G3 iBook LCD brightness in X under kernel 2.4.25 and 2.6.8

Christof Petig lists at petig-baender.de
Fri Nov 26 21:28:55 EST 2004

Frank Murphy schrieb:
> I'm trying to migrate from a 2.4 to a 2.6 kernel, but I have one last problem 
> keeping me with 2.4.25. There's a problem with adjusting screen brightness 
> under X (4.3.0.dfsg.1-8).
> I'm running pbbuttonsd 0.6.6-2 with gtkpbbuttons 0.6.4-3 (which are tools that 
> enable the LCD to be dimmed and brightened with keyboard pressed). When I'm 
> running the Debian kernel-image 2.4.25-8 and I press the brightness up or 
> down keys, I get the on-screen indication from gtkpbbuttons and the LCD dims 
> or brightens as expected in both X and on the console. However, when I boot 
> into kernel-image 2.6.8-6 or 2.6.9-1 and press the brightness keys, I get the 
> on-screen indication in X, but the LCD doesn't change brightness. However, if 
> I switch to a VT with a console, the brightness changes to what I tried to 
> change it to. Also, pressing the brightness buttons works fine when I press 
> them while in the console.
> My video card is a Mach64, and I'm using the 'ati' driver for X. One guess I 
> have is that in 2.6, lots more things are built as kernel modules. I'd like 
> to try build any needed video stuff in, but I don't know what it could be. 
> Does anyone here have an idea what controls screen brightness in X?

Your mouse pointer might get some noisy spots on brightness change, ever 
noticed? I would blame the kernel first (since 2.4 works well).

> The reason this is important for me is that the LCD is not dimmed when I close 
> the lid for sleep, which kind of ruins the point of sleep.
> Does anyone have an idea of what else I need to do to get screen dimming to 
> work under X with Linux 2.6?

Try to ask on the ppc-kernel list (CCed). I suspect that nobody has 
reimplemented power management for mach64 in 2.6. The fact that lid 
closing does not put the display to sleep keeps me locked in 2.4, too 
(though I experienced that 2.6 is way faster).

I played with the thought of fixing it myself (like I plan to fix DRI 
DMA some time) but was unable to allocate ressources (and enough motivation)

So take this as a "I have the problem, too" posting

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