Use a single libusb context

libusb on Windows is limited to only a single context. Trying to open
more than one can cause device enumerations to fail randomly.

libusb is thread-safe and we don't use the manual polling support (with
`poll()`) so this should be safe.

Source/Core/Common/CMakeLists.txt

@@ -34,6 +34,11 @@ set(SRCS Analytics.cpp
          Crypto/ec.cpp
          Logging/LogManager.cpp)
 
+if(LIBUSB_FOUND)
+	set(LIBS ${LIBS} ${LIBUSB_LIBRARIES})
+	set(SRCS ${SRCS} LibusbContext.cpp)
+endif(LIBUSB_FOUND)
+
 if(ANDROID)
 	set(SRCS ${SRCS}
 	         Logging/ConsoleListenerDroid.cpp)

Source/Core/Common/Common.vcxproj

@@ -113,6 +113,7 @@
     <ClInclude Include="Hash.h" />
     <ClInclude Include="IniFile.h" />
     <ClInclude Include="JitRegister.h" />
+    <ClInclude Include="LibusbContext.h" />
     <ClInclude Include="LinearDiskCache.h" />
     <ClInclude Include="MathUtil.h" />
     <ClInclude Include="MD5.h" />
@@ -159,6 +160,9 @@
     <ClCompile Include="Hash.cpp" />
     <ClCompile Include="IniFile.cpp" />
     <ClCompile Include="JitRegister.cpp" />
+    <ClCompile Include="LibusbContext.cpp">
+      <DisableSpecificWarnings>4200;%(DisableSpecificWarnings)</DisableSpecificWarnings>
+    </ClCompile>
     <ClCompile Include="Logging\ConsoleListenerWin.cpp" />
     <ClCompile Include="MathUtil.cpp" />
     <ClCompile Include="MD5.cpp" />

Source/Core/Common/Common.vcxproj.filters

@@ -45,6 +45,7 @@
     <ClInclude Include="FPURoundMode.h" />
     <ClInclude Include="Hash.h" />
     <ClInclude Include="IniFile.h" />
+    <ClInclude Include="LibusbContext.h" />
     <ClInclude Include="LinearDiskCache.h" />
     <ClInclude Include="MathUtil.h" />
     <ClInclude Include="MemArena.h" />
@@ -236,6 +237,7 @@
     <ClCompile Include="FileUtil.cpp" />
     <ClCompile Include="Hash.cpp" />
     <ClCompile Include="IniFile.cpp" />
+    <ClCompile Include="LibusbContext.cpp" />
     <ClCompile Include="MathUtil.cpp" />
     <ClCompile Include="MemArena.cpp" />
     <ClCompile Include="MemoryUtil.cpp" />

Source/Core/Common/LibusbContext.cpp

@@ -0,0 +1,46 @@
+// Copyright 2017 Dolphin Emulator Project
+// Licensed under GPLv2+
+// Refer to the license.txt file included.
+
+#include <libusb.h>
+#include <memory>
+#include <mutex>
+
+#include "Common/LibusbContext.h"
+#include "Common/MsgHandler.h"
+
+namespace LibusbContext
+{
+static std::shared_ptr<libusb_context> s_libusb_context;
+static std::once_flag s_context_initialized;
+
+static libusb_context* Create()
+{
+  libusb_context* context;
+  const int ret = libusb_init(&context);
+  if (ret < LIBUSB_SUCCESS)
+  {
+    bool is_windows = false;
+#ifdef _WIN32
+    is_windows = true;
+#endif
+    if (is_windows && ret == LIBUSB_ERROR_NOT_FOUND)
+      PanicAlertT("Failed to initialize libusb because usbdk is not installed.");
+    else
+      PanicAlertT("Failed to initialize libusb: %s", libusb_error_name(ret));
+    return nullptr;
+  }
+  return context;
+}
+
+std::shared_ptr<libusb_context> Get()
+{
+  std::call_once(s_context_initialized, []() {
+    s_libusb_context.reset(Create(), [](auto* context) {
+      if (context != nullptr)
+        libusb_exit(context);
+    });
+  });
+  return s_libusb_context;
+}
+}

Source/Core/Common/LibusbContext.h

@@ -0,0 +1,15 @@
+// Copyright 2017 Dolphin Emulator Project
+// Licensed under GPLv2+
+// Refer to the license.txt file included.
+
+#include <memory>
+
+struct libusb_context;
+
+namespace LibusbContext
+{
+// libusb on Windows is limited to only a single context. Trying to open more
+// than one can cause issues with device enumerations.
+// libusb is thread-safe so this context can be safely used from different threads.
+std::shared_ptr<libusb_context> Get();
+}

Source/Core/Core/IOS/USB/Bluetooth/BTReal.cpp

@@ -16,6 +16,7 @@
 #include "Common/Assert.h"
 #include "Common/ChunkFile.h"
 #include "Common/CommonFuncs.h"
+#include "Common/LibusbContext.h"
 #include "Common/Logging/Log.h"
 #include "Common/MsgHandler.h"
 #include "Common/Network.h"
@@ -59,8 +60,8 @@ namespace Device
 BluetoothReal::BluetoothReal(u32 device_id, const std::string& device_name)
     : BluetoothBase(device_id, device_name)
 {
-  const int ret = libusb_init(&m_libusb_context);
-  _assert_msg_(IOS_WIIMOTE, ret == 0, "Failed to init libusb.");
+  m_libusb_context = LibusbContext::Get();
+  _assert_msg_(IOS_WIIMOTE, m_libusb_context, "Failed to init libusb.");
 
   LoadLinkKeys();
 }
@@ -78,15 +79,13 @@ BluetoothReal::~BluetoothReal()
     libusb_unref_device(m_device);
   }
 
-  libusb_exit(m_libusb_context);
-
   SaveLinkKeys();
 }
 
 ReturnCode BluetoothReal::Open(const OpenRequest& request)
 {
   libusb_device** list;
-  const ssize_t cnt = libusb_get_device_list(m_libusb_context, &list);
+  const ssize_t cnt = libusb_get_device_list(m_libusb_context.get(), &list);
   _dbg_assert_msg_(IOS, cnt > 0, "Couldn't get device list");
   for (ssize_t i = 0; i < cnt; ++i)
   {
@@ -601,7 +600,7 @@ void BluetoothReal::TransferThread()
   Common::SetCurrentThreadName("BT USB Thread");
   while (m_thread_running.IsSet())
   {
-    libusb_handle_events_completed(m_libusb_context, nullptr);
+    libusb_handle_events_completed(m_libusb_context.get(), nullptr);
   }
 }
 

Source/Core/Core/IOS/USB/Bluetooth/BTReal.h

@@ -76,7 +76,7 @@ private:
 
   libusb_device* m_device = nullptr;
   libusb_device_handle* m_handle = nullptr;
-  libusb_context* m_libusb_context = nullptr;
+  std::shared_ptr<libusb_context> m_libusb_context;
 
   Common::Flag m_thread_running;
   std::thread m_thread;

Source/Core/Core/IOS/USB/Host.cpp

@@ -13,6 +13,7 @@
 #include "Common/Assert.h"
 #include "Common/ChunkFile.h"
 #include "Common/CommonTypes.h"
+#include "Common/LibusbContext.h"
 #include "Common/Logging/Log.h"
 #include "Common/Thread.h"
 #include "Core/ConfigManager.h"
@@ -30,16 +31,8 @@ namespace Device
 USBHost::USBHost(u32 device_id, const std::string& device_name) : Device(device_id, device_name)
 {
 #ifdef __LIBUSB__
-  const int ret = libusb_init(&m_libusb_context);
-  _assert_msg_(WII_IPC_USB, ret == 0, "Failed to init libusb.");
-  libusb_set_debug(m_libusb_context, LIBUSB_LOG_LEVEL_WARNING);
-#endif
-}
-
-USBHost::~USBHost()
-{
-#ifdef __LIBUSB__
-  libusb_exit(m_libusb_context);
+  m_libusb_context = LibusbContext::Get();
+  _assert_msg_(IOS_USB, m_libusb_context, "Failed to init libusb.");
 #endif
 }
 
@@ -125,7 +118,7 @@ bool USBHost::AddNewDevices(std::set<u64>& new_devices, DeviceChangeHooks& hooks
 {
 #ifdef __LIBUSB__
   libusb_device** list;
-  const ssize_t count = libusb_get_device_list(m_libusb_context, &list);
+  const ssize_t count = libusb_get_device_list(m_libusb_context.get(), &list);
   if (count < 0)
   {
     WARN_LOG(IOS_USB, "Failed to get device list: %s", libusb_error_name(static_cast<int>(count)));
@@ -210,7 +203,7 @@ void USBHost::StartThreads()
       while (m_event_thread_running.IsSet())
       {
         static timeval tv = {0, 50000};
-        libusb_handle_events_timeout_completed(m_libusb_context, &tv, nullptr);
+        libusb_handle_events_timeout_completed(m_libusb_context.get(), &tv, nullptr);
       }
     });
   }

Source/Core/Core/IOS/USB/Host.h

@@ -34,7 +34,7 @@ class USBHost : public Device
 {
 public:
   USBHost(u32 device_id, const std::string& device_name);
-  virtual ~USBHost();
+  virtual ~USBHost() = default;
 
   ReturnCode Open(const OpenRequest& request) override;
 
@@ -71,7 +71,7 @@ private:
   void DispatchHooks(const DeviceChangeHooks& hooks);
 
 #ifdef __LIBUSB__
-  libusb_context* m_libusb_context = nullptr;
+  std::shared_ptr<libusb_context> m_libusb_context;
   // Event thread for libusb
   Common::Flag m_event_thread_running;
   std::thread m_event_thread;

Source/Core/InputCommon/GCAdapter.cpp

@@ -4,9 +4,11 @@
 
 #include <algorithm>
 #include <libusb.h>
+#include <memory>
 #include <mutex>
 
 #include "Common/Flag.h"
+#include "Common/LibusbContext.h"
 #include "Common/Logging/Log.h"
 #include "Common/Thread.h"
 #include "Core/ConfigManager.h"
@@ -50,7 +52,7 @@ static Common::Flag s_adapter_detect_thread_running;
 static std::function<void(void)> s_detect_callback;
 
 static bool s_libusb_driver_not_supported = false;
-static libusb_context* s_libusb_context = nullptr;
+static std::shared_ptr<libusb_context> s_libusb_context;
 #if defined(__FreeBSD__) && __FreeBSD__ >= 11
 static bool s_libusb_hotplug_enabled = true;
 #else
@@ -116,8 +118,8 @@ static void ScanThreadFunc()
   if (s_libusb_hotplug_enabled)
   {
     if (libusb_hotplug_register_callback(
-            s_libusb_context, (libusb_hotplug_event)(LIBUSB_HOTPLUG_EVENT_DEVICE_ARRIVED |
-                                                     LIBUSB_HOTPLUG_EVENT_DEVICE_LEFT),
+            s_libusb_context.get(), (libusb_hotplug_event)(LIBUSB_HOTPLUG_EVENT_DEVICE_ARRIVED |
+                                                           LIBUSB_HOTPLUG_EVENT_DEVICE_LEFT),
             LIBUSB_HOTPLUG_ENUMERATE, 0x057e, 0x0337, LIBUSB_HOTPLUG_MATCH_ANY, HotplugCallback,
             nullptr, &s_hotplug_handle) != LIBUSB_SUCCESS)
       s_libusb_hotplug_enabled = false;
@@ -131,7 +133,7 @@ static void ScanThreadFunc()
     if (s_libusb_hotplug_enabled)
     {
       static timeval tv = {0, 500000};
-      libusb_handle_events_timeout(s_libusb_context, &tv);
+      libusb_handle_events_timeout(s_libusb_context.get(), &tv);
     }
     else
     {
@@ -168,11 +170,9 @@ void Init()
 
   s_libusb_driver_not_supported = false;
 
-  int ret = libusb_init(&s_libusb_context);
-
-  if (ret)
+  s_libusb_context = LibusbContext::Get();
+  if (!s_libusb_context)
   {
-    ERROR_LOG(SERIALINTERFACE, "libusb_init failed with error: %d", ret);
     s_libusb_driver_not_supported = true;
     Shutdown();
   }
@@ -203,7 +203,7 @@ void StopScanThread()
 static void Setup()
 {
   libusb_device** list;
-  ssize_t cnt = libusb_get_device_list(s_libusb_context, &list);
+  ssize_t cnt = libusb_get_device_list(s_libusb_context.get(), &list);
 
   for (int i = 0; i < MAX_SI_CHANNELS; i++)
   {
@@ -335,16 +335,11 @@ void Shutdown()
   StopScanThread();
 #if defined(LIBUSB_API_VERSION) && LIBUSB_API_VERSION >= 0x01000102
   if (s_libusb_hotplug_enabled)
-    libusb_hotplug_deregister_callback(s_libusb_context, s_hotplug_handle);
+    libusb_hotplug_deregister_callback(s_libusb_context.get(), s_hotplug_handle);
 #endif
   Reset();
 
-  if (s_libusb_context)
-  {
-    libusb_exit(s_libusb_context);
-    s_libusb_context = nullptr;
-  }
-
+  s_libusb_context.reset();
   s_libusb_driver_not_supported = false;
 }
 

Source/Core/UICommon/USBUtils.cpp

@@ -2,8 +2,11 @@
 // Licensed under GPLv2+
 // Refer to the license.txt file included.
 
+#include <memory>
+
 #ifdef __LIBUSB__
 #include <libusb.h>
+#include "Common/LibusbContext.h"
 #endif
 
 #include "Common/CommonTypes.h"
@@ -11,7 +14,7 @@
 #include "UICommon/USBUtils.h"
 
 #ifdef __LIBUSB__
-static libusb_context* s_libusb_context;
+static std::shared_ptr<libusb_context> s_libusb_context;
 #endif
 
 // Because opening and getting the device name from devices is slow, especially on Windows
@@ -36,14 +39,14 @@ namespace USBUtils
 void Init()
 {
 #ifdef __LIBUSB__
-  libusb_init(&s_libusb_context);
+  s_libusb_context = LibusbContext::Get();
 #endif
 }
 
 void Shutdown()
 {
 #ifdef __LIBUSB__
-  libusb_exit(s_libusb_context);
+  s_libusb_context = nullptr;
 #endif
 }
 
@@ -56,7 +59,7 @@ std::map<std::pair<u16, u16>, std::string> GetInsertedDevices()
     return devices;
 
   libusb_device** list;
-  const ssize_t cnt = libusb_get_device_list(s_libusb_context, &list);
+  const ssize_t cnt = libusb_get_device_list(s_libusb_context.get(), &list);
   for (ssize_t i = 0; i < cnt; ++i)
   {
     libusb_device_descriptor descr;