PAD: Basic support for digital controllers

src/pse/digital_controller.h

@@ -0,0 +1,45 @@
+#pragma once
+#include "common/fifo_queue.h"
+#include "pad_device.h"
+#include <memory>
+
+class DigitalController final : public PadDevice
+{
+public:
+  enum class Button : u8
+  {
+    Select = 0,
+    L3 = 1,
+    R3 = 2,
+    Start = 3,
+    Up = 4,
+    Right = 5,
+    Down = 6,
+    Left = 7,
+    L2 = 8,
+    R2 = 9,
+    L1 = 10,
+    R1 = 11,
+    Triangle = 12,
+    Circle = 13,
+    Cross = 14,
+    Square = 15
+  };
+
+  DigitalController();
+  ~DigitalController() override;
+
+  static std::shared_ptr<DigitalController> Create();
+
+  void SetButtonState(Button button, bool pressed);
+
+  bool Transfer(const u8 data_in, u8* data_out) override;
+
+private:
+  void QueryState();
+
+  // buttons are active low
+  u16 m_button_state = UINT16_C(0xFFFF);
+
+  InlineFIFOQueue<u8, 8> m_transfer_fifo;
+};