SERCX_BUFFER_DESCRIPTOR structure (sercx.h)

The SERCX_BUFFER_DESCRIPTOR structure describes a data buffer for a receive operation or transmit operation.

Syntax

typedef struct SERCX_BUFFER_DESCRIPTOR {
  USHORT Size;
  PUCHAR Buffer;
  ULONG  Length;
} SERCX_BUFFER_DESCRIPTOR, *PSERCX_BUFFER_DESCRIPTOR;

Members

Size

The size, in bytes, of this structure. The SerCxRetrieveReceiveBuffer and SerCxRetrieveTransmitBuffer methods use this member to determine which version of the structure the caller is using. The size of this structure might change in future versions of the Sercx.h header file.

Buffer

The virtual memory address of the buffer. The memory for the buffer is nonpaged.

Length

The number of bytes available in the buffer. This size determines the maximize number of bytes that can be transferred by the receive or transmit operation.

Remarks

The serial controller driver uses the information in this structure to determine where in memory to read data from during a receive operation, and where in memory to write data during a transmit operation.

At any time, there can be no more than one valid receive buffer and one valid transmit buffer. The controller driver calls the SerCxRetrieveReceiveBuffer method to obtain the receive buffer, and calls the SerCxRetrieveTransmitBuffer method to obtain the transmit buffer. Both methods copy buffer descriptions into caller-allocated SERCX_BUFFER_DESCRIPTOR structures. A subsequent call to one of these methods invalidates the previously issued descriptor for the receive buffer or transmit buffer, respectively. The caller must not access a buffer that is described by a buffer descriptor that is no longer valid.

The buffers that are obtained by successive calls to SerCxRetrieveReceiveBuffer or SerCxRetrieveTransmitBuffer are not guaranteed to be contiguous.

The controller driver must call the SERCX_BUFFER_DESCRIPTOR_INIT function to initialize an SERCX_BUFFER_DESCRIPTOR structure before the structure is passed to the SerCxRetrieveReceiveBuffer or SerCxRetrieveTransmitBuffer method. After a buffer descriptor is initialized, it can be reused without being initialized again.

Requirements

See also

SERCX_BUFFER_DESCRIPTOR_INIT

SerCxRetrieveReceiveBuffer

SerCxRetrieveTransmitBuffer