Xbox Controller Emulator (Linux)

A lightweight Linux daemon that turns your keyboard and mouse into a virtual Xbox gamepad, using the kernel's uinput subsystem. No extra drivers, no user-space hacks — the virtual device shows up to games and applications exactly like a real Xbox controller would.

How It Works

The daemon reads raw input events directly from your keyboard and mouse device nodes (/dev/input/eventX), then translates them into gamepad events on a virtual uinput device:

• Keyboard → Buttons & D-Pad / Left Stick: WASD drives the left analog stick, and mapped keys trigger face buttons.
• Mouse movement → Right Stick: mouse deltas are translated into ABS_RX / ABS_RY events, simulating the right analog stick.
• Mouse buttons → Triggers: left/right click map to the analog triggers (BTN_TL2 / BTN_TR2).

Instead of busy-waiting on either device, the daemon uses poll() to block until either the keyboard or mouse actually has new input, so it stays idle when nothing is happening rather than spinning the CPU.

Key Mapping

Input	Gamepad Output
W / A / S / D	Left analog stick
Mouse movement	Right analog stick
Enter / Space	A button
G	Y button
E	X button
C	B button
Left Shift	Left stick click (L3)
Right Shift	Right stick click (R3)
Left Ctrl	Recenter right stick
Mouse Left Click	Left trigger (LT)
Mouse Right Click	Right trigger (RT)
Mouse Middle Click	Recenter right stick
Q then Enter	Quit the daemon

Prerequisites

• Linux with the uinput kernel module available (loaded via modprobe uinput if not already active)
• Root privileges (writing to /dev/uinput and reading raw /dev/input/eventX nodes requires it)
• A C/C++ compiler (gcc or g++)

Setup

1. Find your keyboard and mouse event nodes.

   ls -l /dev/input/by-id/
   # or
   cat /proc/bus/input/devices

   Look for entries like eventX corresponding to your keyboard and mouse.

2. Update the device paths in emulator.cpp to match your system:

   char KEYBOARD_PATH[] = "/dev/input/event0"; // update to your keyboard's event node
   char MOUSE_PATH[]    = "/dev/input/event1"; // update to your mouse's event node

3. Build:

   g++ emulator.cpp -o emulator

4. Run (requires root):

   sudo ./emulator

5. Once running, any application expecting an Xbox controller (Steam, emulators, native Linux games with gamepad support) will detect "Virtual Xbox Gamepad Daemon" as a connected device.

Stopping the Daemon

• Ctrl+C, or
• Press Q then Enter

Either path triggers a clean shutdown: the virtual uinput device is destroyed and both input file descriptors are closed via a signal-safe cleanup routine.

Known Limitations

• Device paths (/dev/input/eventX) are hardcoded and can change across reboots — you may need to re-check and update them periodically, or symlink via /dev/input/by-id/.
• Requires root to access raw input devices and /dev/uinput.
• Currently supports one fixed keyboard/mouse layout; no runtime remapping yet.

Contributing

Issues and PRs are welcome — this started as a personal project to get hands-on with Linux input internals, so there's plenty of room to extend (configurable bindings, multiple controller profiles, a udev rule for non-root access, etc.).

License

MIT