From 4d24f160e300adadc94ad9491f24f43d82ee3847 Mon Sep 17 00:00:00 2001
From: Jordan Woyak <jordan.woyak@gmail.com>
Date: Sun, 10 Nov 2019 08:12:31 -0600
Subject: [PATCH] WiimoteEmu: Minor accuracy fixes.

---
 .../Core/HW/WiimoteCommon/WiimoteConstants.h    | 12 +++++++++---
 .../Core/Core/HW/WiimoteEmu/EmuSubroutines.cpp  | 17 ++++++++++++-----
 2 files changed, 21 insertions(+), 8 deletions(-)

diff --git a/Source/Core/Core/HW/WiimoteCommon/WiimoteConstants.h b/Source/Core/Core/HW/WiimoteCommon/WiimoteConstants.h
index 02313ac048..99cf0e04e7 100644
--- a/Source/Core/Core/HW/WiimoteCommon/WiimoteConstants.h
+++ b/Source/Core/Core/HW/WiimoteCommon/WiimoteConstants.h
@@ -62,16 +62,22 @@ enum class AddressSpace : u8
   // FYI: The EEPROM address space is offset 0x0070 on i2c slave 0x50.
   // However attempting to access this device directly results in an error.
   EEPROM = 0x00,
-  // 0x01 is never used but it does function on a real wiimote:
-  I2CBusAlt = 0x01,
-  I2CBus = 0x02,
+  // I2CBusAlt is never used by games but it does function on a real wiimote.
+  I2CBus = 0x01,
+  I2CBusAlt = 0x02,
 };
 
 enum class ErrorCode : u8
 {
+  // Normal result.
   Success = 0,
+  // Produced by read/write attempts during an active read.
+  Busy = 4,
+  // Produced by using something other than the above AddressSpace values.
   InvalidSpace = 6,
+  // Produced by an i2c read/write with a non-responding slave address.
   Nack = 7,
+  // Produced by accessing invalid regions of EEPROM or the EEPROM directly over i2c.
   InvalidAddress = 8,
 };
 
diff --git a/Source/Core/Core/HW/WiimoteEmu/EmuSubroutines.cpp b/Source/Core/Core/HW/WiimoteEmu/EmuSubroutines.cpp
index 5a11782d63..76d5848336 100644
--- a/Source/Core/Core/HW/WiimoteEmu/EmuSubroutines.cpp
+++ b/Source/Core/Core/HW/WiimoteEmu/EmuSubroutines.cpp
@@ -258,7 +258,12 @@ void Wiimote::HandleRequestStatus(const OutputReportRequestStatus&)
 
 void Wiimote::HandleWriteData(const OutputReportWriteData& wd)
 {
-  // TODO: Are writes ignored during an active read request?
+  if (m_read_request.size)
+  {
+    // FYI: Writes during an active read will occasionally produce a "busy" (0x4) ack.
+    // We won't simulate that as it often does work. Poorly programmed games may rely on it.
+    WARN_LOG(WIIMOTE, "WriteData: write during active read request.");
+  }
 
   u16 address = Common::swap16(wd.address);
 
@@ -416,9 +421,11 @@ void Wiimote::HandleReadData(const OutputReportReadData& rd)
 {
   if (m_read_request.size)
   {
-    // There is already an active read request.
-    // A real wiimote ignores the new one.
-    WARN_LOG(WIIMOTE, "ReadData: ignoring read during active request.");
+    // There is already an active read being processed.
+    WARN_LOG(WIIMOTE, "ReadData: attempting read during active request.");
+
+    // A real wm+ sends a busy ack in this situation.
+    SendAck(OutputReportID::ReadData, ErrorCode::Busy);
     return;
   }
 
@@ -437,7 +444,7 @@ void Wiimote::HandleReadData(const OutputReportReadData& rd)
   // TODO: should this be removed and let Update() take care of it?
   ProcessReadDataRequest();
 
-  // FYI: No "ACK" is sent.
+  // FYI: No "ACK" is sent under normal situations.
 }
 
 bool Wiimote::ProcessReadDataRequest()