No /sys/class/backlight/intel_backlight

GordonGR · 2014-12-08 10:49:51

Hello everyone.

I am trying to use xbacklight to change my monitor's backlight, but I see that:

nikos@Russell:~$ LANG=C ls -l /sys/class/backlight/
total 0

I have my Intel onboard graphics card perfectly set, since everything works fine:

nikos@Russell:~$ lspci -k
…
00:02.0 VGA compatible controller: Intel Corporation 4 Series Chipset Integrated Graphics Controller (rev 03)
	Subsystem: ASRock Incorporation Device 2e32
	Kernel driver in use: i915
	Kernel modules: i915
…

[root@Russell backlight]# less /etc/X11/xorg.conf.d/20-intel.conf
Section "Device"
        Identifier  "card0"
        Driver      "intel"
        Option      "AccelMethod"  "uxa"
        Option      "Backlight"  "intel_backlight"
        BusID       "PCI:0:2:0"
EndSection

Of course, aur/xcalib does the trick, but I'd rather not use an external program.

Any ideas?

Head_on_a_Stick · 2014-12-08 11:16:38

With kernels 3.16 and up, you may need to add this kernel parameter:

video.use_native_backlight=0

YMMV, try "=1" if that doesn't work.

The 20-intel.conf was needed to correct a bug in the driver that no longer exists.

GordonGR · 2014-12-09 12:44:55

I fear not. Still no backlight; no files to give backlight, actually.

Head_on_a_Stick · 2014-12-09 14:20:44

Have you tried the LTS kernel?

I have an Intel card & the backlight worked fine until kernel 3.16

granik · 2014-12-11 08:28:41

I have the same problem, but i have discovered this one after removing external ATI video adapter and swithing on Intel card. The dir /sys/class/backlight is really empty... I'll try LTS kernel, I hope this will help me...

granik · 2014-12-15 07:34:34

I've tried the LTS kernel but with no results.

[granik@seniorengineer ~]$ ls /sys/class/backlight
acpi_video0

No the intel_backlight dir is here.
Current kernel parameters:

[granik@seniorengineer ~]$ cat /proc/cmdline
BOOT_IMAGE=/boot/vmlinuz-linux-lts root=UUID=d944eae2-59b4-43c2-bb57-7e9241592a17 rw quiet

Parameters

acpi_osi=Linux acpi_backlight=vendor

don't work.
I don't know what to do. Any suggestions?

granik · 2014-12-15 07:44:53

I've forgotten

[granik@seniorengineer ~]$ lspci -k
00:02.0 VGA compatible controller: Intel Corporation 2nd Generation Core Processor Family Integrated Graphics Controller (rev 09)
	Subsystem: ASUSTeK Computer Inc. Device 844d
	Kernel driver in use: i915
	Kernel modules: i915

 [granik@seniorengineer ~]$ cat /etc/X11/xorg.conf.d/10-intel.conf 
Section "Device"
	Identifier "Intel Graphics"
	Driver "intel"
	Option "AccelMethod" "sna"
	Option "Backlight"  "intel_backlight"
	BusID "PCI:0:2:0"
EndSection

toz · 2014-12-15 11:33:40

granik wrote:

I've tried the LTS kernel but with no results.
[granik@seniorengineer ~]$ ls /sys/class/backlight
acpi_video0
No the intel_backlight dir is here.

But you do have a backlight interface, acpi_video0. Does using this interface give you backlight control? You can manually test it by echoing values between 0 and the contents of acpi_video0/max_brightness into the acpi_video0/brightness file. More info here.

Otherwise, try with the "video.use_native_backlight=1" kernel parameter to see if it will expose the intel_backlight interface that you are looking for.

Head_on_a_Stick · 2014-12-15 14:09:09

toz wrote:

Otherwise, try with the "video.use_native_backlight=1" kernel parameter to see if it will expose the intel_backlight interface that you are looking for.

^This.

With the 3.14 series (LTS) kernels, this parameter was not needed with my Intel card.

granik · 2014-12-16 08:29:21

"video.use_native_backlight=1" kernel parameter doesn't work
the acpi_video0 backlight interface is for ATI video adapter I've disconnected before. Really, brightness doesn't changed under echoing values into the acpi_video0/brightness file.
I've tried acpi_osi=Linux acpi_backlight=vendor with LTS kernel and I've get

[granik@seniorengineer ~]$ ls /sys/class/backlight/
eeepc-wmi

but

[granik@seniorengineer ~]$ cat /sys/class/backlight/eeepc-wmi/actual_brightness 
0

and this is very strange...
I think my problem is relating to disconnecting of ATI video adapter. I've removed radeon driver, but it seems not enough

GordonGR · 2014-12-16 12:35:08

I hadn't had the time to try the LTS kernel, but, as granik says, "video.use_native_backlight=1" or "0" doesn't make any difference. However, I too was using an AMD card until recenty, with the Catalyst driver, so it must be related to that. Perhaps some leftover which isn't covered in the wiki? I don't know.

queenmedley · 2015-01-28 17:20:58

I have same system which use intel gpu(HD4600) on board, and same problem.
I can see only acpi_video in /sys/class/backlight, any kernel parameteres are useless.
And when try xbacklight command, erroer occurs.

$xbacklight
No outputs have backlight property

I tried backlight optiton in 20-intel.conf, becase there is only that in backlight folder.
yes.. I just tried.. and not work...lol.

Section "Device"
    Identifier "Intel Graphics"
    Driver "intel"
    Option "AccelMethod" "sna"
    Option "Backlight" "acpi_video0"
    BusID "PCI:0:2:0"
EndSection

Last edited by queenmedley (2015-01-28 17:28:50)

Arch Linux

#1 2014-12-08 10:49:51

No /sys/class/backlight/intel_backlight

#2 2014-12-08 11:16:38

Re: No /sys/class/backlight/intel_backlight

#3 2014-12-09 12:44:55

Re: No /sys/class/backlight/intel_backlight

#4 2014-12-09 14:20:44

Re: No /sys/class/backlight/intel_backlight

#5 2014-12-11 08:28:41

Re: No /sys/class/backlight/intel_backlight

#6 2014-12-15 07:34:34

Re: No /sys/class/backlight/intel_backlight

#7 2014-12-15 07:44:53

Re: No /sys/class/backlight/intel_backlight

#8 2014-12-15 11:33:40

Re: No /sys/class/backlight/intel_backlight

#9 2014-12-15 14:09:09

Re: No /sys/class/backlight/intel_backlight

#10 2014-12-16 08:29:21

Re: No /sys/class/backlight/intel_backlight

#11 2014-12-16 12:35:08

Re: No /sys/class/backlight/intel_backlight

#12 2015-01-28 17:20:58

Re: No /sys/class/backlight/intel_backlight

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