Add gamepad user documentation

Mainly copied and adapted from HID keyboard and mouse documentation.

README.md

@@ -37,6 +37,7 @@ Its features include:
  - [camera mirroring](doc/camera.md) (Android 12+)
  - [mirroring as a webcam (V4L2)](doc/v4l2.md) (Linux-only)
  - physical [keyboard][hid-keyboard] and [mouse][hid-mouse] simulation (HID)
+ - [gamepad](doc/gamepad.md) support
  - [OTG mode](doc/otg.md)
  - and more…
 
@@ -111,6 +112,13 @@ Here are just some common examples.
     scrcpy --otg
     ```
 
+ - Control the device using gamepad controllers plugged into the computer:
+
+    ```bash
+    scrcpy --gamepad=uhid
+    scrcpy -G  # short version
+    ```
+
 ## User documentation
 
 The application provides a lot of features and configuration options. They are
@@ -122,6 +130,7 @@ documented in the following pages:
  - [Control](doc/control.md)
  - [Keyboard](doc/keyboard.md)
  - [Mouse](doc/mouse.md)
+ - [Gamepad](doc/gamepad.md)
  - [Device](doc/device.md)
  - [Window](doc/window.md)
  - [Recording](doc/recording.md)

doc/gamepad.md

@@ -0,0 +1,53 @@
+# Gamepad
+
+Several gamepad input modes are available:
+
+ - `--gamepad=disabled` (default)
+ - `--gamepad=uhid` (or `-G`): simulates physical HID gamepads using the UHID
+   kernel module on the device
+ - `--gamepad=aoa`: simulates physical HID gamepads using the AOAv2 protocol
+
+
+## Physical gamepad simulation
+
+Two modes allow to simulate physical HID gamepads on the device, one for each
+physical gamepad plugged into the computer.
+
+
+### UHID
+
+This mode simulates physical HID gamepads using the [UHID] kernel module on the
+device.
+
+[UHID]: https://kernel.org/doc/Documentation/hid/uhid.txt
+
+To enable UHID gamepads, use:
+
+```bash
+scrcpy --gamepad=uhid
+scrcpy -G  # short version
+```
+
+
+### AOA
+
+This mode simulates physical HID gamepads using the [AOAv2] protocol.
+
+[AOAv2]: https://source.android.com/devices/accessories/aoa2#hid-support
+
+To enable AOA gamepads, use:
+
+```bash
+scrcpy --gamepad=aoa
+```
+
+Contrary to the other mode, it works at the USB level directly (so it only works
+over USB).
+
+It does not use the scrcpy server, and does not require `adb` (USB debugging).
+Therefore, it is possible to control the device (but not mirror) even with USB
+debugging disabled (see [OTG](otg.md)).
+
+Note: On Windows, it may only work in [OTG mode](otg.md), not while mirroring
+(it is not possible to open a USB device if it is already open by another
+process like the _adb daemon_).

doc/otg.md

@@ -9,13 +9,15 @@ device (see [keyboard](keyboard.md) and [mouse](mouse.md)).
 [physical mouse]: mouse.md#physical-mouse-simulation
 
 A special mode (OTG) allows to control the device using AOA
-[keyboard](keyboard.md#aoa) and [mouse](mouse.md#aoa), without using _adb_ at
-all (so USB debugging is not necessary). In this mode, video and audio are
-disabled, and `--keyboard=aoa and `--mouse=aoa` are implicitly set.
+[keyboard](keyboard.md#aoa), [mouse](mouse.md#aoa) and
+[gamepad](gamepad.md#aoa), without using _adb_ at all (so USB debugging is not
+necessary). In this mode, video and audio are disabled, and `--keyboard=aoa` and
+`--mouse=aoa` are implicitly set. However, gamepads are disabled by default, so
+`--gamepad=aoa` (or `-G` in OTG mode) must be explicitly set.
 
-Therefore, it is possible to run _scrcpy_ with only physical keyboard and mouse
-simulation, as if the computer keyboard and mouse were plugged directly to the
-device via an OTG cable.
+Therefore, it is possible to run _scrcpy_ with only physical keyboard, mouse and
+gamepad simulation, as if the computer keyboard, mouse and gamepads were plugged
+directly to the device via an OTG cable.
 
 To enable OTG mode:
 
@@ -32,6 +34,13 @@ scrcpy --otg --keyboard=disabled
 scrcpy --otg --mouse=disabled
 ```
 
+and to enable gamepads:
+
+```bash
+scrcpy --otg --gamepad=aoa
+scrcpy --otg -G  # short version
+```
+
 It only works if the device is connected over USB.
 
 ## OTG issues on Windows
@@ -50,9 +59,9 @@ is enabled, then OTG mode is not necessary.
 Instead, disable video and audio, and select UHID (or AOA):
 
 ```bash
-scrcpy --no-video --no-audio --keyboard=uhid --mouse=uhid
-scrcpy --no-video --no-audio -KM  # short version
-scrcpy --no-video --no-audio --keyboard=aoa --mouse=aoa
+scrcpy --no-video --no-audio --keyboard=uhid --mouse=uhid --gamepad=uhid
+scrcpy --no-video --no-audio -KMG  # short version
+scrcpy --no-video --no-audio --keyboard=aoa --mouse=aoa --gamepad=aoa
 ```
 
 One benefit of UHID is that it also works wirelessly.