Gfilui

I have recently installed Ubuntu mate 18.04 on my XPS 15 9560. I cannot adjust the display brightness through any means. I have tried the following:

1. Set the acpi_backlight=vendor in boot parameters


2. used xbacklight, which gives the following results

.

xypnox@xypnox-xps:~$ xbacklight -set 50
No outputs have backlight property

also I followed another question at xbacklight: No outputs have backlight property - No /sys/class/backlight folder, and the output for sudo find /sys/ -type f -iname '*brightness*' is

xypnox@xypnox-xps:~$ sudo find /sys/ -type f -iname '*brightness*'
/sys/devices/platform/dell-laptop/leds/dell::kbd_backlight/brightness_hw_changed
/sys/devices/platform/dell-laptop/leds/dell::kbd_backlight/max_brightness
/sys/devices/platform/dell-laptop/leds/dell::kbd_backlight/brightness
/sys/devices/platform/i8042/serio0/input/input4/input4::capslock/max_brightness
/sys/devices/platform/i8042/serio0/input/input4/input4::capslock/brightness
/sys/devices/platform/i8042/serio0/input/input4/input4::numlock/max_brightness
/sys/devices/platform/i8042/serio0/input/input4/input4::numlock/brightness
/sys/devices/platform/i8042/serio0/input/input4/input4::scrolllock/max_brightness
/sys/devices/platform/i8042/serio0/input/input4/input4::scrolllock/brightness
/sys/module/video/parameters/brightness_switch_enabled
/sys/module/i915/parameters/invert_brightness

I had the same issue on a Dell XPS 13. Found this link that solved the problem for me : https://bugs.archlinux.org/task/58296#comment168869

What I did:

• changed the content of /etc/default/grub by adding video.only_lcd=0 to GRUB_CMDLINE_LINUX_DEFAULT
  


• updated grub with sudo update-grub
  

After restarting the laptop, I was able to control the brightness.

I had the same problem some years ago and was having the same problem again after installing ubuntu 18.04. it was a kernel problem then, and i think it may be a kernel problem now.

After updating the kernel the problem was fixed for me.

To update kernel see:
Updating kernel question

To download last stable kernel (which worked for me):
http://kernel.ubuntu.com/~kernel-ppa/mainline/v4.16.6/

In my case i downloaded:

 linux-headers-4.16.6-041606_4.16.6-041606.201804300418_all.deb

 linux-headers-4.16.6-041606-generic_4.16.6-041606.201804300418_amd64.deb

 linux-image-unsigned-4.16.6-041606-generic_4.16.6-041606.201804300418_amd64.deb

 linux-modules-4.16.6-041606-generic_4.16.6-041606.201804300418_amd64.deb

An alternative method is to install a PPA and brightness APP which also adjusts gamma - AWESOME!, and ... for any individual screen TOO!

Here are the 3 simple steps:

$ sudo add-apt-repository ppa:apandada1/brightness-controller
$ sudo apt update
$ sudo apt install brightness-controller

Then find it ...

Brightness Controller

in your App's/Accessories

Always Trying to help, Mark

It may be related to the display driver.

My issue is solved with the following steps.
Dell latitude 5590 with intel VGA compatible driver.

1. Installed ubuntu with nomodeset option


2. Updated BIOS to 1.2.3


3. Updated /etc/default/grub.

replaced

GRUB_CMDLINE_LINUX_DEFAULT="nomodeset"

with

GRUB_CMDLINE_LINUX_DEFAULT="i915.alpha_support=1"

and

update-grub

I had the same isssue and I added video.only_lcd=0 to GRUB_CMDLINE_LINUX_DEFAULT after quiet splash in /etc/default/grub then updated grub with sudo update-grub rebooted then lcd backlight worked. This was done on a dell xps 14 l421x

I've been struggling for the past week on trying to get Ubuntu working on my Dell XPS 15 9570 and I've had it working for a while with nomodeset but it's been killing my eyes having the display stuck on full brightness.

I finally fixed it today! I updated my kernel to 4.17 (http://kernel.ubuntu.com/~kernel-ppa/mainline/v4.17/) which was last updated two days ago and then restarted, and then finally restarted again without the nomodeset option (and didn't have to replace it with anything) and the display works now!!!

Hope this helps :)