[i945GM] weird behavior of brightness control, especially with Jaunty

Binary package hint: xserver-xorg-video-intel

This resembles Bug #312518, Bug #367309 and Bug #356510, but there is some significant difference, so I decided to file new one. I have a similar problem with flickering screen on Jaunty with my Lenovo 3000 c200 (intel 945GM). It has nothing to do with logging in. It just flickers occasionally from time to time. I think most of the times this happens right after the machine is idle for some time - moving the mouse a bit makes it flicker for a moment until it gets stable. Yet this also happens unpredictably during use.
When flickering, screen does not get completely black, but rather gets to the minimum brightness for a short moment and then back to the adjusted level.

When using Power Manager Brightness Applet to adjust brightness, dragging is extremely slow and accompanied by massive flickering. When using "Set Display Brightness" in Power Manager Preferences, dragging is normal, but yet screen flickers rapidly. In both cases adjustment works. If trying to adjust with keyboard shortcuts (Fn key+F10 or F11), screen gets dimmed and flickers, and I can only adjust one step before it falls back to minimum brightness, so brightness cannot be adjusted. There is also reproducable flickering when launching Power Manager Preferences. Turning off "Dim display when idle" doesn't make things better.

Previously I was using Hardy, and this problem wasn't there, not with the default kernel nor with custom-compiled 2.6.29. I believe this could be connected to another problem which I did have on Hardy and which remains on Jaunty: when switching video modes, brightness falls to minimum, for example when logging out or switching to virtual terminal by pressing ctrl-alt-f2 (also sometimes when playing a video file or 3D game). Strangely right after installing Hardy it was ok, the problems only started after updating bios to the most recent version. Reverting bios had no effect, so I decided to stick with the most recent version.

When trying the proposed solution (Bug #367309):

xrandr --output LVDS --set BACKLIGHT_CONTROL combination

it actually gets better: the hotkeys work again and using the gnome applet is faster (though a bit slow yet). Also switching between video modes doesn't reset brightness anymore. Though now changing brightness gets accomponied by clicking sound, coming probably from my hard disk. I looked into System Log Viewer and I noticed that every little change in brightness, be it via applet, hotkey or Power Management Preferences, triggers this message in auth.log:

<username> dbus-daemon: Rejected send message, 1 matched rules; type="method_call", sender=":1.42" (uid=1000 pid=3586 comm="/usr/lib/indicator-applet/indicator-applet --oaf-a") interface="org.freedesktop.DBus.Properties" member="Get" error name="(unset)" requested_reply=0 destination=":1.140" (uid=111 pid=6568 comm="/usr/lib/policykit/polkit-read-auth-helper 1000 "))

In addition, after the initial command to xrandr I am able to switch back to

xrandr --output LVDS --set BACKLIGHT_CONTROL kernel

without any consequences, everything behaves the same way, the flickering doesn't occur again (until logout). Actually after initial switching to any type of BACKLIGHT_CONTROL but "kernel", it doesn't matter at all which type I select next: nothing appears to change.

I'm using Ubuntu 9.04
xserver-xorg-video-intel: 2:2.6.3-0ubuntu9

[lspci]
00:00.0 Host bridge [0600]: Intel Corporation Mobile 945GM/PM/GMS, 943/940GML and 945GT Express Memory Controller Hub [8086:27a0] (rev 03)
 Subsystem: Lenovo Device [17aa:3800]
00:02.0 VGA compatible controller [0300]: Intel Corporation Mobile 945GM/GMS, 943/940GML Express Integrated Graphics Controller [8086:27a2] (rev 03)
 Subsystem: Lenovo Device [17aa:3801]