[Solved] Backlight not working in kernel 3.16

dodys · 2014-09-16 01:19:28

Hi everyone,

I've a Acer Aspire 5755G and in order to make the brightness keys to work, in previous kernel, I had to add the following to my kernel parameters:

acpi_osi=Linux acpi_backlight=vendor

But since the update to kernel 3.16, the keys are not working anymore.

I tried the suggestion in the Backlight wiki page and in also at this ticket https://bbs.archlinux.org/viewtopic.php?pid=1450688, to add the following kernel parameter:

video.use_native_backlight=0

But it didn't work.

If I do a ls /sys/class/backlight/, it returns:

intel_backlight

What am I missing and how can I check it?

Thanks in advance!

Last edited by dodys (2014-09-17 03:20:06)

Head_on_a_Stick · 2014-09-16 19:40:20

From the backlight wiki page:

video.use_native_backlight=1

https://wiki.archlinux.org/index.php/Ba … ne_options

Also, there is a config option that can be used for Intel cards in /etc/X11/xorg.conf.d/20-intel.conf:

Section "Device"
        Identifier "card0"
        Driver "Intel"
        Option "Backlight" "intel_backlight"
        BusID "PCI:0:2:0"
EndSection

This used to be in the wiki...

Last edited by Head_on_a_Stick (2014-09-16 19:42:15)

AnAkkk · 2014-09-16 19:43:19

There's an old bug report here about 5755G, but I guess you could use it as it's the same issue:
https://bugzilla.kernel.org/show_bug.cgi?id=42777

AnAkkk · 2014-09-16 19:44:10

Head_on_a_Stick wrote:

From the backlight wiki page:
Also, there is a config option that can be used for Intel cards in /etc/X11/xorg.conf.d/20-intel.conf:
Section "Device"
        Identifier "card0"
        Driver "Intel"
        Option "Backlight" "intel_backlight"
        BusID "PCI:0:2:0"
EndSection
This used to be in the wiki...

This was only needed due to a bug in xf86-video-intel, which was fixed some time ago.

matoxxx · 2014-09-16 21:18:58

I dont know if this is related but on my HP 550

00:02.0 VGA compatible controller: Intel Corporation Mobile GME965/GLE960 Integrated Graphics Controller (rev 0c)

I seemed to have lost Fn key functionality for backlight control.

Linux arch 3.16.2-1-ARCH #1 SMP PREEMPT Sat Sep 6 13:12:51 CEST 2014 x86_64 GNU/Linux

-- just to realize after suspend the functionality was back on. The problem is, after a fresh boot, the keycode is not properly registered by the kernel. Dunno why. Maybe a bug ?

Any advice how to approach this problem?

dodys · 2014-09-17 03:10:15

Head_on_a_Stick wrote:

From the backlight wiki page:
video.use_native_backlight=1
https://wiki.archlinux.org/index.php/Ba … ne_options

I've tried to use that parameter but setting it to 0 or 1 didn't make a difference to me.

So I managed to make some tests with the parameters and finally discovered a way to make it work!

Three years ago, when I bought this notebook, I had two use two parameters in order to make the brightness keys work, they were:

 acpi_osi=Linux acpi_backlight=vendor

So when I saw the backlight wiki page comment about the:

video.use_native_backlight=1

what I did was to include such parameter to the other existing two parameters. And it didn't work as I said.

Therefore I did the following tests and got the following results:

Test 1: acpi_osi=Linux acpi_backlight=vendor video.use_native_backlight=1                       Result: Doesn't work
Test 2: acpi_osi=Linux acpi_backlight=vendor video.use_native_backlight=0                       Result: Doesn't work
Test 3: video.use_native_backlight=1                                                            Result: Doesn't work
Test 4: video.use_native_backlight=0                                                            Result: Doesn't work
Test 5: acpi_backlight=vendor video.use_native_backlight=1                                      Result: Doesn't work
Test 6: acpi_backlight=vendor video.use_native_backlight=0                                      Result: Doesn't work
Test 7: acpi_osi=Linux video.use_native_backlight=1                                             Result: Works
Test 8: acpi_osi=Linux video.use_native_backlight=0                                             Result: Works
Test 9: acpi_osi=Linux                                                                          Result: Works
Test 10: acpi_backlight=vendor                                                                  Result: Doesn't work
Test 11: acpi_osi=Linux acpi_backlight=vendor                                                   Result: Doesn't work

I also saw that when I did Tests 7, 8 and 9, ls /sys/class/backlight/ would return me

 acpi_video0  intel_backlight

I also checked in Kernel 3.15 that the brightness keys works on both Test 9 and Test 11 (I didn't tried the other tests), the only difference is when I do ls /sys/class/backlight/:
Test 9 returns:

 acpi_video0  intel_backlight

Test 11 returns:

 intel_backlight

So, for now I only use the acpi_osi=Linux. I will search more to understand what changed in ACPI for Kernel 3.16 but if anyone understands what changed and why acpi_osi=Linux acpi_backlight=vendor cannot be together anymore in my case, please feel free to explain

Thanks for all the help!

Last edited by dodys (2014-09-17 12:29:06)

Head_on_a_Stick · 2014-09-17 06:45:08

@dodys -- I think it must be motherboard-dependent: I'm using an Intel HD4600, never needed any parameters until 3.16. Now I use just the parameter listed in my post.
Strange...
@AnAkkk -- thanks for the info: I should have trusted the wiki

Markof · 2014-09-22 09:47:02

Hi all,

Sorry to barge in with newbie questions, but as a fairly recent user of Linux, I am not confident enough to change important thing on my own before consulting with others.

I have the same problem with backlight on my Acer 5755G running Xubuntu 14.04, but I don't know how to modify GRUB config files. I found one solution, but wanted to ask you first whether this is the right option (from https://wiki.archlinux.org/index.php/ke … ters#GRUB):

To make the change persistent after reboot, while you could manually edit /boot/grub/grub.cfg with the exact line from above, for beginners it's recommended to:
Edit /etc/default/grub and append your kernel options to the GRUB_CMDLINE_LINUX_DEFAULT line:
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"
And then automatically re-generate the grub.cfg file with:
# grub-mkconfig -o /boot/grub/grub.cfg

Again, sorry for newbie question, your advice is greatly appreciated!

ugjka · 2014-09-22 10:18:29

Yeah that is the right option, but this isn't the right place to ask support for xubuntu.

Markof · 2014-09-22 15:21:04

ugjka wrote:

Yeah that is the right option, but this isn't the right place to ask support for xubuntu.

Thanks! And apologies for asking in the wrong forum, this thread was the first hit on Google search and described my problem perfectly, so I thought to ask just in case.

luisfeser · 2015-04-15 19:35:50

Thank you @dodys!!!

In my HP laptop, with hibryd graphics amd/intel, backlight works with this parameters:

GRUB_CMDLINE_LINUX_DEFAULT="acpi_osi=Linux acpi_backlight=vendor quiet"

uname -a
Linux hpluisfe 3.19.3-3-ARCH #1 SMP PREEMPT Wed Apr 8 14:10:00 CEST 2015 x86_64 GNU/Linux

Arch Linux

#1 2014-09-16 01:19:28

[Solved] Backlight not working in kernel 3.16

#2 2014-09-16 19:40:20

Re: [Solved] Backlight not working in kernel 3.16

#3 2014-09-16 19:43:19

Re: [Solved] Backlight not working in kernel 3.16

#4 2014-09-16 19:44:10

Re: [Solved] Backlight not working in kernel 3.16

#5 2014-09-16 21:18:58

Re: [Solved] Backlight not working in kernel 3.16

#6 2014-09-17 03:10:15

Re: [Solved] Backlight not working in kernel 3.16

#7 2014-09-17 06:45:08

Re: [Solved] Backlight not working in kernel 3.16

#8 2014-09-22 09:47:02

Re: [Solved] Backlight not working in kernel 3.16

#9 2014-09-22 10:18:29

Re: [Solved] Backlight not working in kernel 3.16

#10 2014-09-22 15:21:04

Re: [Solved] Backlight not working in kernel 3.16

#11 2015-04-15 19:35:50

Re: [Solved] Backlight not working in kernel 3.16

Board footer