Backlight: intel_backlight disappeared

x-rix · 2013-03-20 14:11:34

Fn-Keys never worked for me to begin with, so I'm suspecting that having them work automagically might rely on hardware drivers.

bongo_fury · 2013-03-20 15:52:42

I have installed a kernel 2.6.8.1 and now brightness control works perfectly. With "acpi_backlight=vendor" i have intel_backlight in /sys/class/backlight. Fn keys work, powerdevil slide works, echoing $number to /sys/.../intel_backlight/brightness works.
I think is a regression of official kernel, not an Arch issue, because i've installed for testing Opensuse 12.3 with 2.7.x kernel that has the same problems of arch.

x-rix · 2013-03-20 15:56:21

Thanks, bongo_fury! I'll try it in the evening when I get home.

BTW, everybody: should I mark this as [SOLVED]? Or as [WORKAROUND]? Technically it is a solution, but I'm not happy at all about being forced to work with an older kernel.

WonderWoofy · 2013-03-20 16:20:17

No I don't think you should mark this as solved. It is an ongoing issue, and it does indeed seem to be kernel related.

I hope by 2.6.8-1, bongo_fury means 3.6.8-1. Though as you probably know, partial updates are not supported, so it might be a better idea to try the LTS kernel, or even the linux-lts34 kernel from the AUR. I actually compiled it the other day, and it works pretty amazingly (it includes efistub and everything).

I too have this issue and have tried various combinations of acpi_backlight/acpi_osi combinations. Still I have no functional backlight stuff all around. I have the keys working, but the /sys stuff doesn't. So for now it is good enough.

bongo_fury · 2013-03-20 16:22:12

x-rix wrote:

Thanks, bongo_fury! I'll try it in the evening when I get home.
BTW, everybody: should I mark this as [SOLVED]? Or as [WORKAROUND]? Technically it is a solution, but I'm not happy at all about being forced to work with an older kernel.

IMHO, [WORKAROUND].
@ WonderWoofy, yes 3.6.8-1 not 2.6.8-1. Sorry

PS:Someone should report the regression to kernel developers. I could do it mysel, but my English is too bad (thank you Google Translate )

Last edited by bongo_fury (2013-03-20 16:24:58)

marvn · 2013-03-20 16:29:11

x-rix wrote:

So, the Fn-keys apparently have access to some brightness-changing-magic. Does anybody know what those functions are or how to find out? Because I always thought, echo-ing into the /sys/class/backlight/.../brightness file was as direct a change as it got. But apparently there are some system functions you can call to change the backlight directly, and if we knew how to call them, we could word around the issue.

I think the FN keys funcionality is added by acer_wmi kernel module. try load it (modprobe acer_wmi) and see if it works for you...

EDIT: missed the page 2, so this ^^ is kinda outdated

Last edited by marvn (2013-03-20 16:35:05)

x-rix · 2013-04-12 14:11:17

Update at long last: Everything still is as it was, BUT: yesterday I installed redshift, and it regulates brightness and RGB-/gamma-values without a problem. So I used it to tune down the brightness a bit in general (-b 0.8) in addition to the normal redshifting ... Problem solved for now.

It seems that while the /sys/class/backlight files don't work, randr still can change brightness or gamma values. So, it isn't perfect, but it isn't a terrible hack either.

kellerman · 2013-04-12 19:42:05

Hmm, redshift doesnt work for me.

redshift

(process:2661): GLib-GObject-CRITICAL **: g_type_instance_get_private: assertion `instance != NULL && instance->g_class != NULL' failed
[1]    2661 segmentation fault (core dumped)  redshift

Seems creating ~/.config/redshift.conf with

; Global settings
[redshift]
temp-day=5700
temp-night=3500
transition=1
gamma=0.8:0.7:0.8
location-provider=manual
adjustment-method=vidmode

; The location provider and adjustment method settings
; are in their own sections.
[manual]
lat=-34.6
lon=-58.3

;screen
[vidmode]
screen=0

fixes it. Is there any cool gui for it? like a slider or smth? the one in aur (redshiftgui) didn't build.

Last edited by kellerman (2013-04-12 19:55:31)

bongo_fury · 2013-04-15 16:55:10

I think redshift is another workaround not a solution. It works changing the gamma settings of the panel but backlight is always at the top. It is not a good thing if your notebook is running on battery power.
IMHO.

kellerman · 2013-04-15 20:49:39

bongo_fury wrote:

I think redshift is another workaround not a solution. It works changing the gamma settings of the panel but backlight is always at the top. It is not a good thing if your notebook is running on battery power.
IMHO.

Agreed.

WonderWoofy · 2013-04-15 23:12:32

So after posting quite a while ago, I found that my machine does indeed work very well with acpi_osi="!Windows 2012". You have to be careful with how you quote in the kernel command line though. It depends on what bootloader or boot manager you are using.

For instance, with gummiboot (my daily driver), the 'options' line has no quotes, so it can be put in exactly as is. Srs5694's rEFInd indicates that you should use double double quotes in the 'options' line (or maybe 'append' I can't remember). So it would be acpi_osi=""!Windows 2012"". In other bootloaders such as grub, I found that simply delimiting/escaping the quotes seemed to work fine. So it would be acpi_osi\"!Windows 2012\". This also works if you are using an efibootmgr entry to directly boot the efistub, and I have also tested with elilo as well. So I presume that what works for elilo would also work for lilo. I think for syslinux, it can be entered like gummiboot since the 'APPEND' line is not quoted in this case either.

I have seen reports that this does not always work, but from threads I have read, it seems to work more often than not if the proper quoting is used. I noticed that when I quoted the whole thing (ie. 'acpi_osi="!Windows 2012"') it borked it pretty good. I can't remember what it did, but it didn't work right for sure.

kellerman · 2013-04-21 14:41:02

No luck for me with that Windows stuff

x-rix · 2013-04-22 08:44:21

I think, you're right, changing gamma values doesn't solving the backlight issue, it's only a workaround. I'm removing the [SOLVED] tag.

kellerman · 2013-05-05 22:11:02

today after upgrading I noticed these lines in dmesg:

[    9.464498] acer_wmi: Acer Laptop ACPI-WMI Extras
[    9.464509] acer_wmi: Function bitmap for Communication Button: 0x801
[    9.464513] acer_wmi: Brightness must be controlled by acpi video driver

Kernel parameter:

acpi_osi=Linux

I found this interesting. It still doesnt work of course

Last edited by kellerman (2013-05-05 22:11:30)

bongo_fury · 2013-05-12 13:51:59

Good News! With the latest kernel 3.9.x backlight works. At this time I've tested my system only with "acpi_becklight=vendor" flag but backlight works (fn button, powerdevil slide etc.). Later other tests.

grobar87 · 2013-05-12 14:20:57

Backlight works again!!!

kellerman · 2013-05-14 15:28:40

Backlight should be set to vendor? Or intel? I have the latest kernel from core.
Tried backlight=vendor. Now the XFCE brightness plugin works! But FN keys doesn't

EDIT:
had to leave acpi_osi=Linux too at the kernel line for my Acer v3-571
Now it really works!
Should we mark this as [SOLVED] ?

Last edited by kellerman (2013-05-14 15:41:32)

Arch Linux

#26 2013-03-20 14:11:34

Re: Backlight: intel_backlight disappeared

#27 2013-03-20 15:52:42

Re: Backlight: intel_backlight disappeared

#28 2013-03-20 15:56:21

Re: Backlight: intel_backlight disappeared

#29 2013-03-20 16:20:17

Re: Backlight: intel_backlight disappeared

#30 2013-03-20 16:22:12

Re: Backlight: intel_backlight disappeared

#31 2013-03-20 16:29:11

Re: Backlight: intel_backlight disappeared

#32 2013-04-12 14:11:17

Re: Backlight: intel_backlight disappeared

#33 2013-04-12 19:42:05

Re: Backlight: intel_backlight disappeared

#34 2013-04-15 16:55:10

Re: Backlight: intel_backlight disappeared

#35 2013-04-15 20:49:39

Re: Backlight: intel_backlight disappeared

#36 2013-04-15 23:12:32

Re: Backlight: intel_backlight disappeared

#37 2013-04-21 14:41:02

Re: Backlight: intel_backlight disappeared

#38 2013-04-22 08:44:21

Re: Backlight: intel_backlight disappeared

#39 2013-05-05 22:11:02

Re: Backlight: intel_backlight disappeared

#40 2013-05-12 13:51:59

Re: Backlight: intel_backlight disappeared

#41 2013-05-12 14:20:57

Re: Backlight: intel_backlight disappeared

#42 2013-05-14 15:28:40

Re: Backlight: intel_backlight disappeared

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