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Old 08-15-2015, 02:51 AM   #1
batabuntu
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Ubuntu 14.04 Brightness Control Not working, only notification


Hello

I have Ubuntu 14.04.3 installed and when I use the fn-key I get the notification OSD shown but there is no change in brightness.

I have edited
Code:
sudo gedit /etc/default/grub
to add
Code:
acpi_osi=Linux acpi_backlight=vendor
to it.

Still doesn't work. The brightness keys are being registered which allows the OSD to show up.

The graphic driver running is nouveau and card is Nvidia.

Output of
Code:
ls /sys/class/backlight/
is
Code:
nv_backlight toshiba
 
Old 08-15-2015, 03:13 AM   #2
Keruskerfuerst
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I would change the brightness using the keys at the monitor.
 
Old 08-15-2015, 04:55 AM   #3
ondoho
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i once had the same problem adn i added only "acpi_backlight=vendor", not the other one.

however, that is just guesswork.

proper troubleshooting, i would first start with trying to change the brightness directly, by echoing the proper value to some file... maybe under /sys/class/backlight... please search for it on your computer & the internet, you will find it.
 
Old 08-16-2015, 01:59 AM   #4
batabuntu
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Quote:
Originally Posted by Keruskerfuerst View Post
I would change the brightness using the keys at the monitor.
It's a notebook. Should have mentioned in my OP.

Quote:
Originally Posted by ondoho View Post
i once had the same problem adn i added only "acpi_backlight=vendor", not the other one.

however, that is just guesswork.

proper troubleshooting, i would first start with trying to change the brightness directly, by echoing the proper value to some file... maybe under /sys/class/backlight... please search for it on your computer & the internet, you will find it.

I have searched a lot to get it fixed.

I just did what you mentioned, added
Code:
acpi_backlight=vendor
. From another place, it was recommended to just to enter
Code:
acpi_osi=
. I also tried it the other forms.

I did the echo thing you mentioned, that doesn't work either. They say its located in /sys/class/backlight/acpi_video0. Did some digging and found the file they are referring to is in /sys/class/backlight/toshiba/ Now in that folder, echo changes the value of brightness.

On my working machine in which works, when I do echo, it the value changes in the brightness folder from 7 to 4 or any value, the brightness. But on the machine I'm trying to trouble shoot, the value does change in /sys/class/backlight/toshiba/brightness but the screen brightness stays the same.

I've read this already and couple of sites before
http://ubuntuforums.org/showthread.php?t=2199695&page=3
http://askubuntu.com/questions/13498...s-in-my-system

The brightness is refusing to change. Thing to do is when I installed Fedora on it, the brightness did change from the Fn-Keys and from the power management. On my 'third' machine which has linuxmint on, the power management doesn't change from the fn+keys but it does change from the "power management daemon" running.

I tried changing the brightness from the power management on the machine I'm trying to troubleshoot, wouldn't change.

The issue isn't to do with "intel_backlight" as well which many online forums tells to edit the Xorg. There isn't even an Xory now I think, like the Xsession file AFAIK.


Note: When I say Fn+keys don't work, I mean that brightness doesn't change but the keys command are being detected like the brightness notification OSD does appear. The brightness thing itself isn't work either via GUI in power managmenet window or terminal echo 5 > sys/class/backlight

Update:

I think the problem is the kernal is confused which backlight to use. Because before I added values/terms into /etc/default/grub. The output of ls /sys/class/backlight was
Code:
acpi_video0 nv_backlight toshiba
Now after doing some change, like with the acpi_osi= in the grub, the output of ls /sys/class/backlight is only
Code:
acpi_video0 nv_backlight
I think is a clue on whats going on.

Update 2

I found the file! It wasn't to echo brightness text file in toshiba or acpi_video but nv_backlight! Now I need to find a way to use it. I think there would be a grub command which 'uses' it like apci_osi= removes toshiba term when doing ls /sys/class/backlight

Last edited by batabuntu; 08-16-2015 at 02:20 AM.
 
Old 08-16-2015, 03:47 PM   #5
ondoho
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i think you can save yourself some headaches if you find out what sort of machine you have, and search the web against that.
with a distro as widespread as ubuntu, there's a good chance that the solution is already out there.
no need to re-invent the wheel, although kudos for finding it!
 
  


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