How to change backlight brightness?

jones · 2017-07-09 21:30:24

With the goal to have redshift change the backlight of my monitor (Dell U2414H), I went googling and wiki-ing. First, AL has to be able to change my monitor's backlight.

xbacklight -set 50

yielded the "No outputs have backlight property" message. Based on this, I ran both

$ cat /sys/class/backlight/acpi_video0/max_brightness

and

$ tee /sys/class/backlight/acpi_video0/brightness <<< 5

Nothing changed.

Some info:

$ ls /sys/class/backlight
acpi_video0

The wiki says

In this case, the backlight is managed by an ATI graphics card. In the case of an Intel card it is called intel_backlight.

This is false, in my case. I have some 5 year old Intel processor whose IGPU I use.

$ lscpu | grep Intel
Anbieterkennung:       GenuineIntel
Modellname:            Intel(R) Core(TM) i5-2320 CPU @ 3.00GHz

Am I missing something? A driver, package or config file?

Last edited by jones (2017-12-29 10:53:15)

Morn · 2017-07-09 22:09:43

I think you are looking for https://github.com/rockowitz/ddcutil

Personally, I no longer use redshift, instead I've made a little GUI for ddcutil (https://github.com/mdoege/PyDDC) and switch display brightness and contrast manually. Works better for me than automatic adjustments. Redshift does not know if it is bright and sunny or overcast outside my window.

adesh · 2017-07-10 13:01:00

First this: https://wiki.archlinux.org/index.php/Re … brightness

For brightness to work (regardless of redshift), you might need to use xf86-video-intel package. https://wiki.archlinux.org/index.php/Ba … xbacklight

jones · 2017-08-21 20:19:16

Would anyone happen to have advice?

jones · 2017-12-29 11:24:58

Although this thread is a couple of months ago, my problem still exists and I argue this isn't a necrobump.
To catch anyone up about my relevant system specs:

$ lscpu | grep Intel
Anbieterkennung:               GenuineIntel
Modellname:                    Intel(R) Core(TM) i5-2320 CPU @ 3.00GHz

The i5-2320 is a pretty old CPU with the iGPU/onboard GPU ("HD2000"), so I am quite confident that drivers should exist, i.e. it should be usable. (Right?)

So. I did some further digging and there are some related discussions, sorted by most interesting first:

Same problem, no solution: https://bbs.archlinux.org/viewtopic.php?id=190817
capoeira actually has the exact same problem, no solution: https://bbs.archlinux.org/viewtopic.php?id=216505
Some of you settled on a workaround (sort of) via acpi_backlight=vendor in https://bbs.archlinux.org/viewtopic.php?id=157263
Kind of interesting, not really helpful: https://unix.stackexchange.com/question … cpi-video0

So far I only tried setting the backlight brightness via the command line. I do not have any Fn-keys on my PC keyboard. I used "xbacklight -set 50" and "echo 5 > /sys/class/backlight/acpi_video0/brightness" and so forth. Both did not work.
I haven't run through all the possible kernel parameters (from capoeira's thread):

acpi_backlight=video
acpi_backlight=vendor
acpi_backlight=native
acpi_backlight=none
acpi_backlight=legacy
video.use_native_backlight=0
acpi_osi=Linux

but so far I can say, none of these work:

acpi_osi=Linux
acpi_backlight=native
acpi_backlight=vendor
video.use_native_backlight=1

With these,

ls /sys/class/backlight/

now yields an empty output instead of producing "acpi_video0" as before. I don't get it.

Help!

Last edited by jones (2017-12-29 11:28:36)

jones · 2017-12-29 11:49:55

There is a post in https://bbs.archlinux.org/viewtopic.php?id=207069 which states:

I have a suspicion that brightness control only works for laptop lcds, whereas I am using a Dell U2711 beastly CCFL 27" monitor connected to a full tower via DP!

Head_on_a_stick confirms this.

But there are threads/posts on the web about this which say something different... weird.
https://www.google.com/search?q=linux+b … al+monitor

So, basically the posts above all are relevant for changing brightness on a laptop.

Last edited by jones (2017-12-29 12:01:35)

Trilby · 2017-12-29 12:05:53

Stop bumping your own thread. You can edit your post to add more information if no one else has posted since you last did.

Also, what in the world is this:

jones wrote:

Would anyone happen to have advice?

Aside from being an empty bump which is against our standards, you posted that directly after two people tried to give you advice! Are they not supposed to interpret that as a slap in the face? Are other would be helpers not supposed to be disuaded? I am.

jones · 2017-12-29 13:00:54

Trilby wrote:

Stop bumping your own thread. You can edit your post to add more information if no one else has posted since you last did.
Also, what in the world is this:
jones wrote:
Would anyone happen to have advice?
Aside from being an empty bump which is against our standards, you posted that directly after two people tried to give you advice! Are they not supposed to interpret that as a slap in the face? Are other would be helpers not supposed to be disuaded? I am.

I'm sorry for these bumps. You are right. So this is just a reply for you. I am going to edit further info into my previous post.

I am convinced adesh's answer qualifies for that typical low effort-attempt at "helping". He listed wiki sites I quoted code and advice snippets from. I mean, come on.

About Morn's post, you are spot-on. I neglected that bit of information as I at first thought it was irrelevant because all the other posts on the net talked of different things. Sorry. But I now learned a great deal more and thus am in fact using DDC tools (not exactly the oen he posted, but still). So that will also go into an edit of my previous posts.

Trilby · 2017-12-29 13:39:06

jones wrote:

I am convinced adesh's answer qualifies for that typical low effort-attempt at "helping".

Ah, thanks for clarifying ... that this wasn't an exception but instead was illustrative of your general character: you're ego is far to big for you to even accept help.

On the present topic, you are incorrect. Your commands are distinctly different from those in the wiki page, and yours undoubtedly gave you a permission error you are not sharing. Beyond that you're on your own. If you think you are smarter than everyone and want to ridicule those who offer help, don't expect anyone else to step up to try.

EDIT: And do not email me further, you will not get a reply.

Last edited by Trilby (2017-12-29 20:28:24)

Arch Linux

#1 2017-07-09 21:30:24

How to change backlight brightness?

#2 2017-07-09 22:09:43

Re: How to change backlight brightness?

#3 2017-07-10 13:01:00

Re: How to change backlight brightness?

#4 2017-08-21 20:19:16

Re: How to change backlight brightness?

#5 2017-12-29 11:24:58

Re: How to change backlight brightness?

#6 2017-12-29 11:49:55

Re: How to change backlight brightness?

#7 2017-12-29 12:05:53

Re: How to change backlight brightness?

#8 2017-12-29 13:00:54

Re: How to change backlight brightness?

#9 2017-12-29 13:39:06

Re: How to change backlight brightness?

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