Find and eject a USB device based on its VID/PID

I want to send an eject command to a specific USB device identified by it's VID and PID. I can find the device by using SetupDiEnumDeviceInfo() and SetupDiGetDeviceRegistryProperty() and matching the VID/PID numbers in the HARDWAREID string but that's as far as I've got.

I have a SP_DEVINFO_DATA struct and a HDEVINFO handle. How would I relate these to a dr开发者_C百科ive letter or volume path so I can send it an eject command?

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Well, I figured it out. The CodeProject article linked to by Luke shows how to match the drive letter to a device interface which is half the way there so I'll +1 that answer but it doesn't solve the whole problem.

I needed to figure out how to find the device instance for my USB device and find a way to match that to the device interface. The CM_Locate_DevNode() and CM_Get_Child() functions were the key to this. Finally I can use an IOCTL to eject the device.

The device I am dealing with is a USB CD-ROM drive which is why I have hard-coded the device type to CDROM. I can't believe how much code is required to do what I thought would be a fairly straightforward task (I quoted my client 2 hours to write this code, it's taken me four days to figure it all out!). Here's the final working code which will hopefully save one of you out there from going through the same hell as I just have:

#include <SetupAPI.h>
#include <cfgmgr32.h>
#include <winioctl.h>

// Finds the device interface for the CDROM drive with the given interface number.
DEVINST GetDrivesDevInstByDeviceNumber(long DeviceNumber)
{
    const GUID *guid = &GUID_DEVINTERFACE_CDROM;

// Get device interface info set handle
// for all devices attached to system
    HDEVINFO hDevInfo = SetupDiGetClassDevs(guid, NULL, NULL, DIGCF_PRESENT | DIGCF_DEVICEINTERFACE);
    if(hDevInfo == INVALID_HANDLE_VALUE)
        return 0;

// Retrieve a context structure for a device interface of a device information set.
    BYTE                             buf[1024];
    PSP_DEVICE_INTERFACE_DETAIL_DATA pspdidd = (PSP_DEVICE_INTERFACE_DETAIL_DATA)buf;
    SP_DEVICE_INTERFACE_DATA         spdid;
    SP_DEVINFO_DATA                  spdd;
    DWORD                            dwSize;

    spdid.cbSize = sizeof(spdid);

// Iterate through all the interfaces and try to match one based on
// the device number.
    for(DWORD i = 0; SetupDiEnumDeviceInterfaces(hDevInfo, NULL,guid, i, &spdid); i++)
    {
    // Get the device path.
        dwSize = 0;
        SetupDiGetDeviceInterfaceDetail(hDevInfo, &spdid, NULL, 0, &dwSize, NULL);
        if(dwSize == 0 || dwSize > sizeof(buf))
            continue;

        pspdidd->cbSize = sizeof(*pspdidd);
        ZeroMemory((PVOID)&spdd, sizeof(spdd));
        spdd.cbSize = sizeof(spdd);
        if(!SetupDiGetDeviceInterfaceDetail(hDevInfo, &spdid, pspdidd,
                                            dwSize, &dwSize, &spdd))
            continue;

    // Open the device.
        HANDLE hDrive = CreateFile(pspdidd->DevicePath,0,
                                   FILE_SHARE_READ | FILE_SHARE_WRITE,
                                   NULL, OPEN_EXISTING, 0, NULL);
        if(hDrive == INVALID_HANDLE_VALUE)
            continue;

    // Get the device number.
        STORAGE_DEVICE_NUMBER sdn;
        dwSize = 0;
        if(DeviceIoControl(hDrive,
                           IOCTL_STORAGE_GET_DEVICE_NUMBER,
                           NULL, 0, &sdn, sizeof(sdn),
                           &dwSize, NULL))
        {
        // Does it match?
            if(DeviceNumber == (long)sdn.DeviceNumber)
            {
                CloseHandle(hDrive);
                SetupDiDestroyDeviceInfoList(hDevInfo);
                return spdd.DevInst;
            }
        }
        CloseHandle(hDrive);
    }

    SetupDiDestroyDeviceInfoList(hDevInfo);
    return 0;
}


// Returns true if the given device instance belongs to the USB device with the given VID and PID.
bool matchDevInstToUsbDevice(DEVINST device, DWORD vid, DWORD pid)
{
// This is the string we will be searching for in the device harware IDs.
    TCHAR hwid[64];
    _stprintf(hwid, _T("VID_%04X&PID_%04X"), vid, pid);

// Get a list of hardware IDs for all USB devices.
    ULONG ulLen;
    CM_Get_Device_ID_List_Size(&ulLen, NULL, CM_GETIDLIST_FILTER_NONE);
    TCHAR *pszBuffer = new TCHAR[ulLen];
    CM_Get_Device_ID_List(NULL, pszBuffer, ulLen, CM_GETIDLIST_FILTER_NONE);

// Iterate through the list looking for our ID.
    for(LPTSTR pszDeviceID = pszBuffer; *pszDeviceID; pszDeviceID += _tcslen(pszDeviceID) + 1)
    {
    // Some versions of Windows have the string in upper case and other versions have it
    // in lower case so just make it all upper.
        for(int i = 0; pszDeviceID[i]; i++)
            pszDeviceID[i] = toupper(pszDeviceID[i]);

        if(_tcsstr(pszDeviceID, hwid))
        {
        // Found the device, now we want the grandchild device, which is the "generic volume"
            DEVINST MSDInst = 0;
            if(CR_SUCCESS == CM_Locate_DevNode(&MSDInst, pszDeviceID, CM_LOCATE_DEVNODE_NORMAL))
            {
                DEVINST DiskDriveInst = 0;
                if(CR_SUCCESS == CM_Get_Child(&DiskDriveInst, MSDInst, 0))
                {
                // Now compare the grandchild node against the given device instance.
                    if(device == DiskDriveInst)
                        return true;
                }
            }
        }
    }

    return false;
}

// Eject the given drive.
void ejectDrive(TCHAR driveletter)
{
    TCHAR devicepath[16];
    _tcscpy(devicepath, _T("\\\\.\\?:"));
    devicepath[4] = driveletter;

    DWORD dwRet = 0;
    HANDLE hVol = CreateFile(devicepath, GENERIC_READ, FILE_SHARE_WRITE, NULL, OPEN_EXISTING, 0, NULL);
    if(hVol == INVALID_HANDLE_VALUE)
        return;

    if(!DeviceIoControl(hVol, FSCTL_LOCK_VOLUME, 0, 0, 0, 0, &dwRet, 0))
        return;

    if(!DeviceIoControl(hVol, FSCTL_DISMOUNT_VOLUME, 0, 0, 0, 0, &dwRet, 0))
        return;

    DeviceIoControl(hVol, IOCTL_STORAGE_EJECT_MEDIA, 0, 0, 0, 0, &dwRet, 0);

    CloseHandle(hVol);
}

// Find a USB device by it's Vendor and Product IDs. When found, eject it.
void usbEjectDevice(unsigned vid, unsigned pid)
{
    TCHAR devicepath[8];
    _tcscpy(devicepath, _T("\\\\.\\?:"));

    TCHAR drivepath[4];
    _tcscpy(drivepath, _T("?:\\"));

// Iterate through every drive letter and check if it is our device.
    for(TCHAR driveletter = _T('A'); driveletter <= _T('Z'); driveletter++)
    {
    // We are only interested in CDROM drives.
        drivepath[0] = driveletter;
        if(DRIVE_CDROM != GetDriveType(drivepath))
            continue;

    // Get the "storage device number" for the current drive.
        long DeviceNumber = -1;
        devicepath[4]     = driveletter;
        HANDLE hVolume    = CreateFile(devicepath, 0, FILE_SHARE_READ | FILE_SHARE_WRITE,
                                        NULL, OPEN_EXISTING, 0, NULL);
        if(INVALID_HANDLE_VALUE == hVolume)
            continue;

        STORAGE_DEVICE_NUMBER sdn;
        DWORD dwBytesReturned = 0;
        if(DeviceIoControl(hVolume, IOCTL_STORAGE_GET_DEVICE_NUMBER,
                            NULL, 0, &sdn, sizeof(sdn), &dwBytesReturned, NULL))
            DeviceNumber = sdn.DeviceNumber;
        CloseHandle(hVolume);
        if(DeviceNumber < 0)
            continue;

    // Use the data we have collected so far on our drive to find a device instance.
        DEVINST DevInst = GetDrivesDevInstByDeviceNumber(DeviceNumber);

    // If the device instance corresponds to the USB device we are looking for, eject it.
        if(DevInst)
        {
            if(matchDevInstToUsbDevice(DevInst, vid, pid))
                ejectDrive(driveletter);
        }   
    }
}