7 files changed, 913 insertions, 0 deletions

diff --git a/src/input_common/CMakeLists.txt b/src/input_common/CMakeLists.txt
index a9c2392b1..3bd76dd23 100644
--- a/src/input_common/CMakeLists.txt
+++ b/src/input_common/CMakeLists.txt
@@ -7,6 +7,10 @@ add_library(input_common STATIC
     main.h
     motion_emu.cpp
     motion_emu.h
+    gcadapter/gc_adapter.cpp
+    gcadapter/gc_adapter.h
+    gcadapter/gc_poller.cpp
+    gcadapter/gc_poller.h
     sdl/sdl.cpp
     sdl/sdl.h
     udp/client.cpp
@@ -26,5 +30,7 @@ if(SDL2_FOUND)
     target_compile_definitions(input_common PRIVATE HAVE_SDL2)
 endif()
 
+target_link_libraries(input_common PUBLIC ${LIBUSB_LIBRARIES})
+
 create_target_directory_groups(input_common)
 target_link_libraries(input_common PUBLIC core PRIVATE common Boost::boost)
diff --git a/src/input_common/gcadapter/gc_adapter.cpp b/src/input_common/gcadapter/gc_adapter.cpp
new file mode 100644
index 000000000..b39d2a3fb
--- /dev/null
+++ b/src/input_common/gcadapter/gc_adapter.cpp
@@ -0,0 +1,379 @@
+// Copyright 2014 Dolphin Emulator Project
+// Licensed under GPLv2+
+// Refer to the license.txt file included.
+
+#include <chrono>
+#include <thread>
+#include "common/logging/log.h"
+#include "input_common/gcadapter/gc_adapter.h"
+
+namespace GCAdapter {
+
+/// Used to loop through and assign button in poller
+constexpr std::array<PadButton, 12> PadButtonArray{
+    PadButton::PAD_BUTTON_LEFT, PadButton::PAD_BUTTON_RIGHT, PadButton::PAD_BUTTON_DOWN,
+    PadButton::PAD_BUTTON_UP,   PadButton::PAD_TRIGGER_Z,    PadButton::PAD_TRIGGER_R,
+    PadButton::PAD_TRIGGER_L,   PadButton::PAD_BUTTON_A,     PadButton::PAD_BUTTON_B,
+    PadButton::PAD_BUTTON_X,    PadButton::PAD_BUTTON_Y,     PadButton::PAD_BUTTON_START,
+};
+
+Adapter::Adapter() {
+    if (usb_adapter_handle != nullptr) {
+        return;
+    }
+    LOG_INFO(Input, "GC Adapter Initialization started");
+
+    current_status = NO_ADAPTER_DETECTED;
+    libusb_init(&libusb_ctx);
+
+    StartScanThread();
+}
+
+GCPadStatus Adapter::GetPadStatus(int port, const std::array<u8, 37>& adapter_payload) {
+    GCPadStatus pad = {};
+    bool get_origin = false;
+
+    ControllerTypes type = ControllerTypes(adapter_payload[1 + (9 * port)] >> 4);
+    if (type != ControllerTypes::None) {
+        get_origin = true;
+    }
+
+    adapter_controllers_status[port] = type;
+
+    static constexpr std::array<PadButton, 8> b1_buttons{
+        PadButton::PAD_BUTTON_A,    PadButton::PAD_BUTTON_B,    PadButton::PAD_BUTTON_X,
+        PadButton::PAD_BUTTON_Y,    PadButton::PAD_BUTTON_LEFT, PadButton::PAD_BUTTON_RIGHT,
+        PadButton::PAD_BUTTON_DOWN, PadButton::PAD_BUTTON_UP,
+    };
+
+    static constexpr std::array<PadButton, 4> b2_buttons{
+        PadButton::PAD_BUTTON_START,
+        PadButton::PAD_TRIGGER_Z,
+        PadButton::PAD_TRIGGER_R,
+        PadButton::PAD_TRIGGER_L,
+    };
+
+    if (adapter_controllers_status[port] != ControllerTypes::None) {
+        const u8 b1 = adapter_payload[1 + (9 * port) + 1];
+        const u8 b2 = adapter_payload[1 + (9 * port) + 2];
+
+        for (std::size_t i = 0; i < b1_buttons.size(); ++i) {
+            if ((b1 & (1U << i)) != 0) {
+                pad.button |= static_cast<u16>(b1_buttons[i]);
+            }
+        }
+
+        for (std::size_t j = 0; j < b2_buttons.size(); ++j) {
+            if ((b2 & (1U << j)) != 0) {
+                pad.button |= static_cast<u16>(b2_buttons[j]);
+            }
+        }
+
+        if (get_origin) {
+            pad.button |= PAD_GET_ORIGIN;
+        }
+
+        pad.stick_x = adapter_payload[1 + (9 * port) + 3];
+        pad.stick_y = adapter_payload[1 + (9 * port) + 4];
+        pad.substick_x = adapter_payload[1 + (9 * port) + 5];
+        pad.substick_y = adapter_payload[1 + (9 * port) + 6];
+        pad.trigger_left = adapter_payload[1 + (9 * port) + 7];
+        pad.trigger_right = adapter_payload[1 + (9 * port) + 8];
+    }
+    return pad;
+}
+
+void Adapter::PadToState(const GCPadStatus& pad, GCState& state) {
+    for (const auto& button : PadButtonArray) {
+        const u16 button_value = static_cast<u16>(button);
+        state.buttons.insert_or_assign(button_value, pad.button & button_value);
+    }
+
+    state.axes.insert_or_assign(static_cast<u8>(PadAxes::StickX), pad.stick_x);
+    state.axes.insert_or_assign(static_cast<u8>(PadAxes::StickY), pad.stick_y);
+    state.axes.insert_or_assign(static_cast<u8>(PadAxes::SubstickX), pad.substick_x);
+    state.axes.insert_or_assign(static_cast<u8>(PadAxes::SubstickY), pad.substick_y);
+    state.axes.insert_or_assign(static_cast<u8>(PadAxes::TriggerLeft), pad.trigger_left);
+    state.axes.insert_or_assign(static_cast<u8>(PadAxes::TriggerRight), pad.trigger_right);
+}
+
+void Adapter::Read() {
+    LOG_DEBUG(Input, "GC Adapter Read() thread started");
+
+    int payload_size_in, payload_size_copy;
+    std::array<u8, 37> adapter_payload;
+    std::array<u8, 37> adapter_payload_copy;
+    std::array<GCPadStatus, 4> pads;
+
+    while (adapter_thread_running) {
+        libusb_interrupt_transfer(usb_adapter_handle, input_endpoint, adapter_payload.data(),
+                                  sizeof(adapter_payload), &payload_size_in, 16);
+        payload_size_copy = 0;
+        // this mutex might be redundant?
+        {
+            std::lock_guard<std::mutex> lk(s_mutex);
+            std::copy(std::begin(adapter_payload), std::end(adapter_payload),
+                      std::begin(adapter_payload_copy));
+            payload_size_copy = payload_size_in;
+        }
+
+        if (payload_size_copy != sizeof(adapter_payload_copy) ||
+            adapter_payload_copy[0] != LIBUSB_DT_HID) {
+            LOG_ERROR(Input, "error reading payload (size: {}, type: {:02x})", payload_size_copy,
+                      adapter_payload_copy[0]);
+            adapter_thread_running = false; // error reading from adapter, stop reading.
+            break;
+        }
+        for (std::size_t port = 0; port < pads.size(); ++port) {
+            pads[port] = GetPadStatus(port, adapter_payload_copy);
+            if (DeviceConnected(port) && configuring) {
+                if (pads[port].button != PAD_GET_ORIGIN) {
+                    pad_queue[port].Push(pads[port]);
+                }
+
+                // Accounting for a threshold here because of some controller variance
+                if (pads[port].stick_x > pads[port].MAIN_STICK_CENTER_X + pads[port].THRESHOLD ||
+                    pads[port].stick_x < pads[port].MAIN_STICK_CENTER_X - pads[port].THRESHOLD) {
+                    pads[port].axis = GCAdapter::PadAxes::StickX;
+                    pads[port].axis_value = pads[port].stick_x;
+                    pad_queue[port].Push(pads[port]);
+                }
+                if (pads[port].stick_y > pads[port].MAIN_STICK_CENTER_Y + pads[port].THRESHOLD ||
+                    pads[port].stick_y < pads[port].MAIN_STICK_CENTER_Y - pads[port].THRESHOLD) {
+                    pads[port].axis = GCAdapter::PadAxes::StickY;
+                    pads[port].axis_value = pads[port].stick_y;
+                    pad_queue[port].Push(pads[port]);
+                }
+                if (pads[port].substick_x > pads[port].C_STICK_CENTER_X + pads[port].THRESHOLD ||
+                    pads[port].substick_x < pads[port].C_STICK_CENTER_X - pads[port].THRESHOLD) {
+                    pads[port].axis = GCAdapter::PadAxes::SubstickX;
+                    pads[port].axis_value = pads[port].substick_x;
+                    pad_queue[port].Push(pads[port]);
+                }
+                if (pads[port].substick_y > pads[port].C_STICK_CENTER_Y + pads[port].THRESHOLD ||
+                    pads[port].substick_y < pads[port].C_STICK_CENTER_Y - pads[port].THRESHOLD) {
+                    pads[port].axis = GCAdapter::PadAxes::SubstickY;
+                    pads[port].axis_value = pads[port].substick_y;
+                    pad_queue[port].Push(pads[port]);
+                }
+                if (pads[port].trigger_left > pads[port].TRIGGER_THRESHOLD) {
+                    pads[port].axis = GCAdapter::PadAxes::TriggerLeft;
+                    pads[port].axis_value = pads[port].trigger_left;
+                    pad_queue[port].Push(pads[port]);
+                }
+                if (pads[port].trigger_right > pads[port].TRIGGER_THRESHOLD) {
+                    pads[port].axis = GCAdapter::PadAxes::TriggerRight;
+                    pads[port].axis_value = pads[port].trigger_right;
+                    pad_queue[port].Push(pads[port]);
+                }
+            }
+            PadToState(pads[port], state[port]);
+        }
+        std::this_thread::yield();
+    }
+}
+
+void Adapter::ScanThreadFunc() {
+    LOG_INFO(Input, "GC Adapter scanning thread started");
+
+    while (detect_thread_running) {
+        if (usb_adapter_handle == nullptr) {
+            std::lock_guard<std::mutex> lk(initialization_mutex);
+            Setup();
+        }
+        std::this_thread::sleep_for(std::chrono::milliseconds(500));
+    }
+}
+
+void Adapter::StartScanThread() {
+    if (detect_thread_running) {
+        return;
+    }
+    if (!libusb_ctx) {
+        return;
+    }
+
+    detect_thread_running = true;
+    detect_thread = std::thread([=] { ScanThreadFunc(); });
+}
+
+void Adapter::StopScanThread() {
+    detect_thread_running = false;
+    detect_thread.join();
+}
+
+void Adapter::Setup() {
+    // Reset the error status in case the adapter gets unplugged
+    if (current_status < 0) {
+        current_status = NO_ADAPTER_DETECTED;
+    }
+
+    adapter_controllers_status.fill(ControllerTypes::None);
+
+    // pointer to list of connected usb devices
+    libusb_device** devices;
+
+    // populate the list of devices, get the count
+    const std::size_t device_count = libusb_get_device_list(libusb_ctx, &devices);
+
+    for (std::size_t index = 0; index < device_count; ++index) {
+        if (CheckDeviceAccess(devices[index])) {
+            // GC Adapter found and accessible, registering it
+            GetGCEndpoint(devices[index]);
+            break;
+        }
+    }
+}
+
+bool Adapter::CheckDeviceAccess(libusb_device* device) {
+    libusb_device_descriptor desc;
+    const int get_descriptor_error = libusb_get_device_descriptor(device, &desc);
+    if (get_descriptor_error) {
+        // could not acquire the descriptor, no point in trying to use it.
+        LOG_ERROR(Input, "libusb_get_device_descriptor failed with error: {}",
+                  get_descriptor_error);
+        return false;
+    }
+
+    if (desc.idVendor != 0x057e || desc.idProduct != 0x0337) {
+        // This isn't the device we are looking for.
+        return false;
+    }
+    const int open_error = libusb_open(device, &usb_adapter_handle);
+
+    if (open_error == LIBUSB_ERROR_ACCESS) {
+        LOG_ERROR(Input, "Yuzu can not gain access to this device: ID {:04X}:{:04X}.",
+                  desc.idVendor, desc.idProduct);
+        return false;
+    }
+    if (open_error) {
+        LOG_ERROR(Input, "libusb_open failed to open device with error = {}", open_error);
+        return false;
+    }
+
+    int kernel_driver_error = libusb_kernel_driver_active(usb_adapter_handle, 0);
+    if (kernel_driver_error == 1) {
+        kernel_driver_error = libusb_detach_kernel_driver(usb_adapter_handle, 0);
+        if (kernel_driver_error != 0 && kernel_driver_error != LIBUSB_ERROR_NOT_SUPPORTED) {
+            LOG_ERROR(Input, "libusb_detach_kernel_driver failed with error = {}",
+                      kernel_driver_error);
+        }
+    }
+
+    if (kernel_driver_error && kernel_driver_error != LIBUSB_ERROR_NOT_SUPPORTED) {
+        libusb_close(usb_adapter_handle);
+        usb_adapter_handle = nullptr;
+        return false;
+    }
+
+    const int interface_claim_error = libusb_claim_interface(usb_adapter_handle, 0);
+    if (interface_claim_error) {
+        LOG_ERROR(Input, "libusb_claim_interface failed with error = {}", interface_claim_error);
+        libusb_close(usb_adapter_handle);
+        usb_adapter_handle = nullptr;
+        return false;
+    }
+
+    return true;
+}
+
+void Adapter::GetGCEndpoint(libusb_device* device) {
+    libusb_config_descriptor* config = nullptr;
+    libusb_get_config_descriptor(device, 0, &config);
+    for (u8 ic = 0; ic < config->bNumInterfaces; ic++) {
+        const libusb_interface* interfaceContainer = &config->interface[ic];
+        for (int i = 0; i < interfaceContainer->num_altsetting; i++) {
+            const libusb_interface_descriptor* interface = &interfaceContainer->altsetting[i];
+            for (u8 e = 0; e < interface->bNumEndpoints; e++) {
+                const libusb_endpoint_descriptor* endpoint = &interface->endpoint[e];
+                if (endpoint->bEndpointAddress & LIBUSB_ENDPOINT_IN) {
+                    input_endpoint = endpoint->bEndpointAddress;
+                } else {
+                    output_endpoint = endpoint->bEndpointAddress;
+                }
+            }
+        }
+    }
+    // This transfer seems to be responsible for clearing the state of the adapter
+    // Used to clear the "busy" state of when the device is unexpectedly unplugged
+    unsigned char clear_payload = 0x13;
+    libusb_interrupt_transfer(usb_adapter_handle, output_endpoint, &clear_payload,
+                              sizeof(clear_payload), nullptr, 16);
+
+    adapter_thread_running = true;
+    current_status = ADAPTER_DETECTED;
+    adapter_input_thread = std::thread([=] { Read(); }); // Read input
+}
+
+Adapter::~Adapter() {
+    StopScanThread();
+    Reset();
+}
+
+void Adapter::Reset() {
+    std::unique_lock<std::mutex> lock(initialization_mutex, std::defer_lock);
+    if (!lock.try_lock()) {
+        return;
+    }
+    if (current_status != ADAPTER_DETECTED) {
+        return;
+    }
+
+    if (adapter_thread_running) {
+        adapter_thread_running = false;
+    }
+    adapter_input_thread.join();
+
+    adapter_controllers_status.fill(ControllerTypes::None);
+    current_status = NO_ADAPTER_DETECTED;
+
+    if (usb_adapter_handle) {
+        libusb_release_interface(usb_adapter_handle, 1);
+        libusb_close(usb_adapter_handle);
+        usb_adapter_handle = nullptr;
+    }
+
+    if (libusb_ctx) {
+        libusb_exit(libusb_ctx);
+    }
+}
+
+bool Adapter::DeviceConnected(int port) {
+    return adapter_controllers_status[port] != ControllerTypes::None;
+}
+
+void Adapter::ResetDeviceType(int port) {
+    adapter_controllers_status[port] = ControllerTypes::None;
+}
+
+void Adapter::BeginConfiguration() {
+    for (auto& pq : pad_queue) {
+        pq.Clear();
+    }
+    configuring = true;
+}
+
+void Adapter::EndConfiguration() {
+    for (auto& pq : pad_queue) {
+        pq.Clear();
+    }
+    configuring = false;
+}
+
+std::array<Common::SPSCQueue<GCPadStatus>, 4>& Adapter::GetPadQueue() {
+    return pad_queue;
+}
+
+const std::array<Common::SPSCQueue<GCPadStatus>, 4>& Adapter::GetPadQueue() const {
+    return pad_queue;
+}
+
+std::array<GCState, 4>& Adapter::GetPadState() {
+    return state;
+}
+
+const std::array<GCState, 4>& Adapter::GetPadState() const {
+    return state;
+}
+
+} // namespace GCAdapter
diff --git a/src/input_common/gcadapter/gc_adapter.h b/src/input_common/gcadapter/gc_adapter.h
new file mode 100644
index 000000000..0ea6263eb
--- /dev/null
+++ b/src/input_common/gcadapter/gc_adapter.h
@@ -0,0 +1,160 @@
+// Copyright 2014 Dolphin Emulator Project
+// Licensed under GPLv2+
+// Refer to the license.txt file included.
+
+#pragma once
+#include <algorithm>
+#include <functional>
+#include <mutex>
+#include <thread>
+#include <libusb.h>
+#include "common/common_types.h"
+#include "common/threadsafe_queue.h"
+
+namespace GCAdapter {
+
+enum {
+    PAD_USE_ORIGIN = 0x0080,
+    PAD_GET_ORIGIN = 0x2000,
+    PAD_ERR_STATUS = 0x8000,
+};
+
+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
+    u8 stick_x{};       // 0 <= stick_x       <= 255
+    u8 stick_y{};       // 0 <= stick_y       <= 255
+    u8 substick_x{};    // 0 <= substick_x    <= 255
+    u8 substick_y{};    // 0 <= substick_y    <= 255
+    u8 trigger_left{};  // 0 <= trigger_left  <= 255
+    u8 trigger_right{}; // 0 <= trigger_right <= 255
+
+    static constexpr u8 MAIN_STICK_CENTER_X = 0x80;
+    static constexpr u8 MAIN_STICK_CENTER_Y = 0x80;
+    static constexpr u8 MAIN_STICK_RADIUS = 0x7f;
+    static constexpr u8 C_STICK_CENTER_X = 0x80;
+    static constexpr u8 C_STICK_CENTER_Y = 0x80;
+    static constexpr u8 C_STICK_RADIUS = 0x7f;
+    static constexpr u8 THRESHOLD = 10;
+
+    // 256/4, at least a quarter press to count as a press. For polling mostly
+    static constexpr u8 TRIGGER_THRESHOLD = 64;
+
+    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 };
+
+enum {
+    NO_ADAPTER_DETECTED = 0,
+    ADAPTER_DETECTED = 1,
+};
+
+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();
+
+    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;
+
+private:
+    GCPadStatus GetPadStatus(int port, const std::array<u8, 37>& adapter_payload);
+
+    void PadToState(const GCPadStatus& pad, GCState& state);
+
+    void Read();
+    void ScanThreadFunc();
+    /// Begin scanning for the GC Adapter.
+    void StartScanThread();
+
+    /// Stop scanning for the adapter
+    void StopScanThread();
+
+    /// Returns true if there is a device connected to port
+    bool DeviceConnected(int port);
+
+    /// Resets status of device connected to port
+    void ResetDeviceType(int 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();
+
+    int current_status = NO_ADAPTER_DETECTED;
+    libusb_device_handle* usb_adapter_handle = nullptr;
+    std::array<ControllerTypes, 4> adapter_controllers_status{};
+
+    std::mutex s_mutex;
+
+    std::thread adapter_input_thread;
+    bool adapter_thread_running;
+
+    std::mutex initialization_mutex;
+    std::thread detect_thread;
+    bool detect_thread_running = false;
+
+    libusb_context* libusb_ctx;
+
+    u8 input_endpoint = 0;
+    u8 output_endpoint = 0;
+
+    bool configuring = false;
+
+    std::array<Common::SPSCQueue<GCPadStatus>, 4> pad_queue;
+    std::array<GCState, 4> state;
+};
+
+} // namespace GCAdapter
diff --git a/src/input_common/gcadapter/gc_poller.cpp b/src/input_common/gcadapter/gc_poller.cpp
new file mode 100644
index 000000000..385ce8430
--- /dev/null
+++ b/src/input_common/gcadapter/gc_poller.cpp
@@ -0,0 +1,272 @@
+// Copyright 2020 yuzu Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#include <atomic>
+#include <list>
+#include <mutex>
+#include <utility>
+#include "common/threadsafe_queue.h"
+#include "input_common/gcadapter/gc_adapter.h"
+#include "input_common/gcadapter/gc_poller.h"
+
+namespace InputCommon {
+
+class GCButton final : public Input::ButtonDevice {
+public:
+    explicit GCButton(int port_, int button_, GCAdapter::Adapter* adapter)
+        : port(port_), button(button_), gcadapter(adapter) {}
+
+    ~GCButton() override;
+
+    bool GetStatus() const override {
+        return gcadapter->GetPadState()[port].buttons.at(button);
+    }
+
+private:
+    const int port;
+    const int button;
+    GCAdapter::Adapter* gcadapter;
+};
+
+class GCAxisButton final : public Input::ButtonDevice {
+public:
+    explicit GCAxisButton(int port_, int axis_, float threshold_, bool trigger_if_greater_,
+                          GCAdapter::Adapter* adapter)
+        : port(port_), axis(axis_), threshold(threshold_), trigger_if_greater(trigger_if_greater_),
+          gcadapter(adapter) {
+        // L/R triggers range is only in positive direction beginning near 0
+        // 0.0 threshold equates to near half trigger press, but threshold accounts for variability.
+        if (axis > 3) {
+            threshold *= -0.5;
+        }
+    }
+
+    bool GetStatus() const override {
+        const float axis_value = (gcadapter->GetPadState()[port].axes.at(axis) - 128.0f) / 128.0f;
+        if (trigger_if_greater) {
+            // TODO: Might be worthwile to set a slider for the trigger threshold. It is currently
+            // always set to 0.5 in configure_input_player.cpp ZL/ZR HandleClick
+            return axis_value > threshold;
+        }
+        return axis_value < -threshold;
+    }
+
+private:
+    const int port;
+    const int axis;
+    float threshold;
+    bool trigger_if_greater;
+    GCAdapter::Adapter* gcadapter;
+};
+
+GCButtonFactory::GCButtonFactory(std::shared_ptr<GCAdapter::Adapter> adapter_)
+    : adapter(std::move(adapter_)) {}
+
+GCButton::~GCButton() = default;
+
+std::unique_ptr<Input::ButtonDevice> GCButtonFactory::Create(const Common::ParamPackage& params) {
+    const int button_id = params.Get("button", 0);
+    const int port = params.Get("port", 0);
+
+    constexpr int PAD_STICK_ID = static_cast<u16>(GCAdapter::PadButton::PAD_STICK);
+
+    // button is not an axis/stick button
+    if (button_id != PAD_STICK_ID) {
+        auto button = std::make_unique<GCButton>(port, button_id, adapter.get());
+        return std::move(button);
+    }
+
+    // For Axis buttons, used by the binary sticks.
+    if (button_id == PAD_STICK_ID) {
+        const int axis = params.Get("axis", 0);
+        const float threshold = params.Get("threshold", 0.25f);
+        const std::string direction_name = params.Get("direction", "");
+        bool trigger_if_greater;
+        if (direction_name == "+") {
+            trigger_if_greater = true;
+        } else if (direction_name == "-") {
+            trigger_if_greater = false;
+        } else {
+            trigger_if_greater = true;
+            LOG_ERROR(Input, "Unknown direction {}", direction_name);
+        }
+        return std::make_unique<GCAxisButton>(port, axis, threshold, trigger_if_greater,
+                                              adapter.get());
+    }
+}
+
+Common::ParamPackage GCButtonFactory::GetNextInput() {
+    Common::ParamPackage params;
+    GCAdapter::GCPadStatus pad;
+    auto& queue = adapter->GetPadQueue();
+    for (std::size_t port = 0; port < queue.size(); ++port) {
+        while (queue[port].Pop(pad)) {
+            // This while loop will break on the earliest detected button
+            params.Set("engine", "gcpad");
+            params.Set("port", static_cast<int>(port));
+            for (const auto& button : GCAdapter::PadButtonArray) {
+                const u16 button_value = static_cast<u16>(button);
+                if (pad.button & button_value) {
+                    params.Set("button", button_value);
+                    break;
+                }
+            }
+
+            // For Axis button implementation
+            if (pad.axis != GCAdapter::PadAxes::Undefined) {
+                params.Set("axis", static_cast<u8>(pad.axis));
+                params.Set("button", static_cast<u16>(GCAdapter::PadButton::PAD_STICK));
+                if (pad.axis_value > 128) {
+                    params.Set("direction", "+");
+                    params.Set("threshold", "0.25");
+                } else {
+                    params.Set("direction", "-");
+                    params.Set("threshold", "-0.25");
+                }
+                break;
+            }
+        }
+    }
+    return params;
+}
+
+void GCButtonFactory::BeginConfiguration() {
+    polling = true;
+    adapter->BeginConfiguration();
+}
+
+void GCButtonFactory::EndConfiguration() {
+    polling = false;
+    adapter->EndConfiguration();
+}
+
+class GCAnalog final : public Input::AnalogDevice {
+public:
+    GCAnalog(int port_, int axis_x_, int axis_y_, float deadzone_, GCAdapter::Adapter* adapter)
+        : port(port_), axis_x(axis_x_), axis_y(axis_y_), deadzone(deadzone_), gcadapter(adapter) {}
+
+    float GetAxis(int axis) const {
+        std::lock_guard lock{mutex};
+        // division is not by a perfect 128 to account for some variance in center location
+        // e.g. my device idled at 131 in X, 120 in Y, and full range of motion was in range
+        // [20-230]
+        return (gcadapter->GetPadState()[port].axes.at(axis) - 128.0f) / 95.0f;
+    }
+
+    std::pair<float, float> GetAnalog(int axis_x, int axis_y) const {
+        float x = GetAxis(axis_x);
+        float y = GetAxis(axis_y);
+
+        // Make sure the coordinates are in the unit circle,
+        // otherwise normalize it.
+        float r = x * x + y * y;
+        if (r > 1.0f) {
+            r = std::sqrt(r);
+            x /= r;
+            y /= r;
+        }
+
+        return {x, y};
+    }
+
+    std::tuple<float, float> GetStatus() const override {
+        const auto [x, y] = GetAnalog(axis_x, axis_y);
+        const float r = std::sqrt((x * x) + (y * y));
+        if (r > deadzone) {
+            return {x / r * (r - deadzone) / (1 - deadzone),
+                    y / r * (r - deadzone) / (1 - deadzone)};
+        }
+        return {0.0f, 0.0f};
+    }
+
+    bool GetAnalogDirectionStatus(Input::AnalogDirection direction) const override {
+        const auto [x, y] = GetStatus();
+        const float directional_deadzone = 0.4f;
+        switch (direction) {
+        case Input::AnalogDirection::RIGHT:
+            return x > directional_deadzone;
+        case Input::AnalogDirection::LEFT:
+            return x < -directional_deadzone;
+        case Input::AnalogDirection::UP:
+            return y > directional_deadzone;
+        case Input::AnalogDirection::DOWN:
+            return y < -directional_deadzone;
+        }
+        return false;
+    }
+
+private:
+    const int port;
+    const int axis_x;
+    const int axis_y;
+    const float deadzone;
+    mutable std::mutex mutex;
+    GCAdapter::Adapter* gcadapter;
+};
+
+/// An analog device factory that creates analog devices from GC Adapter
+GCAnalogFactory::GCAnalogFactory(std::shared_ptr<GCAdapter::Adapter> adapter_)
+    : adapter(std::move(adapter_)) {}
+
+/**
+ * Creates analog device from joystick axes
+ * @param params contains parameters for creating the device:
+ *     - "port": the nth gcpad on the adapter
+ *     - "axis_x": the index of the axis to be bind as x-axis
+ *     - "axis_y": the index of the axis to be bind as y-axis
+ */
+std::unique_ptr<Input::AnalogDevice> GCAnalogFactory::Create(const Common::ParamPackage& params) {
+    const int port = params.Get("port", 0);
+    const int axis_x = params.Get("axis_x", 0);
+    const int axis_y = params.Get("axis_y", 1);
+    const float deadzone = std::clamp(params.Get("deadzone", 0.0f), 0.0f, .99f);
+
+    return std::make_unique<GCAnalog>(port, axis_x, axis_y, deadzone, adapter.get());
+}
+
+void GCAnalogFactory::BeginConfiguration() {
+    polling = true;
+    adapter->BeginConfiguration();
+}
+
+void GCAnalogFactory::EndConfiguration() {
+    polling = false;
+    adapter->EndConfiguration();
+}
+
+Common::ParamPackage GCAnalogFactory::GetNextInput() {
+    GCAdapter::GCPadStatus pad;
+    auto& queue = adapter->GetPadQueue();
+    for (std::size_t port = 0; port < queue.size(); ++port) {
+        while (queue[port].Pop(pad)) {
+            if (pad.axis == GCAdapter::PadAxes::Undefined ||
+                std::abs((pad.axis_value - 128.0f) / 128.0f) < 0.1) {
+                continue;
+            }
+            // An analog device needs two axes, so we need to store the axis for later and wait for
+            // a second input event. The axes also must be from the same joystick.
+            const u8 axis = static_cast<u8>(pad.axis);
+            if (analog_x_axis == -1) {
+                analog_x_axis = axis;
+                controller_number = port;
+            } else if (analog_y_axis == -1 && analog_x_axis != axis && controller_number == port) {
+                analog_y_axis = axis;
+            }
+        }
+    }
+    Common::ParamPackage params;
+    if (analog_x_axis != -1 && analog_y_axis != -1) {
+        params.Set("engine", "gcpad");
+        params.Set("port", controller_number);
+        params.Set("axis_x", analog_x_axis);
+        params.Set("axis_y", analog_y_axis);
+        analog_x_axis = -1;
+        analog_y_axis = -1;
+        controller_number = -1;
+        return params;
+    }
+    return params;
+}
+
+} // namespace InputCommon
diff --git a/src/input_common/gcadapter/gc_poller.h b/src/input_common/gcadapter/gc_poller.h
new file mode 100644
index 000000000..e96af7d51
--- /dev/null
+++ b/src/input_common/gcadapter/gc_poller.h
@@ -0,0 +1,67 @@
+// Copyright 2020 yuzu Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#pragma once
+
+#include <memory>
+#include "core/frontend/input.h"
+#include "input_common/gcadapter/gc_adapter.h"
+
+namespace InputCommon {
+
+/**
+ * A button device factory representing a gcpad. It receives gcpad events and forward them
+ * to all button devices it created.
+ */
+class GCButtonFactory final : public Input::Factory<Input::ButtonDevice> {
+public:
+    explicit GCButtonFactory(std::shared_ptr<GCAdapter::Adapter> adapter_);
+
+    /**
+     * Creates a button device from a button press
+     * @param params contains parameters for creating the device:
+     *     - "code": the code of the key to bind with the button
+     */
+    std::unique_ptr<Input::ButtonDevice> Create(const Common::ParamPackage& params) override;
+
+    Common::ParamPackage GetNextInput();
+
+    /// For device input configuration/polling
+    void BeginConfiguration();
+    void EndConfiguration();
+
+    bool IsPolling() const {
+        return polling;
+    }
+
+private:
+    std::shared_ptr<GCAdapter::Adapter> adapter;
+    bool polling = false;
+};
+
+/// An analog device factory that creates analog devices from GC Adapter
+class GCAnalogFactory final : public Input::Factory<Input::AnalogDevice> {
+public:
+    explicit GCAnalogFactory(std::shared_ptr<GCAdapter::Adapter> adapter_);
+
+    std::unique_ptr<Input::AnalogDevice> Create(const Common::ParamPackage& params) override;
+    Common::ParamPackage GetNextInput();
+
+    /// For device input configuration/polling
+    void BeginConfiguration();
+    void EndConfiguration();
+
+    bool IsPolling() const {
+        return polling;
+    }
+
+private:
+    std::shared_ptr<GCAdapter::Adapter> adapter;
+    int analog_x_axis = -1;
+    int analog_y_axis = -1;
+    int controller_number = -1;
+    bool polling = false;
+};
+
+} // namespace InputCommon
diff --git a/src/input_common/main.cpp b/src/input_common/main.cpp
index 95e351e24..fd0af1019 100644
--- a/src/input_common/main.cpp
+++ b/src/input_common/main.cpp
@@ -4,8 +4,11 @@
 
 #include <memory>
 #include <thread>
+#include <libusb.h>
 #include "common/param_package.h"
 #include "input_common/analog_from_button.h"
+#include "input_common/gcadapter/gc_adapter.h"
+#include "input_common/gcadapter/gc_poller.h"
 #include "input_common/keyboard.h"
 #include "input_common/main.h"
 #include "input_common/motion_emu.h"
@@ -22,8 +25,16 @@ static std::shared_ptr<MotionEmu> motion_emu;
 static std::unique_ptr<SDL::State> sdl;
 #endif
 static std::unique_ptr<CemuhookUDP::State> udp;
+static std::shared_ptr<GCButtonFactory> gcbuttons;
+static std::shared_ptr<GCAnalogFactory> gcanalog;
 
 void Init() {
+    auto gcadapter = std::make_shared<GCAdapter::Adapter>();
+    gcbuttons = std::make_shared<GCButtonFactory>(gcadapter);
+    Input::RegisterFactory<Input::ButtonDevice>("gcpad", gcbuttons);
+    gcanalog = std::make_shared<GCAnalogFactory>(gcadapter);
+    Input::RegisterFactory<Input::AnalogDevice>("gcpad", gcanalog);
+
     keyboard = std::make_shared<Keyboard>();
     Input::RegisterFactory<Input::ButtonDevice>("keyboard", keyboard);
     Input::RegisterFactory<Input::AnalogDevice>("analog_from_button",
@@ -48,6 +59,11 @@ void Shutdown() {
     sdl.reset();
 #endif
     udp.reset();
+    Input::UnregisterFactory<Input::ButtonDevice>("gcpad");
+    Input::UnregisterFactory<Input::AnalogDevice>("gcpad");
+
+    gcbuttons.reset();
+    gcanalog.reset();
 }
 
 Keyboard* GetKeyboard() {
@@ -58,6 +74,14 @@ MotionEmu* GetMotionEmu() {
     return motion_emu.get();
 }
 
+GCButtonFactory* GetGCButtons() {
+    return gcbuttons.get();
+}
+
+GCAnalogFactory* GetGCAnalogs() {
+    return gcanalog.get();
+}
+
 std::string GenerateKeyboardParam(int key_code) {
     Common::ParamPackage param{
         {"engine", "keyboard"},
diff --git a/src/input_common/main.h b/src/input_common/main.h
index 77a0ce90b..0e32856f6 100644
--- a/src/input_common/main.h
+++ b/src/input_common/main.h
@@ -7,6 +7,7 @@
 #include <memory>
 #include <string>
 #include <vector>
+#include "input_common/gcadapter/gc_poller.h"
 
 namespace Common {
 class ParamPackage;
@@ -30,6 +31,10 @@ class MotionEmu;
 /// Gets the motion emulation factory.
 MotionEmu* GetMotionEmu();
 
+GCButtonFactory* GetGCButtons();
+
+GCAnalogFactory* GetGCAnalogs();
+
 /// Generates a serialized param package for creating a keyboard button device
 std::string GenerateKeyboardParam(int key_code);