mbp-nvidia-bl-dkms 0.25~lucid broken on MacBookPro6,2

Bug #659780 reported by Kurt Smolderen on 2010-10-13
18
This bug affects 3 people
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Mactel Support
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Bug Description

After updating mbp-nvidia-bl-dkms 0.24.3~lucid to 0.25~lucid, backlight control is broken on MacBook Pro 6,2.
- Control keys to adjust brightness do not work anymore
- When unplugging the MacBook Pro from its power supply, the backlight is completely dimmed. Re-plugging the power supply restores the brightness to the value as it was before the laptop was unplugged.
- When the laptop is disconnected from its power supply and is booted, screen brightness is normal but not adjustable.

Running Ubuntu Lucid 64bit with generic kernel 2.6.32-25-generic.44
Using NVIDIA current drivers (195.36.24-0ubuntu1~lucid)
nvidia-bl-dkms is not installed as the backlight is steered by the Intel graphical adapter on the MacBook Pro 6,2

indium (indium) wrote :

Dear Kurt,

since an automatic update of by the update-manager I also have problems with the keys and the lcd backlight.

I first had 0.24 installed, for which all was working fine. With 0.25 I got a completely dimmed screen. After reading some posts on the internet, I thought I should have installed the nvidia-bl-dkms instead of the mbp-.... version. This didn't help, and I now have both installed at the same time.

Backlight control is not possible anymore, since /sys/class/backlight/ was empty. I then saw that mbp-.... was not loaded so I did

sudo modprob mbp_nvidia_bl , which fills this directory again. I can now manually adjust by echo XXX >/sys/class/backlight/mbp_backlight/brightness.

I noticed that the max_brightness value is ***** 110400 **** INSTEAD OF 15 !!

So now, when I start pommed manually (pommed -d), it sets the brightness to practically zero (15/110400).

Pommed won't accept a initial level of more than 15 in the /etc/pommed.conf file, so as soon as pommed runs, your screen goes off.
I __CAN__ adjust it with pommed, but it takes forever, with these small steps of 1. Somehow, it _does_ allow you to change the stepsize to 500 or so.

Now it seems to work, with these keys (f1,f2), but I do not the notify window popping up for this (but I do for volume control, or eject).

SO: the problem is partially related to the levels, which were 1-15 and now are 1-110400

Kurt Smolderen (kurt.smolderen) wrote :

Indium,

Two days ago, a new version was released (0.25.1~maverick). This fixes the blank screen and reenables controlling the backlight with F1 and F2. However, you have now only 8 instead of 15 steps to control the brightness.

indium (indium) wrote :

Okay, thanks for the tip. I'm always hesitating to upgrade, if everything's working. Are there any peculiarities for you?

Kurt Smolderen (kurt.smolderen) wrote :

Apart from the 8 instead of 15 steps, not really. But regarding this, I noticed something strange however. It seems like increasing or decreasing the brightness is done by two steps instead of one, that is when you compare it with the initial 15 steps you got. This means that when you start at maximum brightness (15) and you start dimming to zero, you got 15 - 13 - 11 - ... - 3 - 1 - 0. But when you increase the brightness once you reached zero (which is absolutely dimmed), you got 0 - 2 - 4 - ... - 10 - 12 - 14. As 16 is not a valid value, the maximum brightness you got is 14 instead of 15.
So although the 0.25.1 version does support the MacBook pro better compared to 0.25, version 0.24.3 is still more accurate.

Mario Schwalbe (schwalbe) wrote :

Actually it is a bit different: Version 0.25 of mbp-nvidia-bl added (and enabled by default) a new approach of setting the backlight on MacBook Pro 6,1 and 6,2, that has been reported to work. Its new maximum is correctly 110400 (0x1af40). As of version 0.25.1, the old approach, supporting 16 levels (0-15) is the default again, while the new one can be enabled using the
'use_gmux=1' driver option.

However, the problem seems to be pommed, which doesn't cope well with large numbers of brightness levels, because 15 out of 110400 is practically off and a step size of 1 is fairly too small. On the other hand, pommed isn't required anymore as gnome-power-manager takes care of display backlight (if the driver is loaded) appropriately. Can someone test the new approach (use_gmux=1) without pommed running?

Using the old approach, pommed interferes as well. As you noticed, the backlight gets adjusted with a step size of 2, because both pommed and gnome-power-manager attempt to respond to the brightness keys. Hence, it jumps 0-2-4-8-10-12-14-15 and 15-13-11-9-7-5-3-1-0 back (or 8 levels in total). The same behaviour should be experienced using 0.24 and below, because there are no differences.

I'll try to contact the maintainer to disable pommed's display backlight in a default install.

 Mario, just did some testing in order to verify everything. I
 completely removed pommed, so this deamon is not interfering anymore
 with gnome-power-manager.

 The results:
 * The module correctly detects the version of my macbook
 * Without the option use_gmux, the 16 levels are back again. This
 provides the user with a stable, working solution.
 * With use_gmux=1 (and debugging enabled), the brightness of the
 backlight is adjusted by increments or decrements of size 1, just as you
 expected. So from a technical point of view it is working, from a user
 point of view it is alas not workable ;-)

 On Thu, 28 Oct 2010 15:41:50 -0000, Mario Schwalbe
 <email address hidden> wrote:
> Actually it is a bit different: Version 0.25 of mbp-nvidia-bl added
> (and enabled by default) a new approach of setting the backlight on
> MacBook Pro 6,1 and 6,2, that has been reported to work. Its new
> maximum is correctly 110400 (0x1af40). As of version 0.25.1, the old
> approach, supporting 16 levels (0-15) is the default again, while the
> new one can be enabled using the
> 'use_gmux=1' driver option.
>
> However, the problem seems to be pommed, which doesn't cope well with
> large numbers of brightness levels, because 15 out of 110400 is
> practically off and a step size of 1 is fairly too small. On the
> other
> hand, pommed isn't required anymore as gnome-power-manager takes care
> of
> display backlight (if the driver is loaded) appropriately. Can
> someone
> test the new approach (use_gmux=1) without pommed running?
>
> Using the old approach, pommed interferes as well. As you noticed,
> the
> backlight gets adjusted with a step size of 2, because both pommed
> and
> gnome-power-manager attempt to respond to the brightness keys. Hence,
> it
> jumps 0-2-4-8-10-12-14-15 and 15-13-11-9-7-5-3-1-0 back (or 8 levels
> in
> total). The same behaviour should be experienced using 0.24 and
> below,
> because there are no differences.
>
> I'll try to contact the maintainer to disable pommed's display
> backlight
> in a default install.
>
> --
> mbp-nvidia-bl-dkms 0.25~lucid broken on MacBookPro6,2
> https://bugs.launchpad.net/bugs/659780
> You received this bug notification because you are a direct
> subscriber
> of the bug.
>
> Status in Mactel Support: New
>
> Bug description:
> After updating mbp-nvidia-bl-dkms 0.24.3~lucid to 0.25~lucid,
> backlight control is broken on MacBook Pro 6,2.
> - Control keys to adjust brightness do not work anymore
> - When unplugging the MacBook Pro from its power supply, the
> backlight is completely dimmed. Re-plugging the power supply restores
> the brightness to the value as it was before the laptop was
> unplugged.
> - When the laptop is disconnected from its power supply and is
> booted, screen brightness is normal but not adjustable.
>
> Running Ubuntu Lucid 64bit with generic kernel 2.6.32-25-generic.44
> Using NVIDIA current drivers (195.36.24-0ubuntu1~lucid)
> nvidia-bl-dkms is not installed as the backlight is steered by the
> Intel graphical adapter on the MacBook Pro 6,2
>
> To unsubscribe from this bug, go to:
> https://bugs.launchpad.net/mactel-support/+bug/659780/+subscribe

Mario Schwalbe (schwalbe) wrote :

Great. If you're using use_gmux=1, you most probably unloaded and reloaded the driver with the new option. Then, gnome-power-manager still uses its previous settings. In order to get more appropriate settings, you also have to kill and restart gnome-power-manager. What happens then? Does the backlight change? Does gnome-power-manager employ a reasonable step size?

Kurt Smolderen (kurt.smolderen) wrote :

Tried it out: gnome-power-manager gives the user a total of 20 steps.
Works like a charm, so now using gmux as default!

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