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coffee_addict

Member

From: Canada

Registered: 2011-06-14

Posts: 12

Software controlled screen brightness on Dell laptop not working

Hi,

I'm running a fully updated system on an old Dell laptop with KDE 4.6.
The brightness controls are functioning and KDE's onscreen brightness display is showing the correct value with the correct number of steps.
However, I cannot control the brightness via KDE's battery monitor applet, i.e., the onscreen brightness display changes but the actual screen brightness does not. KDE's battery monitor applet also is unable to change the brightness when the laptop is idle.

I've ventured into "/sys/class/backlight/dell_backlight", I see that the file "brightness" is appropriately changed via the function keys and via the battery monitor applet. However, the file "actual_brightness" is only changed via the function keys.

It's only a small issue, but I'd like to get everything working perfectly!

Any ideas?

ewaller

Administrator

From: Pasadena, CA

Registered: 2009-07-13

Posts: 19,791

Re: Software controlled screen brightness on Dell laptop not working

Can you change the brightness by writing values to actual_brightness ?

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Nothing is too wonderful to be true, if it be consistent with the laws of nature -- Michael Faraday
Sometimes it is the people no one can imagine anything of who do the things no one can imagine. -- Alan Turing
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coffee_addict

Member

From: Canada

Registered: 2011-06-14

Posts: 12

Re: Software controlled screen brightness on Dell laptop not working

Unfortunately not. By default it doesn't have write permissions.
But as root I tried this anyways:

chmod +w actual_brightness
echo 4 > actual_brightness

I got the following error "bash: echo: write error: Input/output error".
Writing to "brightness" does not result in any errors, but the actual screen brightness does not change.

ewaller

Administrator

From: Pasadena, CA

Registered: 2009-07-13

Posts: 19,791

Re: Software controlled screen brightness on Dell laptop not working

Well, it was worth a try  

I've now seen a couple threads where brightness seems to be uncoupled from the hardware.  Seems to be a recent development.

---

Nothing is too wonderful to be true, if it be consistent with the laws of nature -- Michael Faraday
Sometimes it is the people no one can imagine anything of who do the things no one can imagine. -- Alan Turing
---
How to Ask Questions the Smart Way

coffee_addict

Member

From: Canada

Registered: 2011-06-14

Posts: 12

Re: Software controlled screen brightness on Dell laptop not working

Well I got a bit of time over the next week, so I'll keep at it.
I'll post any results here if I figure something out.