Backlight: intel_backlight disappeared

x-rix · 2013-02-01 06:50:47

Hello everyone,

up until a month or two ago, I used to change my brightness with a script that would echo a value into my /sys/class/backlight/intel_backlight/brightness. I havn't used this script for a while. When I tried to change my brightness today, I discovered that the whole intel_backlight directory was gone.

This wouldn't be too bad (though high adjustability is really nice), because there still is acpi_video0, right? Nope. Well, it's still there, but it doesn't change my brightness at all; neither does xbacklight.
Edit: Adding acpi_backlight=vendor to the boot options makes the screen go really bright and removes the acpi_video0 directory. Not the intended effect.
Adding acpi_backlight=legacy leaves everything the same; acpi_video0 is there and doesn't change the brightness.

I'm running an Acer V5, Arch is up to date, and I've got an Intel graphics chip (and a nVidia card, but I don't think that that would have anything to do with it).

I'd be grateful for any ideas for troubleshooting/debugging.

-rix

Second Edit: What the frag! I re-installed my intel drivers, now I still haven't got the intel directory, acpi_video0 is still too lazy to do its job, but at the brightness is turned way down after the reboot. How can I find out what's going on here? This went away after installing the intel drivers from AUR (git version) instead. I am now throughly confused.

Last edited by x-rix (2013-04-22 08:44:36)

Pse · 2013-02-04 19:48:56

This happened to me as well when going from Linux 3.6 to 3.7 (Acer V3). For now, I fixed this by adding acpi_osi=Linux to the command line. This will allow you to change the brightness with the fn+left/right keys, though you won't be able to adjust it from the command line (I think Linux does not control the backlight anymore when acpi_osi=Linux is set, that's why it works). I'd like to be able to control it as I did before.

x-rix · 2013-02-04 21:17:47

How do you have your Fn keys configured? I'm using a WM (i3) and up until now I haven't used the Fn keys at all.

the sad clown · 2013-02-16 04:31:20

nvm...reading comprehension problems again.

Last edited by the sad clown (2013-02-16 04:32:03)

x-rix · 2013-02-16 11:16:59

Does anybody else have any ideas? I have tried everything I could think of and also everything that seemed loosely connected, and everything thorough searching got me.

Help?

grobar87 · 2013-02-17 00:46:51

I have the same problem... Acer Aspire V5-571 laptop.I can't control backlight with acpi_video0, only with intel, but there is no intel directory in /sys/class/backlight/ only acpi_video folder...

x-rix · 2013-02-17 04:47:20

Did this happen recently or has it always been that way for you?

Also: Did you tried the stuff I described in my first post with the same results?

Last edited by x-rix (2013-02-17 04:47:52)

grobar87 · 2013-02-17 13:25:14

Yes i did tried the stuff you described... but problem is still there.Before reinstalling arch i can control brightness with intel_backlight only have to add this lines at the end of /etc/acpi/handler.sh file:

BRIGHTNESS_FILE="/sys/class/backlight/intel_backlight/brightness"

case "$1" in
    video/brightnessdown)
        brightness=`cat $BRIGHTNESS_FILE`
        brightness=`expr $brightness - 75`
        echo $brightness > $BRIGHTNESS_FILE
    ;;

    video/brightnessup)
        brightness=`cat $BRIGHTNESS_FILE`
        brightness=`expr $brightness + 75`
        echo $brightness > $BRIGHTNESS_FILE

esac

and backlight works,fn keys work too.

x-rix · 2013-02-17 13:27:24

But this script won't work anymore, will it? Because the intel_backlight directory is missing.

grobar87 · 2013-02-18 17:18:37

Yeah that's the problem...

kellerman · 2013-03-14 21:55:54

I'm gonna bump this up, because I'm having the same problem. no more intel_backlight under /sys/class/backlight
Laptop Acer V3-571

x-rix · 2013-03-15 08:12:32

Seems hardware related then, since all of us have an Acer V3 or V5.

hadrons123 · 2013-03-15 08:27:22

I do have this issue in my lenovo Y580. Someone should file a bug in upstream. I have to use acpi_backlight=vendor since kernel =>3.7.

x-rix · 2013-03-15 08:35:29

Hm, that is interesting. Kellerman, does acpi_backlight=vendor work for you?

Because I can't regulate my backlight atm, neither via the (missing) intel_backlight nor via acpi.

dontbugme · 2013-03-15 09:41:39

I don't have an Acer Notebook, but I have experienced something similar since 3.7 on my ultrabook. What helped according to a thread was the following in grub cmd line : "acpi_osi="!Windows 2012"" . In my case the backlight didn't work prior to 3.7 due to some strange bios initializations missing. This was fixed in 3.7 but then due to Windows 8 acpi support, which appeared in 3.7 too (probably the problem here in this thread too), my backlight still didn't work -> acpi_osi to the rescue.

kellerman · 2013-03-15 15:22:37

x-rix:
The Fn keys start to work when

acpi_osi=Linux

is added.
I tried setting acpi_backlight together with this to vendor, intel, acer. Nothing worked, with one of those options, which I can't remember, there was nothing at all in /sys/class/backlight folder (xfce panel plugin shows a red warning sign).
By default this is my folder:

 ls /sys/class/backlight
acpi_video0  acpi_video1

Last edited by kellerman (2013-03-15 15:23:45)

bongo_fury · 2013-03-18 21:58:36

Sorry for my poor english...
Same problem with my Travelmate P253-M Ivy Bridge.
With grub "vanilla" or with "acpi_backlight=legacy" parameter I have "acpi_video0" subdirectory in /sys/class/backlight, Fn keys don't work and I have no control about backlight
With "acpi_backlight=vendor" no subdirectory in /sys/class/backlight, Fn key don't work and I have no control about backlight
With "acpi_osi=Linux" parameter I have "acpi_video0" subdirectory in /sys/class/backlight, I have no control about backlight but Fn key work.
With "acpi_osi="!Windows 2012""... read "acpi_backlight=vendor"
Ultimately, only "acpi_osi=Linux" has some effects on the system, all other parameters are completely useless.
I have added "Option "Backlight" "intel_backlight"" in /etc/X11/xorg.conf.d/20-intel-conf: nothing changed
And, last but not least, backligth control don't works by setpci.
Thank you in advance

PS: Backlight control works perfectly on Kubuntu 12.10 with "acpi_backlight=vendor" : I can adjust LCD brightness via Fn keys or KDE powerdevil slide Backlight interface is in intel_backlight directory.

Last edited by bongo_fury (2013-03-18 22:20:23)

kellerman · 2013-03-19 09:33:43

That's because the kernel on Kubuntu is older probably, or isn't it?

marvn · 2013-03-19 10:46:30

have the same issue on acer. and it works fine with older kernels, so that's probably the reason why it works on 12.10 - with the acpi_backlight option, I can at least use the fn keys. powerdevil doesnt work unfortunatly...

Last edited by marvn (2013-03-19 10:46:43)

x-rix · 2013-03-19 10:59:49

Wait - you can use the fn-keys? Have you tried, if you can also regulate the backlight via

 sudo echo $NUMBER > /sys/class/backlight/..

?

Because it would be really curious if the one worked and the other didn't.

bongo_fury · 2013-03-19 11:18:22

x-rix wrote:

Wait - you can use the fn-keys? Have you tried, if you can also regulate the backlight via
 sudo echo $NUMBER > /sys/class/backlight/..
?
Because it would be really curious if the one worked and the other didn't.

With "acpi_osi=Linux" option Fn keys works perfectly.
Yes, I tried to run echo echo $NUMBER > /sys/class/backlight/... No effect
For example: max brightness set by Fn keys

cat  /sys/class/backlight/acpi_video0/brightess
9
echo 5> /sys/class/backlight/acpi_video0/brightess
cat  /sys/class/backlight/acpi_video0/brightess
5

And the brightness does not change

x-rix · 2013-03-19 11:53:25

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.

kellerman · 2013-03-19 21:55:25

That's right. No other way to change the brightness.

x-rix · 2013-03-20 05:55:50

Damn. Kellerman, what GUI/WM are you using? Most major ones give you some kind of direct support for Fn-keys, but mine is a smaller tiling WM and I've never used the Fn-keys so far.

(Has anyone tried using an older kernel? Otherwise I'm going to do that today or tomorrow.)

kellerman · 2013-03-20 13:51:21

I'm using XFCE and I can adjust the brightness with Fn keys as soon as the kernel loads. I guess it has nothing to do with the window manager or desktop environment.
An older kernel will probably work, I don't have that time to dig to the problem much deeper.
And XFCE brightness plugin just don't work.

Arch Linux

#1 2013-02-01 06:50:47

Backlight: intel_backlight disappeared

#2 2013-02-04 19:48:56

Re: Backlight: intel_backlight disappeared

#3 2013-02-04 21:17:47

Re: Backlight: intel_backlight disappeared

#4 2013-02-16 04:31:20

Re: Backlight: intel_backlight disappeared

#5 2013-02-16 11:16:59

Re: Backlight: intel_backlight disappeared

#6 2013-02-17 00:46:51

Re: Backlight: intel_backlight disappeared

#7 2013-02-17 04:47:20

Re: Backlight: intel_backlight disappeared

#8 2013-02-17 13:25:14

Re: Backlight: intel_backlight disappeared

#9 2013-02-17 13:27:24

Re: Backlight: intel_backlight disappeared

#10 2013-02-18 17:18:37

Re: Backlight: intel_backlight disappeared

#11 2013-03-14 21:55:54

Re: Backlight: intel_backlight disappeared

#12 2013-03-15 08:12:32

Re: Backlight: intel_backlight disappeared

#13 2013-03-15 08:27:22

Re: Backlight: intel_backlight disappeared

#14 2013-03-15 08:35:29

Re: Backlight: intel_backlight disappeared

#15 2013-03-15 09:41:39

Re: Backlight: intel_backlight disappeared

#16 2013-03-15 15:22:37

Re: Backlight: intel_backlight disappeared

#17 2013-03-18 21:58:36

Re: Backlight: intel_backlight disappeared

#18 2013-03-19 09:33:43

Re: Backlight: intel_backlight disappeared

#19 2013-03-19 10:46:30

Re: Backlight: intel_backlight disappeared

#20 2013-03-19 10:59:49

Re: Backlight: intel_backlight disappeared

#21 2013-03-19 11:18:22

Re: Backlight: intel_backlight disappeared

#22 2013-03-19 11:53:25

Re: Backlight: intel_backlight disappeared

#23 2013-03-19 21:55:25

Re: Backlight: intel_backlight disappeared

#24 2013-03-20 05:55:50

Re: Backlight: intel_backlight disappeared

#25 2013-03-20 13:51:21

Re: Backlight: intel_backlight disappeared

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