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I just installed 14.04 on my Macbook Pro 8,2 and I noticed that I have two "Built-In displays". Some applications open on the second display with no way to get to them. If I disable either display, I get no image on my screen.

I'm also having trouble with my mouse pointer flickering which others have fixed by disabling a phantom "Unknown Display" : (Mouse cursor flickering and disappearing). For me though, my phantom display is a secondary "Built-In" display.

Any idea how to properly remove the extra display?

Screenshot: https://www.dropbox.com/s/6m9n1f4nq8rqgms/Built-in.png

Community
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Justin Miller
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2 Answers2

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I fixed this for anyone who comes across this issue in the future. Apparently having power to both the integrated and discrete graphics cards was causing each to create a display, resulting in two Built-in displays and mouse flickering.

I turned off the intigrated graphics by doing:

sudo gedit /etc/rc.local

And add the following lines:

chown "username" /sys/kernel/debug/vgaswitcheroo/switch # change "username" with your user name
echo OFF > /sys/kernel/debug/vgaswitcheroo/switch

Then reboot.

When I now run sudo cat /sys/kernel/debug/vgaswitcheroo/switch I get the following result and no more second monitor/mouse flickering.

0:IGD: :Off:0000:00:02.0
1:DIS-Audio: :Pwr:0000:01:00.1
2:DIS:+:Pwr:0000:01:00.0

`

Justin Miller
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2

Edit: my first answer (kept at the end for posterity) isn't great, so I ended up with the following instead.

Disabling the phantom display in X

I encountered a this issue on a MacBook Pro 5,3 running Ubuntu 20.04, but without the flickering cursor. Running echo OFF > /sys/kernel/debug/vgaswitcheroo/switch caused my system to freeze for some reason, so I had to find another fix. The one I landed on was to disable the "phantom" display in the X configuration.

First, work out the identifier of the phantom display with xrandr:

$ xrandr --listmonitors

This should show two displays, one of which is the phantom one. In my case it showed LVDS-1 and LVDS-1-2. I guessed that LVDS-1-2 was phantom because LVDS-1 had a * next to it, but I'm not sure if that's the right way to tell. In any case, verify your guess by turning it off with xrandr:

$ xrandr --output LVDS-1-2 --off

If that works, you can then make it permanent in the X configuration. Create a new file in /usr/share/X11/xorg.conf.d/:

$ sudoedit /usr/share/X11/xorg.conf.d/01-disable-phantom-screen.conf

...and put the following in it, replacing LVDS-1-2 with the ID of your phantom screen:

Section "Monitor"
    Identifier "LVDS-1-2"
    Option "Ignore" "true"
EndSection

After this, though, I still had the problem on the login screen (GDM), and in fact it was worse because GDM was showing its UI on the phantom screen. To fix this, force GDM to use X by editing /etc/gdm3/custom.conf to remove the # from #WaylandEnable=false. (If you happen to be using Ubuntu's OEM install mode, there'll also be a /etc/gdm3/custom.conf.oem file. You'll want to change that, too, so that the fix persists once the end user completes the setup wizard.)

Old answer: disable Nouveau

Like I said above, this answer isn't great (turns out disabling your graphics driver is rather bad for performance), but I've kept it here in case it helps someone.

I disabled vgaswitcheroo entirely. To do this, add nouveau.modeset=0 to the GRUB_CMDLINE_LINUX_DEFAULT line in /etc/default/grub. For example, mine looks like this afterwards:

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash nouveau.modeset=0"

Then run sudo update-grub and reboot.

The HybridGraphics page in the community documentation has more details that helped me work this out.

Harry Cutts
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