GET_DMA_ADAPTER callback function (wdm.h)

The GetDmaAdapter routine returns a DMA_ADAPTER structure for the target device.

Syntax

GET_DMA_ADAPTER GetDmaAdapter;

_DMA_ADAPTER * GetDmaAdapter(
  [in]  PVOID Context,
  [in]  _DEVICE_DESCRIPTION *DeviceDescriptor,
  [out] PULONG NumberOfMapRegisters
)
{...}

Parameters

[in] Context

A pointer to interface-specific context information. The caller passes the value that is passed as the Context member of the BUS_INTERFACE_STANDARD structure for the interface.

[in] DeviceDescriptor

A pointer to a DEVICE_DESCRIPTION structure that describes the attributes of the physical device.

[out] NumberOfMapRegisters

A pointer to, on output, the maximum number of map registers that the driver can allocate for any DMA transfer operation. The caller must allocate a LONG variable to receive this data.

Return value

The GetDmaAdapter routine returns a pointer to a DMA_ADAPTER structure when successful. If an adapter structure cannot be allocated, the routine returns NULL.

Remarks

If the driver is executing at IRQL = PASSIVE_LEVEL, it should obtain a device's DMA adapter object by calling the IoGetDmaAdapter function. IoGetDmaAdapter detects whether the bus driver supports the BUS_INTERFACE_STANDARD interface; if it does, IoGetDmaAdapter calls the routine pointed to by the GetDmaAdapter member of this interface to obtain the adapter object. Otherwise, IoGetDmaAdapter calls an equivalent legacy routine.

However, if a driver must obtain an adapter object while running at IRQL ≥ DISPATCH_LEVEL, it cannot do so with the IoGetDmaAdapter function. In such a case, the driver must query for the BUS_INTERFACE_STANDARD interface while still at IRQL = PASSIVE_LEVEL by issuing an IRP_MN_QUERY_INTERFACE request.

Requirements

See also

BUS_INTERFACE_STANDARD

DEVICE_DESCRIPTION

DMA_ADAPTER

IoGetDmaAdapter