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#1 2012-06-19 15:59:26
- wolf12
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- Registered: 2012-06-19
- Posts: 3
Cant control Brightness after Update Dell L401x NVIDIA GT425M
Before full system update I was able to control brightness with brightness slider keys, but the screen was turning off at some brightness levels.
After update I cant control brightness. Its fully bright. What can be the reason?
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#2 2012-06-19 17:09:42
- Inxsible
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- From: Chicago
- Registered: 2008-06-09
- Posts: 9,183
Re: Cant control Brightness after Update Dell L401x NVIDIA GT425M
Have you searched the forums before posting? There was another thread with the same issue. Maybe that thread has a solution.
There's no such thing as a stupid question, but there sure are a lot of inquisitive idiots !
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#3 2012-06-19 17:23:50
- wolf12
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- Registered: 2012-06-19
- Posts: 3
Re: Cant control Brightness after Update Dell L401x NVIDIA GT425M
Sorry, I cant control brightness even from powerdevil, and xbacklight also returns "no ouputs have backlight property". Yes I saw the post about the toshiba laptop. But he mentions only that his fn keys don't work. My other fn keys work.
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#4 2012-06-19 17:25:53
- Inxsible
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- From: Chicago
- Registered: 2008-06-09
- Posts: 9,183
Re: Cant control Brightness after Update Dell L401x NVIDIA GT425M
Nope, I mean this thread which talks about an update breaking brightness control -- exactly what your issue is and he also has a solution 
There's no such thing as a stupid question, but there sure are a lot of inquisitive idiots !
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#5 2012-06-19 18:13:17
- wolf12
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- Registered: 2012-06-19
- Posts: 3
Re: Cant control Brightness after Update Dell L401x NVIDIA GT425M
I reinstalled systemd-tools-185-1 according that thread. But still I cant control brightness.
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#6 2012-06-20 03:58:37
- perbh
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- From: Republic of Texas
- Registered: 2005-03-04
- Posts: 765
Re: Cant control Brightness after Update Dell L401x NVIDIA GT425M
not to hijack a thread - but I have exactly the same problem with my dell precision m90 (nvidia quattro fx 2500), using the nouveau driver.
the brightness level in /sys/class/backlight/acpi_video0/brightness changes when using the function keys, but the display is still extremely dark - almost unreadable.
'xbacklight' will momentarily change the brightness - and then it returns to it former self.
My system (i686) was updated today - and personally I suspect the new version of the nouveau driver.
If I use 'nomodeset', I have full brightness, but then I only get 1280x1024 instead of my usual 1920x1200 ... :-(
And yes - the systemd-tools is at 185-1 and was updated together with the kernel (and nouveau) earlier today. Everything worked honkey-dory _before_ the update.
[edit]
also tried 'acpi_backlight=vendor' on the kernel invocation line which gave me /sys/class/backlight/dell_backlight instead of acpi_video0 - but as before, the Fn-key just adjusts the value in the 'brightness'-file, display never changes ... *sigh*
Last edited by perbh (2012-06-20 04:58:47)
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#7 2012-06-20 12:51:04
- damdim
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- Registered: 2010-03-13
- Posts: 48
Re: Cant control Brightness after Update Dell L401x NVIDIA GT425M
It must be this bug:
https://bugzilla.kernel.org/show_bug.cgi?id=43168
There is a patch that fixes it.
I experience the same bug, but with more catastrophic way. My screen remains black and no way to turn it up, so now I use LTS kernel until it's fixed
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#8 2012-06-23 20:45:05
- villiansv
- Member
- Registered: 2010-05-02
- Posts: 2
Re: Cant control Brightness after Update Dell L401x NVIDIA GT425M
It must be this bug:
https://bugzilla.kernel.org/show_bug.cgi?id=43168
There is a patch that fixes it.
I experience the same bug, but with more catastrophic way. My screen remains black and no way to turn it up, so now I use LTS kernel until it's fixed
Indeed the patch on that link (post #15 I believe) fixed the issue for me as well (acpi_backlight=vendor and any other commandline options in grub did not help at all). This was on a Clevo P170HM laptop (with nvidia 485m). Other options include reverting to kernel 3.3.8, of course.
Overall I actually benefited from this bug. Haven't used Linux much at all, but learned how to apply a patch to the kernel source and compiled the patched kernel myself via ABS :-). Have dabbled with many other distros in my spare time, but Arch has by far the most informative wiki and helpful forum posts that I've encountered.
Last edited by villiansv (2012-06-23 20:46:13)
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