Arch Linux

sentenza

Member

Registered: 2011-12-28

Posts: 12

screen-backlight settings on a Thinkpad T550

Hello,

i got a new T550 and put in the ssd of my old R500 running Archlinux.
When I press one of the hardware buttons for increasing or decreasing the screen brightness, Gnome shows the actual overlay on which the bar gets moved, by pressing the buttons. But the actual screen brightness does not change.

This could be a problem:

# ls /sys/class/backlight/
acpi_video0  intel_backlight

I was reading the Backlight wiki-site and I adjustet the Kernel-parameter "video.use_native_backlight" once to "1" and once to "0", didn't help. If it is set to "0", the Gnome overlay even does not appear.

I would very much appreciate some help! Thanks.

Head_on_a_Stick

Member

From: The Wirral

Registered: 2014-02-20

Posts: 8,999

Website

Re: screen-backlight settings on a Thinkpad T550

You may need to try some others (in combinations and in isolation):

acpi_backlight=vendor
acpi_osi=Linux
acpi_osi="!Windows 2012"

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Jin, Jîyan, Azadî

sentenza

Member

Registered: 2011-12-28

Posts: 12

Re: screen-backlight settings on a Thinkpad T550

I'm afraid it doesn't work!

Head_on_a_Stick

Member

From: The Wirral

Registered: 2014-02-20

Posts: 8,999

Website

Re: screen-backlight settings on a Thinkpad T550

it doesn't work

*What* doesn't work?

Describe exactly what you have tried.

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Jin, Jîyan, Azadî

sentenza

Member

Registered: 2011-12-28

Posts: 12

Re: screen-backlight settings on a Thinkpad T550

I tried every possible combination of the parameters acpi_backlight and acpi_osi as you suggested

Last edited by sentenza (2015-05-07 13:20:31)

Head_on_a_Stick

Member

From: The Wirral

Registered: 2014-02-20

Posts: 8,999

Website

Re: screen-backlight settings on a Thinkpad T550

Oh dear, sorry.

I don't know what else to suggest.

EDIT: Does the `xbacklight` command work?

If so, you could bind the commands to a key.

Last edited by Head_on_a_Stick (2015-05-07 13:20:03)

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Jin, Jîyan, Azadî

sentenza

Member

Registered: 2011-12-28

Posts: 12

Re: screen-backlight settings on a Thinkpad T550

Does the `xbacklight` command work?

No it has no effect but changing the brightness value, but not the actual brightness.

Head_on_a_Stick

Member

From: The Wirral

Registered: 2014-02-20

Posts: 8,999

Website

Re: screen-backlight settings on a Thinkpad T550

Try changing the values in both the intel_backlight/brightness & acpi_video0/brightness files -- sometimes one has an effect but not the other.

If this is the case, you can write a script to alter the value in the "active" file.

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Jin, Jîyan, Azadî

sentenza

Member

Registered: 2011-12-28

Posts: 12

Re: screen-backlight settings on a Thinkpad T550

echo 500 | sudo tee /sys/class/backlight/intel_backlight/brightness

works!

Now how do I tell the gnome brightness-control to change that value?

Mercader1902

Member

Registered: 2014-09-01

Posts: 55

Re: screen-backlight settings on a Thinkpad T550

https://wiki.archlinux.org/index.php/In … adjustable

@Head_on_a_Stick didn't metion the last two. Did you tried it?

sentenza

Member

Registered: 2011-12-28

Posts: 12

Re: screen-backlight settings on a Thinkpad T550

https://wiki.archlinux.org/index.php/In … adjustable

@Head_on_a_Stick didn't metion the last two. Did you tried it?

Does not work, sorry...

Head_on_a_Stick

Member

From: The Wirral

Registered: 2014-02-20

Posts: 8,999

Website

Re: screen-backlight settings on a Thinkpad T550

echo 500 | sudo tee /sys/class/backlight/intel_backlight/brightness

sudo tee /sys/class/backlight/intel_backlight/brightness <<< 500

Now how do I tell the gnome brightness-control to change that value?

I don't think you can -- that's what all those kernel parameters are supposed to do

You will have to bind some keys to a script that changes the value of the intel_backlight/brightness file.

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Jin, Jîyan, Azadî

sentenza

Member

Registered: 2011-12-28

Posts: 12

Re: screen-backlight settings on a Thinkpad T550

So is that a kernel issue? Can I somewhere file a bug for this?