PFREE_ADAPTER_CHANNEL callback function (wdm.h)

Article
02/22/2024

The FreeAdapterChannel routine releases the system DMA controller when a driver has completed all DMA operations necessary to satisfy the current IRP.

Syntax

PFREE_ADAPTER_CHANNEL PfreeAdapterChannel;

void PfreeAdapterChannel(
  [in] PDMA_ADAPTER DmaAdapter
)
{...}

Parameters

[in] DmaAdapter

Pointer to the DMA_ADAPTER structure returned by IoGetDmaAdapter that represents the bus-master adapter or DMA controller.

Return value

None

Remarks

FreeAdapterChannel is not a system routine that can be called directly by name. This routine is callable only by pointer from the address returned in a DMA_OPERATIONS structure. Drivers obtain the address of this routine by calling IoGetDmaAdapter.

After a driver has transferred all the data and called FlushAdapterBuffers, it calls FreeAdapterChannel to release the system DMA controller that was previously allocated with a call to AllocateAdapterChannel.

FreeAdapterChannel frees any map registers that were allocated by an earlier call to AllocateAdapterChannel. A driver calls this routine only if its AdapterControl routine returns KeepObject.

Requirements

Requirement	Value
Minimum supported client	Available starting with Windows 2000.
Target Platform	Desktop
Header	wdm.h (include Wdm.h, Ntddk.h, Ntifs.h)
IRQL	DISPATCH_LEVEL
DDI compliance rules	IrqlDispatch(storport), IrqlDispatch(storport), IrqlDispatch(wdm)