ADC Home > Reference Library > Reference > Darwin > Kernel Framework Reference

IOMbufDBDMAMemoryCursor

Inherits from:	IOMbufMemoryCursor
Declared In:	IOMbufMemoryCursor.h

Overview

An IOMbufMemoryCursor subclass that outputs a vector of IODBDMADescriptors.

Functions

getPhysicalSegments: Generates a DBDMA descriptor list from a given mbuf.
getPhysicalSegmentsWithCoalesce: Generates a DBDMA descriptor list from a given mbuf.
withSpecification: Factory function that creates and initializes an IOMbufDBDMAMemoryCursor in one operation.

getPhysicalSegments

Generates a DBDMA descriptor list from a given mbuf.

public

UInt32 getPhysicalSegments(
    mbuf_t packet, 
    struct IODBDMADescriptor *vector, 
    UInt32 numVectorSegments = 0);

Parameters

packet: The mbuf packet.
vector: Pointer to an array of IODBDMADescriptor for the output list.
numVectorSegments: Maximum number of IODBDMADescriptors accepted.

Return Value

Returns the number of segments that were filled in, or 0 if an error occurred.

getPhysicalSegmentsWithCoalesce

Generates a DBDMA descriptor list from a given mbuf.

public

UInt32 getPhysicalSegmentsWithCoalesce(
    mbuf_t packet, 
    struct IODBDMADescriptor *vector, 
    UInt32 numVectorSegments = 0);

Parameters

packet: The mbuf packet.
vector: Pointer to an array of IODBDMADescriptor for the output list.
numVectorSegments: Maximum number of IODBDMADescriptors accepted.

Return Value

Returns the number of segments that were filled in, or 0 if an error occurred.

Discussion

Generate a DBDMA descriptor list from a given mbuf. Coalesce mbuf chain when the number of elements in the list exceeds numVectorSegments.

withSpecification

Factory function that creates and initializes an IOMbufDBDMAMemoryCursor in one operation.

public

static IOMbufDBDMAMemoryCursor * withSpecification(
    UInt32 maxSegmentSize, 
    UInt32 maxNumSegments);

Parameters

maxSegmentSize: Maximum allowable size for one segment.
maxNumSegments: Maximum number of segments.

Return Value

Returns a new mbuf cursor if successfully created and initialized, 0 otherwise.

Discussion

See also IOMbufMemoryCursor::initWithSpecification.

Did this document help you?

Yes: Tell us what works for you.

It’s good, but: Report typos, inaccuracies, and so forth.

It wasn’t helpful: Tell us what would have helped.

Last Updated: 2008-12-19