[jaunty] screen brightness level on battery power unsteady and too dark

[Uwe Schilling]

Binary package hint: gnome-power-manager

Since I updated to from hardy to jaunty, the behavior of the screen brightness on battery power is strange. On unplugging, the overall brightness goes down (expected), but cannot be brought up to the level without battery power (unexpected). I can still use the hotkeys to adjust the brightness, but the intervall is in a lower range than on AC power. Furthermore, with a period of about one minute, the brightness goes down even further, bringing it the brightness to a level, where it is impossible to work, even with the brightness set to maximum. In the dark periods, the minimum setting seems to turn off the backlight completely, while maximum is a bit brighter, but still unusable. Then after about a minute it goes back to the brightness of "only some levels below AC power, but usable", after a minute dark again and so on.

A similar behavior is described in two bugs: For one bug 284550. However, in contrast to that report, I have the problem only when running on battery power. Additionally, it says in that bug report that a fix was released in gnome 2.24.4, but I still have the problem working in gnome 2.26.1. Bug 325789 describes the same behavior also only on battery power, but it claims that it doesn't occur any more in jaunty. Therefore, I decided to file a new bug report.

I am working on a Samsung X20 with intel graphics chipset.

btw.: how do I link other bugs?

[Uwe Schilling (uschilling)]

Actually, it is not always switching to the "cyclic mode". This time, the screen went black right after unplugging, and I could bring it with the hotkeys to a level at which it was barely usable in a completely dark room. However, it did not become brighter by itself this time, as described above. Here is the output of lshal -m during unplugging, using the hotkeys to see at least a little bit on the screen and replugging.

[Uwe Schilling (uschilling)]

Logging this information, I had again the "cyclic" behavior.

[Uwe Schilling (uschilling)]

The bug gets ever more confusing: while logging this information, I had the expected bahavior (for the first time ever, I think). The monitor went a little darker after unplugging, and I could turn it up to maximum brightness using the hotkeys. I'll rerecord that information trying to reproduce the buggy behavior....

[Uwe Schilling (uschilling)]

Ok, here the same log with the "cyclic" behavior.

[Scott Howard (showard314)]

Good job debugging this, those logs are helpful.

The issue that you reported is one that should be reproducible with the live environment of the Desktop CD of the development release - Karmic Koala. It would help us greatly if you could test with it so we can work on getting it fixed in the next release of Ubuntu. You can find out more about the development release at http://www.ubuntu.com/testing/.

There have been many changes in power-management since Jaunty, it would be best to do future debugging in Karmic so that we could get it fixed if it exists in Karmic.

Thanks again and we appreciate your help.

[Uwe Schilling (uschilling)]

The behavior has changed already under jaunty: now working on battery
power always allows for medium brightness, and only not touching the
keyboard for a while dims the screen completely. I guess that is the
desired behavior. I didn't notice this change since I haven't tried
working on battery for a while.

I would like to be able to bring the screen even on battery power to
100% brightness, but I guess not being able to do so is also desired
behavior and my wish would be more a thing for a whishlist. In my
opinion, this bug can be marked as fixed (I haven't checked on karmic
though)

Scott Howard schrieb:
> Good job debugging this, those logs are helpful.
>
> The issue that you reported is one that should be reproducible with the
> live environment of the Desktop CD of the development release - Karmic
> Koala. It would help us greatly if you could test with it so we can
> work on getting it fixed in the next release of Ubuntu. You can find
> out more about the development release at
> http://www.ubuntu.com/testing/.
>
> There have been many changes in power-management since Jaunty, it would
> be best to do future debugging in Karmic so that we could get it fixed
> if it exists in Karmic.
>
> Thanks again and we appreciate your help.
>
> ** Changed in: gnome-power-manager (Ubuntu)
> Status: New => Incomplete
>

[Scott Howard (showard314)]

Thanks for checking. Marking as fixed released. New feature request (or changed to default performance) should be send directly to the upstream authors at bugzilla.gnome.org, for forwarding instructions please have a look to http://wiki.ubuntu.com/Bugs/Upstream/GNOME. Thanks for helping make ubuntu better, and please report any additional bugs you find.