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Blåklinten

Member

From: Gothenburg

Registered: 2017-12-29

Posts: 9

[SOLVED] Backlight keyboard stopped working properly after update

Since the last update I did on my laptop my keyboard backlight stopped working like before. The timeout until the keyboard goes black used to be like a couple of minutes of no activity but now it's more like a second. This is really annoying since it lights up when I press a key but goes dark as soon as I don't. I can still change the intensity of the light as usual. I have looked around and figured that I could control my keyborad backlight by the dbus interface but I haven't figured out how to control the timeout and I would also very much like to understand how this problem can occur.  Does anybody have any clue to what might be causing this or a possible solution?

I am kind of a noob (first time posting, yay!)  so I don't know what information exactly to attach, sorry.

Last edited by Blåklinten (2018-02-14 15:25:09)

jasonwryan

Anarchist

From: .nz

Registered: 2009-05-09

Posts: 30,424

Website

Re: [SOLVED] Backlight keyboard stopped working properly after update

Some information about your hardware, what was updated, the version of the kernel you are running, what sort of backlight, anything in your journal, etc.

See How To Ask Questions The Smart Way.

Moving to NC...

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Arch + dwm   •   Mercurial repos  •   Surfraw

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Blåklinten

Member

From: Gothenburg

Registered: 2017-12-29

Posts: 9

Re: [SOLVED] Backlight keyboard stopped working properly after update

Im running an Dell Latitude E7240, the action that led to trouble I think was

[2018-02-06 19:21] [ALPM] transaction started
[2018-02-06 19:21] [ALPM] upgraded libvpx (1.6.1-1 -> 1.7.0-1)
[2018-02-06 19:21] [ALPM] upgraded libice (1.0.9-1 -> 1.0.9-2)
[2018-02-06 19:21] [ALPM] upgraded libtirpc (1.0.2-2 -> 1.0.2-3)
[2018-02-06 19:21] [ALPM] upgraded libxau (1.0.8-2 -> 1.0.8-3)
[2018-02-06 19:21] [ALPM] upgraded libxfixes (5.0.3-1 -> 5.0.3-2)
[2018-02-06 19:21] [ALPM] upgraded libxdamage (1.1.4-2 -> 1.1.4-3)
[2018-02-06 19:21] [ALPM] upgraded ffmpeg (1:3.4.1-3 -> 1:3.4.1-4)
[2018-02-06 19:21] [ALPM] upgraded ffmpeg2.8 (2.8.13-4 -> 2.8.13-5)
[2018-02-06 19:21] [ALPM] upgraded libxrandr (1.5.1-1 -> 1.5.1-2)
[2018-02-06 19:21] [ALPM] upgraded xkeyboard-config (2.22-1 -> 2.23.1-2)
[2018-02-06 19:21] [ALPM] upgraded firefox (58.0.1-1 -> 58.0.1-2)
[2018-02-06 19:22] [ALPM] upgraded linux (4.14.15-1 -> 4.15.1-2)
[2018-02-06 19:22] [ALPM] upgraded man-db (2.7.6.1-3 -> 2.8.0-1)
[2018-02-06 19:22] [ALPM] upgraded man-pages (4.14-1 -> 4.15-1)
[2018-02-06 19:22] [ALPM] upgraded vlc (2.2.8-3 -> 2.2.8-4)
[2018-02-06 19:22] [ALPM] transaction completed

Im running kernel 4.15.1-2-ARCH . What kind of journal infor would be helpful?

Thanks

jasonwryan

Anarchist

From: .nz

Registered: 2009-05-09

Posts: 30,424

Website

Re: [SOLVED] Backlight keyboard stopped working properly after update

Please use code tags when pasting to the boards: https://wiki.archlinux.org/index.php/Co … s_and_code

Did you read the link I posted? Do some investigating yourself. Try downgrading the kernel, see if that restores the functionality. Look at the difference between what modules are loaded, etc.

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Arch + dwm   •   Mercurial repos  •   Surfraw

Registered Linux User #482438

Blåklinten

Member

From: Gothenburg

Registered: 2017-12-29

Posts: 9

Re: [SOLVED] Backlight keyboard stopped working properly after update

Yes, I've read the link before but obviously I still need to improve me posting skills, again sorry about that.

I have tried downgrading the kernel and this does restore the desired functionality, this was the reason for me to blame the upgrade in the first place. From your answer I understand that some module in the updated kernel makes my keyboard back light change its functionality.

To clarify; I have a fix for my problem in just holding back updates for the kernel. This however feels like a short term solution and the research I have done left me stuck on this page.

Is there some nice way to control the time before my keyboard back light goes out or is the best solution to manually load the older kernels module in to the new kernel?  It seems to me that this is controlled on a low "kernel level", so there are no "user level" application to control this behavior, like with e.g. sound or screen brightness level. Perhaps there are some documentation that can be recommended to read so that I can understand this better?

/B

Blåklinten

Member

From: Gothenburg

Registered: 2017-12-29

Posts: 9

Re: [SOLVED] Backlight keyboard stopped working properly after update

So, I've found what I think is a better solution.

I tried explicilty writing a reasonable value (like 60s) to the file  /sys/devices/platform/dell-laptop/leds/dell::kbd_backlight/stop_timeout and it works. To make this happen at boot I created a service to systemd by following the instruction on this link.

/B