G3 iBook LCD brightness in X under kernel 2.4.25 and 2.6.8

Frank Murphy murphyf+xfree86 at f-m.fm
Sat Nov 27 19:48:06 EST 2004

On Saturday 27 November 2004 2:02, Benjamin Herrenschmidt wrote:
> On Fri, 2004-11-26 at 11:28 +0100, Christof Petig wrote:
> > > 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.
> What machine model precisely ? If it's an iBook, only the very first one
> had a mach64 based chip and indeed used atyfb-based brightness control,
> that might have been broken...

It's a first generation iBook SE (Special Edition). The SE means that it came 
with a 6GB HD, more RAM, and a slightly faster CPU (366MHz), but it does have 
a Mach64.

> > > 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?
> Some earlier models have PMU-controlled brightness, independently on the
> video card...

So I don't think it's an "early model" because it came out later than the 
fruit-colored iBooks (it's grey and white, not <color>-berry like the real 
first gen iBooks).

> > Your mouse pointer might get some noisy spots on brightness change, ever
> > noticed? I would blame the kernel first (since 2.4 works well).
> Ah ? Haven't noticed that ? what machine ?
> > > 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?
> You may be missing the atyfb kernel driver.

So I've tried this using the stock Debian 2.6.8 and 2.6.9 PPC kernels with the 
same results.

$ grep ATY /boot/config-2.6.9-powerpc
# CONFIG_FB_ATY_XL_INIT is not set

It seems that the atyfb module is compiled in. Is there another way to check?


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