3

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
CPLTarun
  • 213
  • This is a wrong solution anyway. It is an http://meta.stackexchange.com/questions/66377/what-is-the-xy-problem – Pilot6 Jan 19 '17 at 20:56
  • you made a copy/paste error Those ... do NOT belong in the command. – Rinzwind Jan 19 '17 at 21:01
  • 1
    @Rinzwind Even if OP didn't use the periods an ellipsis and actually used them in the command, no error message would be displayed. The link created would just be broken. – UTF-8 Jan 19 '17 at 21:16
  • 3
    You can't create files in /sys; they are created by the kernel to represent real hardware. Why are you trying to do this? – psusi Jan 19 '17 at 23:40
  • As I understand, I need those files in /sys/class/backlight in order to have any meaningful and convenient way to change my led backlight levels with a gui, correct? I read making a symlink can accomplish this, from another stackexchange answer. http://askubuntu.com/questions/715306/xbacklight-no-outputs-have-backlight-property-no-sys-class-backlight-folder – CPLTarun Jan 20 '17 at 18:41
  • There are some informations left they could be helpful to determine your issue. Add the exact model of your iMac and the port you use for the connection between pc and iMac. Also paste the output of lsb_release -a and lspci -nnk | grep "VGA" -A2. – Hölderlin Jan 22 '17 at 09:14
  • Okay I just added my iMac model and port used in my question above, along with the outputs of the commands you suggested I input. – CPLTarun Jan 23 '17 at 03:40
  • Did you tried to use noveau driver? – Hölderlin Feb 02 '17 at 22:38
  • I can't use Noveau drivers because I need to use my GPU for CUDA. I found a work around to dim my brightness: connecting my keyboard to my iMac while it's in Targeted Display Mode, and pressing the brightness control keys reduces the actual brightness of the screen. I then reconnect my keyboard to my pc. – CPLTarun Feb 14 '17 at 07:36

0 Answers0