IWDFIoRequest2::Requeue method

[Warning: UMDF 2 is the latest version of UMDF and supersedes UMDF 1. All new UMDF drivers should be written using UMDF 2. No new features are being added to UMDF 1 and there is limited support for UMDF 1 on newer versions of Windows 10. Universal Windows drivers must use UMDF 2. For more info, see Getting Started with UMDF.]

The Requeue method returns an I/O request to the head of the I/O queue from which it was delivered to the driver.

Syntax


HRESULT Requeue();

Parameters

This method has no parameters.

Return value

Requeue returns S_OK if the operation succeeds. Otherwise, this method might return one of the following values:

Return codeDescription
HRESULT_FROM_WIN32 (ERROR_INVALID_OPERATION)

This value is returned if one of the following occurs:

  • The specified I/O request did not come from an I/O queue.

  • The driver does not own the I/O request.

  • The request is cancelable.

  • The queue's dispatching method is not manual.

 

This method might return one of the other values that Winerror.h contains.

Remarks

A driver can call Requeue only if it uses the manual dispatching method for the I/O queue.

Examples

The following code example shows a segment of an IQueueCallbackStateChange::OnStateChange callback function. The segment obtains an I/O request from the I/O and then returns the request to the queue.


void 
CMyQueue::OnStateChange(
    __in IWDFIoQueue* pWdfQueue,
    __in WDF_IO_QUEUE_STATE 
    )
{
    HRESULT hr;
    IWDFIoRequest* Request;
...
    //
    // Get the IWDFIoRequest interface of the next request.
    //
    hr = pWdfQueue->RetrieveNextRequest(&Request);
...
    //
    // Declare an IWDFIoRequest2 interface pointer and obtain the
    // IWDFIoRequest2 interface from the IWDFIoRequest interface.
    //
    CComQIPtr<IWDFIoRequest2> r2 = Request;

    //
    // Add code here to determine whether to process or requeue the request.
    //
...
    //
    // Requeue the request.
    //
    hr = r2->Requeue();
    if (FAILED(hr)) goto Error;
...
}

Requirements

Target platform

Desktop

End of support

Unavailable in UMDF 2.0 and later.

Minimum UMDF version

1.9

Header

Wudfddi.h (include Wudfddi.h)

DLL

WUDFx.dll

See also

IWDFIoRequest2
IWDFIoQueue::RetrieveNextRequest

 

 

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