Unable to control backlight Thinkpad P50

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Unable to control backlight Thinkpad P50

Postby conn » 2017-12-18 19:38

I'm running into a similar issue to this post: http://forums.debian.net/viewtopic.php?f=7&t=132688.

I'm on the same laptop and on the latest version of stretch. My desktop environment is mate. I'm using the nouveau driver for my Nvidia card and not the proprietary driver.
Using the proprietary driver consistently borked my docking station setup and caused the main screen to flicker. This is not an issue with nouveau.

/sys/class/backlight is empty, xbacklight returns "No outputs have backlight property". I can't figure out any way to alter the screen brightness.

inxi -G
Code: Select all
Graphics:  Card: NVIDIA GM107GLM [Quadro M1000M]
           Display Server: X.Org 1.19.2 drivers: modesetting,nouveau (unloaded: fbdev,vesa)
           Resolution: 1920x1080@60.02hz, 2560x1440@59.95hz
           GLX Renderer: Gallium 0.4 on NV117 GLX Version: 3.0 Mesa 13.0.6


Any ideas how to get my backlight controls working? If possible it would help me if the solution doesn't require either a reinstall or installing the proprietary drivers (which mess with my docking setup)

Let me know if any more information is needed.
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Re: Unable to control backlight Thinkpad P50

Postby Capitain_Jack » 2017-12-18 19:43

conn wrote:Any ideas how to get my backlight controls working? If possible it would help me if the solution doesn't require either a reinstall or installing the proprietary drivers (which mess with my docking setup)
Let me know if any more information is needed.

This post looks like your problem, down the way at the end there is a file you must edit at driver configuration to enable brightness control.
http://blog.pearce.org.nz/2012/08/enabl ... enovo.html
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Re: Unable to control backlight Thinkpad P50

Postby conn » 2017-12-18 19:56

Capitain_Jack wrote:
conn wrote:Any ideas how to get my backlight controls working? If possible it would help me if the solution doesn't require either a reinstall or installing the proprietary drivers (which mess with my docking setup)
Let me know if any more information is needed.

This post looks like your problem, down the way at the end there is a file you must edit at driver configuration to enable brightness control.
http://blog.pearce.org.nz/2012/08/enabl ... enovo.html


Thanks for the response. However, this post is not relevant to my situation because that blog post is for a proprietary Nvidia driver issue. I tried adding the snippet to my xorg and it just crashes lightdm.
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Re: Unable to control backlight Thinkpad P50

Postby Head_on_a_Stick » 2017-12-19 06:39

Try the kernel parameters listed on this ArchWiki page:

https://wiki.archlinux.org/index.php/Ba ... ne_options
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Re: Unable to control backlight Thinkpad P50

Postby conn » 2017-12-19 13:32

Head_on_a_Stick wrote:Try the kernel parameters listed on this ArchWiki page:

https://wiki.archlinux.org/index.php/Ba ... ne_options


Just tried each acpi_backlight kernel parameter option and none of them did the trick. Each one had xbacklight still saying "No outputs have backlight property" and nothing listed in /sys/class/backlight/.
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Re: Unable to control backlight Thinkpad P50

Postby bw123 » 2017-12-19 14:12

Sounds frustrating. I'll never get with nvidia, I know they are good at a lot of things though

What about some of the nouveau params? or something like this?

Code: Select all
# modinfo -p video
brightness_switch_enabled: (bool)
allow_duplicates: (bool)
disable_backlight_sysfs_if: (int)
report_key_events:0: none, 1: output changes, 2: brightness changes, 3: all (int)
device_id_scheme: (bool)
only_lcd: (bool)


have no idea what they do, so just guessing.
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Re: Unable to control backlight Thinkpad P50

Postby conn » 2017-12-19 14:27

Code: Select all
# cat /sys/module/video/parameters/brightness_switch_enabled
Y


It looks like the video module has the brightness switch enabled? I'm not sure too sure how this works.
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