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Last reply by 06-08-2013 Unsolved
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2 Bronze
2 Bronze
26810

Backlight control broke

Ubuntu and sputnik updates from 5/7 broke backlight control.

Using Ubuntu LTS12.04.

Tried reinstalling but now, it's broke real good. Meaning, after a full Ubuntu re-install backlight control does not work.

Any help or suggestions?

Thanks!!

Replies (16)
2 Jasper
2 Jasper
511

Kamal's repo doesn't support 13.04, so the problem remains even with a new kernel today versioned 3.8.0.23

2 Bronze
2 Bronze
511

13.04 is supposed to have the backlight support baked into it from upstream, hence, no need for a PPA.    I'm not sure what the problem is exactly, but there are two camps involved with this so far.    One set of users with the FHD XPS 13 running 13.04 are reporting that their backlights are working great with 3.8.0.22 while others are complaining that it *was* working with 3.8.0.21 and it doesn't with .22 and higher.   For anyone running into this now with the .22 and .23 kernels did anyone, by chance, have this kernel installed before updating to the latest bits?:

http://people.canonical.com/~kamal/lp1169376/

..or had anyone that's suffering from this been running with the pre-release 13.04 versions where the backlight was working, quit working, worked again with the kernel from the link above and then quit working again with the production kernels? 

 This is also being logged here in launchpad:

https://bugs.launchpad.net/dell-sputnik/+bug/1169376

If anyone is running into this on 13.04, this is the place to start logging information and any history you've had with your backlights.   The goal is to get this 'right' in the 3.8 kernels so that we're not having to lean on separate PPA's going forward.  

2 Bronze
2 Bronze
511

Upgraded from 12.10 to 13.04 and backlight control doesn't work anymore. Running kernel 3.8.0-23-generic

2 Bronze
2 Bronze
511

I received my brand new XPS 13 Developer's Edition laptop this morning.  This afternoon, I did a clean install of 13.04 and let it pull the latest updates.  It is now running 3.8.0-23-generic.

The back-light control does not work (it did work with the originally installed 12.04).

I posted this information on the Launchpad site, also.

2 Bronze
2 Bronze
511

The 12.04 kernels from the sputnik ppa contain specially-backported versions of the upstream backlight fixes so that the LTS edition will continue to work.  The 13.04 kernels contain the latest and greatest commits that, as you can see, have yielded mixed results for folks.  

For the test machine I have, 3.8.0-19 through 3.8.0-22 worked and then -23 broke, while others report almost the opposite.

At any rate, this appears to look more and more like a generic bug rather than a specific one to the XPS 13 for 13.04.  

Someone updated the bug a little while ago indicating the same thing has happened on a MacBook Pro with the same 13.04 kernels (i.e. -23 and higher seems to  have broken the backlight controls). 

2 Bronze
2 Bronze
511

I just posted this up on Launchpad:

Today, I got down the latest source to the Ubuntu kernel and took a look at what was changed that broke the brightness control.  On April 8th, they decided to take out a line that applied to Ivy Bridge processors in the file drivers/gpu/drm/i915/intel_display.c.  I put the line back in, recompiled the kernel and installed it and now the brightness control is working fine on my laptop (a new XPS 13 Developer's Edition, which has an Ivy Bridge processor).

I'm not qualified to determine what the proper fix is for this, but apparently at least some machines with Ivy Bridge processors require that the 'quirk' be left in.

3 Silver
511

I have an original sputnik from last September, and I've never had issues with the backlight, even after upgrading to 13.04. I recently wiped my drive and reinstalled 13.04 without the Dell ppa's and everything still works. I didn't need any tweak whatsoever.

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