[arch-general] Nvidia backlight control - acpi_video0/brightness changes - display doesn't?

Warp sylvain.pascou at rez-gif.supelec.fr
Fri Nov 18 09:56:57 UTC 2016



On November 18, 2016 6:42:40 AM GMT+01:00, "David C. Rankin" <drankinatty at suddenlinkmail.com> wrote:
>On 11/17/2016 04:31 PM, David C. Rankin wrote:
>> All,
>> 
>>   Laptop: HP 8760w, Quadro 3000M, nvidia-340xx packages.
>> 
>>   The driver works perfectly (no errors in Xorg.0.log), but I have no
>way to
>> control the screen brightness. I've followed the suggestions in:
>> 
>> https://wiki.archlinux.org/index.php/NVIDIA/Tips_and_tricks
>> 
>>   but I still have no backlight control. Using the laptop function
>keys, the
>> values in /sys/class/backlight/acpi_video0/brightness are properly
>set, e.g.
>> 
>> $ cat /sys/class/backlight/acpi_video0/brightness
>> 8
>> 
>> (now tap the [func][F9], brightness lower, twice)
>> 
>> $ cat /sys/class/backlight/acpi_video0/brightness
>> 6
>> 
>> (actual_brightness value tracks brightness)
>> 
>> $ cat /sys/class/backlight/acpi_video0/max_brightness
>> 20
>> 
>>   This works with OR without /etc/X11/xorg.conf.d/20-nvidia.conf:
>> 
>>         Option "RegistryDwords" "EnableBrightnessControl=1"
>> 
>>   Does anyone have any suggestions on anything else to try before I
>start
>> loading the aur nvidia-bl or nvidiabl packages? I don't mind adding
>more
>> software, but if there are a few more tweaks to try before going that
>route, I
>> would like to try them first. Anybody get backlight working with a
>similar
>> model laptop?
>> 
>
>Let me add to this, that powerdevil is seeing the screen brightness
>changes
>and Udev is evidently applying them correctly. For example, pressing
>the
>function key to raise/lower brightness seems to generate the correct
>log entries:
>
>Nov 17 23:36:37 seidr org_kde_powerdevil[710]: powerdevil: Screen
>brightness
>value:  6
>Nov 17 23:36:37 seidr org_kde_powerdevil[710]: powerdevil: Screen
>brightness
>value max:  20
>Nov 17 23:36:37 seidr dbus[334]: [system] Activating service
>name='org.kde.powerdevil.backlighthelper' (using servicehelper)
>Nov 17 23:36:37 seidr org_kde_powerdevil[710]: powerdevil: set screen
>brightness value:  7
>Nov 17 23:36:37 seidr org_kde_powerdevil[710]: powerdevil: Screen
>brightness
>value max:  20
>Nov 17 23:36:37 seidr dbus[334]: [system] Successfully activated
>service
>'org.kde.powerdevil.backlighthelper'
>Nov 17 23:36:37 seidr org_kde_powerdevil[710]: powerdevil: Udev device
>changed
>"/sys/devices/pci0000:00/0000:00:01.0/0000:01:00.0/backlight/acpi_video0"
>"/sys/devices/pci0000:00/0000:00:01.0/0000:01:00.0/backlight/acpi_video0"
>
>  And, as noted above, the values in
>/sys/class/backlight/acpi_video0/brightness are changing as they
>should.
>
>I'll give both the aur packages a try (I have both built -- but the
>nvidiabl
>package is currently disowwned and needs a maintainer if anyone is
>interested)

Do you use any special kernel boot parameters? 

Using "acpi_backlight=vendor" helped me in a similar situation, though it was about another option interfering with backlight control.

Sylvain


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