Public bug reported:
[Kubuntu 25.10] Silicon Motion USB Display (VID:345f:PID:9133) creates
EVDI devices but KWin (Wayland) fails to expose as monitor
**Problem Description**
On Kubuntu 25.10 (Questing) with Kernel 6.17.0-19-generic, a Silicon Motion USB
display (VID:345f:PID:9133) connected internally via USB header is not
recognized as a usable monitor.
The driver installation (SMIUSBDisplay-driver 2.24.7.0) completes successfully:
1. The EVDI kernel module compiles and loads correctly for kernel 6.17.0-19.
2. The `smiusbdisplay.service` starts and runs.
3. Virtual DRM devices (`/dev/dri/card2` through `card5`) are created.
However, the Wayland compositor (KWin) immediately closes these devices
upon detection, preventing them from appearing in `xrandr` or System
Settings. The devices exist at the kernel level but are invisible to the
display server.
**Expected Behavior**
The 4" USB touchscreen should appear as an additional output (e.g., `USB-1` or
`EVDI-1`) in `xrandr --listmonitors` and be configurable in KDE Plasma Display
Settings.
**Actual Behavior**
- `xrandr --listmonitors` shows only the primary HDMI-A-2 display.
- `cat /sys/class/drm/card2/status` returns "No such file or directory" (status
files missing).
- Journal logs show KWin opening and immediately closing the EVDI cards: `evdi:
[I] (card2) Closed by Task 2167 (kwin_wayland)`
**Environment**
- Distribution: Kubuntu 25.10 (Questing)
- Kernel: 6.17.0-19-generic
- Desktop: KDE Plasma 6.5.6 (Wayland session)
- CPU: AMD Ryzen 7 8745HS
- GPU: AMD iGPU 780M
- Hardware: Internal 4" USB Touchscreen (Silicon Motion chipset,
VID:345f:PID:9133)
- Touch Controller: PUYA (VID:374a:PID:a401)
- Detected via usbhid
**Steps to Reproduce**
1. Install Silicon Motion SMIUSBDisplay-driver 2.24.7.0 (`.run` file).
2. Ensure kernel headers for 6.17.0-19 are installed.
3. Manually trigger DKMS build: `sudo dkms install /opt/siliconmotion/module/`
4. Start service: `sudo systemctl start smiusbdisplay.service`
5. Verify EVDI module loads: `lsmod | grep evdi` (Should show loaded).
6. Check DRM devices: `ls /dev/dri/` (Should show card2, card3, etc.).
7. Check monitor list: `xrandr –listmonitors`.
**Result:**
No new monitors appear. KWin logs show EVDI cards being closed immediately.
**Workarounds Attempted**
- Disabled USB autosuspend.
- Verified BIOS USB settings (Enabled).
- Tried DisplayLink driver (same KWin rejection behavior).
- Rebuilt EVDI module manually for current kernel (successful build, same
failure).
- Checked for X11 session (Unavailable in Kubuntu 25.10).
**Suspected Root Cause**
KWin on Wayland lacks explicit support for EVDI virtual displays created by the
Silicon Motion driver. While the kernel module builds successfully, the
compositor probes the device and rejects it, likely due to missing Wayland
protocol support or a regression in KWin 6.5.6 regarding EVDI.
**Attachments Required**
See attached .tar.gz for .txt logs.
** Affects: kwin (Ubuntu)
Importance: Undecided
Status: New
** Tags: evdi kubuntu-25.10 kwin usb-display wayland
** Attachment added: ".tar.gz containing logs for reference"
https://bugs.launchpad.net/bugs/2145155/+attachment/5954908/+files/wizarro_logs.tar.gz
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https://bugs.launchpad.net/bugs/2145155
Title:
Integrated USB display fails to register as device
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