2.6.27-11 makes brightness not work [2.6.28-4.10 also affected]

[Nicolò Chieffo]

Binary package hint: linux-image-2.6.27-11-generic

After an upgrade from linux-image-2.6.27-10 to 2.6.27-11 brightness controls do not work anymore (keys and applet).
I've just done a clean install of ubuntu 8.10 and immediately updated it. Rolling back to previous version fixes the problem.

Hp dv6627 laptop, lshal attached

[Scott G (scotta-g1967)]

I have noticed the same problem, though mine happened after a kernel update from the proposed branch 2.6.27-11-generic, When I boot in too 2.6.27-9 all is fine, though 2.6.27-11 kills the brightness control.

Other power management seems OK though I have not really tested this yet, but CPU scaling is certainly ok

My machine is an Acer Aspire 5920G

[Nicolò Chieffo (yelo3)]

I have to say that a downgrade of g-p-m was only enough to re-enable
the brightness panel applet. But when moving the cursor up and down
the brightness does not change.

Maybe I should try to boot into linux 2.6.27-9 like you Scott!

[Nicolò Chieffo (yelo3)]

The problem is in the kernel 2.6.27-10 works correctly even in new gnome-power-manager, you were definitely right

[Christian Busch (christianbusch)]

Same thing here on a HP Paviliion 6870eg.
Wenn I unplug the power cord, brightness decreases. When I plug the cord in, the brightness increases.
I can't neither controll the brightness with the fn keys nor the brightness applet. Also the OSD doesn't show up.

The other fn keys work just fine.

Workaround now is booting another kernel.

[Nicolò Chieffo (yelo3)]

Not working also in jaunty, 2.6.28-4-generic

[sasha (sasha123-deactivatedaccount)]

i have upgraded the 2.6.27-11-generic today and now the screen brightness control works fine.

[Nicolò Chieffo (yelo3)]

I don't have intrepid anymore, but foru sure jaunty does not work.

[Christian Busch (christianbusch)]

I also upgraded 2.6.27-11-generic now.
It works without flaws. Bug solved?

[Nicolò Chieffo (yelo3)]

Not for jaunty

[Dana Goyette (danagoyette)]

I'm on Jaunty, and the latest 2.6.28-4.10 generic x86-64 kernel entirely removes my ability to change brightness levels; the previous kernel works perfectly.

Under the old kernel, /proc/acpi/video/DGFX/LCD/brightness returns this:
levels: 100 51 30 37 44 51 58 65 72 79 86 93 100
current: 100

Under the new kernel, it returns this:
<not supported>

Under the old kernel, HAL uses /sys/class/backlight/acpi_video0 to control brightness; under the new kernel, the /sys/class/backlight directory is completely empty.

I believe the fix for the "reversed brightness" bug ( https://bugs.launchpad.net/ubuntu/+source/linux/+bug/311716 ) is most likely what broke my brightness control. Also note this comment in that bug description: "Risks: as we are supressing ACPI brightness support we may suppress it where it is required"

Laptop is a customized-to-order HP EliteBook 8530w.

[Dana Goyette (danagoyette)]

Okay, I just tested, and the same version (but 32-bit) kernel on my old Gateway M685 also breaks backlight control. Same symptoms: proc has <not supported> and sys is empty.

[Dana Goyette (danagoyette)]

Another system affected: an old Toshiba Satellite 1415 laptop. ACPI Video module normally gives levels labeled as 0%, 40%, and 100%, but now gives nothing. For better backlight control, this laptop needs toshiba-acpi instead of tlsup, but that's an entirely different issue.

[Nicolò Chieffo (yelo3)]

The fix is only for Intrepid, Jaunty still needs it

[Dana Goyette (danagoyette)]

Aah, I see it now in the Intrepid changelogs. Cool, so now I can just wait, and it'll be fixed with an upcoming Jaunty kernel, right?

(By the way, the "tlsup" bug is also fixed in intrepid-proposed but not in jaunty: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/261318 )

linux (2.6.27-11.24) intrepid-proposed; urgency=low

  [ Stefan Bader ]

  * Revert "SAUCE: don't use buggy _BCL/_BCM/_BQC for backlight control"
    - LP: #311716
  * SAUCE: acpi: Hack to enable video and vendor backlight implementations
    - LP: #311716
  * SAUCE: Force vendor backlight control on ThinkPad T61
    - LP: #311716

  [ Upstream Kernel Changes ]

  * Revert "thinkpad_acpi: fingers off backlight if video.ko is serving
    this functionality"
    - LP: #311716

 -- Stefan Bader <email address hidden> Thu, 08 Jan 2009 15:08:52 +0100

[David Gibson (dwg)]

I still see the problem on Intrepid with2.6.27-11.27 on a Thinkpad X61. Neither Fn-keys nor the sliders in System|Preferences|Power Management alter the screen brightness.

[Charles (cistearns)]

I will echo that, on the Thinkpad X61s I have the same problem 2.6.27-11-generic, the brightness control doesn't work.

Booting back in 2.6.27-7-generic works fine.

[Chris Jones (cmsj)]

should this be marked as a duplicate of bug #311716 ?

[Dana Goyette (danagoyette)]

For me on Jaunty, the 2.6.28-7-generic kernel has been fixed now -- it seems they've reverted the "don't use _BCM and _BCL" patches. I'm not sure about the Intrepid kernel, though. Also, this is not quite a duplicate -- it's more of a "fixing that one broke this one" issue.

[Behnam Esfahbod "ZWNJ" (behnam)]

As it's a kernel problem, not gnome-power-manater, this is a duplicate of bug 313231 which has a couple other dups as well.

[Natale Vinto (ebballon)]

Hi, on my ubuntu jaunty is working with the 2.6.28-8 but not with the last 2.6.28.7 from kernel.org, how to fix it in that kernel?

[penalvch (penalvch)]

Nicolò Chieffo, thank you for reporting this and helping make Ubuntu better. Hardy desktop reached EOL on May 12, 2011.
Please see this document for currently supported Ubuntu releases:
https://wiki.ubuntu.com/Releases

We were wondering if this is still an issue in a supported release? If so, can you try with the latest development release of Ubuntu? ISO CD images are available from http://cdimage.ubuntu.com/releases/ .

If it remains an issue, could you run the following command in a supported release from a Terminal (Applications->Accessories->Terminal). It will automatically gather and attach updated debug information to this report.

apport-collect -p linux <replace-with-bug-number>

Also, if you could test the latest upstream kernel available that would be great. It will allow additional upstream developers to examine the issue. Refer to https://wiki.ubuntu.com/KernelMainlineBuilds . Once you've tested the upstream kernel, please remove the 'needs-upstream-testing' tag. This can be done by clicking on the yellow pencil icon next to the tag located at the bottom of the bug description and deleting the 'needs-upstream-testing' text.

If this bug is fixed in the mainline kernel, please add the following tag 'kernel-fixed-upstream'.

If the mainline kernel does not fix this bug, please add the tag: 'kernel-bug-exists-upstream'.

If you are unable to test the mainline kernel, for example it will not boot, please add the tag: 'kernel-unable-to-test-upstream'.

Please let us know your results. Thanks in advance.

[Launchpad Janitor (janitor)]

[Expired for linux (Ubuntu) because there has been no activity for 60 days.]