Add hotplug support for USB devices

Author: sthenic

include/hotplug_linux.h

@@ -17,6 +17,7 @@ class HotplugLinux : public Hotplug
     struct udev *m_handle;
     int m_nof_devices;
 
+    int Enumerate(const char *subsystem, const char *sysattr, const char *value);
     void CheckForEvents();
     int CreateHandle();
     void DestroyHandle();

include/hotplug_windows.h

@@ -17,9 +17,11 @@ class HotplugWindows : public Hotplug
     void MainLoop() override;
 
 private:
-    static constexpr char *GUID = "{46c58a4e-05fb-441e-84f5-55aa37e4b412}";
+    static constexpr char *GUID_PCI = "{46c58a4e-05fb-441e-84f5-55aa37e4b412}";
+    static constexpr char *GUID_USB = "{9f4ef953-49da-47a0-a3e9-820fbfad4a24}";
     size_t m_nof_devices;
 
     static std::vector<std::string> SplitDeviceList(const std::string &list);
+    size_t Enumerate(const char *guid);
     void CheckForEvents();
 };

src/hotplug_linux.cpp

@@ -21,20 +21,19 @@ HotplugLinux::~HotplugLinux()
     Stop();
 }
 
-void HotplugLinux::CheckForEvents()
+int HotplugLinux::Enumerate(const char *subsystem, const char *sysattr, const char *value)
 {
     struct udev_enumerate *enumerator = udev_enumerate_new(m_handle);
     try
     {
-        /* Filter the PCI subsystem for devices w/ vendor id 0x1b37. */
         if (enumerator == NULL)
             throw HotplugLinuxException("Failed to create libudev enumerator.");
 
-        if (udev_enumerate_add_match_subsystem(enumerator, "pci") < 0)
-            throw HotplugLinuxException("Failed to add libudev enumerator filter.");
+        if (udev_enumerate_add_match_subsystem(enumerator, subsystem) < 0)
+            throw HotplugLinuxException("Failed to add libudev enumerator subsystem filter.");
 
-        if (udev_enumerate_add_match_sysattr(enumerator, "vendor", "0x1b37") < 0)
-            throw HotplugLinuxException("Failed to add libudev enumerator vendor filter.");
+        if (udev_enumerate_add_match_sysattr(enumerator, sysattr, value) < 0)
+            throw HotplugLinuxException("Failed to add libudev enumerator sysattr filter.");
 
         udev_enumerate_scan_devices(enumerator);
 
@@ -44,22 +43,32 @@ void HotplugLinux::CheckForEvents()
         udev_list_entry_foreach(entry, devices)
             nof_devices++;
 
-        if (nof_devices > m_nof_devices)
-            _EmplaceMessage(HotplugEvent::CONNECT);
-        else if (nof_devices < m_nof_devices)
-            _EmplaceMessage(HotplugEvent::DISCONNECT);
-
-        m_nof_devices = nof_devices;
         udev_enumerate_unref(enumerator);
+        return nof_devices;
     }
     catch (const HotplugLinuxException& e)
     {
         if (enumerator != NULL)
             udev_enumerate_unref(enumerator);
         Log::log->error(e.what());
+        return 0;
     }
 }
 
+void HotplugLinux::CheckForEvents()
+{
+    /* Filter the PCI subsystem for devices with vendor id 0x1b37 and the USB
+       subsystem for devices with vendor id 0x1d73. */
+    int nof_devices = Enumerate("pci", "vendor", "0x1b37") + Enumerate("usb", "idVendor", "1d73");
+
+    if (nof_devices > m_nof_devices)
+        _EmplaceMessage(HotplugEvent::CONNECT);
+    else if (nof_devices < m_nof_devices)
+        _EmplaceMessage(HotplugEvent::DISCONNECT);
+
+    m_nof_devices = nof_devices;
+}
+
 int HotplugLinux::CreateHandle()
 {
     if (m_handle != NULL)

src/hotplug_windows.cpp

@@ -33,44 +33,50 @@ std::vector<std::string> HotplugWindows::SplitDeviceList(const std::string &list
     return result;
 }
 
-void HotplugWindows::CheckForEvents()
+size_t HotplugWindows::Enumerate(const char *guid);
 {
     /* We check for events by polling the Windows kernel for devices
          - present on the system; and
-         - matching the setup class GUID for a TSPD digitizer.
-
-       We simply take the difference between the number of devices we got in the
-       last call and the number we get from a new call. This obviously misses
-       the case when a digitizer gets removed and added between polling events
-       but that's so rare that it basically shouldn't happen in practice. */
+         - matching the target setup class GUID. */
 
     const ULONG LIST_FLAGS = CM_GETIDLIST_FILTER_CLASS | CM_GETIDLIST_FILTER_PRESENT;
     ULONG list_size = 0;
 
-    CONFIGRET result = CM_Get_Device_ID_List_SizeA(&list_size, GUID, LIST_FLAGS);
+    CONFIGRET result = CM_Get_Device_ID_List_SizeA(&list_size, guid, LIST_FLAGS);
     if (result != CR_SUCCESS)
     {
         Log::log->error("CM_Get_Device_ID_List_SizeA failed, code {}.", result);
-        return;
+        return 0;
     }
 
     /* Allocate a string of the prescribed size (includes the NULL terminator). */
     auto list = std::string(list_size, '\0');
 
-    result = CM_Get_Device_ID_ListA(GUID, (PZZSTR)list.data(), (ULONG)list.capacity(), LIST_FLAGS);
+    result = CM_Get_Device_ID_ListA(guid, (PZZSTR)list.data(), (ULONG)list.capacity(), LIST_FLAGS);
     if (result != CR_SUCCESS)
     {
         Log::log->error("CM_Get_Device_ID_ListA failed, code {}.", result);
-        return;
+        return 0;
     }
 
-    auto devices = std::move(SplitDeviceList(list));
-    if (devices.size() > m_nof_devices)
+    return SplitDeviceList(list).size();
+}
+
+void HotplugWindows::CheckForEvents()
+{
+    size_t nof_devices = Enumerate(GUID_PCI) + Enumerate(GUID_USB);
+
+    /* We simply take the difference between the number of devices we got in the
+       last call and the number we get from a new call. This obviously misses
+       the case when a digitizer gets removed and added between polling events
+       but that's so rare that it basically shouldn't happen in practice. */
+
+    if (nof_devices > m_nof_devices)
         _EmplaceMessage(HotplugEvent::CONNECT);
-    else if (devices.size() < m_nof_devices)
+    else if (nof_devices < m_nof_devices)
         _EmplaceMessage(HotplugEvent::DISCONNECT);
 
-    m_nof_devices = devices.size();
+    m_nof_devices = nof_devices;
 }
 
 void HotplugWindows::MainLoop()