ray
85 lines
3.2 KiB
Markdown
85 lines
3.2 KiB
Markdown
# Kernel 7.0 uinput regression: UI_DEV_SETUP required
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## Summary
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Kernel 7.0.0-22-generic broke the legacy uinput creation sequence.
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Sunshine's Inputtino and libevdev both use the old method and fail silently.
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## Pre-diagnostic: is uinput built-in or a module?
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Before running the C or Python diagnostic below, check if uinput is a loadable module or built into the kernel:
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```bash
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modinfo uinput 2>&1 | grep filename
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# "filename: (builtin)" → uinput is compiled into the kernel
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# "filename: /lib/modules/..." → uinput is a loadable module
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grep CONFIG_INPUT_UINPUT /boot/config-$(uname -r)
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# "CONFIG_INPUT_UINPUT=y" → built-in (no modprobe needed)
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# "CONFIG_INPUT_UINPUT=m" → module (modprobe uinput to load)
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```
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**If built-in:** `modprobe uinput` will succeed silently but `lsmod | grep uinput` will show nothing — this is expected. The device node at `/dev/uinput` exists regardless. Permissions (user in `input` group) are what matter. Skip any module-loading troubleshooting steps.
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**If a module:** `sudo modprobe uinput` and verify with `lsmod | grep uinput`. To persist across reboots: `echo "uinput" | sudo tee /etc/modules-load.d/uinput.conf`.
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## Root cause
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The uinput subsystem on kernel 7.0+ REQUIRES `UI_DEV_SETUP` ioctl before
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`UI_DEV_CREATE`. The old method (writing `struct uinput_user_dev` via write()
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or calling `UI_DEV_CREATE` without prior setup) is rejected with EINVAL (-22).
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Sunshine v2026.516.143833 links against libevdev 1.13.6, which uses the old method.
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Inputtino (Sunshine's actual input backend, not libevdev) also uses the old method.
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## Diagnostic (C test)
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```c
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#include <linux/uinput.h>
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int fd = open("/dev/uinput", O_WRONLY);
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ioctl(fd, UI_DEV_CREATE); // FAILS: EINVAL on kernel 7.0
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// Correct kernel 7.0 sequence:
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struct uinput_setup usetup;
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memset(&usetup, 0, sizeof(usetup));
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usetup.id.bustype = BUS_USB;
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strcpy(usetup.name, "test");
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ioctl(fd, UI_DEV_SETUP, &usetup); // NEW: Required on 7.0+
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ioctl(fd, UI_DEV_CREATE); // SUCCESS
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```
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## Diagnostic (Python test)
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```python
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import ctypes
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libevdev = ctypes.CDLL('libevdev.so.2')
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dev = libevdev.libevdev_new()
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libevdev.libevdev_set_name(dev, b'test')
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libevdev.libevdev_enable_event_type(dev, 1)
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uifd = ctypes.c_int(-1)
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ret = libevdev.libevdev_uinput_create_from_device(dev, 3, ctypes.byref(uifd))
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# Returns -25 (ENOTTY) on kernel 7.0 — uinput broken
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# Returns 0 on kernel 6.x — uinput works
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```
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## Why the LD_PRELOAD shim may not work
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The shim (`scripts/uinput-shim.c`) intercepts `libevdev_uinput_create_from_device`.
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However, Sunshine's PRIMARY input backend is **Inputtino** (subproject inside Sunshine
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binary), not libevdev. Inputtino creates keyboard/mouse devices through a separate
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code path that may not call through libevdev's public API. If the shim is deployed
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and input still doesn't work, Inputtino is bypassing it.
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## Proven workarounds
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1. **xdotool bridge** (`scripts/sunshine-input-bridge.py`) — tails Sunshine log,
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injects via xdotool XTEST. Works on any kernel.
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2. **Steam Remote Play** (`templates/remote_play.vdf`) — different protocol,
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no uinput involved.
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3. **Boot kernel 6.x** if available.
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## Kernel version
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Tested broken: 7.0.0-22-generic (Ubuntu 26.04)
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Tested working: Linux 6.x series
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