feat(profiles): add Valve Steam Deck gamepad

README.md

@@ -43,8 +43,8 @@ behind backend implementations.
 ## 🎮 Capabilities
 
 - Gamepad profiles for generic HID, Xbox 360, Xbox One, Xbox Series,
-  DualShock 4, DualSense, and Nintendo Switch Pro-style controllers.
-- Descriptor-driven PlayStation gamepads through Linux `uhid`; Generic, Xbox,
+  DualShock 4, DualSense, Nintendo Switch Pro-style, and Steam Deck controllers.
+- Descriptor-driven PlayStation and Steam Deck gamepads through Linux `uhid`; Generic, Xbox,
   and Switch Pro gamepads plus keyboard, mouse, touchscreen, trackpad, and pen
   tablet devices through `uinput`.
 - Windows gamepads through a user-mode UMDF2 control driver backed by Virtual
@@ -149,6 +149,7 @@ Alternatives exist if `libvirtualhid` does not meet your needs.
 | DualShock 4 gamepad               | ✅                                                | ✅                                                | ✅                                                       | ❌                                                        | ✅<sup><a href="#alternatives-note-4">4</a></sup> |
 | DualSense gamepad                 | ✅                                                | ❌                                                | ✅                                                       | ✅                                                        | ✅<sup><a href="#alternatives-note-4">4</a></sup> |
 | Nintendo Switch Pro-style gamepad | ✅                                                | ❌                                                | ✅                                                       | ✅                                                        | ✅<sup><a href="#alternatives-note-4">4</a></sup> |
+| Steam Deck gamepad                | ✅                                                | ❌                                                | ❌                                                       | ❌                                                        | ❌                                                |
 | Rumble or output callbacks        | ✅                                                | ❌                                                | ✅                                                       | ✅                                                        | ✅<sup><a href="#alternatives-note-4">4</a></sup> |
 | Data-driven profiles              | ❌                                                | ❌                                                | ✅                                                       | ❌                                                        | ❌                                                |
 | Actively developed                | ✅                                                | ❌                                                | ✅                                                       | ✅                                                        | ✅                                                |

docs/platform-support.md

@@ -75,7 +75,17 @@ The VHF driver answers the calibration, pairing, and firmware feature reports
 used to initialize DualShock 4 and DualSense HIDAPI output. It also answers the
 Switch Pro USB and subcommand initialization sequence and accepts the native
 `0x30` input layout, so descriptor-aware consumers can initialize those
-controllers before sending their native output reports.
+controllers before sending their native output reports. The Steam Deck profile
+uses Valve's `0x28DE:0x1205` USB identity and native 64-byte state and feature
+reports. Its single top-level collection is identified as a Generic Desktop
+Game Pad while retaining the Valve-native report bytes, so Windows Game
+Controllers and generic HID clients can enumerate it even if the Valve-specific
+path is unavailable. SDL/HIDAPI can recognize it as a Steam Deck, disable its
+desktop mappings, and send native rumble without exposing Valve protocol details
+through the public C++ API. The driver seeds a neutral report before exposing the
+device, the backend submits another synchronously during creation, and periodic
+updates continue afterward. Each backend packet carries an advancing native
+sequence number.
 
 See [Windows driver package](windows-driver.md) for build, install, validation,
 and signing details.
@@ -84,7 +94,7 @@ and signing details.
 
 The Linux backend uses standard user-space kernel interfaces:
 
-- `uhid` for descriptor-driven HID gamepads.
+- `uhid` for descriptor-driven HID gamepads, including Steam Deck.
 - `uinput` for Generic, Xbox 360, Xbox One, Xbox Series, and Switch Pro
   gamepads, plus keyboard, mouse, touchscreen, trackpad, and pen tablet
   devices.
@@ -131,13 +141,24 @@ buttons, Guide, L3, and R3 at their expected indices. D-pad directions are
 reported through the hat axes and exposed as logical buttons by standard
 gamepad consumers.
 
-DualShock 4 and DualSense remain on `uhid` so their descriptors, motion,
+DualShock 4, DualSense, and Steam Deck remain on `uhid` so their descriptors, motion,
 touchpad, battery, feature reports, and profile-specific output reports stay
 available. The backend accepts PlayStation output through both UHID interrupt
 and control channels. Numbered control-channel output is normalized before
 parsing, whether the kernel includes the report number in the payload or
 provides it separately on the UHID event.
 
+Steam Deck retains Valve's native identity and emits the 64-byte Deck state
+packet periodically so SDL's direct HIDAPI path can initialize before the first
+client input arrives. Linux exposes that endpoint as Bluetooth HID so SDL can
+own the native hidraw stream directly; advertising it as USB would make the
+kernel's `hid-steam` driver claim the virtual endpoint and substitute an evdev
+controller. The Generic Desktop/Game Pad descriptor remains available as an
+evdev fallback. The backend answers the unit-serial feature query, accepts the
+desktop-mapping/settings commands used by SDL, and forwards native `0xEB`
+rumble requests through the portable output callback. Each submitted native
+packet carries an advancing sequence number.
+
 The backend opens `/dev/uhid` in nonblocking mode, matching the original
 asynchronous gamepad registration path. Its event reader is active before
 device registration begins, and creation does not report success until the
@@ -246,8 +267,8 @@ The FreeBSD backend uses the native evdev compatibility stack through
 FreeBSD path, and `/dev/uinput` for environments that provide the Linux-style
 alias. It supports the same uinput device categories as the Linux backend:
 
-- Generic, Xbox 360, Xbox One, Xbox Series, DualShock 4, DualSense, and Switch
-  Pro gamepads.
+- Generic, Xbox 360, Xbox One, Xbox Series, DualShock 4, DualSense, Switch Pro,
+  and Steam Deck gamepads.
 - Keyboard and mouse devices, with X11/XTest available as a fallback.
 - Touchscreen, trackpad, and pen tablet devices.
 
@@ -259,8 +280,8 @@ with the kernel HID bus. FreeBSD CUSE applications such as
 a `uhid(4)`-compatible character device for direct consumers, but that is a
 different integration surface and is not used by the current backend.
 
-Generic, Xbox-family, Switch Pro, DualShock 4, and DualSense behavior therefore
-uses uinput. Ordinary buttons, sticks, analog triggers, and rumble are available,
+Generic, Xbox-family, Switch Pro, DualShock 4, DualSense, and Steam Deck behavior
+therefore uses uinput. Ordinary buttons, sticks, analog triggers, and rumble are available,
 but raw HID reports and descriptor-driven features are not.
 
 For each created gamepad, `Gamepad::profile()` reports the effective FreeBSD

docs/streaming-host-integration.md

@@ -51,9 +51,11 @@ The core API and adapter shape cover the major streaming-host requirements:
 - Rich controller metadata.
 - Gamepad output callbacks.
 - Keyboard and mouse input paths.
-- Linux PlayStation gamepads through `uhid`, Generic/Xbox/Switch Pro gamepads
-  through `uinput`, and `uinput` keyboard/pointer devices.
+- Linux PlayStation and Steam Deck gamepads through `uhid`, Generic/Xbox/Switch
+  Pro gamepads through `uinput`, and `uinput` keyboard/pointer devices.
 - Linux DualSense and DualShock 4 USB/Bluetooth report handling.
+- Native Steam Deck identity, input, feature-report initialization, touch/motion,
+  rear-button, Quick Access, and rumble handling on Windows and Linux.
 - Linux touchscreen, trackpad, and pen tablet device types.
 - FreeBSD uinput gamepads and pointer devices, with basic PlayStation input and
   rumble but without Linux UHID-only PlayStation features.

docs/usage.md

@@ -212,6 +212,7 @@ Built-in gamepad profiles and their platform-neutral default device names are:
 | DualShock 4 USB and Bluetooth | `(libvirtualhid) PS4 Controller`          |
 | DualSense USB and Bluetooth   | `(libvirtualhid) PS5 Controller`          |
 | Nintendo Switch Pro           | `(libvirtualhid) Nintendo Pro Controller` |
+| Steam Deck                    | `(libvirtualhid) Steam Deck Controller`   |
 
 Consumers may replace `DeviceProfile::name` before creating a gamepad, for
 example, to prepend an application name while preserving the default controller
@@ -226,6 +227,8 @@ Profiles advertise support for features such as rumble, trigger rumble, RGB
 LEDs, adaptive triggers, motion sensors, touchpads, battery state,
 profile-specific buttons, and raw output reports. Consumers should query profile and
 backend capabilities before warning users about unsupported client features.
-The `misc1` button represents Share/Capture/Mic Mute-style controls and is
-available on the generic, Xbox Series, DualSense, and Switch Pro profiles; Xbox
-360 and Xbox One do not advertise that extra button.
+The `misc1` button represents Share/Capture/Mic Mute/Quick Access-style controls
+and is available on the generic, Xbox Series, DualSense, Switch Pro, and Steam
+Deck profiles; Xbox 360 and Xbox One do not advertise that extra button. Steam
+Deck also exposes its two trackpads through the two portable touch contacts and
+maps its L4/R4/L5/R5 rear controls to the four paddle buttons.

docs/windows-driver.md

@@ -381,6 +381,17 @@ gamepad.
 DualShock 4 and DualSense answer the calibration, pairing, and firmware feature
 requests used by their Windows HIDAPI initialization paths. Switch Pro answers
 the native USB and subcommand handshake and submits native `0x30` input reports.
+Steam Deck uses Valve's `VID_28DE&PID_1205` identity, responds to the unnumbered
+feature-report sequence used by SDL/HIDAPI, submits native 64-byte Deck state
+reports, and normalizes native `0xEB` rumble requests into the public callback.
+The same native report is described by a Generic Desktop/Game Pad top-level
+collection, allowing Windows' Game Controllers control panel and generic HID
+clients to classify the VHF child as a gamepad. The backend begins sending a
+sequenced neutral Deck state immediately after creation and repeats the latest
+state every four milliseconds, keeping a packet available throughout SDL's
+short endpoint-probe window. The driver also queues a neutral state before
+starting VHF and handles Deck feature requests as unnumbered reports regardless
+of the initial contents of the transfer buffer.
 The built-in Generic profile is presented to Windows as a DirectInput PID
 Joystick with the complete output-report set required for DirectInput
 enumeration. Constant Force and Sine output is normalized to the portable

examples/gamepad_adapter.cpp

@@ -39,6 +39,9 @@ namespace {
     if (name == "switch") {
       return lvh::profiles::switch_pro();
     }
+    if (name == "steamdeck") {
+      return lvh::profiles::steam_deck();
+    }
 
     return std::nullopt;
   }
@@ -58,6 +61,7 @@ namespace {
       case switch_pro:
         return nintendo;
       case generic:
+      case steam_deck:
         return unknown;
     }
 

src/core/gamepad_adapter.cpp

@@ -47,6 +47,7 @@ namespace lvh {
         case xbox_series:
         case dualsense:
         case switch_pro:
+        case steam_deck:
           return true;
         case xbox_360:
         case xbox_one:
@@ -88,6 +89,9 @@ namespace lvh {
     support.supports_battery = profile.capabilities.supports_battery;
     support.supports_misc1_button = supports_common_misc1_button(profile.gamepad_kind);
     support.supports_touchpad_button = profile.capabilities.supports_touchpad;
+    if (profile.gamepad_kind == GamepadProfileKind::steam_deck) {
+      support.supported_rear_paddle_count = 4U;
+    }
 
     return support;
   }