From ab2d18ebf0e3fefa976a2dfe4c15b9f83133d35c Mon Sep 17 00:00:00 2001
From: Joe Stringer <1243336+joestringer@users.noreply.github.com>
Date: Sun, 18 Aug 2024 14:42:57 -0700
Subject: [PATCH] USB: Add passthrough support to DenshaCon

Enable an option to use native Densha De Go! controllers and pass the axis inputs from the controller directly through to the game.
---
 pcsx2/USB/usb-pad/usb-train.cpp | 34 +++++++++++++++++++++++++++------
 pcsx2/USB/usb-pad/usb-train.h   |  3 +++
 2 files changed, 31 insertions(+), 6 deletions(-)

diff --git a/pcsx2/USB/usb-pad/usb-train.cpp b/pcsx2/USB/usb-pad/usb-train.cpp
index 9ef6939fa2..5989dfd3b1 100644
--- a/pcsx2/USB/usb-pad/usb-train.cpp
+++ b/pcsx2/USB/usb-pad/usb-train.cpp
@@ -141,6 +141,27 @@ namespace usb_pad
 		return true;
 	}
 
+	void TrainDevice::UpdateSettings(USBDevice* dev, SettingsInterface& si) const
+	{
+		TrainDeviceState* s = USB_CONTAINER_OF(dev, TrainDeviceState, dev);
+
+		s->passthrough = USB::GetConfigBool(si, s->port, TypeName(), "Passthrough", false);
+	}
+
+	std::span<const SettingInfo> TrainDevice::Settings(u32 subtype) const
+	{
+		static constexpr const SettingInfo passthrough = {
+			SettingInfo::Type::Boolean,
+			"Passthrough",
+			TRANSLATE_NOOP("USB", "Axes Passthrough"),
+			TRANSLATE_NOOP("USB", "Passes through the unprocessed input axis to the game. Enable if you are using a compatible Densha De Go! controller. Disable if you are using any other joystick."),
+			"false",
+		};
+
+		static constexpr const SettingInfo info[] = {passthrough};
+		return info;
+	}
+
 	static constexpr u32 button_mask(u32 bind_index)
 	{
 		return (1u << (bind_index - TrainControlID::BUTTONS_OFFSET));
@@ -444,8 +465,8 @@ namespace usb_pad
 			{
 				TrainConData_Type2 out = {};
 				out.control = 0x1;
-				out.brake = dct01_brake(s->data.brake);
-				out.power = dct01_power(s->data.power);
+				out.brake = s->passthrough ? s->data.brake : dct01_brake(s->data.brake);
+				out.power = s->passthrough ? s->data.power : dct01_power(s->data.power);
 				out.horn = 0xFF; // Button C doubles as horn.
 				out.hat = s->data.hatswitch;
 				out.buttons = dct01_buttons(s->data.buttons);
@@ -455,8 +476,8 @@ namespace usb_pad
 			case TRAIN_SHINKANSEN:
 			{
 				TrainConData_Shinkansen out = {};
-				out.brake = dct02_brake(s->data.brake);
-				out.power = dct02_power(s->data.power);
+				out.brake = s->passthrough ? s->data.brake : dct02_brake(s->data.brake);
+				out.power = s->passthrough ? s->data.power : dct02_power(s->data.power);
 				out.horn = 0xFF; // Button C doubles as horn, skip.
 				out.hat = s->data.hatswitch;
 				out.buttons = dct02_buttons(s->data.buttons);
@@ -466,8 +487,8 @@ namespace usb_pad
 			case TRAIN_RYOJOUHEN:
 			{
 				TrainConData_Ryojouhen out = {};
-				out.brake = dct03_brake(s->data.brake);
-				out.power = dct03_power(s->data.power);
+				out.brake = s->passthrough ? s->data.brake : dct03_brake(s->data.brake);
+				out.power = s->passthrough ? s->data.power : dct03_power(s->data.power);
 				out.horn = 0xFF; // Dedicated horn button, skip.
 				out.hat = s->data.hatswitch & 0x0F;
 				out.buttons = dct03_buttons(s->data.buttons);
@@ -524,6 +545,7 @@ namespace usb_pad
 		usb_desc_init(&s->dev);
 		usb_ep_init(&s->dev);
 		train_handle_reset(&s->dev);
+		UpdateSettings(&s->dev, si);
 
 		return &s->dev;
 
diff --git a/pcsx2/USB/usb-pad/usb-train.h b/pcsx2/USB/usb-pad/usb-train.h
index 29a8ec03f3..f63c2d70df 100644
--- a/pcsx2/USB/usb-pad/usb-train.h
+++ b/pcsx2/USB/usb-pad/usb-train.h
@@ -24,6 +24,8 @@ namespace usb_pad
 		const char* Name() const override;
 		const char* TypeName() const override;
 		std::span<const char*> SubTypes() const override;
+		void UpdateSettings(USBDevice* dev, SettingsInterface& si) const override;
+		std::span<const SettingInfo> Settings(u32 subtype) const override;
 		float GetBindingValue(const USBDevice* dev, u32 bind_index) const override;
 		void SetBindingValue(USBDevice* dev, u32 bind_index, float value) const override;
 		std::span<const InputBindingInfo> Bindings(u32 subtype) const override;
@@ -79,6 +81,7 @@ namespace usb_pad
 
 		u32 port = 0;
 		TrainDeviceTypes type = TRAIN_TYPE2;
+		bool passthrough = false;
 
 		struct
 		{