IWDFIoRequest2::Requeue method (wudfddi.h)

Article
02/22/2024

[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();

Return value

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

Return code	Description
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

Requirement	Value
End of support	Unavailable in UMDF 2.0 and later.
Target Platform	Desktop
Minimum UMDF version	1.9
Header	wudfddi.h (include Wudfddi.h)
DLL	WUDFx.dll