Re: G3 iBook LCD brightness in X under kernel 2.4.25 and 2.6.8

Re: G3 iBook LCD brightness in X under kernel 2.4.25 and 2.6.8

[Christof Petig]

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
    Christof

Re: G3 iBook LCD brightness in X under kernel 2.4.25 and 2.6.8

[murphyf+xfree86]

On Fri, 26 Nov 2004 11:28:55 +0100, "Christof Petig" said:
> 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).

I have noticed it, acutally. I don't know what it means exactly, but it
seems that some small set of pixels near the cursor is affected. These
corrupted pixels then move around with the cursor as 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

Well, that's something. What is your hardware? I have an original iBook
(actually, it's the 1.5 generation that came with a slightly faster CPU
and a bigger HD).

Frank

Re: G3 iBook LCD brightness in X under kernel 2.4.25 and 2.6.8

[Benjamin Herrenschmidt]

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...

> > 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...

> 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.

> 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).

It is, provided you have the right driver.

> 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
>     Christof
> _______________________________________________
> Linuxppc-dev mailing list
> Linuxppc-dev@ozlabs.org
> https://ozlabs.org/mailman/listinfo/linuxppc-dev
-- 
Benjamin Herrenschmidt <benh@kernel.crashing.org>

Re: G3 iBook LCD brightness in X under kernel 2.4.25 and 2.6.8

[Frank Murphy]

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_ATY128=y
CONFIG_FB_ATY=y
CONFIG_FB_ATY_CT=y
CONFIG_FB_ATY_GX=y
# CONFIG_FB_ATY_XL_INIT is not set

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

Frank

Re: G3 iBook LCD brightness in X under kernel 2.4.25 and 2.6.8

[Benjamin Herrenschmidt]

> r.
> 
> 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_ATY128=y
> CONFIG_FB_ATY=y
> CONFIG_FB_ATY_CT=y
> CONFIG_FB_ATY_GX=y
> # CONFIG_FB_ATY_XL_INIT is not set
> 
> It seems that the atyfb module is compiled in. Is there another way to check?

Check the bits in CONFIG_PMAC_BACKLIGHT in atyfb (like, add some
printk's to see if they are reached etc..)

Ben

Re: G3 iBook LCD brightness in X under kernel 2.4.25 and 2.6.8

[Frank Murphy]

On Sunday 28 November 2004 2:58, Benjamin Herrenschmidt wrote:
> >
> > 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_ATY128=y
> > CONFIG_FB_ATY=y
> > CONFIG_FB_ATY_CT=y
> > CONFIG_FB_ATY_GX=y
> > # CONFIG_FB_ATY_XL_INIT is not set
> >
> > It seems that the atyfb module is compiled in. Is there another way to
> > check?
>
> Check the bits in CONFIG_PMAC_BACKLIGHT in atyfb (like, add some
> printk's to see if they are reached etc..)

So I added a couple of printk()s like you asked. I added one to 
aty128fb_blank() in aty128fb.c:2037 and two to aty_init() in 
atyfb_base.c:1793 and 1802 (inside the 'if (M64_HAS(MOBIL_BUS))'). The one I 
added to aty128fb didn't print (as expected), but both of them from 
atyfb_base.c printed. So it seems that CONFIG_PMAC_BACKLIGHT is properly 
defined. Anything you'd specifically like me to try?

I find it interesting that in the console the dimming works. I thought that on 
PPC the console used the framebuffer. Another notable thing is that while in 
X, the dimming doesn't work, but when I switch to one of the VTs, the screen 
brightness is adjusted to what it should have been in X.

Thanks for your help on this,

Frank

Re: G3 iBook LCD brightness in X under kernel 2.4.25 and 2.6.8

[Benjamin Herrenschmidt]

On Sun, 2004-11-28 at 21:14 +0100, Frank Murphy wrote:
> On Sunday 28 November 2004 2:58, Benjamin Herrenschmidt wrote:
> > >
> > > 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_ATY128=y
> > > CONFIG_FB_ATY=y
> > > CONFIG_FB_ATY_CT=y
> > > CONFIG_FB_ATY_GX=y
> > > # CONFIG_FB_ATY_XL_INIT is not set
> > >
> > > It seems that the atyfb module is compiled in. Is there another way to
> > > check?
> >
> > Check the bits in CONFIG_PMAC_BACKLIGHT in atyfb (like, add some
> > printk's to see if they are reached etc..)
> 
> So I added a couple of printk()s like you asked. I added one to 
> aty128fb_blank() in aty128fb.c:2037 and two to aty_init() in 
> atyfb_base.c:1793 and 1802 (inside the 'if (M64_HAS(MOBIL_BUS))'). The one I 
> added to aty128fb didn't print (as expected), but both of them from 
> atyfb_base.c printed. So it seems that CONFIG_PMAC_BACKLIGHT is properly 
> defined. Anything you'd specifically like me to try?

Well, the backlight control is done by writing to one of the LCD
register, you can try to track down the values in there and eventually
compare with 2.4

> I find it interesting that in the console the dimming works. I thought that on 
> PPC the console used the framebuffer. Another notable thing is that while in 
> X, the dimming doesn't work, but when I switch to one of the VTs, the screen 
> brightness is adjusted to what it should have been in X.

Ah ? What do you mean by "dimming" ? blanking ? or backlight control ?

Could be some crap done by the X driver ... It's notoriously allergic to
fbdev's ... I'll have to double check.

> Thanks for your help on this,
> 
> Frank
-- 
Benjamin Herrenschmidt <benh@kernel.crashing.org>

Re: G3 iBook LCD brightness in X under kernel 2.4.25 and 2.6.8

[Frank Murphy]

On Mon, 29 Nov 2004 07:39:39 +1100, "Benjamin Herrenschmidt" said:
> On Sun, 2004-11-28 at 21:14 +0100, Frank Murphy wrote:
> > On Sunday 28 November 2004 2:58, Benjamin Herrenschmidt wrote:
> > > >
> > > > 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_ATY128=y
> > > > CONFIG_FB_ATY=y
> > > > CONFIG_FB_ATY_CT=y
> > > > CONFIG_FB_ATY_GX=y
> > > > # CONFIG_FB_ATY_XL_INIT is not set
> > > >
> > > > It seems that the atyfb module is compiled in. Is there another way to
> > > > check?
> > >
> > > Check the bits in CONFIG_PMAC_BACKLIGHT in atyfb (like, add some
> > > printk's to see if they are reached etc..)
> > 
> > So I added a couple of printk()s like you asked. I added one to 
> > aty128fb_blank() in aty128fb.c:2037 and two to aty_init() in 
> > atyfb_base.c:1793 and 1802 (inside the 'if (M64_HAS(MOBIL_BUS))'). The one I 
> > added to aty128fb didn't print (as expected), but both of them from 
> > atyfb_base.c printed. So it seems that CONFIG_PMAC_BACKLIGHT is properly 
> > defined. Anything you'd specifically like me to try?
> 
> Well, the backlight control is done by writing to one of the LCD
> register, you can try to track down the values in there and eventually
> compare with 2.4

I'll try to look at this, but I don't know very much about it.

> > I find it interesting that in the console the dimming works. I thought that on 
> > PPC the console used the framebuffer. Another notable thing is that while in 
> > X, the dimming doesn't work, but when I switch to one of the VTs, the screen 
> > brightness is adjusted to what it should have been in X.
> 
> Ah ? What do you mean by "dimming" ? blanking ? or backlight control ?

OK, the F1 and F2 keys on my keyboard have little "brighter"/"dimmer"
icons on them. When I press them when running X on 2.4.25, the screen
brightness changes. So for me, that's "dimming." I believe that it's the
"backlight control" that does this. When I press the "dimmer" button
enough (8 times, I think), then the backlight turns totally off, and I
can't see anything on the screen. For me that's "blanking" in this
context. It's true that something else (X, I think) will kind of blank
the screen, but the backlight stays lit. I noticed this when I closed
the lid to make the iBook sleep, but the backlight stayed on, warming
the keyboard. I then noticed the same problem with the dimmer keys.

> Could be some crap done by the X driver ... It's notoriously allergic to
> fbdev's ... I'll have to double check.

It probably is. But it's strange because I use all the same software
except the kernel to get this behavior. So there's something with the
kernel / X interface that has changed, either for 2.6 or the way Debian
builds 2.6. I have a hard time with this because there are so many
interactions:  is it the PMU? The APM emulation? X driver? Kernel
driver? I don't have a good idea about how these things interact.

Let me know what you find out.

Frank

Re: G3 iBook LCD brightness in X under kernel 2.4.25 and 2.6.8

[Christof Petig]

Frank Murphy schrieb:
>>Well, the backlight control is done by writing to one of the LCD
>>register, you can try to track down the values in there and eventually
>>compare with 2.4
> 
> 
> I'll try to look at this, but I don't know very much about it.

is it possible that using acceleration in the X server puts the chip in 
a state which makes it hard for the kernel framebuffer to set brightness.

>>>I find it interesting that in the console the dimming works. I thought that on 
>>>PPC the console used the framebuffer. Another notable thing is that while in 
>>>X, the dimming doesn't work, but when I switch to one of the VTs, the screen 
>>>brightness is adjusted to what it should have been in X.
>>
>>Ah ? What do you mean by "dimming" ? blanking ? or backlight control ?
> 
> 
> OK, the F1 and F2 keys on my keyboard have little "brighter"/"dimmer"
> icons on them. When I press them when running X on 2.4.25, the screen
> brightness changes. So for me, that's "dimming." I believe that it's the
> "backlight control" that does this. When I press the "dimmer" button
> enough (8 times, I think), then the backlight turns totally off, and I
> can't see anything on the screen. For me that's "blanking" in this
> context. It's true that something else (X, I think) will kind of blank
> the screen, but the backlight stays lit. I noticed this when I closed
> the lid to make the iBook sleep, but the backlight stayed on, warming
> the keyboard. I then noticed the same problem with the dimmer keys.
> 
> 
>>Could be some crap done by the X driver ... It's notoriously allergic to
>>fbdev's ... I'll have to double check.
> 
> It probably is. But it's strange because I use all the same software
> except the kernel to get this behavior. So there's something with the
> kernel / X interface that has changed, either for 2.6 or the way Debian
> builds 2.6. I have a hard time with this because there are so many
> interactions:  is it the PMU? The APM emulation? X driver? Kernel
> driver? I don't have a good idea about how these things interact.

I don't think that this problem is debian related (I use a stock kernel 
for my tests). It _might_ theoretically be a strange result of the 
debian X server patches, but I don't think so.

If I enter snooze in _2.4_ my screen gets strangely garbaged (blue 
patterns which are somewhat related to the X11 screen but with wrong 
line offset, perhaps displayed at 640x480x8bpp?), then the hard disc 
parks, then backlight is turned off. If I press a key, the cdrom spins 
up, the backlight is turned on (screen garbaged) and the screen is 
restored. I would say that this is the correct behaviour.

My last experiment with 2.6.9 gave me (IIRC): The console is switched to 
a text console, some power management transition messages appear, the 
hard disc parks, the text remains readable ... Pressing a screen gives 
CD spinup, more messages and the computer switches back to the X console.

I will retry with Linus latest tree.

    Christof

Re: G3 iBook LCD brightness in X under kernel 2.4.25 and 2.6.8

[Christof Petig]

Christof Petig schrieb:
> My last experiment with 2.6.9 gave me (IIRC): The console is switched to 
> a text console, some power management transition messages appear, the 
> hard disc parks, the text remains readable ... Pressing a screen gives 
> CD spinup, more messages and the computer switches back to the X console.
> 
> I will retry with Linus latest tree.

I can confirm that everything works well with Linus' 2.6.10-rc2-bk6. So 
consider the problem as solved (writing from said version).

snooze and the brightness keys work well.

    Christof

PS: related (?) config settings

CONFIG_ADB=y
# CONFIG_ADB_CUDA is not set
CONFIG_ADB_PMU=y
CONFIG_PMAC_PBOOK=y
CONFIG_PMAC_APM_EMU=y
CONFIG_PMAC_BACKLIGHT=y
# CONFIG_ADB_MACIO is not set
CONFIG_INPUT_ADBHID=y
CONFIG_MAC_EMUMOUSEBTN=y

# CONFIG_FB_ATY128 is not set
CONFIG_FB_ATY=y
CONFIG_FB_ATY_CT=y
CONFIG_FB_ATY_GENERIC_LCD=y
# CONFIG_FB_ATY_XL_INIT is not set
# CONFIG_FB_ATY_GX is not set

Re: G3 iBook LCD brightness in X under kernel 2.4.25 and 2.6.8

[Frank Murphy]

On Tue, 30 Nov 2004 09:02:52 +0100, "Christof Petig"
<lists@petig-baender.de> said:
> I can confirm that everything works well with Linus' 2.6.10-rc2-bk6. So 
> consider the problem as solved (writing from said version).
> 
> snooze and the brightness keys work well.

Well *that's* good news. I'll retry here as well and confirm.

Frank

Re: G3 iBook LCD brightness in X under kernel 2.4.25 and 2.6.8

[murphyf+xfree86]

OK, works for me here as well. I think I'm seeing some weird color
artifacts, but I'll bring it up with the guy who's doing all the Mach64
work. There seems to be a lot in 2.6.10.

Frank

On Tue, 30 Nov 2004 10:05:00 +0100, "Frank Murphy"
<murphyf+xfree86@f-m.fm> said:
> 
> On Tue, 30 Nov 2004 09:02:52 +0100, "Christof Petig"
> <lists@petig-baender.de> said:
> > I can confirm that everything works well with Linus' 2.6.10-rc2-bk6. So 
> > consider the problem as solved (writing from said version).
> > 
> > snooze and the brightness keys work well.
> 
> Well *that's* good news. I'll retry here as well and confirm.
> 
> Frank

Re: G3 iBook LCD brightness in X under kernel 2.4.25 and 2.6.8

[Benjamin Herrenschmidt]

On Mon, 2004-11-29 at 10:42 +0100, Frank Murphy wrote:

> It probably is. But it's strange because I use all the same software
> except the kernel to get this behavior. So there's something with the
> kernel / X interface that has changed, either for 2.6 or the way Debian
> builds 2.6. I have a hard time with this because there are so many
> interactions:  is it the PMU? The APM emulation? X driver? Kernel
> driver? I don't have a good idea about how these things interact.
> 
> Let me know what you find out.

It has to do with interactions between the X driver and the atyfb driver
I suppose...

Ben.

Re: G3 iBook LCD brightness in X under kernel 2.4.25 and 2.6.8

[Christof Petig]

Benjamin Herrenschmidt schrieb:
> 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...

My machine is an orange iBook (300MHz), lspci:
0000:00:0b.0 Host bridge: Apple Computer Inc. UniNorth AGP
0000:00:10.0 VGA compatible controller: ATI Technologies Inc Rage 
Mobility L AGP 2x (rev 64)
0000:10:0b.0 Host bridge: Apple Computer Inc. UniNorth PCI
0000:10:17.0 ff00: Apple Computer Inc. KeyLargo Mac I/O (rev 02)
0000:10:18.0 USB Controller: Apple Computer Inc. KeyLargo USB
0000:10:19.0 USB Controller: Apple Computer Inc. KeyLargo USB
0000:20:0b.0 Host bridge: Apple Computer Inc. UniNorth Internal PCI
0000:20:0f.0 ffff: Apple Computer Inc. UniNorth GMAC (Sun GEM) (rev ff)

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

I don't think this is the case for us.

>>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 ? 

I would blame X to leaving the mach64 in a 'strange' state which makes 
the kernel unable to set the brightness the way it uses to do. Since 2.4 
was able to do it, it must be possible (might be less efficient).

>>>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.

CONFIG_ADB=y
# CONFIG_ADB_CUDA is not set
CONFIG_ADB_PMU=y
CONFIG_PMAC_PBOOK=y
CONFIG_PMAC_APM_EMU=y
CONFIG_PMAC_BACKLIGHT=y
# CONFIG_ADB_MACIO is not set

# CONFIG_FB_ATY128 is not set
CONFIG_FB_ATY=y
CONFIG_FB_ATY_CT=y
# CONFIG_FB_ATY_GX is not set
# CONFIG_FB_ATY_XL_INIT is not set

>>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).
> 
> 
> It is, provided you have the right driver.

I really would like to work this out.

Yours
    Christof