[SOLVED] Backlight getting on my nerves

maxo · 2013-12-12 10:12:52

So I bought a laptop a little over a year ago and didn't expect everything to work out of the box. Especially since it has one of the fancy Nvidia Optimus labels on it.

Anyway i have literally tried everything from installing nvidia driver(which doesn't allow me to start x) to placing boot parameters to trying less minimal distros like Linux Mint and nothing has worked.

Hardware:
lspci gives

lspci 
00:02.0 VGA compatible controller: Intel Corporation 3rd Gen Core processor Graphics Controller (rev 09)

01:00.0 3D controller: NVIDIA Corporation GF117M [GeForce 610M/710M / GT 620M/625M/630M/720M] (rev a1)

As you can see the Nvidia isn't listed as a VGA compatble device even if the driver is installed.

Also xrandr only lists one provider

xrandr --listproviders
Providers: number : 1
Provider 0: id: 0x46 cap: 0xb, Source Output, Sink Output, Sink Offload crtcs: 3 outputs: 4 associated providers: 0 name:Intel

Basically i have tracked the problem down to the kernel module i915 trying to control backlight via /sys/class/backlight/acpi_video0/ but the brightness controlling file is in /sys/class/backlight/intel_backlight.

I tried to tell acpid via handlers to use the other file but X seems to automatically set a kernel for the hotkeys which i can't seem to overwrite. Does anybody have a clue on how i could tell X to change the correct file?

Thank you for your help!

Last edited by maxo (2013-12-13 10:48:15)

socials · 2013-12-12 12:52:55

Did you read the Wiki page for Backlight? I think you didn't.

Try setting

acpi_backlight=vendor

into your kernel parameters.

maxo · 2013-12-13 10:10:26

Cheers for pointing out the obvious. I have tried adding the boot parameters described in the wiki. Unfortunately no combination of them yields a positive result. The only change I get by adding

 acpi_backlight = acer

and all facets there of is the fact that I no longer have the FN + UP and DOWN Arrows giving any acpi_listen event. I reckon the wiring of hotbottons is different somehow.

I can manually change backlight by editing the file

 /sys/class/backlight/intel_backlight/brightness

. What I am basically asking is not necessarily for a solution but a new point of attack on how to change the behvaviour of the backlight i915 driver to tell the kernel and all following applictions like xbacklight to use the right directory. Unfortunately, similiarly to the intel_p_state driver there is not much info on how to control it presistently.

Thanks for the reply anyway! Does anybody else have any ideas?

HalosGhost · 2013-12-13 10:28:10

Just throwing this out there, but it would appear that you are having troubles with your backlight, not a blacklight.

And please, for the love of all that is sacred, use code tags for terminal output.

All the best,

-HG

Last edited by HalosGhost (2013-12-13 10:28:44)

maxo · 2013-12-13 10:53:35

@ HalosGhost Thanks. My brain sometimes gets ahed of my fingers.

Basically, I for some reason decided to look at the driver again. I looking at my Xorg config, it was pretty empty as Xorg autoconfigures pretty well nowadays.

Anyway in the manual pages for intel (man intel), there is this bad boy.

 Option "Backlight" "string"
              Override the probed backlight control interface. Sometimes the automatically selected backlight interface may  not  corre‐
              spond to the correct, or simply most useful, interface available on the system. This allows you to override that choice by
              specifying the entry under /sys/class/backlight to use.

              Default: Automatic selection.

It seems the automatic selection always went for acpi_video0 instead of intel_backlight. As such if you change your

 /etc/X11/xorg.conf.d/20-intel.conf

such that it looks like this

Section "Device"
  Identifier    "Intel Graphics"
  Driver        "intel"
  Option        "AccelMethod"   "sna"
  Option        "Backlight"     "intel_backlight"
  
EndSection

It works perfectly fine. Hope this helps a few ppl and thanks for the help!

Last edited by maxo (2013-12-13 10:56:21)

artoo · 2013-12-14 14:40:19

Same here, maxo, but with nvidia gt 720m

What laptop model/manufacturer is it?

https://bbs.archlinux.org/viewtopic.php?id=173281

To clarify, your issue resolved by using intel_backlight?

Arch Linux

#1 2013-12-12 10:12:52

[SOLVED] Backlight getting on my nerves

#2 2013-12-12 12:52:55

Re: [SOLVED] Backlight getting on my nerves

#3 2013-12-13 10:10:26

Re: [SOLVED] Backlight getting on my nerves

#4 2013-12-13 10:28:10

Re: [SOLVED] Backlight getting on my nerves

#5 2013-12-13 10:53:35

Re: [SOLVED] Backlight getting on my nerves

#6 2013-12-14 14:40:19

Re: [SOLVED] Backlight getting on my nerves

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