title: Why do some devices not enumerate with SetupDiGetDeviceInterfaceDetail()?
body: <p>I am maintaining an application that uses SetupDiGetDeviceInterfaceDetail() to find out information on the installed serial ports on the computer.  I have noticed while testing this that there are some devices, such as my Lucent WinModem, that do not show up in that enumeration.  It turns out that I am having a similar issue with a set of devices manufactured by my company that implement the serial port interface.  My assumption is that there is something that is missing from the INF file for the device.  Does anyone know what kinds of conditions can result in this kind of omission?</p>
  
  <p>Edit: Here is a sample of the code that I am using to enumerate the serial ports.  I have tried various combinations of flags but have not seen any significant difference in behaviour.</p>
  
  <pre><code>DEFINE_GUID(GUID_CLASS_COMPORT, 0x4d36e978, 0xe325, 0x11ce, 0xbf, 0xc1, \
              0x08, 0x00, 0x2b, 0xe1, 0x03, 0x18);
  
  
  GUID *serial_port_guid = const_cast&lt;GUID *&gt;(&amp;GUID_CLASS_COMPORT);
  HDEVINFO device_info = INVALID_HANDLE_VALUE;
  SP_DEVICE_INTERFACE_DETAIL_DATA *detail_data = 0;
  
  device_info = SetupDiGetClassDevs(
     serial_port_guid, 0, 0, DIGCF_PRESENT | DIGCF_DEVICEINTERFACE);
  if(device_info != INVALID_HANDLE_VALUE)
  {
     uint4 const detail_data_size = sizeof(SP_DEVICE_INTERFACE_DETAIL_DATA) + 256;
     detail_data = reinterpret_cast&lt;SP_DEVICE_INTERFACE_DETAIL_DATA *&gt;(new char[detail_data_size]);
     SP_DEVICE_INTERFACE_DATA ifc_data;
     bool more_interfaces = true;
     int rcd;
     memset(&amp;ifc_data, 0, sizeof(ifc_data)); 
     memset(detail_data, 0, detail_data_size);
     ifc_data.cbSize = sizeof(ifc_data);
     detail_data-&gt;cbSize = sizeof(SP_DEVICE_INTERFACE_DETAIL_DATA);
     for(uint4 index = 0; more_interfaces; ++index)
     {
        rcd = SetupDiEnumDeviceInterfaces(device_info, 0, serial_port_guid, index, &amp;ifc_data);
        if(rcd)
        {
           // we need to get the details of this device
           SP_DEVINFO_DATA device_data = { sizeof(SP_DEVINFO_DATA) };
           rcd = SetupDiGetDeviceInterfaceDetail(
              device_info, &amp;ifc_data, detail_data, detail_data_size, 0, &amp;device_data);
           if(rcd)
           {
              StrAsc device_path(detail_data-&gt;DevicePath);
              byte friendly_name[256];
  
              rcd = SetupDiGetDeviceRegistryProperty(
                 device_info, &amp;device_data, SPDRP_FRIENDLYNAME, 0, friendly_name, sizeof(friendly_name), 0);
              if(rcd)
              {
                 std::for_each(
                    port_names.begin(),
                    port_names.end(),
                    update_friendly_name(
                       reinterpret_cast&lt;char const *&gt;(friendly_name)));
              }
           }
           else
              more_interfaces = false;
        }
     }
  }
  </code></pre>