Brightness function broken by 2.6.27-11-generic

[lguk]

Thinkpad R61i laptop the Fn Up and down for brightness no longer work and are very slow in responding.
(The laptop volume controls work perfectly still and have a fast response.)

The brightness popup appears and takes ages to change its progress bar but screen no longer dims or brightens. This worked perfectly on this laptop with 8.04 and 8.10 including 2.6.27-7 kernel but the 2.6.27-11 today broke it.

I noticed dmesg said :
"[ 22.474604] thinkpad_acpi: Disabling thinkpad-acpi brightness events by default..."
which doesn't sound helpful.

[krankor (mike-mhp)]

I'm having basically the same problem since installing 2.6.27-11 on my Thinkpad X301. I haven't noticed any slowness in the power manager brightness meter, which goes up and down as normal, but it doesn't change the screen brightness at all.

Running

xrandr --output LVDS --set BACKLIGHT_CONTROL native

enables the Fn Up and Down keys to control the screen brightness (though it's flaky), so it's not a hardware issue.

[lguk (leegib)]

Thanks. That worked for me also.
The keys started working again and the brightness goes up and down.

If I press it say 4 times, then it takes a while for it to process all 4 key presses unlike the volume meter which is very fast. But at least the brightness is working again with your xrandr command.

Thanks again.

[Kelson (emmanuel-engelhart)]

I can confirm this problem with a X61S and using linux-image-2.6.27-9-generic is an efficient workaround.

[Leann Ogasawara (leannogasawara)]

This seems like it might be a duplicate of bug 311716. Care to take a look. Thanks.

[lguk (leegib)]

Yes, sorry, this does indeed look like a duplicate of bug 311716 and that bug page has a lot more useful info.
Thanks.

[Stefan Hammer (j-4-deactivatedaccount)]

Hi!
Brightness control works still fine on my T400 and my X200 after update to 27-11. But there appears an other problem:
Brightness level is set to very low after reboot, suspend and hibernate. The screen is nearly black then. If you try to change the level, it suddenly jumps to your previous adjustment.

Can you confirm this behaviour?

jango

[aliencam (cameronk)]

I have the same issue on my thinkpad x61t. Still occuring, I get around it by using the 2.6.27-10 kernel or earlier.

[lguk (leegib)]

Hi Jango,

I don't get the same. Mine also boots in full brightness, from cold and from suspend. It has never remembered the brightness level for me. Laptop didn't change brightness level or go black via suspend/hibernate.

But with the very latest kernel 2.6.27-11, my brightness keys no longer work. The issue of the brightness popup being slow (1 sec response between changes) has been there, for me, for a while.
I tried another distro and the worked well, so not a hardware issue.

My workaround is to boot an earlier kernel (2.6.27-9).

[Stefan Hammer (j-4-deactivatedaccount)]

@ Iguk:
I think your problem is also discussed in this bug: bug 311716
There are also a lot of suggestions for workarounds!

Today i received a new update for kernel 27-11, which changed the situation a little bit.
On start-up, the brightness is on lowest level, when brightness-control-applet loaded it jumps to my default brightness level. After suspend and hibernate it is still mysteriously on lowest level again. And on shut-down the boot-splash is shown on lowest level too.

[phorminx (phorminx)]

On my lenovo x300, brightness control doesn't work anymore with 2.6.27-11. Like a couple of others, I've gone back to 2.6.27-9.

[Stefan Hammer (j-4-deactivatedaccount)]

Hi!
Today i found out, that my problem with lowest brightness level on startup and after suspend and hibernate does not occur on battery mode. There everything works perfect!
With Jaunty alpha 4 there are no problems too.