Fixes third monitor not showing with DisplayLink on Proxmox VE / Debian trixie with kernel 7.0+ and GNOME Wayland. Re-connect dock after run.

fix-displaylink.sh

#!/bin/bash
# fix-displaylink.sh
#
# Fixes DisplayLink on Proxmox VE / Debian trixie with kernel 7.0+ and GNOME Wayland.
#
# Root cause: DisplayLinkManager uses dlopen("libevdi.so") at runtime, but the
# Debian package install does NOT build/install libevdi.so into /usr/lib/displaylink/.
# Without it, DLM silently fails to open any evdi virtual displays.
#
# Additionally, the Debian evdi package (1.14.8) does not build against kernel 7.0+
# due to DRM API changes, so evdi 1.14.15 must be built from source via DKMS.
#
# Requirements before running this script:
#   - Kernel 7.0.0-3-pve (or later) running: uname -r
#   - displaylink-driver package installed (provides /usr/lib/displaylink/)
#   - DisplayLink dock plugged in
#
# What this script does:
#   1. Builds evdi 1.14.15 kernel module via DKMS (if not already installed)
#   2. Builds libevdi.so from DisplayLink's bundled evdi.tar.gz
#   3. Installs libevdi.so into /usr/lib/displaylink/
#   4. Restarts the displaylink-driver service

set -e

KERNEL=$(uname -r)
DL_DIR="/usr/lib/displaylink"
EVDI_TAR="$DL_DIR/evdi.tar.gz"
BUILD_DIR="/tmp/evdi-dl-build"
EVDI_DKMS_VER="1.14.15"
EVDI_DKMS_SRC="/usr/src/evdi-${EVDI_DKMS_VER}"

# Must run as root
if [ "$(id -u)" -ne 0 ]; then
    echo "Error: run this script as root (sudo $0)" >&2
    exit 1
fi

# Check DisplayLink is installed
if [ ! -f "$DL_DIR/DisplayLinkManager" ]; then
    echo "Error: $DL_DIR/DisplayLinkManager not found." >&2
    echo "Install the displaylink-driver Debian package first." >&2
    exit 1
fi

echo "=== Step 1: Install build dependencies ==="
apt-get install -y --no-install-recommends dkms libdrm-dev build-essential git

echo ""
echo "=== Step 2: Build evdi $EVDI_DKMS_VER kernel module via DKMS ==="

if dkms status evdi/$EVDI_DKMS_VER | grep -q "installed.*$KERNEL"; then
    echo "evdi $EVDI_DKMS_VER already installed for $KERNEL, skipping."
else
    if [ ! -d "$EVDI_DKMS_SRC" ]; then
        echo "Cloning evdi $EVDI_DKMS_VER from GitHub..."
        REPO_DIR=$(mktemp -d)
        git clone --branch "v${EVDI_DKMS_VER}" --depth 1 \
            https://github.com/DisplayLink/evdi.git "$REPO_DIR"
        cp -r "$REPO_DIR/module" "$EVDI_DKMS_SRC"
        rm -rf "$REPO_DIR"
    fi

    # Unregister any conflicting evdi versions from DKMS
    for old_ver in $(dkms status evdi | awk -F'[,/]' '{print $2}' | tr -d ' ' | sort -u); do
        if [ "$old_ver" != "$EVDI_DKMS_VER" ]; then
            echo "Removing conflicting evdi DKMS version: $old_ver"
            dkms remove evdi/"$old_ver" --all 2>/dev/null || true
        fi
    done

    dkms add -m evdi -v "$EVDI_DKMS_VER"
    dkms build evdi/"$EVDI_DKMS_VER" -k "$KERNEL"
    dkms install evdi/"$EVDI_DKMS_VER" -k "$KERNEL"
    echo "evdi $EVDI_DKMS_VER installed for $KERNEL."
fi

echo ""
echo "=== Step 3: Build libevdi.so from DisplayLink's bundled evdi source ==="

if [ ! -f "$EVDI_TAR" ]; then
    echo "Error: $EVDI_TAR not found." >&2
    echo "Is the displaylink-driver package properly installed?" >&2
    exit 1
fi

rm -rf "$BUILD_DIR"
mkdir -p "$BUILD_DIR"
tar -xzf "$EVDI_TAR" -C "$BUILD_DIR"

make -C "$BUILD_DIR/library"

LIBEVDI_VER=$(grep 'LIBVER' "$BUILD_DIR/library/Makefile" | head -1 | awk -F':=' '{print $2}' | tr -d ' ')
echo "Built libevdi.so.$LIBEVDI_VER"

echo ""
echo "=== Step 4: Install libevdi.so into $DL_DIR ==="

install -m 0755 "$BUILD_DIR/library/libevdi.so.$LIBEVDI_VER" "$DL_DIR/libevdi.so"
echo "Installed $DL_DIR/libevdi.so"

rm -rf "$BUILD_DIR"

echo ""
echo "=== Step 5: Load evdi module and restart DisplayLink service ==="

modprobe evdi 2>/dev/null || true
systemctl restart displaylink-driver

echo ""
echo "=== Done ==="
echo "Waiting 3 seconds for DLM to initialize..."
sleep 3

REFCNT=$(cat /sys/module/evdi/refcnt 2>/dev/null || echo "unknown")
echo "evdi refcount: $REFCNT (should be >= 1 if DLM opened it)"

CONNECTORS=$(ls /sys/class/drm/ | grep -v 'card1\|card0\|render\|version' || echo "none")
echo "DisplayLink DRM connectors: $CONNECTORS"

for connector in $(ls /sys/class/drm/ | grep -E '^card[2-9]'); do
    status=$(cat /sys/class/drm/${connector}-*/status 2>/dev/null | head -1)
    echo "  $connector: $status"
done

if [ "$REFCNT" -ge 1 ] 2>/dev/null; then
    echo ""
    echo "Success! Open GNOME Settings -> Displays to configure your DisplayLink monitor."
else
    echo ""
    echo "Warning: evdi refcount is $REFCNT — DLM may not have loaded libevdi.so correctly."
    echo "Check: strings $DL_DIR/DisplayLinkManager | grep 'libevdi'"
fi