WdfRequestRetrieveOutputWdmMdl function (wdfrequest.h)
[Applies to KMDF only]
The WdfRequestRetrieveOutputWdmMdl method retrieves a memory descriptor list (MDL) that represents an I/O request's output buffer.
Syntax
NTSTATUS WdfRequestRetrieveOutputWdmMdl(
[in] WDFREQUEST Request,
[out] PMDL *Mdl
);
Parameters
[in] Request
A handle to a framework request object.
[out] Mdl
A pointer to a location that receives a pointer to an MDL.
Return value
WdfRequestRetrieveOutputWdmMdl returns STATUS_SUCCESS if the operation succeeds. Otherwise, this method might return one of the following values:
Return code | Description |
---|---|
|
An input parameter is invalid. |
|
The request type is not valid or the request is using neither buffered nor direct I/O. For more information about supported methods for accessing data buffers, see the following Remarks section. |
|
The request has already been completed. |
|
The input buffer's length is zero. |
|
There is insufficient memory. |
This method might also return other NTSTATUS values.
A bug check occurs if the driver supplies an invalid object handle.
Remarks
A request's output buffer receives information, such as data from a disk, that the driver provides to the originator of the request. Your driver can call WdfRequestRetrieveOutputWdmMdl for a read request or a device I/O control request, but not for a write request (because write requests do not provide output data).
The WdfRequestRetrieveOutputWdmMdl method retrieves the output buffer's MDL for I/O requests that use the buffered I/O method or the direct I/O method for accessing data buffers. If the request's I/O control code is IRP_MJ_INTERNAL_DEVICE_CONTROL, or if the request came from another kernel-mode driver, WdfRequestRetrieveOutputWdmMdl also supports I/O requests that use neither buffered nor direct I/O.
If WdfRequestRetrieveOutputWdmMdl returns STATUS_SUCCESS, the driver receives a pointer to an MDL that describes the output buffer.
The driver must not access a request's MDL after completing the I/O request.
For more information about WdfRequestRetrieveOutputWdmMdl, see Accessing Data Buffers in Framework-Based Drivers.
Examples
The following code example is part of an EvtIoRead callback function that obtains an MDL for an I/O request's input buffer. If the call to WdfRequestRetrieveOutputWdmMdl fails, the driver completes the request with the error status that WdfRequestRetrieveOutputWdmMdl returns.
VOID
MyDrvEvtIoRead(
IN WDFQUEUE Queue,
IN WDFREQUEST Request,
IN size_t Length
)
{
NTSTATUS status;
PMDL mdl = NULL;
...
status = WdfRequestRetrieveOutputWdmMdl(
Request,
&mdl
);
if (!NT_SUCCESS(status))
{
WdfRequestCompleteWithInformation(
Request,
status,
0
);
}
...
}
Requirements
Requirement | Value |
---|---|
Target Platform | Universal |
Minimum KMDF version | 1.0 |
Header | wdfrequest.h (include Wdf.h) |
Library | Wdf01000.sys (see Framework Library Versioning.) |
IRQL | <=DISPATCH_LEVEL |
DDI compliance rules | DriverCreate(kmdf), InvalidReqAccess(kmdf), InvalidReqAccessLocal(kmdf), KmdfIrql(kmdf), KmdfIrql2(kmdf), KmdfIrqlExplicit(kmdf), MdlAfterReqCompletedIntIoctl(kmdf), MdlAfterReqCompletedIntIoctlA(kmdf), MdlAfterReqCompletedIoctl(kmdf), MdlAfterReqCompletedIoctlA(kmdf), MdlAfterReqCompletedRead(kmdf), MdlAfterReqCompletedReadA(kmdf), MdlAfterReqCompletedWrite(kmdf), OutputBufferAPI(kmdf) |