Strange Backlight Behavior

albertalbert · 2013-09-20 05:02:58

Arch Linux 3.10.10-1 installed on a MacBook Air 2013 (6,1) with Intel 5000 graphics.

If I change the backlight brightness with xbacklight it works fine, however after closing the lid and opening it again the backlight is off, but the screen is on.
There isn't any way I could make it come back on unless I rebooted the machine.

Running

$ cat /sys/class/backlight/intel_backlight/brightness
2777

I can change the brightness with by changing the value in the file, but when I shut the lid of the computer and open it again the backlight is back to full brightness.
Checking the value in /sys/class/backlight/intel_backlight/brightness shows me the value is back to 2777.
If I try to change it to anything below 2280 the backlight turns off, but I can turn it back on by changing the value back to something above 2280. Changing the brightness to anything below 2777 but above 2280 doesn't have any effect.

Running

$ cat /sys/class/backlight/acpi_video0/brightness
15

I can change the brightness of the backlight by changing the value in /acpi_video0/brightness but when I shut the lid and open it again the backlight is off and I can't figure out how to get it back on.

I've been googling around for a number of days but every other similar problem seems to deal specifically with a certain power manager or the like. So I'm really not sure where to start.

How do I know what's managing what happens when I close the lid of my computer or what manages my power settings?

Last edited by albertalbert (2013-09-20 17:37:50)

brebs · 2013-09-20 05:32:46

albertalbert wrote:

when I close the lid of my computer

I believe that's usually an ACPI event, so you can edit an acpid script.

albertalbert · 2013-09-20 05:35:37

brebs wrote:

albertalbert wrote:
when I close the lid of my computer
I believe that's usually an ACPI event, so you can edit an acpid script.

Humm, I don't have acpid installed (running `pacman -Qs acpid` returns nothing, also just trying to run `acpid` returns "command not found"), would it still be an acpid event in that case?

madeye · 2013-09-20 10:10:16

Have you tried booting your machine with the kernel parameters for the backlight?

acpi_osi=Linux acpi_backlight=vendor

I use that on my laptop to get the backlight under control.

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

albertalbert · 2013-09-20 17:50:20

madeye wrote:

Have you tried booting your machine with the kernel parameters for the backlight?
acpi_osi=Linux acpi_backlight=vendor
I use that on my laptop to get the backlight under control.
https://wiki.archlinux.org/index.php/Backlight

I added `acpi_osi=Linux and acpi_backlight=vendor` to the line starting with "linux", I'm assuming those are the kernel parameters.

After doing that I can adjust the backlight with xbacklight, however after changing it, then shutting the lid of the computer and opening it again the backlight is off. I can turn it back on by (blindly) using xbacklight to set the value to something over 82. Even then it's only on/off and there's no dimming of the display with xbacklight.

What method do you use to control your backlight? Do you use xbacklight or change the values in the /sys/class/backlight/etc/brightness file? Could xbacklight be changing the wrong file or making the setting change in the wrong way?

madeye · 2013-09-20 20:04:12

I am in the lucky position that I can use the shortcut keys on my laptop to increase and decrease the backlight, so I never directly use a program to do it.

In the wiki page there are a couple of different variations on the kernel parameters. Maybe one of the others can help you?

Pse · 2013-09-21 03:57:46

On my Acer laptop (Intel HD4000) I had to remove the 'acpi_osi' and 'acpi_backlight' lines from the kernel command line and add the following file: '/etc/X11/xorg.conf.d/20-intel.conf' to make the backlight work as it should.

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

Last edited by Pse (2013-09-21 03:58:21)

albertalbert · 2013-09-30 20:41:34

Pse wrote:

On my Acer laptop (Intel HD4000) I had to remove the 'acpi_osi' and 'acpi_backlight' lines from the kernel command line and add the following file: '/etc/X11/xorg.conf.d/20-intel.conf' to make the backlight work as it should.
Section "Device"
	Identifier "Intel Graphics"
	Driver "intel"
	Option      "Backlight"  "intel_backlight"
EndSection

Interesting, and how do you control your backlight? Xbacklight?

Also, are you using a MacBook Air or something with Intel Integrated graphics?

Pse · 2013-09-30 22:02:35

Gnome controls the backlight in my current config. It binds to the backlight keys in my laptop. This is on an Acer Aspire V3-571 (Core i5-3210M, Intel HD4000).

Unfortunately I experience something similar to what you describe after unplugging an external monitor connected through HDMI. The display remains off until I hit one of the backlight keys.

Last edited by Pse (2013-09-30 22:03:02)

Arch Linux

#1 2013-09-20 05:02:58

Strange Backlight Behavior

#2 2013-09-20 05:32:46

Re: Strange Backlight Behavior

#3 2013-09-20 05:35:37

Re: Strange Backlight Behavior

#4 2013-09-20 10:10:16

Re: Strange Backlight Behavior

#5 2013-09-20 17:50:20

Re: Strange Backlight Behavior

#6 2013-09-20 20:04:12

Re: Strange Backlight Behavior

#7 2013-09-21 03:57:46

Re: Strange Backlight Behavior

#8 2013-09-30 20:41:34

Re: Strange Backlight Behavior

#9 2013-09-30 22:02:35

Re: Strange Backlight Behavior

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