I have a DEVINST, I need the Device Path

Question

I\'m trying to open a WinUSB device that is part of a composite device. I have located the correct child device using cfgmgr32, and have its DEVINST number. In order to open

Answer 1

This function returns a list of NULL-terminated Device Paths (that's what we get from CM_Get_Device_Interface_List)

You need to pass it the DEVINST, and the wanted interface GUID.

Since both the DEVINST and interface GUID are specified, it is highly likely that CM_Get_Device_Interface_List will return a single Device Path for that interface, but technically you should be prepared to get more than one result.

I used this function successfully in production code for getting the Device Interface of a USB HUB (GUID_CLASS_USBHUB): I used the resulting Device Path with CreateFile and opened it succesfully.

It is responsibility of the caller to delete[] the returned list if the function returns successfully (return code 0)

int GetDevInstInterfaces(DEVINST dev, LPGUID interfaceGUID, wchar_t**outIfaces, ULONG* outIfacesLen)
{
    CONFIGRET cres;
    if (!outIfaces)
        return -1;
    if (!outIfacesLen)
        return -2;

    // Get System Device ID
    WCHAR sysDeviceID[256];
    cres = CM_Get_Device_ID(dev, sysDeviceID, sizeof(sysDeviceID) / sizeof(sysDeviceID[0]), 0);
    if (cres != CR_SUCCESS)
        return -11;

    // Get list size
    ULONG ifaceListSize = 0;
    cres = CM_Get_Device_Interface_List_Size(&ifaceListSize, interfaceGUID, sysDeviceID, CM_GET_DEVICE_INTERFACE_LIST_PRESENT);
    if (cres != CR_SUCCESS)
        return -12;

    // Allocate memory for the list
    wchar_t* ifaceList = new wchar_t[ifaceListSize];

    // Populate the list
    cres = CM_Get_Device_Interface_List(interfaceGUID, sysDeviceID, ifaceList, ifaceListSize, CM_GET_DEVICE_INTERFACE_LIST_PRESENT);
    if (cres != CR_SUCCESS) {
        delete[] ifaceList;
        return -13;
    }

    // Return list
    *outIfaces = ifaceList;
    *outIfacesLen = ifaceListSize;

    return 0;
}