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#1 2011-05-22 09:36:37

musiKk
Member
Registered: 2011-05-21
Posts: 12

Brightness controls skipping more and more steps

Now this is a problem that pretty much plagues me for a couple of years but now it's getting out of hand.

I have a Thinkpad R60e. According to the values I read from /sys/class/backlight/acpi_video0/brightness the possible brightness values for my display are 0 to 7 inclusive. As long as I'm early in the boot process (don't know how to describe it better) or say in the BIOS configuration, I can access all 8 brightness levels with Fn+BrightnessUp/Down.

In the beginning (maybe 2008/9? Ubuntu and Fedora) it started with brightness controls skipping every other level. Not nice but no biggie. I could still access all levels by going to max and then 7 - 5 - 3 - 1 or to min and then 0 - 2 - 4 - 6.

Maybe a year ago another skip was added. Not so nice anymore as I can only go 7 - 4 - 1 and 0 - 3 - 6.

Yesterday I noticed that another skip was added. Now it's merely 7 - 3 and 0 - 4. Incidentally yesterday I switched to Xfce. But I just might not have noticed and the three skips might have been there a bit longer.

When I switch to a tty, I'm back to one skip.

Now I know this all is kinda vague but I have absolutely no idea how to diagnose something like this. Maybe it has to do with Kernel versions, display driver versions, X, ... It seems like more and more tools are placing a hook on that particular key combination and thinking they're responsible to change my brightness. But how do I find out what those are and how do I bring them to ignore it?

Thanks
mK

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#2 2011-05-22 21:45:29

MartinZ
Member
From: Chiloé, Chile
Registered: 2005-06-10
Posts: 379

Re: Brightness controls skipping more and more steps

I'm having the same problem in KDE. The funny thing is that Power Management's applet slider does support all steps (0-8 in my case).
Under KDE, using Fn + F5 goes 0 - 2 - 5 - 8.
In console, it goes 0 - 2 - 4 - 6 - 8.

Is there any way to set the Fn keys no to skip any level?


All your base are belong to us

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#3 2011-05-23 17:03:12

musiKk
Member
Registered: 2011-05-21
Posts: 12

Re: Brightness controls skipping more and more steps

MartinZ wrote:

I'm having the same problem in KDE. The funny thing is that Power Management's applet slider does support all steps (0-8 in my case).

I think this is because it sets the brightness values via sys or a similar low level mechanism. That's why I think the issue is that there are too many applications looking for Fn-BrightnessUp/Down and act accordingly.

It's strange that it's so difficult to find information about this online (or my Google-fu failed me).

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