sometimes, ACPI does not work well due to different motherboard implementations and ACPI quirks. This includes some laptops with dual graphics (e.g. Nvidia/Radeon dedicated GPU with Intel/AMD integrated GPU).
On Nvidia Optimus laptops, the kernel parameter nomodeset can interfere with the ability to adjust the backlight. Additionally, ACPI sometimes needs to register its own acpi_video0 backlight even if one already exists (such as intel_backlight), which can be done by adding one of the following kernel parameters in your bootloader:
acpi_backlight=video acpi_backlight=vendor acpi_backlight=native
Since acpi_video0 backlight did not change the brightness, you may need to use
acpi_backlight=none as an argument as well. This line disables the
acpi_video0 module from kernel parameters so that only
intel_backlight handles the brightness controls.
You need to modify the bootloader file
/etc/default/grub to add the above mentioned arguments. It should look something like this.
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_backlight=native"
native does not work try with
Update the grub configuration:
Reboot your system, the brightness controls should now work.
More details on my blog.
If all else fails, you might want to try out the command-line utility
You can install it by running
sudo apt-get install xbacklight
Then if you want to make the screen brighter you can type
(or replace 50 with whatever percentage you'd like)
Or if you wanted to dim the screen you can type
Also if you really had the time, you might want to mess with key-bindings to make running those commands more convenient.
I also have a Lenovo z570 and this worked for me with 16.04 and now with 18.04.
The problem in my case is because the system has added the acpi_video0 module incorrectly, and the brightness keys use this module instead of correct one for my hardware (intel_backlight).
See my full answer here.
To cut a long story short, for the z570, the answer is to add the boot option
acpi_backlight=none which will remove the directory
/sys/class/backlight/. This makes the system use
/sys/class/backlight/intel_backlight as required.