Phantom "Unknown Display" shown in Settings after installing the Nvidia driver

[Daniel van Vugt]

[ Impact ]

After installing Nvidia driver 545 on a single (27") monitor system, Settings shows a phantom 46" monitor of the same resolution.

It looks like the phantom monitor is /dev/dri/card0 which is still controlled by simpledrm, while Nvidia uses /dev/dri/card1.

[ Workaround ]

1. sudo rm /dev/dri/card0
2. Log in again.

[ Test Plan ]

Open Settings and verify the only monitors shown are your real monitors.

[ Where problems could occur ]

Removing the simpledrm card is only safe when it's not being used. If somehow a machine wasn't using the installed Nvidia driver then there could be a risk of deleting the only working display.

[ Other Info ]

ProblemType: Bug
ApportVersion: 2.28.0-0ubuntu1
Architecture: amd64
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/seq: dan 4631 F.... pipewire
 /dev/snd/controlC1: dan 4636 F.... wireplumber
CRDA: N/A
CasperMD5CheckResult: pass
DistroRelease: Ubuntu 24.04
InstallationDate: Installed on 2024-01-04 (92 days ago)
InstallationMedia: Ubuntu 24.04 "Noble Numbat" - Daily amd64 (20231127)
MachineType: Intel(R) Client Systems NUC12DCMi7
NonfreeKernelModules: nvidia_modeset nvidia
Package: linux (not installed)
ProcEnviron:
 LANG=en_US.UTF-8
 PATH=(custom, no user)
 SHELL=/bin/bash
 TERM=xterm-256color
 XDG_RUNTIME_DIR=<set>
ProcFB: 0 simpledrmdrmfb
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-6.8.0-11-generic root=UUID=8434774e-88f2-4e3f-adb8-2eb07dff3cf9 ro quiet loglevel=3 splash vt.handoff=7
ProcVersionSignature: Ubuntu 6.8.0-11.11-generic 6.8.0-rc4
RelatedPackageVersions:
 linux-restricted-modules-6.8.0-11-generic N/A
 linux-backports-modules-6.8.0-11-generic N/A
 linux-firmware 20240318.git3b128b60-0ubuntu1
Tags: noble
Uname: Linux 6.8.0-11-generic x86_64
UpgradeStatus: No upgrade log present (probably fresh install)
UserGroups: adm cdrom dip lpadmin plugdev sudo users
_MarkForUpload: True
dmi.bios.date: 12/20/2021
dmi.bios.release: 5.24
dmi.bios.vendor: Intel Corp.
dmi.bios.version: EDADL579.0046.2021.1220.2351
dmi.board.name: NUC12EDBi7
dmi.board.vendor: Intel Corporation
dmi.board.version: M27908-302
dmi.chassis.type: 35
dmi.chassis.vendor: Intel Corporation
dmi.chassis.version: 2.0
dmi.ec.firmware.release: 3.7
dmi.modalias: dmi:bvnIntelCorp.:bvrEDADL579.0046.2021.1220.2351:bd12/20/2021:br5.24:efr3.7:svnIntel(R)ClientSystems:pnNUC12DCMi7:pvrM30143-302:rvnIntelCorporation:rnNUC12EDBi7:rvrM27908-302:cvnIntelCorporation:ct35:cvr2.0:skuRNUC12DCMi70000:
dmi.product.family: DC
dmi.product.name: NUC12DCMi7
dmi.product.sku: RNUC12DCMi70000
dmi.product.version: M30143-302
dmi.sys.vendor: Intel(R) Client Systems

[Daniel van Vugt (vanvugt)]

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[Daniel van Vugt (vanvugt)]

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[Daniel van Vugt (vanvugt)]

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[Daniel van Vugt (vanvugt)]

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[Daniel van Vugt (vanvugt)]

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[Daniel van Vugt (vanvugt)]

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[Daniel van Vugt (vanvugt)]

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[Daniel van Vugt (vanvugt)]

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[Daniel van Vugt (vanvugt)]

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[Daniel van Vugt (vanvugt)]

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[Daniel van Vugt (vanvugt)]

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[Daniel van Vugt (vanvugt)]

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[Daniel van Vugt (vanvugt)]

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[Daniel van Vugt (vanvugt)]

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[Daniel van Vugt (vanvugt)]

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[Daniel van Vugt (vanvugt)]

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[Daniel van Vugt (vanvugt)]

It looks like i915 avoids this by deleting /dev/dri/card0 (simpledrm) after /dev/dri/card1 (i915) exists. Although I don't really know exactly where that's implemented.

[Mario Limonciello (superm1)]

Probably nvidia.ko is missing a call to drm_aperture_remove_conflicting_pci_framebuffers()

[Daniel van Vugt (vanvugt)]

There's probably nothing to do in the kernel task here.

[Daniel van Vugt (vanvugt)]

I'm guessing this might also be the cause of the oversized panning login screen I get with Nvidia 470?

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Daniel van Vugt (vanvugt)]

If you're careful you can just delete /dev/dri/card0 to work around it :)

[Cristiano Fraga G. Nunes (cfgnunes)]

I recently installed Ubuntu 24.04 for testing purposes and have encountered the same issue:

The 'Displays' configuration indicates the presence of three monitors, like this:
1) Dell Inc. 27"
2) Dell Inc. 27"
3) Unknown Display
However, I only have two displays and not a third one.

When moving the cursor to the extreme right corner of the screen, the entire display shifts to the right.

My configuration:
- Utilizing: two monitors
- Graphics Card: NVIDIA GeForce GTX 1660 SUPER
- Environment: Xorg
- Driver Version: Nvidia driver 535.161.07

[Cristiano Fraga G. Nunes (cfgnunes)]

More information: listing the display outputs:

$ find /sys/devices -name "edid"

/sys/devices/platform/simple-framebuffer.0/drm/card0/card0-Unknown-1/edid
/sys/devices/pci0000:00/0000:00:01.0/0000:01:00.0/drm/card2/card2-DP-2/edid
/sys/devices/pci0000:00/0000:00:01.0/0000:01:00.0/drm/card2/card2-DVI-D-1/edid
/sys/devices/pci0000:00/0000:00:01.0/0000:01:00.0/drm/card2/card2-HDMI-A-3/edid
/sys/devices/pci0000:00/0000:00:02.0/drm/card1/card1-HDMI-A-1/edid
/sys/devices/pci0000:00/0000:00:02.0/drm/card1/card1-HDMI-A-2/edid
/sys/devices/pci0000:00/0000:00:02.0/drm/card1/card1-DP-1/edid

I've tried to delete the /dev/dri/card0 with:
$ sudo rm -f /dev/dri/card0

But this workaround not worked for me.

[Michel Hanzen (papymichmich)]

Same problem with Nvidia driver 535.171.04 on Ubuntu 24.04

[Momo77 (zeronoid)]

I upgraded from 23.10 to 24.04 and I have the same issues plus other problems:
+Two monitors designated as Unknown display (I use one).
+most gnome apps (like Setting, alert message) don't render the characters as in https://askubuntu.com/questions/1511575/ubuntu-24-04-screen-glitches-on-gnome-apps-after-install
+The resolution is stuck at 1024*768 but I could change it in NVIDIA x server setting but it is reset after restart
+Only 470 works on my gt710

[Alexandre Hen (atropine07)]

Same problem for me on Ubuntu 24.04 fresh install on X11 AND on Wayland.

I tried updating my nvidia driver to nvidia-driver-550, but I keep getting this "phantom" monitor in Gnome settings.

I have two physical monitors :
- Main one : AOC 27" AG271QG with G-Sync
- Other one : Dell 25"

$ find /sys/devices -name "edid"
/sys/devices/platform/simple-framebuffer.0/drm/card0/card0-Unknown-1/edid
/sys/devices/pci0000:00/0000:00:03.1/0000:0e:00.0/drm/card1/card1-HDMI-A-1/edid
/sys/devices/pci0000:00/0000:00:03.1/0000:0e:00.0/drm/card1/card1-DP-2/edid
/sys/devices/pci0000:00/0000:00:03.1/0000:0e:00.0/drm/card1/card1-Unknown-2/edid
/sys/devices/pci0000:00/0000:00:03.1/0000:0e:00.0/drm/card1/card1-DP-3/edid
/sys/devices/pci0000:00/0000:00:03.1/0000:0e:00.0/drm/card1/card1-DP-1/edid

[ Workaround ]
I type in terminal : sudo rm -f /dev/dri/card0

*After relogin : Phantom monitor has disappeared, but I lost my monitors' configuration (Main becoming second and vice versa, losing refresh rate too for the AOC).
No sign of the phantom screen in Gnome settings.

/dev/dri$ ls -l
total 0
drwxr-xr-x 2 root root 100 avril 28 14:52 by-path
crw-rw----+ 1 root video 226, 1 avril 28 14:52 card1
crw-rw----+ 1 root render 226, 128 avril 28 14:52 renderD128

I set my monitors like before (refresh rate at 144Hz and main monitor for the AOC), and reboot.

* After rebooting : phantom monitor is there again in Gnome settings. I kept my monitors' configuration.

/dev/dri$ ls -l
total 0
drwxr-xr-x 2 root root 100 avril 28 15:21 by-path
crw-rw----+ 1 root video 226, 0 avril 28 15:21 card0
crw-rw----+ 1 root video 226, 1 avril 28 15:21 card1
crw-rw----+ 1 root render 226, 128 avril 28 15:21 renderD128

Other informations about my PC :

# Rapport d’informations du système
---

## Détails du compte rendu
- **Date de génération :** 2024-04-28 15:07:02

## Informations liées au matériel :
- **Modèle du matériel :** ASRock X570 Taichi
- **Mémoire :** 32,0 Gio
- **Processeur :** AMD Ryzen™ 7 5800X3D × 16
- **Carte graphique :** NVIDIA GeForce RTX™ 2080
- **Capacité du disque :** 8,5 To

## Informations liées au logiciel :
- **Version du micrologiciel :** P5.01
- **Nom du système d’exploitation :** Ubuntu 24.04 LTS
- **Construction du système d’exploitation :** (null)
- **Type de système d’exploitation :** 64 bits
- **Version de GNOME :** 46
- **Système de fenêtrage :** X11
- **Version du noyau :** Linux 6.8.0-31-generic

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Per Overgaard (perove1980)]

Another Workaround:
This is using the Nvidia driver and not nouveau, right? I believe this is a driver in the Nvidia driver that is not asking for the conflicting framebuffers to be unregistered.
You can try to add "initcall_blacklist=simpledrm_platform_driver_init" to your kernel command line parameters to prevent the simpledrm driver to not be loaded.

Add to your kernel command line this. Open your terminal:
sudo nano /etc/default/grub
add "initcall_blacklist=simpledrm_platform_driver_init" to where it says GRUB_CMDLINE_LINUX_DEFAULT=”quiet splash..., so it looks like this:
GRUB_CMDLINE_LINUX_DEFAULT=”quiet splash initcall_blacklist=simpledrm_platform_driver_init”
ctrl+O for save and ctrl+X for quit. Back in the terminal write:
sudo update-grub
rebbot

This fixed the issue for me.

[Miguel Elias Machado (miguelemachado)]

> GRUB_CMDLINE_LINUX_DEFAULT=”quiet splash initcall_blacklist=simpledrm_platform_driver_init”

This workaround worket for me too.

Thanks.