LibUsbDotNet SymbolicName Error

Question

i can't read out the SymbolicName from the LibUsb. This is some example code:

static void Main(string[] args)
{
var devs = UsbDevice.AllDevices;
foreach (UsbRegistry usbRegistry in devs)
{
    String name = usbRegistry.SymbolicName;
}
Console.ReadLine();
UsbDevice.Exit();
}

The string name does not contain the right symbolic name. I have no idea why.

The problem seems to be in the LibUsbRegistry.cs. The function:

internal ErrorCode GetCustomDeviceKeyValue(SafeFileHandle usbHandle, string key, out byte[] propData, int maxDataLength)

calls the LibUsbDriverIO.UsbIOSync whith the Parameter: LibUsbIoCtl.GET_CUSTOM_REG_PROPERTY and in the LibUsbDriverIO.cs the function UsbIOSync calls the Kernel32.DeviceIoControlAsObject. This function return false.

Some Code:

LibUsbRegistry:

bool bSuccess = LibUsbDriverIO.UsbIOSync(usbHandle,
                                                 LibUsbIoCtl.GET_CUSTOM_REG_PROPERTY,
                                                 bytesReq,
                                                 bytesReq.Length,
                                                 gcbytesReq.AddrOfPinnedObject(),
                                                 bytesReq.Length,
                                                 out iReturnBytes);

LibUsbDriverIO:

!Kernel32.DeviceIoControlAsObject(dev, code, inBuffer, inSize, outBuffer, outSize, ref ret, deviceIoOverlapped.GlobalOverlapped)

The problem just appears with the LibUsbIoCtl.GET_CUSTOM_REG_PROPERTY. But this all is precompiled code from LibUsb .. so why is't it possible to read out the symbolic name.

Answer 1

You should interpret that as "there is no SymbolicName". You can correlate what you get with the content of the registry. Start Regedit.exe and navigate to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\USB. You'll see the VID&PID keys for devices your machine as seen. The interface subkey has the "Device Parameters" subkey which contains the "SymbolicName" value.

I've got several on my machine that don't have that value. You'd expect this for the kind of USB driver that provides an alternative way to talk to the device, like a serial port emulator for example.