How to Restart a USB Port

• Download source code - 1.8 KB

Introduction

Sometimes, USB devices stop working as expected and re-plugging them helps. Performing the re-plug by code might be handy.

If you want to try if restarting a USB port is helpful, you can try with my UsbTreeView or RestartUsbPort.

Background

Microsoft says IOCTL_USB_HUB_CYCLE_PORT power-cycles the USB port and thus initiates a re-enumeration of the attached device.

The function is available under XP but usually only for hubs which run with the Microsoft standard driver. Third party drivers usually return ERROR_UNKNOWN_FUNCTION.

Under Vista and Windows 7, it is no more supported by the Windows standard drivers, it always fails with ERROR_NOT_SUPPORTED.

Since Windows 8, it works again but in contrast to XP, admin privileges are required. Without admin privileges, it fails as under Vista and Win7 with ERROR_NOT_SUPPORTED or since Win10 version 1903 with ERROR_GEN_FAILURE, both of which are quite misleading here since it's a privilege issue.

Using the Code

I have put everything in one single function which expects the USB device's Device Instance ID as only parameter.

//--------------------------------------------------------------------------------
bool CycleUsbDevice(char* pszUsbDeviceId)
{
    // Step 1: find the USB device in the device manager
    DEVINST DevInst = 0;
    if ( CR_SUCCESS != CM_Locate_DevNode(&DevInst, pszUsbDeviceId, 0) ) {
        return false; //----
    }

    // Step 2: Determine the USB port number. 
    // Since Vista it can be read reliably from the device location info:
    char szLocation[64] = "";
    DWORD dwType = 0;
    ULONG uLen = sizeof(szLocation);
    if ( CR_SUCCESS != CM_Get_DevNode_Registry_Property
       (DevInst, CM_DRP_LOCATION_INFORMATION, &dwType, szLocation, &uLen, 0) ) {
        return false; //----
    }

    //               0123456789
    // must be like "Port_#0004.Hub_#0014"
    if ( 0 != strncmp(szLocation, "Port_#", 6) ) {
        return false; //----
    }

    int PortNumber = atoi(szLocation + 6); // leading zeros are ok with atoi

    // Step 3: the USB hub is the parent device
    DEVINST DevInstHub = 0;
    if ( CR_SUCCESS != CM_Get_Parent(&DevInstHub, DevInst, 0) ) {
        return false; //----
    }
    
    // Step 4: scan all USB hubs for this DEVINST to get its DevicePath
    // which we need to open the hub
    char szHubDevPath[MAX_PATH] = "";

    const GUID* DevIfGuid = &GUID_DEVINTERFACE_USB_HUB;

    HDEVINFO hDevInfo = SetupDiGetClassDevs
             (DevIfGuid, NULL, NULL, DIGCF_DEVICEINTERFACE | DIGCF_PRESENT);

    if ( INVALID_HANDLE_VALUE == hDevInfo ) {
        return false; //----
    }

    char DataBuf[1024];
    PSP_DEVICE_INTERFACE_DETAIL_DATA pDevIfDetailData = 
                         (PSP_DEVICE_INTERFACE_DETAIL_DATA)DataBuf;
    SP_DEVICE_INTERFACE_DATA         DevIfData   = { sizeof(SP_DEVICE_INTERFACE_DATA) };
    SP_DEVINFO_DATA                  DevInfoData = { sizeof(SP_DEVINFO_DATA) };
    DWORD                            dwSize;

    for ( DWORD dwIndex = 0; SetupDiEnumDeviceInterfaces
        (hDevInfo, NULL, DevIfGuid, dwIndex, &DevIfData); dwIndex++ ) {

        pDevIfDetailData->cbSize = 
            sizeof(*pDevIfDetailData); // yes, 5 (or 6 if UNICODE)

        dwSize = sizeof(DataBuf);
        
        if ( SetupDiGetDeviceInterfaceDetail(hDevInfo, 
             &DevIfData, pDevIfDetailData, dwSize, &dwSize, &DevInfoData) ) {
            if ( DevInfoData.DevInst == DevInstHub ) {
                // hub found, keep its DevicePath
                strcpy(szHubDevPath, pDevIfDetailData->DevicePath);
                break;
            }
        }
    }

    SetupDiDestroyDeviceInfoList(hDevInfo);

    if ( ! szHubDevPath[0] ) {
        return false; //----
    }
    
    // Step 5: open the hub
    HANDLE hHub = CreateFile(szHubDevPath, GENERIC_WRITE, 
                  FILE_SHARE_READ | FILE_SHARE_WRITE, NULL, OPEN_EXISTING, 0, NULL);

    if ( INVALID_HANDLE_VALUE == hHub ) {
        return false; //----
    }

    // Step 6: call IOCTL_USB_HUB_CYCLE_PORT
    typedef struct _USB_CYCLE_PORT_PARAMS {
        ULONG ConnectionIndex;
        ULONG StatusReturned;
    } USB_CYCLE_PORT_PARAMS, *PUSB_CYCLE_PORT_PARAMS;

    USB_CYCLE_PORT_PARAMS CyclePortParams  = { PortNumber, 0 }; // in and out

    DWORD dwBytes;
    int res = DeviceIoControl(hHub, IOCTL_USB_HUB_CYCLE_PORT,
                              &CyclePortParams, sizeof(CyclePortParams), 
                              &CyclePortParams, sizeof(CyclePortParams), 
                              &dwBytes, NULL);
    CloseHandle(hHub);
    
    return ( (0 != res) && (0 == CyclePortParams.StatusReturned) );
}
//--------------------------------------------------------------------------------------

Points of Interest

Microsoft's documentation for IOCTL_USB_HUB_CYCLE_PORT is wrong: It says "Output buffer: None" which is wrong. The StatusReturned struct member leads to the conclusion that the USB_CYCLE_PORT_PARAMS struct is intended as in and out buffer. It works that way and dwBytes contains 8 afterwards, which is the expected sizeof(USB_CYCLE_PORT_PARAMS).

What makes it fail

In contrast to an attempt to restart a device by means of the Device Manager IOCTL_USB_HUB_CYCLE_PORT does not ask for permission, so no driver can veto it and so it always succeeds.
But the port must have a USB device attached and a driver installed. Otherwise it fails with error 433 (ERROR_NO_SUCH_DEVICE) or since Windows 10 21H2 with error 50 (ERROR_NOT_SUPPORTED) which again is missleading.
Windows 11 comes with a proper error 1167 (ERROR_DEVICE_NOT_CONNECTED).

History

• 18^th June, 2023 - First release