Dual Sense

[InquiringMinds-AI]

So, I was on the canonical snap, but i decided i wanted to get a fresher version of FEX to see if it would solve for problems I was having. I can immediately tell that things are faster loading and.. smoother? but, my dual sense controller is being detected and read by steam, but not the games. so, I set Claude Code on figuring it out, and after trying alot of things, we got it working. Here's the report on that which I asked Claude Code for.

Fix: DualSense (PS5) Controller Not Working in Proton Games Under FEX-Emu

Problem

When running Steam via FEX-Emu on ARM64 (e.g., NVIDIA DGX Spark, Snapdragon X, other aarch64 devices), the DualSense controller is detected by Steam — the controller test screen shows all inputs correctly — but no Proton/Wine games receive controller input. This happens regardless of whether Steam Input is enabled or disabled.

Environment

• Hardware: ARM64 / aarch64 (tested on NVIDIA DGX Spark / GB10)
• OS: Ubuntu 24.04
• FEX-Emu: 2601 from PPA (ppa:fex-emu/fex)
• Steam: Native .deb (steam-launcher package)
• Proton: 10.0 and GE-Proton10-28 (both affected)
• Controller: DualSense Wireless Controller (PS5) over Bluetooth

Root Cause

Wine's winebus.sys has two backends for detecting controllers:

1. udev/hidraw backend — finds the DualSense via /dev/hidraw* and registers it with is_gamepad = 0
2. SDL backend — finds the same controller via SDL2 and correctly identifies it with is_gamepad = 1

Under FEX-Emu, the SDL backend fails to create its device after the hidraw backend has already registered the controller. The failure appears to be specific to running under FEX's x86-64 emulation — the same Proton versions work fine on native x86-64.

Since the hidraw backend registered the controller with is_gamepad = 0, Windows games using XInput, DirectInput, or Windows.Gaming.Input APIs don't see a gamepad. The controller exists in Wine's HID subsystem but is not recognized as a game controller.

Diagnosis

You can confirm this is your issue by launching a game with debug logging:

PROTON_LOG=1 WINEDEBUG=+winebus,+hid %command%

In ~/steam-APPID.log, look for:

trace:hid:hidraw_device_create ... desc {vid 054c, pid 0ce6, ... is_gamepad 0, is_hidraw 1, ...}
trace:hid:sdl_add_device ... desc {vid 054c, pid 0ce6, ... is_gamepad 1, is_hidraw 0, ...}
warn:hid:bus_main_thread failed to create device for L"SDL" bus device ...

If you see the SDL backend failing to create the device while hidraw succeeded with is_gamepad 0, this fix applies to you.

Fix

Disable Wine's hidraw backend so that SDL is the sole controller handler. This is done by adding a registry key to each Proton prefix.

Manual Fix (Single Game)

Edit the file:

~/.local/share/Steam/steamapps/compatdata/APPID/pfx/system.reg

Find the section:

[System\\ControlSet001\\Services\\winebus]

Add this line inside that section:

"DisableHidraw"=dword:00000001

Script Fix (All Games)

Save this as fix-proton-controllers.sh and run it:

#!/bin/bash
# Fix DualSense controller in Proton games running under FEX-Emu
# Disables Wine's hidraw backend so SDL can properly register the gamepad

COMPATDATA="$HOME/.local/share/Steam/steamapps/compatdata"
FIXED=0
SKIPPED=0

for reg in "$COMPATDATA"/*/pfx/system.reg; do
    [ -f "$reg" ] || continue
    appid=$(echo "$reg" | grep -oP 'compatdata/\K[0-9]+')

    if grep -q "DisableHidraw" "$reg" 2>/dev/null; then
        SKIPPED=$((SKIPPED + 1))
        continue
    fi

    if grep -q 'Services\\\\winebus\]' "$reg" 2>/dev/null; then
        sed -i '/\[System\\\\ControlSet001\\\\Services\\\\winebus\]/,/^$/{
            /^"Description"=/i\
"DisableHidraw"=dword:00000001
        }' "$reg"
        echo "Patched appid $appid"
        FIXED=$((FIXED + 1))
    fi
done

echo "Done: $FIXED patched, $SKIPPED already fixed"

Re-run this script whenever you install a new game, as new Proton prefixes won't have the fix.

Notes

• This fix should apply to any controller that Wine detects via both hidraw and SDL backends, not just DualSense. If you have an Xbox, Switch Pro, or other controller that Steam detects but games ignore, try this fix.
• The trade-off is that disabling hidraw means Wine can't use advanced HID features (adaptive triggers, haptic feedback) for controllers that support them. For most games, SDL provides everything needed.
• This issue is specific to running under FEX-Emu. On native x86-64 Linux, both backends coexist without conflict.
• Tested and confirmed working with Proton 10.0 and GE-Proton10-28 on FEX 2601.

Additional FEX + Steam Tips

• GPU thunks required: Enable GL, Vulkan, and drm thunks in ~/.fex-emu/Config.json for GPU acceleration:

  {
    "Config": {
      "RootFS": "Ubuntu_24_04.sqsh",
      "ThunkConfig": "/usr/share/fex-emu/ThunksDB.json"
    },
    "ThunksDB": {
      "GL": 1,
      "Vulkan": 1,
      "drm": 1
    }
  }

• Video cutscenes may crash: GStreamer plugins fail to load under FEX (wrong ELF class: ELFCLASS64). For games that freeze or crash on video playback, add to launch options:

  WINEDLLOVERRIDES="mfplat,mfplay,mf=d" %command%
  

  Note: This breaks games where XAudio2 depends on mfplat (e.g., Melty Blood: Type Lumina). Test without the override first.
• AppArmor user namespaces: Steam requires kernel.apparmor_restrict_unprivileged_userns=0 on Ubuntu 24.04. Set via:

  echo 'kernel.apparmor_restrict_unprivileged_userns=0' | sudo tee /etc/sysctl.d/99-userns.conf
  sudo sysctl -w kernel.apparmor_restrict_unprivileged_userns=0

[Sonicadvance1]

The issue of gamepads not working stems from incorrect data being read from the device due to bitness checks in the kernel. Asahi Linux runs a kernel patch to work around the problem.
See #4106 and slp/linux@897560f for more information.

FEX can't solve this problem from userspace.