C#: Error in getting device instance handle

Question

In my C# code I am trying to use C++ functions: CM_Locate_DevNodeW and CM_Open_DevNode_Key (using pinvoke). My code seems something like this:

String deviceId = "PCI\\VEN_8086&DEV_591B&SUBSYS_22128086&REV_01\\3&11583659&0&10";
int devInst = 0;
cmStatus = CM_Locate_DevNodeW(&devInst, deviceId, CM_LOCATE_DEVNODE_NORMAL);
if (cmStatus == CR_SUCCESS)
{
    UIntPtr pHKey = new UIntPtr();
    cmStatus = CM_Open_DevNode_Key(devInst, KEY_ALL_ACCESS, 0, RegDisposition_OpenExisting, pHKey, CM_REGISTRY_SOFTWARE);
    if (cmStatus == CR_SUCCESS)
    {
        //but here cmStatus=3 (Invalid Pointer)
    }
}

After calling to CM_Locate_DevNodeW, the devInst becomes 1, and the cmStatus is 0 = CR_SUCCESS. But the call to CM_Open_DevNode_Key fails. I don't know if CM_Locate_DevNodeW returns CR_SUCCESS but puts incorrect data within devInst? ('1' does not seems like real device instance handle...)

Or maybe the call to CM_Open_DevNode_Key is wrong?

I declared the functions like this:

[DllImport("cfgmgr32.dll", SetLastError = true, CharSet = CharSet.Unicode)]
public static extern unsafe int CM_Locate_DevNodeW(
    int* pdnDevInst,  
    string pDeviceID, 
    ulong ulFlags);

[DllImport("cfgmgr32.dll", SetLastError = true, CharSet = CharSet.Unicode)]
    public static extern unsafe int CM_Open_DevNode_Key(
     int dnDevNode,
     int samDesired,
     int ulHardwareProfile,
     int Disposition,
     IntPtr phkDevice,
     int ulFlags);

Any help would be appreciated!

CM_Locate_DevNodeW isn't a C++ function. It's a C function provided by the Windows API. — Mark Ingram
– Mark Ingram, Commented Feb 6, 2019 at 16:13

Oleksandr · Accepted Answer · 2019-02-06 16:08:12Z

1

I fiddled around with your code and this is what I've got so far. After reading some docs I found out that phkDevice parameter of CM_Open_DevNode_Key function was likely an out parameter so I updated function signature

[DllImport("cfgmgr32.dll", SetLastError = true, CharSet = CharSet.Unicode)]
public static extern unsafe int CM_Open_DevNode_Key(
    int dnDevNode,
    int samDesired,
    int ulHardwareProfile,
    int Disposition,
    out IntPtr phkDevice, //added out keyword
    int ulFlags);

And I tried to run the following code

IntPtr pHKey;

string deviceId = @"my keyboard pci id";
int devInst = 0;
int cmStatus = CM_Locate_DevNodeW(&devInst, deviceId, CM_LOCATE_DEVNODE_NORMAL);
if (cmStatus == CR_SUCCESS)
{
    int opencmStatus = CM_Open_DevNode_Key(devInst, KEY_ALL_ACCESS, 0, RegDisposition_OpenExisting, out pHKey, CM_REGISTRY_SOFTWARE);
    if (opencmStatus == CR_SUCCESS)
    {
        // 
    }
}

I got opencmStatus 51 which corresponds to CR_ACCESS_DENIED. Then I thought "Hmm, don't I just requesting to much access? Let's try only read access options" So I replaced KEY_ALL_ACCESS with 1 (KEY_QUERY_VALUE) and ran the following code

IntPtr pHKey;

string deviceId = @"my keyboard pci id";
int devInst = 0;
int cmStatus = CM_Locate_DevNodeW(&devInst, deviceId, CM_LOCATE_DEVNODE_NORMAL);
if (cmStatus == CR_SUCCESS)
{
    int opencmStatus = CM_Open_DevNode_Key(devInst, 1, 0, RegDisposition_OpenExisting, out pHKey, CM_REGISTRY_SOFTWARE);
    if (opencmStatus == CR_SUCCESS)
    {
        //
    }
}

It worked as expected. Finally, this version gave me opencmStatus equals to 0.

I did all tests against my keyboard PCI identifier, dont know if it matters.

answered Feb 6, 2019 at 16:08

Oleksandr

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1 Comment

RK Coder Over a year ago

Adding the out keyword was enough for solving my issue. I didn't get CR_ACCESS_DENIED even when using KEY_ALL_ACCESS, maybe this is because my app is running with Administrator privilege. Thanks for your quick and efficient support!

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