Brightness Control/xrandr Errors in 18.04

Question

I want to adjust the brightness on my laptop, which is currently fixed at the highest brightness.

My specs:

• Dell XPS 13 9310 OLED laptop, Ubuntu 18.04 (can't upgrade at the moment)

• Graphics card: 0000:00:02.0 VGA compatible controller: Intel Corporation Device 9a49 (rev 03)

• Kernel version: 5.4.0-90-generic

Did not work:

• adding acpi_osi, and/or acpi_osi='!Windows 2012', to the /etc/default/grub at GRUB_CMDLINE_LINUX_DEFAULT
• Replacing#GRUB_GFXMODE=640x480 with GRUB_GFXMODE=3456x2160
• installing theicc-brightness package
• installing thebrightness-controller package
• Tried running the repo at https://github.com/MuDiAhmed/Ubuntu-Dell-XPS-15-2019, but having issues with xrandr as mentioned below.

Worked...a little?

• added acpi_backlight=vendor to GRUB_CMDLINE_LINUX_DEFAULT
  • did make the brightness bar appear in the GUI, and enabled the keyboard brightness buttons, but the brightness still doesn't change.

Is it a xrandr issue?

I've tried to solve this using xrandr commands as some have had success with.

• Dell's mentions this issue (dell issue url), but on running xrandr to test I get:

  xrandr: Failed to get size of gamma for output default
  Screen 0: minimum 3456 x 2160, current 3456 x 2160, maximum 3456 x 2160
  default connected primary 3456x2160+0+0 0mm x 0mm
     3456x2160     89.00* 
  

  I've tried to figure out this xrandr problem. I've noticed that some Intel hardware drivers seem to be unloaded in this excerpt of my /var/log/Xorg.0.log file when I run cat /var/log/Xorg.0.log | grep "intel"

  [     2.919] Kernel command line: BOOT_IMAGE=/boot/vmlinuz-5.4.0-90-generic root=UUID=59687312-a405-46c0-8bb7-5f4c10008c94 ro quiet splash snd_hda_intel.dmic_detect=0 acpi_backlight=vendor "acpi_osi=!Windows 2012" vt.handoff=1
  [     2.922] (II) LoadModule: "intel"
  [     2.922] (II) Loading /usr/lib/xorg/modules/drivers/intel_drv.so
  [     2.923] (II) Module intel: vendor="X.Org Foundation"
  [     2.923] (II) intel: Driver for Intel(R) Integrated Graphics Chipsets:
  [     2.923] (II) intel: Driver for Intel(R) HD Graphics
  [     2.923] (II) intel: Driver for Intel(R) Iris(TM) Graphics
  [     2.923] (II) intel: Driver for Intel(R) Iris(TM) Pro Graphics
  [     2.923] (II) intel: Driver for Intel(R) Integrated Graphics Chipsets:
  [     2.923] (II) intel: Driver for Intel(R) HD Graphics
  [     2.923] (II) intel: Driver for Intel(R) Iris(TM) Graphics
  [     2.923] (II) intel: Driver for Intel(R) Iris(TM) Pro Graphics
  [     2.924] (II) UnloadModule: "intel"
  [     2.924] (II) Unloading intel
  

  which I believe this answer seemed to associate with this topic and might answer my question, but a bit confused where to go from here:

  Ah, if the Intel driver is being unloaded, then that may explain why screen brightness adjustment is not working. It is likely that a basic framebuffer driver (eg fbdev or vesa) is in use.