Idd — guest-local NVIDIA display for Linux Wayland

Expose a software monitor on an unused connector of the NVIDIA GPU inside a PCI-passthrough Linux VM. No dummy plug, host EDID configuration, Xorg dummy server, or extra software-rendered DRM card. The output belongs to nvidia-drm.

Includes an executable implementation, installer, boot service, hotplug rule, EDID generator, rollback, and tests. It uses NVIDIA's existing KMS connector-force and EDID path. An existing DP-1/HDMI-A-1 becomes a connected monitor; a new connector name is not allocated. Idd NVIDIA advertises configurable SDR modes from /etc/idd/modes.json, with 1920×1080/60 Hz preferred initially. This is not an implementation of Windows IddCx.

Validation status: the user has confirmed a working software monitor on CachyOS/RTX 3080 Ti/615.78.08. Both supplied probe reports show forced DP-1 using an active NVIDIA CRTC at 1080p60. The additional high-resolution/refresh modes are generated and tested in CI; their availability still depends on NVIDIA's mode validation. See the guide.

Edit /etc/idd/modes.json, then apply it:

sudo nano /etc/idd/modes.json
sudo idd apply

Default requested modes:

Choose an advertised mode in the desktop display settings. preferred is a hint for new desktop configurations; it does not override a mode already saved by your compositor. The installer preserves edited profiles. Existing original 1080p-only configurations adopt the mode file automatically after upgrading; explicit custom EDIDs are preserved. See upgrade and config examples.

The same NVIDIA DRM display works with Hyprland. After updating/installing Idd, run this as your desktop user in a Hyprland terminal, without sudo:

idd hyprland setup --mode 2560x1440@144
idd hyprland status

This detects Idd NVIDIA, checks the rate against Hyprland's actual advertised modes, enables it, and adds a managed monitor include to your existing config. It supports both Hyprlang (hyprland.conf) and Lua (hyprland.lua), preserves other monitor rules, and backs up the main file before changing it. Monitor settings persist across login, config reload, and Idd hotplug.

Edit ~/.config/idd/hyprland.json for the selected mode, position and scale, then run idd hyprland apply. The guest's /etc/idd/modes.json still controls the available EDID modes; use sudo idd apply after changing that file.

See the Hyprland guide for setup, Lua/custom config paths, NVIDIA GPU selection, recovery and removal.

When the guest is available, run this from the checkout:

sudo python3 src/idd.py probe --guest-only

src/idd.py is self-contained and can also be downloaded on its own. The probe automatically selects a single NVIDIA GPU and up to two unused connector types, briefly registers a monitor, waits for the compositor, and restores physical detection. It saves one idd-report-*.json in the current directory. There is no service installation, package download, desktop restart, or reboot. Existing Idd displays are inspected without changing them. It never uploads the report. Encoder assignment is reported separately from unverified moving frames. See probe details.

Requires Python 3.9+, systemd/udev, NVIDIA DRM KMS, and accessible DRM debugfs.

git clone https://github.com/oltrar/Idd.git
cd Idd
# Before merge, check out the implementation branch shown in the PR.
sudo bash scripts/install.sh --guest-only
idd list
# This address and unused port match the supplied 3080 Ti guest report:
sudo idd configure --guest-only --pci 0000:03:00.0 --connector DP-1
sudo systemctl enable --now idd-display.service
sudo idd verify
# After enabling this output in the Wayland desktop:
sudo idd verify --active

Read the full guide before removing your temporary cable. verify checks enumeration; --active also requires an assigned NVIDIA encoder. Confirm moving frames through guest capture/remote desktop software. The service enables the output before the next login screen.

sudo systemctl disable --now idd-display.service
sudo idd down

This restores physical detection and clears Idd's EDID override. No monitor EEPROM is programmed. With the GPU kept on vfio-pci in the host, the guest monitor ceases to exist when the guest stops.

python3 -m unittest discover -s tests -v
python3 src/idd.py edid /tmp/idd.edid
edid-decode --check /tmp/idd.edid

scripts/guest-gpu-diagnostics.sh remains read-only. No telemetry is uploaded.