I'm using my iMac in targeted display mode as my ubuntu pc display, but I can't control the backglight levels at all. My /sys/class/backlight folder is empty.
I located the brightness and maxbrightness files in another folder and am trying to create a symlink:
sudo ln -s /sys/devices/pci0000:00/0000:00:1c.3/0000:06:00.0/leds/phy0-led /sys/class/backlight
However, I get this message:
ln: failed to create symbolic link '/sys/class/backlight/phy0-led': Operation not permitted
The reason I am trying to create a symlink is because I read that there must be brightness and maxbrightness files in my /sys/class/backlight folder if I want to be able to easily change my screen's backlight levels. Is this correct? Or is there another way to allow for a gui app to conviently control led backlight levels? FYI: I'm a complete noob at ubuntu and linux in general.
My iMac is the iMac 11,3. I am using the GTX 970's second DisplayPort from the left GTX 970 Ports, using a DisplayPort to Mini DisplayPort cable.
In terminal I ran the command lsb release -a and got:
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 16.04.1 LTS
Release: 16.04
Codename: xenial
I then ran the code: lspci -nnk | grep "VGA" -A2 and got:
03:00.0 VGA compatible controller [0300]: NVIDIA Corporation GM204 [GeForce GTX 970] [10de:13c2] (rev a1)
Subsystem: Gigabyte Technology Co., Ltd GM204 [GeForce GTX 970] [1458:3683]
Kernel driver in use: nvidia
