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#1 2014-04-19 13:54:20

newbie115
Member
Registered: 2014-04-13
Posts: 10

Cannot change brightness after recent upgrade.

Recent upgrade has left me unable to change the backlight on my netbook using:
setpci -s 00:02.0 f4.b=??

It's really important for me to have a second way to change the brightness (I need to set it lower than the predefined minimum when switching the brightness using keyboard keys). Did the register change places due to kernel upgrade or intel driver upgrade? I thought about blindly changing every single byte with setpci but I don't think it's such a great idea. How can I fix the command to make it work as it did before? My graphics card is the GMA3150.

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#2 2014-04-19 15:35:32

mcloaked
Member
From: Yorkshire, UK
Registered: 2012-02-02
Posts: 692

Re: Cannot change brightness after recent upgrade.

Can you change the brightness using xrandr?

e.g. see the post https://bbs.archlinux.org/viewtopic.php … 0#p1404840


Mike C

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#3 2014-04-19 15:51:27

newbie115
Member
Registered: 2014-04-13
Posts: 10

Re: Cannot change brightness after recent upgrade.

Well I can. Every other way of changing the brightness except the setpci one works. However I don't want to use xrandr. When I used the setpci method, the LCD backlight level was lowered, thus when in a dark room I could save battery by switching to lower than minimal allowed brightness. If I use xrandr it simply dims the image transmitted to the LCD and does not decrease the strength at which the LCD backlight is actually working. For instance: if I used setpci to set the brightness to 0 the LCD would be completely off, but if I use xrandr to set the brightness to 0 the LCD's leds are still working at previous brightness (you can see the black screen isn't really black, it's still illuminated).

Maybe there's another command which works similarly to the setpci method? Or maybe there's a way of fixing it?

Last edited by newbie115 (2014-04-19 16:33:28)

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#4 2014-04-19 17:17:37

mcloaked
Member
From: Yorkshire, UK
Registered: 2012-02-02
Posts: 692

Re: Cannot change brightness after recent upgrade.

I would be interested to see a proper fix for this too!


Mike C

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#5 2014-04-19 18:22:46

ewaller
Administrator
From: Pasadena, CA
Registered: 2009-07-13
Posts: 12,744

Re: Cannot change brightness after recent upgrade.

Have you a /sys/class/backlight directory?

ewaller$@$odin /sys/class/backlight/acpi_video0 1013 %ll                      
total 0
-r--r--r-- 1 root root 4096 Apr 19 11:19 actual_brightness
-rw-r--r-- 1 root root 4096 Apr 19 11:19 bl_power
-rw-r--r-- 1 root root 4096 Apr 19 11:21 brightness
lrwxrwxrwx 1 root root    0 Apr 19 11:19 device -> ../../../0000:00:02.0
-r--r--r-- 1 root root 4096 Apr 19 11:19 max_brightness
drwxr-xr-x 2 root root    0 Apr 19 11:19 power
lrwxrwxrwx 1 root root    0 Apr 16 21:34 subsystem -> ../../../../../class/backlight
-r--r--r-- 1 root root 4096 Apr 19 11:19 type
-rw-r--r-- 1 root root 4096 Apr 19 11:19 uevent
ewaller$@$odin /sys/class/backlight/acpi_video0 1014 %cat actual_brightness          
1
ewaller$@$odin /sys/class/backlight/acpi_video0 1015 %cat brightness          
1
ewaller$@$odin /sys/class/backlight/acpi_video0 1016 %sudo bash -c 'echo 10 > brightness'         
ewaller$@$odin /sys/class/backlight/acpi_video0 1017 %cat brightness                     
10
ewaller$@$odin /sys/class/backlight/acpi_video0 1018 %

Nothing is too wonderful to be true, if it be consistent with the laws of nature -- Michael Faraday
Like you, I have no idea what you are doing, but I am pretty sure it is wrong...Jasonwryan
----
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#6 2014-04-21 17:26:11

mcloaked
Member
From: Yorkshire, UK
Registered: 2012-02-02
Posts: 692

Re: Cannot change brightness after recent upgrade.

I found that I had a somewhat frustrating backlight problem on two laptops with integrated Intel graphics - after the update to kernel 3.14 the machine initially boots normally but the screen dims to an unusable level when X starts and also when the login to KDE is nearing login completion.  I added some comments to a bug report upstream which hopefully will help one or two people.

https://bugs.freedesktop.org/show_bug.cgi?id=76276#c31

In my case I can use the Fn key to reset the brightness but this is clearly due to a problematic patch in the 3.14 kernel which I am hoping will get a fix before long and hopefully by 3.15 at the latest.


Mike C

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#7 2014-05-12 02:56:11

DanielH
Member
From: Mar del Plata, Argentina
Registered: 2014-03-11
Posts: 11

Re: Cannot change brightness after recent upgrade.

Hi!
I have Arch Linux + OpenBox + Tint2 installed on a Samsung N150 netbook (Atom N450 processor with Intel GMA3150 Integrated Graphics Processor and integrated shared graphics memory).

Since this model of Samsung netbooks don't allow to change the LVDS1 display brightness via Fn keys, I have set two key bindings in OpenBox (editing /home/daniel/.config/openbox/rc.xml):
...
</keybind>
    <keybind key="XF86MonBrightnessUp">
      <action name="Execute">
        <command>xbacklight -inc 13</command>
      </action>
    </keybind>
    <keybind key="XF86MonBrightnessDown">
      <action name="Execute">
        <command>xbacklight -dec 12</command>
      </action>
    </keybind>
...
(Note: in Samsung N150, backlight brightness is managed by /sys/class/backlight/samsung/brightness value, not by /sys/class/backlight/intel_backlight/brightness value).

This works for me until the upgrade to 3.14.1-1-ARCH kernel.

Now, I have the same troubles that newbie115 reports (recent upgrades to 3.14.2-1-ARCH and 3.14.3-1-ARCH kernel doesn't solves this issue):

- keybindings doesn't work at all, and - xbacklight -dec nn and xbacklight -inc nn statements from command line doesn't work (no brightness change), but xbacklight -get reports all value changes (from 100.000000 to 0.000000 and back),
- setpci -s 00:02.0 f4.b=?? commands doesn't work at all,
- xrandr --output LVDS1  --brightness nn command works (0.00 to 9.99 values), but it isn't a real change in display brightness, only an appearance change (xrandr doesn't control the PWM cycle of the LCD tube).

¿Any idea? I have no clues...
Best regards,

DanielH
PS: please, forgive my bad english, I'm argentinian and only speak spanish...

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