PFREE_CONTIGUOUS_DMA_BUFFER callback function (hdaudio.h)

Article
10/21/2021

The FreeContiguousDmaBuffer routine frees a DMA buffer and buffer descriptor list (BDL) that were allocated by a call to AllocateContiguousDmaBuffer.

The function pointer type for a FreeContiguousDmaBuffer routine is defined as follows.

Syntax

PFREE_CONTIGUOUS_DMA_BUFFER PfreeContiguousDmaBuffer;

NTSTATUS PfreeContiguousDmaBuffer(
  [in] PVOID _context,
  [in] HANDLE Handle
)
{...}

Parameters

[in] _context

Specifies the context value from the Context member of the HDAUDIO_BUS_INTERFACE_BDL structure.

[in] Handle

Handle identifying the DMA engine. This handle value was obtained from a previous call to AllocateCaptureDmaEngine or AllocateRenderDmaEngine.

Return value

FreeContiguousDmaBuffer returns STATUS_SUCCESS if the call succeeds. Otherwise, the routine returns an appropriate error code. The following table shows some of the possible return status codes.

Return code	Description
STATUS_UNSUCCESSFUL	Indicates that the caller is running at an IRQL that is too high.
STATUS_INVALID_HANDLE	Indicates that the handle parameter value is invalid.
STATUS_INVALID_DEVICE_REQUEST	Indicates that the stream is not in the reset state or that no buffer is currently allocated for the DMA engine.

Remarks

The FreeContiguousDmaBuffer routine is used in conjunction with the SetupDmaEngineWithBdl and AllocateContiguousDmaBuffer routines. These three routines are available only in the HDAUDIO_BUS_INTERFACE_BDL version of the HD Audio DDI. This DDI does not include the AllocateDmaBuffer and FreeDmaBuffer routines, which are never used in conjunction with AllocateContiguousDmaBuffer, SetupDmaEngineWithBdl, and FreeContiguousDmaBuffer. Unlike SetupDmaEngineWithBdl, which configures the DMA engine to use a previously allocated DMA buffer, AllocateDmaBuffer both allocates a DMA buffer and configures the DMA engine to use the buffer. For more information, see Differences between the Two DDI Versions.

The routine fails and returns error code STATUS_INVALID_DEVICE_REQUEST in either of the following circumstances:

The client calls FreeContiguousDmaBuffer when no buffer is currently allocated for the DMA engine.
The stream is in a state other than reset.

Requirements

Requirement	Value
Target Platform	Desktop
Header	hdaudio.h (include Hdaudio.h)
IRQL	PASSIVE_LEVEL