WdfIoTargetFormatRequestForIoctl function (wdfiotarget.h)

Article
04/18/2022

[Applies to KMDF and UMDF]

The WdfIoTargetFormatRequestForIoctl method builds a device control request for an I/O target but does not send the request.

Syntax

NTSTATUS WdfIoTargetFormatRequestForIoctl(
  [in]           WDFIOTARGET       IoTarget,
  [in]           WDFREQUEST        Request,
  [in]           ULONG             IoctlCode,
  [in, optional] WDFMEMORY         InputBuffer,
  [in, optional] PWDFMEMORY_OFFSET InputBufferOffset,
  [in, optional] WDFMEMORY         OutputBuffer,
  [in, optional] PWDFMEMORY_OFFSET OutputBufferOffset
);

Parameters

[in] IoTarget

A handle to a local or remote I/O target object that was obtained from a previous call to WdfDeviceGetIoTarget or WdfIoTargetCreate, or from a method that a specialized I/O target supplies.

[in] Request

A handle to a framework request object. For more information, see the following Remarks section.

[in] IoctlCode

An I/O control code (IOCTL) that the I/O target supports.

[in, optional] InputBuffer

A handle to a framework memory object. This object represents a buffer that contains data that will be sent to the I/O target. For more information, see the following Remarks section.

[in, optional] InputBufferOffset

A pointer to a caller-allocated WDFMEMORY_OFFSET structure that supplies optional byte offset and length values. The framework uses these values to determine the beginning address and length, within the input buffer, for the data transfer. If this pointer is NULL, the data transfer begins at the beginning of the input buffer, and the transfer size is the buffer size.

[in, optional] OutputBuffer

A handle to a framework memory object. This object represents a buffer that will receive data from the I/O target. For more information, see the following Remarks section.

[in, optional] OutputBufferOffset

A pointer to a caller-allocated WDFMEMORY_OFFSET structure that supplies optional byte offset and length values. The framework uses these values to determine the beginning address and length, within the output buffer, for the data transfer. If this pointer is NULL, the data transfer begins at the beginning of the output buffer, and the transfer size is the buffer size.

Return value

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

Return code	Description
STATUS_INVALID_PARAMETER	An invalid parameter was detected.
STATUS_INVALID_DEVICE_REQUEST	The transfer length was larger than the buffer length, or the I/O request was already queued to an I/O target.
STATUS_INSUFFICIENT_RESOURCES	The framework could not allocate system resources (typically memory).
STATUS_REQUEST_NOT_ACCEPTED	The I/O request packet (IRP) that the Request parameter represents does not provide enough IO_STACK_LOCATION structures to allow the driver to forward the request.

This method also might return other NTSTATUS values.

A bug check occurs if the driver supplies an invalid object handle.

Remarks

Use the WdfIoTargetFormatRequestForIoctl method, followed by the WdfRequestSend method, to send device control requests either synchronously or asynchronously. Alternatively, use the WdfIoTargetSendIoctlSynchronously method to send device control requests synchronously.

For more information about device control requests, see Using I/O Control Codes.

You can forward a device control request that your driver received in an I/O queue, or you can create and send a new request. In either case, the framework requires a request object and some buffer space.

To forward a device control request that your driver received in an I/O queue:

Specify the received request's handle for the WdfIoTargetFormatRequestForIoctl method's Request parameter.
Use the received request's input buffer for the WdfIoTargetFormatRequestForIoctl method's InputBuffer parameter.
The driver must call WdfRequestRetrieveInputMemory to obtain a handle to a framework memory object that represents the request's input buffer, and it must use that handle as the value for InputBuffer.
Use the received request's output buffer for the WdfIoTargetFormatRequestForIoctl method's OutputBuffer parameter.
The driver must call WdfRequestRetrieveOutputMemory to obtain a handle to the request's output buffer, and it must use that handle as the value for OutputBuffer.

For more information about forwarding an I/O request, see Forwarding I/O Requests.

Drivers often divide received I/O requests into smaller requests that they send to an I/O target, so your driver might create new requests.

To create a new I/O request:

Create a new request object and supply its handle for the WdfIoTargetFormatRequestForIoctl method's Request parameter.
Call WdfRequestCreate to preallocate one or more request objects. You can reuse these request objects by calling WdfRequestReuse. Your driver's EvtDriverDeviceAdd callback function can preallocate request objects for a device.
Provide buffer space, and supply the buffer's handle for the WdfIoTargetFormatRequestForIoctl method's InputBuffer and OutputBuffer parameters.
Your driver must specify this buffer space as WDFMEMORY handles to framework-managed memory. Your driver can do either of the following:
- Call WdfMemoryCreate or WdfMemoryCreatePreallocated to create a new memory buffer, if you want the driver to pass a new buffer to the I/O target.
- Call WdfRequestRetrieveInputMemory or WdfRequestRetrieveOutputMemory to obtain a handle to the memory object that represents a received I/O request's buffer, if you want the driver to pass that buffer's contents to the I/O target.
Note that if your driver calls WdfRequestRetrieveInputMemory or WdfRequestRetrieveOutputMemory and passes the memory handle to WdfIoTargetFormatRequestForIoctl, the driver must not complete the received I/O request until after the driver deletes, reuses, or reformats the new, driver-created request object. (WdfIoTargetFormatRequestForIoctl increments the memory object's reference count. Deleting, reusing, or reformatting a request object decrements the memory object's reference count.)

After a driver calls WdfIoTargetFormatRequestForIoctl to format a device control request, the driver must call WdfRequestSend to send the request (either synchronously or asynchronously) to an I/O target.

Multiple calls to WdfIoTargetFormatRequestForIoctl that use the same request do not cause additional resource allocations. Therefore, to reduce the chance that WdfRequestCreate will return STATUS_INSUFFICIENT_RESOURCES, your driver's EvtDriverDeviceAdd callback function can call WdfRequestCreate to preallocate one or more request objects for a device. The driver can subsequently reuse (call WdfRequestReuse), reformat (call WdfIoTargetFormatRequestForIoctl), and resend (call WdfRequestSend) each request object without risking a STATUS_INSUFFICIENT_RESOURCES return value from a later call to WdfRequestCreate. All subsequent calls to WdfIoTargetFormatRequestForIoctl for the reused request object will return STATUS_SUCCESS, if parameter values do not change. (If the driver does not call the same request-formatting method each time, additional resources might be allocated. Additionally, if the I/O control code specifies a transfer type of METHOD_BUFFERED, the framework must allocate a system buffer for each request and that allocation could fail because of insufficient memory resources.)

For information about obtaining status information after an I/O request completes, see Obtaining Completion Information.

For more information about WdfIoTargetFormatRequestForIoctl, see Sending I/O Requests to General I/O Targets.

For more information about I/O targets, see Using I/O Targets.

Examples

The following code reuses a preallocated request object and preallocated memory objects. The example assigns input and output buffers to the memory objects, formats the request object, registers a CompletionRoutine callback function, and sends the request to an I/O target.

NTSTATUS
NICSendOidRequestToTargetAsync(
    IN WDFIOTARGET  IoTarget,
    IN WDFREQUEST  Request,
    IN PFILE_OBJECT  FileObject,
    IN ULONG  IoctlControlCode,
    IN OUT PVOID  InputBuffer,
    IN ULONG  InputBufferLength,
    IN OUT PVOID  OutputBuffer,
    IN ULONG  OutputBufferLength,
    OUT PULONG  BytesReadOrWritten
    )
{
    NTSTATUS  status;
    PREQUEST_CONTEXT  reqContext;
    WDF_REQUEST_REUSE_PARAMS  params;
    WDFMEMORY  inputMem, outputMem;
 
    WDF_REQUEST_REUSE_PARAMS_INIT(
                                  &params, 
                                  WDF_REQUEST_REUSE_NO_FLAGS, 
                                  STATUS_SUCCESS
                                  );
    status = WdfRequestReuse(Request, &params);
    if (!NT_SUCCESS(status)){
        return status;
    }

    reqContext = GetRequestContext(Request);

    inputMem = outputMem = NULL;
 
    if (InputBuffer != NULL) {
        status = WdfMemoryAssignBuffer(
                                       reqContext->InputMemory,
                                       InputBuffer, 
                                       InputBufferLength
                                       );
        if (!NT_SUCCESS(status)) {
             return status;
        }
        inputMem = reqContext->InputMemory;
    }

    if (OutputBuffer != NULL) {
        status = WdfMemoryAssignBuffer(
                                       reqContext->OutputMemory,
                                       OutputBuffer, 
                                       OutputBufferLength
                                       );
        if (!NT_SUCCESS(status)) {
            return status;
        }
        outputMem = reqContext->OutputMemory;
    }

    status = WdfIoTargetFormatRequestForIoctl(
                                              IoTarget,
                                              Request,
                                              IoctlControlCode,
                                              inputMem,
                                              NULL,
                                              outputMem,
                                              NULL
                                              );
    if (!NT_SUCCESS(status)) {
        return status;
    }

    WdfRequestSetCompletionRoutine(
                                   Request,
                                   NICSendOidRequestToTargetAsyncCompletionRoutine,
                                   BytesReadOrWritten
                                   );

    if (WdfRequestSend(
                       Request,
                       IoTarget,
                       WDF_NO_SEND_OPTIONS
                       ) == FALSE) {
        status = WdfRequestGetStatus(Request);
    }
    return status;
}

Requirements

Requirement	Value
Target Platform	Universal
Minimum KMDF version	1.0
Minimum UMDF version	2.0
Header	wdfiotarget.h (include Wdf.h)
Library	Wdf01000.sys (KMDF); WUDFx02000.dll (UMDF)
IRQL	<=DISPATCH_LEVEL
DDI compliance rules	DriverCreate(kmdf), KmdfIrql(kmdf), KmdfIrql2(kmdf), KmdfIrqlExplicit(kmdf), RequestFormattedValid(kmdf), RequestSendAndForgetNoFormatting(kmdf), RequestSendAndForgetNoFormatting2(kmdf)

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