input_common: Add support for GameCube Adapter

This is a port of the initial GameCube adapter input support i added into yuzu emulator.
It requires the same setup as when it was first introduced in yuzu, requiring the Zadig driver be installed for the adapter to allow it to interface with libusb.

src/input_common/gcadapter/gc_adapter.h

@@ -0,0 +1,132 @@
+// Copyright 2014 Dolphin Emulator Project
+// Licensed under GPLv2+
+// Refer to the license.txt file included.
+
+#pragma once
+
+#include <algorithm>
+#include <array>
+#include <functional>
+#include <mutex>
+#include <thread>
+#include <unordered_map>
+#include "common/common_types.h"
+#include "common/threadsafe_queue.h"
+
+struct libusb_context;
+struct libusb_device;
+struct libusb_device_handle;
+
+namespace GCAdapter {
+
+enum class PadButton {
+    PAD_BUTTON_LEFT = 0x0001,
+    PAD_BUTTON_RIGHT = 0x0002,
+    PAD_BUTTON_DOWN = 0x0004,
+    PAD_BUTTON_UP = 0x0008,
+    PAD_TRIGGER_Z = 0x0010,
+    PAD_TRIGGER_R = 0x0020,
+    PAD_TRIGGER_L = 0x0040,
+    PAD_BUTTON_A = 0x0100,
+    PAD_BUTTON_B = 0x0200,
+    PAD_BUTTON_X = 0x0400,
+    PAD_BUTTON_Y = 0x0800,
+    PAD_BUTTON_START = 0x1000,
+    // Below is for compatibility with "AxisButton" type
+    PAD_STICK = 0x2000,
+};
+
+extern const std::array<PadButton, 12> PadButtonArray;
+
+enum class PadAxes : u8 {
+    StickX,
+    StickY,
+    SubstickX,
+    SubstickY,
+    TriggerLeft,
+    TriggerRight,
+    Undefined,
+};
+
+struct GCPadStatus {
+    u16 button{}; // Or-ed PAD_BUTTON_* and PAD_TRIGGER_* bits
+
+    std::array<u8, 6> axis_values{};    // Triggers and sticks, following indices defined in PadAxes
+    static constexpr u8 THRESHOLD = 50; // Threshold for axis press for polling
+
+    u8 port{};
+    PadAxes axis{PadAxes::Undefined};
+    u8 axis_value{255};
+};
+
+struct GCState {
+    std::unordered_map<int, bool> buttons;
+    std::unordered_map<int, u16> axes;
+};
+
+enum class ControllerTypes { None, Wired, Wireless };
+
+class Adapter {
+public:
+    /// Initialize the GC Adapter capture and read sequence
+    Adapter();
+
+    /// Close the adapter read thread and release the adapter
+    ~Adapter();
+    /// Used for polling
+    void BeginConfiguration();
+    void EndConfiguration();
+
+    /// Returns true if there is a device connected to port
+    bool DeviceConnected(std::size_t port);
+
+    std::array<Common::SPSCQueue<GCPadStatus>, 4>& GetPadQueue();
+    const std::array<Common::SPSCQueue<GCPadStatus>, 4>& GetPadQueue() const;
+
+    std::array<GCState, 4>& GetPadState();
+    const std::array<GCState, 4>& GetPadState() const;
+
+    int GetOriginValue(int port, int axis) const;
+
+private:
+    GCPadStatus GetPadStatus(std::size_t port, const std::array<u8, 37>& adapter_payload);
+
+    void PadToState(const GCPadStatus& pad, GCState& state);
+
+    void Read();
+
+    /// Resets status of device connected to port
+    void ResetDeviceType(std::size_t port);
+
+    /// Returns true if we successfully gain access to GC Adapter
+    bool CheckDeviceAccess(libusb_device* device);
+
+    /// Captures GC Adapter endpoint address,
+    void GetGCEndpoint(libusb_device* device);
+
+    /// For shutting down, clear all data, join all threads, release usb
+    void Reset();
+
+    /// For use in initialization, querying devices to find the adapter
+    void Setup();
+
+    libusb_device_handle* usb_adapter_handle = nullptr;
+
+    std::thread adapter_input_thread;
+    bool adapter_thread_running;
+
+    libusb_context* libusb_ctx;
+
+    u8 input_endpoint = 0;
+    u8 output_endpoint = 0;
+
+    bool configuring = false;
+
+    std::array<GCState, 4> state;
+    std::array<bool, 4> get_origin;
+    std::array<GCPadStatus, 4> origin_status;
+    std::array<Common::SPSCQueue<GCPadStatus>, 4> pad_queue;
+    std::array<ControllerTypes, 4> adapter_controllers_status{};
+};
+
+} // namespace GCAdapter