DMA_COMPLETION_ROUTINE callback function (wdm.h)

The DmaCompletionRoutine callback routine notifies the driver that previously requested a system DMA transfer that this transfer is complete.

Syntax

DMA_COMPLETION_ROUTINE DmaCompletionRoutine;

void DmaCompletionRoutine(
  [in] PDMA_ADAPTER DmaAdapter,
  [in] PDEVICE_OBJECT DeviceObject,
  [in] PVOID CompletionContext,
  [in] DMA_COMPLETION_STATUS Status
)
{...}

Parameters

[in] DmaAdapter

A pointer to a DMA_ADAPTER structure. This structure is the adapter object that represents the driver's system DMA channel.

[in] DeviceObject

A pointer to a DEVICE_OBJECT structure. This structure is the physical device object (PDO) that represents the target device for the requested DMA operation.

[in] CompletionContext

A pointer to a driver-determined context for the DmaCompletionRoutine routine. This context is the CompletionContext parameter value that the driver previously passed to the MapTransferEx call that initiated the system DMA transfer.

[in] Status

The completion status of the DMA transfer. This parameter is a DMA_COMPLETION_STATUS enumeration value that indicates whether the DMA transfer completed successfully.

Return value

None

Remarks

As an option, a driver can implement a DmaCompletionRoutine routine. When the driver requests a system DMA transfer, the driver can supply a pointer to this routine with the request. After the DMA transfer completes, the DmaCompletionRoutine routine is automatically called to notify the driver.

A driver's DmaCompletionRoutine routine is called only if the DMA transfer requested by the driver uses a system DMA controller that can generate an interrupt after a DMA transfer completes. A driver that uses a bus-master DMA device, or that uses a system DMA controller that does not generate interrupts, must use other means to determine when a DMA transfer completes. For example, this driver might use a timer interrupt to periodically poll the status of the DMA transfer.

A driver can supply a pointer to a DmaCompletionRoutine routine as an optional parameter to the MapTransferEx routine.

Examples

To define a DmaCompletionRoutine callback routine, you must first provide a function declaration that identifies the type of callback routine you're defining. Windows provides a set of callback function types for drivers. Declaring a function using the callback function types helps Code Analysis for Drivers, Static Driver Verifier (SDV), and other verification tools find errors, and it's a requirement for writing drivers for the Windows operating system.

For example, to define a DmaCompletionRoutine callback routine that is named MyDmaCompletionRoutine, use the DMA_COMPLETION_ROUTINE type as shown in this code example:

DMA_COMPLETION_ROUTINE MyDmaCompletionRoutine;

Then, implement your callback routine as follows:

_Use_decl_annotations_
VOID
  MyDmaCompletionRoutine(
    PDMA_ADAPTER DmaAdapter,
    PDEVICE_OBJECT DeviceObject,
    PVOID CompletionContext,
    DMA_COMPLETION_STATUS Status
    )
  {
      // Function body
  }

The DMA_COMPLETION_ROUTINE function type is defined in the Wdm.h header file. To more accurately identify errors when you run the code analysis tools, be sure to add the _Use_decl_annotations_ annotation to your function definition. The _Use_decl_annotations_ annotation ensures that the annotations that are applied to the DMA_COMPLETION_ROUTINE function type in the header file are used. For more information about the requirements for function declarations, see Declaring Functions by Using Function Role Types for WDM Drivers. For information about _Use_decl_annotations_, see Annotating Function Behavior.

Requirements

See also

BuildScatterGatherListEx

DEVICE_OBJECT

DMA_ADAPTER

DMA_COMPLETION_STATUS

DMA_OPERATIONS

GetScatterGatherListEx

MapTransferEx