libusb中的热插拔使用举例

以下为判断usb设备是插入还是拔出状态(热插拔)的测试代码： 在Windows下是不支持的，在Linux是支持的，下一个版本可能会支持Windows下的热插拔：

  

   

    

     

    
    

     

      #include <chrono>
     
    
   

    

     

    
    

     

      #include <thread>
     
    
   

    

     

    
    

     

      #include <iostream>
     
    
   

    

     

    
    

     

      #include <libusb.h>
     
    
   

    

     

    
    

     
 
     
    
   

    

     

    
    

     

      namespace {
     
    
   

    

     

    
    

     
 
     
    
   

    

     

    
    

     

      bool running = 
      true;
     
    
   

    

     

    
    

     
 
     
    
   

    

     

    
    

     

      int LIBUSB_CALL hotplug_callback(libusb_context* ctx, libusb_device* dev, libusb_hotplug_event event, void* user_data)
     
    
   

    

     

    
    

     

      {
     
    
   

    

     

    
    

     
	
      struct libusb_device_descriptor desc;
     
    
   

    

     

    
    

     
	
      int ret = libusb_get_device_descriptor(dev, &desc);
     
    
   

    

     

    
    

     
	
      if (LIBUSB_SUCCESS != ret) {
     
    
   

    

     

    
    

     
		
      fprintf(
      stderr, 
      "fail to get device descriptor: %d, %s\n", ret, libusb_error_name(ret));
     
    
   

    

     

    
    

     
		
      //return -1;
     
    
   

    

     

    
    

     

      	}
     
    
   

    

     

    
    

     
 
     
    
   

    

     

    
    

     
	
      if (event == LIBUSB_HOTPLUG_EVENT_DEVICE_ARRIVED)
     
    
   

    

     

    
    

     
		
      fprintf(
      stdout, 
      "device attached: %04x:%04x\n", desc.idVendor, desc.idProduct);
     
    
   

    

     

    
    

     
	
      else 
      if (event == LIBUSB_HOTPLUG_EVENT_DEVICE_LEFT)
     
    
   

    

     

    
    

     
		
      fprintf(
      stdout, 
      "device detached: %04x:%04x\n", desc.idVendor, desc.idProduct);
     
    
   

    

     

    
    

     
	
      else
     
    
   

    

     

    
    

     
		
      fprintf(
      stderr, 
      "Error: unsupported hotplug events\n");
     
    
   

    

     

    
    

     
 
     
    
   

    

     

    
    

     
	
      return 
      0;
     
    
   

    

     

    
    

     

      }
     
    
   

    

     

    
    

     
 
     
    
   

    

     

    
    

     

      void run()
     
    
   

    

     

    
    

     

      {
     
    
   

    

     

    
    

     
	
      for (
      int i = 
      0; i < 
      60; ++i)
     
    
   

    

     

    
    

     
		
      std::this_thread::sleep_for(
      std::chrono::seconds(
      1));
     
    
   

    

     

    
    

     

      	running = 
      false;
     
    
   

    

     

    
    

     

      }
     
    
   

    

     

    
    

     
 
     
    
   

    

     

    
    

     

      } 
      // namespace
     
    
   

    

     

    
    

     
 
     
    
   

    

     

    
    

     

      int test_libusb_hotplug()
     
    
   

    

     

    
    

     

      {
     
    
   

    

     

    
    

     
	
      // reference: examples/hotplugtest.c
     
    
   

    

     

    
    

     

      #ifdef _MSC_VER
     
    
   

    

     

    
    

     
	
      const 
      char* platform = 
      "Windows";
     
    
   

    

     

    
    

     

      #else
     
    
   

    

     

    
    

     
	
      const 
      char* platform = 
      "Linux";
     
    
   

    

     

    
    

     

      #endif
     
    
   

    

     

    
    

     
 
     
    
   

    

     

    
    

     
	
      int ret = libusb_init(
      nullptr);
     
    
   

    

     

    
    

     
	
      if (ret != 
      0) {
     
    
   

    

     

    
    

     
		
      fprintf(
      stderr, 
      "fail to init: %d, %s\n", ret, libusb_error_name(ret));
     
    
   

    

     

    
    

     
		
      return 
      -1;
     
    
   

    

     

    
    

     

      	}
     
    
   

    

     

    
    

     
 
     
    
   

    

     

    
    

     
	
      if (!libusb_has_capability(LIBUSB_CAP_HAS_HOTPLUG)) {
     
    
   

    

     

    
    

     
		
      fprintf(
      stderr, 
      "hotplug capabilites are not supported on this platform: %s\n", platform);
     
    
   

    

     

    
    

     

      		libusb_exit(
      nullptr);
     
    
   

    

     

    
    

     
		
      return 
      -1;
     
    
   

    

     

    
    

     

      	}
     
    
   

    

     

    
    

     
 
     
    
   

    

     

    
    

     
	
      int vendor_id = 
      0x046d, product_id = 
      0x081b;
     
    
   

    

     

    
    

     

      	libusb_hotplug_callback_handle hp[
      2];
     
    
   

    

     

    
    

     

      	ret = libusb_hotplug_register_callback(
      nullptr, LIBUSB_HOTPLUG_EVENT_DEVICE_ARRIVED, LIBUSB_HOTPLUG_NO_FLAGS, vendor_id,
     
    
   

    

     

    
    

     

      		product_id, LIBUSB_HOTPLUG_MATCH_ANY, hotplug_callback, 
      nullptr, &hp[
      0]);
     
    
   

    

     

    
    

     
	
      if (LIBUSB_SUCCESS != ret) {
     
    
   

    

     

    
    

     
		
      fprintf(
      stderr, 
      "fail to register callback arrived: %d, %s\n", ret, libusb_error_name(ret));
     
    
   

    

     

    
    

     

      		libusb_exit(
      nullptr);
     
    
   

    

     

    
    

     
		
      return 
      -1;
     
    
   

    

     

    
    

     

      	}
     
    
   

    

     

    
    

     
 
     
    
   

    

     

    
    

     

      	ret = libusb_hotplug_register_callback(
      nullptr, LIBUSB_HOTPLUG_EVENT_DEVICE_LEFT, LIBUSB_HOTPLUG_NO_FLAGS, vendor_id,
     
    
   

    

     

    
    

     

      		product_id, LIBUSB_HOTPLUG_MATCH_ANY, hotplug_callback, 
      nullptr, &hp[
      1]);
     
    
   

    

     

    
    

     
	
      if (LIBUSB_SUCCESS != ret) {
     
    
   

    

     

    
    

     
		
      fprintf(
      stderr, 
      "fail to register callback left: %d, %s\n", ret, libusb_error_name(ret));
     
    
   

    

     

    
    

     

      		libusb_exit(
      nullptr);
     
    
   

    

     

    
    

     
		
      return 
      -1;
     
    
   

    

     

    
    

     

      	}
     
    
   

    

     

    
    

     
 
     
    
   

    

     

    
    

     
	
      std::
      thread th(run);
     
    
   

    

     

    
    

     
 
     
    
   

    

     

    
    

     
	
      while (running) {
     
    
   

    

     

    
    

     
		
      //ret = libusb_handle_events(nullptr);
     
    
   

    

     

    
    

     

      		timeval tv = {
      1, 
      0};
     
    
   

    

     

    
    

     

      		ret = libusb_handle_events_timeout(
      nullptr, &tv);
     
    
   

    

     

    
    

     
		
      if (ret < 
      0)
     
    
   

    

     

    
    

     
			
      fprintf(
      stderr, 
      "fail to libusb_handle_events: %d, %s\n", ret, libusb_error_name(ret));
     
    
   

    

     

    
    

     

      	}
     
    
   

    

     

    
    

     
 
     
    
   

    

     

    
    

     

      	libusb_exit(
      nullptr);
     
    
   

    

     

    
    

     

      	th.join();
     
    
   

    

     

    
    

     
 
     
    
   

    

     

    
    

     
	
      return 
      0;
     
    
   

    

     

    
    

     

      }
     
    
  

在Windows下执行结果如下：

在Linux下执行结果如下：对usb视频设备进行反复插拔

GitHub：https://github.com//fengbingchun/OpenCV_Test