ASUS ROG G752VS: Nvidia GTX 1070 Mobile, Brightness of internal display is not adjustable


Kernel parameters: GRUB_CMDLINE_LINUX_DEFAULT=“splash acpi_osi= acpi_backlight=video video. use_native_backlight=1”

NVIDIA Driver v390 installed on Ubuntu 18.04

This is the only configuration where the function keys fn f5/f6 do something which strongly correspond to /sys/class/backlight/acpi_video0/brightness, but visually the brightness stays the same. If the laptop will turn the screen off after the minutes configured, the display stays black (but you could heavily recognize some letters on the display.

In all other kernel parameter configs I have tried , there was no reaction to the function keys nor to the sys class described above (i.e. acpi_backlight=vendor or none).

Changes to the xorg.conf in the way described here:

$sudo vim /usr/share/X11/xorg.conf.d/10-nvidia.conf =>
  1 Section "OutputClass"
  2     Identifier "nvidia"
  3     MatchDriver "nvidia-drm"
  4     Driver "nvidia"
  5     Option "AllowEmptyInitialConfiguration"
  6     ModulePath "/usr/lib/x86_64-linux-gnu/nvidia/xorg"
  7 EndSection
  8 Section "Device"
  9     Identifier  "PEGP"
 10     Driver      "nvidia"
 11     VendorName  "NVIDIA Corporation"
 12     Option      "Backlight" "acpi_video0"
 13     BusID       "PCI:0:1:0"
 14 EndSection

or changes directly to the NVIDIA generated xorg.conf:
 39 Section "Device"
 40     Identifier     "Device0"
 41     Driver         "nvidia"
 42     VendorName     "NVIDIA Corporation"
 43     BoardName      "GeForce GTX 1070 Mobile"
 44     Option         "RegistryDwords" "EnableBrightnessControl=1"
 45 EndSection

did not take any effect, though I am not sure that the Option or the Bus Id was derived in the right way (the device name was changed from Device0 to PEGP, derived from:

$dmesg|grep 'ACPI: Video'
[    1.173170] ACPI: Video Device [PEGP] (multi-head: yes  rom: yes  post: no)
$ lspci -D |grep VGA
0000:01:00.0 VGA compatible controller: NVIDIA Corporation GP104M [GeForce GTX 1070 Mobile] (rev a1)

I am running out of options, could it maybe be a bug?? Is there a solution out there??

Would be glad to hear from you!

Does using either xbacklight or nvidia-settings -n -a BacklightBrightness=VALUE work?


xbacklight is working, but as far as I know it is only handling the contrast and indirect controls like this.

My main problem is not the dimming alone, but also the failure behaviour in case of screen is turned off. After screen is turned off, there is no possibility to turn it on again.

Meanwhile I proved with Ubuntu 16.04 with nvidia 384, 18.04 with nvidia 390. All the same behaviour. With my other netbook ASUS BU201a in Ubuntu 16.04 it is totally different, but it has got an intel chipset and graphic card. Nearly all function keys are working.

In Windows it is the same, everything works (on both of my laptops).

So for me this is a heavy issue of the nvidia graphics card, or? And it seems to persist for a very long time, it seems.

Anybody here from NVidia team? Can I assist? Do I get any assistance :-)?

What’s the output of
ls -l /sys/class/backlight/*

Hi, here’s an explanation (10/25/2017) of Aaron Plattner from Nvidia: