Backlight management with xbacklight /sys/class/backlight/asus_laptop

66 · 2013-09-02 20:10:07

I am able to change backlight with Fn-F4/F5 shortcuts.
As root I can change backlight with echo 8 > /sys/class/backlight/asus_laptop/brightness

But 'xbacklight -get' gives me: "No outputs have backlight property"

Additional info:
Laptop ASMobile Z96jm
3.10.10-1-ARCH
lspci | grep ATI:
01:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] RV530/M56-P [Mobility Radeon X1600]

I generated new grub config with options:
GRUB_CMDLINE_LINUX_DEFAULT="quiet acpi_osi=Linux acpi_backlight=vendor splash"
with no effect.

I changed /sys/class/backlight/asus_laptop/ owner from root:root to myuser:users with no effect.

I create new file /etc/X11/xorg.conf.d/10-backlight.conf

Section "Device"
Identifier "Card0"
Option "RegistryDwords" "EnableBrightnessControl=1"
Option "Backlight" "asus_laptop"
Driver "radeon"
BusID "PCI:1:0:0"
EndSection

But still with no success.

If my x86-video-ati driver does not support backlight option, then how can I change it with function keys
and by echoing backlight/asus_laptop/brightness? (I should read more about ACPI and non-ACPI)

Maybe some user had similar problem and can help here?

My main goal is to automatically control backlight during the day like redshift controls color shift.
calise works, but it needs access to webcam.

I appreciate any help.

Related links:
Missing backlight property in xrandr -> https://bugzilla.redhat.com/show_bug.cgi?id=645841
Generating xorg.conf -> http://ubuntuforums.org/showthread.php?t=1994526
Solution for Thinkpad -> http://www.thinkwiki.org/wiki/LCD_Brightness
xrandr works, but not xbacklight -> http://www.archivum.info/ubuntu-bugs@li … light.html
Pseudo backlight script [deprecated version of bltool below]-> http://forums.bodhilinux.com/index.php? … entry56911

bltool -> https://code.google.com/p/bltool/ This tool should be added to arch wiki page about backlight
Available in AUR https://aur.archlinux.org/packages/bltool-svn/
Backlight patch for x86-video-ati ->
1. http://lists.x.org/archives/xorg-driver … 24786.html
2. http://lists.x.org/archives/xorg-driver … 24787.html

Last edited by 66 (2013-09-03 21:23:09)

thegala · 2013-09-03 08:29:58

Please read this on wiki

https://wiki.archlinux.org/index.php/Backlight

and maybe this help

https://bbs.archlinux.org/viewtopic.php?id=134972
https://bbs.archlinux.org/viewtopic.php?id=102060

66 · 2013-09-03 10:02:55

thegala wrote:

Please read this on wiki
...

Are you kidding me? I read them all.
I can provide 50 links related to this topic.

Can you point me to a solution in links provided by you?
Or you only wanted to show that you are able to use Google search engine?

Last edited by 66 (2013-09-03 10:03:43)

Zamajalo · 2013-09-03 13:28:49

66 wrote:

My main goal is to automatically control backlight during the day like redshift controls color shift.
xcalib works, but it needs access to webcam.
I appreciate any help.

If any of existing solutions don't work, try to make your own.

Here is an idea how: write a script which changes backlight level depending of current time, and set a cron job which will call it every hour or so (I don't know your preferences about screen backlight). You can change backlight level neither with echoing value in /sys/class/backlight or by using xrandr, whatever works for you.

I've done something similar for my laptop (using xrandr) since default backlight controls don't work at all.

66 · 2013-09-03 16:13:59

Zamajalo wrote:

If any of existing solutions don't work, try to make your own.
...
I've done something similar for my laptop (using xrandr) since default backlight controls don't work at all.

xrandr is a software solution, it still drains your battery,
this is why I'm asking specifically about xbacklight - it is a hardware driven solution.

I am aware that I can create cron job with simple script.
I want to know why xbacklight do not work, if echoing works and Fn-F4/F5 works, and calise works.

Should I change sth in my grub? In my xorg.conf? Recompile kernel with some specific settings?

I asking this, because maybe somebody had similar issue and can share experiences,
before I lookup xbacklight's sourcecode or fork calise, wasting whole weekend or a week,
if maybe i can fix this with some simple flag somewhere.

That's the point.

Last edited by 66 (2013-09-03 20:58:39)

Raynman · 2013-09-03 19:46:30

xbacklight only works with the RandR backlight property. The radeon driver does not support this (and apparently the devs are not going to change that). The Backlight property in xorg.conf is an intel-specific setting. At least part of the ArchWiki page is a mess, I was going to work on that when I researched this stuff a few months ago, but I forgot.

The sysfs interface is probably your best (or only) option. I can think of at least two solutions to use this as a regular user:

Configure sudo to allow your user to use
```
tee /sys/class/backlight/asus_laptop/brightness
```
without a password, then use
```
echo 8 | sudo tee /sys/class/backlight/asus_laptop/brightness
```
(this is what I did before systemd/tmpfiles.d)
Create a file in /etc/tmpfiled.d/ with something like
```
f /sys/class/backlight/asus_laptop/brightness 0664 root users - -
```
to make it writable for the users group (this is now my preferred method)

Last edited by Raynman (2013-09-03 19:47:22)

66 · 2013-09-03 20:52:54

Raynman wrote:

xbacklight only works with the RandR backlight property. The radeon driver does not support ...

And this is an excellent answer. Thank you sir!
Thank you very much.

Also I will be experimenting with this patch:
http://lists.x.org/archives/xorg-driver … 24786.html
http://lists.x.org/archives/xorg-driver … 24787.html

But maybe this is an overkill if I can gain the same with echoing to brightness file.

Arch Linux

#1 2013-09-02 20:10:07

Backlight management with xbacklight /sys/class/backlight/asus_laptop

#2 2013-09-03 08:29:58

Re: Backlight management with xbacklight /sys/class/backlight/asus_laptop

#3 2013-09-03 10:02:55

Re: Backlight management with xbacklight /sys/class/backlight/asus_laptop

#4 2013-09-03 13:28:49

Re: Backlight management with xbacklight /sys/class/backlight/asus_laptop

#5 2013-09-03 16:13:59

Re: Backlight management with xbacklight /sys/class/backlight/asus_laptop

#6 2013-09-03 19:46:30

Re: Backlight management with xbacklight /sys/class/backlight/asus_laptop

#7 2013-09-03 20:52:54

Re: Backlight management with xbacklight /sys/class/backlight/asus_laptop

Board footer