Intel IXP400 manual Queue Field Description Eth

Intel® IXP400 Software

Access-Layer Components: Ethernet Access (IxEthAcc) API

Table 19. IX_OSAL_MBUF Header Definitions for the Ethernet Subsystem (Sheet 1 of 3)

			Queue
Field	Description
		Eth	Eth	Eth	Eth
		Rx			Tx
			Rx	Tx
		Free			Done
	Physical address of the next IX_OSAL_MBUF in a linked list (chain)
ixp_ne_next	of buffers. For the last IX_OSAL_MBUF in a chain (including the	R	W	R
	case of a single, unchained IX_OSAL_MBUF containing an entire
	frame), ixp_ne_next contains the value 0x00000000.
	The interpretation of this field depends on how the
	IX_OSAL_MBUF is being used:
	• For IX_OSAL_MBUFs submitted to the EthTx or EthTxDone
	queues, ixp_ne_len represents the size (in bytes) of the valid
	frame data in the associated data cluster prior to any frame
	modifications that may occur on the NPE transmit data path. In
	this case, the value of ixp_ne_len must always be greater than
	0, unless the frame length (as specified by the ixp_ne_pkt_len
	field in the first IX_OSAL_MBUF header of the current chain) is
	exhausted before the current IX_OSAL_MBUF is reached. In
ixp_ne_len	other words, it is acceptable for a number of zero-length	R	W	R
	IX_OSAL_MBUFs to be present at the end of a chain, provided
	that the frame ends before the first zero-length buffer is
	reached.
	• For IX_OSAL_MBUFs submitted to the EthRx queues,
	ixp_ne_len represents the size (in bytes) of the valid frame data
	in the associated data cluster. In this case, the value of
	ixp_ne_len must always be greater than 0.
	• For IX_OSAL_MBUFs submitted to the EthRxFree queue,
	ixp_ne_len represents the space in the associated data cluster
	(in bytes) available for buffering a received frame. In this case,
	its value must always be at least 128.
	The value of this field depends on how the IX_OSAL_MBUF is
	being used:
	• For IX_OSAL_MBUFs submitted to the EthTx, EthTxDone, and
	EthRx queues, ixp_ne_pkt_len represents the size (in bytes) of
	the frame contained within the IX_OSAL_MBUF. It is valid only
	in the first IX_OSAL_MBUF in a series of chained
	IX_OSAL_MBUFs. In the event that a frame is contained in a
ixp_ne_pkt_len	single, unchained IX_OSAL_MBUF, the value of this field will		W(6)	R
	be equal to the value of the ixp_ne_len field. For use with these
	queues, the value of ixp_ne_pkt_len must always be greater
	than 0. In the case of IX_OSAL_MBUFs submitted to the EthTx
	and EthTxDone queues, this field represents the length of the
	frame prior to any modifications that may occur on the NPE
	transmit data path.
	• For IX_OSAL_MBUFs submitted to the EthRxFree queue, the
	value of ixp_ne_pkt_len must always be 0.
ixp_ne_data	Physical address of the IX_OSAL_MBUF data cluster.	R		R
	Physical port to which an Ethernet frame is to be forwarded. Refer
ixp_ne_dest_port	to (Table 22 and Table 20). A value of 0xFF indicates that the		W(6)	R(1)
	destination port is unknown, i.e., no entry for the destination MAC
	address could be found in the filtering/forwarding database.
	Either the physical MII port (see Table 22 and Table 20) through		W(6)
ixp_ne_src_port	which an Ethernet frame was received or the port ID extracted from
	the VLAN TPID field of a VLAN-tagged frame.

Programmer’s Guide	IXP400 Software Version 2.0	April 2005
	Document Number: 252539, Revision: 007	149