IWDFIoTarget2::FormatRequestForFlush 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 FormatRequestForFlush method builds an I/O request for a flush operation but does not send the request to an I/O target.

Syntax

HRESULT FormatRequestForFlush(
  [in]           IWDFIoRequest *pRequest,
  [in, optional] IWDFFile      *pFile
);

Parameters

[in] pRequest

A pointer to the IWDFIoRequest interface of the request object that represents the I/O request.

[in, optional] pFile

A pointer to the IWDFFile interface of the file object that is associated with the I/O request. This parameter is optional and can be NULL, but it is required for the default I/O target.

Return value

FormatRequestForFlush returns S_OK if the operation succeeds. Otherwise, the method might return one of the following value:

Return code	Description
E_OUTOFMEMORY	The framework was unable to allocate memory.

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

Remarks

Some drivers must flush cached buffers that exist in either a lower driver or the device. For example, drivers that exist in a driver stack for a serial device or a storage device might support this operation.

Use the FormatRequestForFlush method, followed by the IWDFIoRequest::Send method, to send flush requests either synchronously or asynchronously.

Examples

The following code example is part of an IQueueCallbackDefaultIoHandler::OnDefaultIoHandler callback function. If the callback function receives a flush request, it sends the request to the device's default I/O target.

void
CMyQueue::OnDefaultIoHandler(
 IWDFIoQueue*  pQueue,
 IWDFIoRequest*  pRequest
    )
{
    HRESULT hr;
    IWDFDevice *pDevice;
    IWDFIoTarget *pTarget;
    IWDFFile *pFile;

    //
    // Obtain the device, default I/O target, and file object.
    //
    pQueue->GetDevice(&pDevice);
    pDevice->GetDefaultIoTarget(&pTarget);
    pRequest->GetFileObject(&pFile);

    if (WdfRequestFlushBuffers==pRequest->GetType())
    {
        // 
        // Declare an IWDFIoTarget2 interface pointer and obtain the
        // IWDFIoTarget2 interface from the IWDFIoTarget interface.
        //
        CComQIPtr<IWDFIoTarget2> target2(pTarget);

        //
        // Format a flush request and send it to the I/O target.
        //
        hr = target2->FormatRequestForFlush(pRequest, 
                                            pFile);

        if (SUCCEEDED(hr))
        {
            hr = pRequest->Send(pTarget,
                                WDF_REQUEST_SEND_OPTION_SYNCHRONOUS,
                                0);
        }
    }
...
    //
    // Release objects.
    //
    SAFE_RELEASE(pDevice);
    SAFE_RELEASE(pTarget);
    SAFE_RELEASE(pFile);
}

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

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