Display Brightness Cannot be Changed

[David Syengo]

I am using HP Probook 450 G0...It uses dicrete graphics (Intel GMA + AMD Radeon). I installed UbuntuMATE (DEsktop Env version 1.8.1). Under power management preferences the screen brightness cannot be changed no matter what value you set on the slider.

[Martin Wimpress  (flexiondotorg)]

What version of Ubuntu MATE?

[John (john-looney)]

Hallo
I have the same problem on a MacBook Pro (bought 2010) which I upgraded a few days ago from "Mavericks" to ubuntu-mate 15.04. 32 bit. I don't have the technical details to hand but the screen brightness slider responds to trackpad adjustment - even the keyboard keys cause the little "pop-ups" to show how the brightness is being increased/decreased. BUT, nothing actually happens to the brightness - the screen still blasts out maximum brightness (battery-life!). The Mac has a 4 core i7 processor and 4 GB RAM. So far this is the only fly in the ointment. Please see what you can do to help. I'm not a programmer etc. but have been using ubuntu for close to two years. If you need more details please state what you need and I'll try to pull it out with the "benchmaker" program. Thanks for looking at this.

[David Syengo (davysyengo)]

Hi Martin,

Am using ubuntuMATE 14.04.1 final desktop.

[John (john-looney)]

https://help.ubuntu.com/community/MacBookPro6-2/Precise

LCD Brightness Control:
Installing the proprietary nvidia driver appears to provide the backlight control.

... and it did for me too.
I should have known, I've read enough over the last two years about the recurring theme of graphics card drivers. I installed the recommended NVIDIA driver, rebooted (some VERY interesting messages appeared during that process!) and the brightness control works.
Have a happy FOSS day everyone (with the exception of the odd proprietary driver I suppose :-)

[BadBone2k (badbone2k)]

Same issue here with Ubuntu Mate 15.04, Mate Version 1.8.2 on an Toshiba Tecra A11, Intel Core I5 M520 with integrated graphics.

[Brad Figg (brad-figg)]

This bug is missing log files that will aid in diagnosing the problem. From a terminal window please run:

apport-collect 1462221

and then change the status of the bug to 'Confirmed'.

If, due to the nature of the issue you have encountered, you are unable to run this command, please add a comment stating that fact and change the bug status to 'Confirmed'.

This change has been made by an automated script, maintained by the Ubuntu Kernel Team.

[BadBone2k (badbone2k)]

Found a workaround for my Toshiba Tecra A11: http://ubuntuforums.org/showthread.php?t=2275437&p=13272746#post13272746

TL;DR
edit /etc/default/grub
GRUB_CMDLINE_LINUX_DEFAULT="quiet acpi_backlight=vendor"

[Launchpad Janitor (janitor)]

[Expired for linux (Ubuntu) because there has been no activity for 60 days.]