Description

The StreamClassGetPhysicalAddress routine translates a virtual memory address to a physical memory address and locks the corresponding physical memory for a DMA operation.

Parameters

HwDeviceExtension [in]

Pointer to the minidriver's device extension. The minidriver specifies the size of this buffer in the HW_INITIALIZATION_DATA structure it passes when it registers itself via StreamClassRegisterMinidriver. The class driver then passes pointers to the buffer in the HwDeviceExtension member of the HW_STREAM_REQUEST_BLOCK, HW_STREAM_OBJECT, HW_TIME_CONTEXT, and PORT_CONFIGURATION_INFORMATION structures it passes to the minidriver.

HwSRB [in, optional]

Specifies a stream request block. This parameter is used only if the Type parameter has the value SRBDataBuffer, otherwise HwSRB should be NULL. This parameter is optional.

VirtualAddress [in]

Specifies the virtual address to be translated.

Type [in]

Specifies the type of buffer pointed to by VirtualAddress. This value may be PerRequestExtension, DmaBuffer, or SRBDataBuffer.

Length [out]

Specifies the length, in bytes, of the buffer.

Return value

StreamClassGetPhysicalAddress returns the translated virtual address as a physical memory address.

Remarks

The type of buffer to be used is specified in the Type parameter. The meanings of these values are shown in the following table.