HP UX 11i v1 I/O Cards manual Queue Flags

ZCOM Tables and Data Structures

Queue Header

QFLAG - Queue flags

This field contains some indicators which may affect the processing of a queue. The format is shown in Table 3-29.

Table 3-29	Queue Flags
15-8		7	6	5	4		3		2	1	0
					COL		SEL		FUNC	BLT	ENB
	Symbol					Value (hex)		Meaning
	ZCOM_QFLAG_ENB					0x0001		Queue is enabled
	ZCOM_QFLAG_BLT					0x0002		Queue limit on byte size
	ZCOM_QFLAG_FUNC					0x0004		Queue uses wakeup function
	ZCOM_QFLAG_SEL					0x0008		Queue has a failed “select”
	ZCOM_QFLAG_COL					0x0010		Queue has a “select” collision

When the FUNC bit is set, it indicates the kernel function kept in qfunc is to be called whenever data is added to the queue. This feature may only be used by kernel drivers (via the zsetkfunc routine).

The BLT bit is set if the queue limit check is performed on the number of bytes rather than the number of messages. Currently, only the PTT unacknowledged transmit queue uses it.

Queue manipulation is allowed only when the ENB bit is set. All queues are set to disabled by TTGEN initially, and enabled by the zopen( ) call (where a buffer queue is assigned to a ZLU). During ZCOM subsystem shutdown, the LDM will disable the program queues by clearing this bit.

The SEL and COL bits are used internally for the “select-for-read” function on program ZLUs. When a program ZLU has been “selected” while it has no data, the LDM sets the SEL bit. If more than one program selects this empty ZLU, the COL bit is set. When data arrives for this ZLU the LDM uses these two bits to decide whether to wake up one or multiple programs waiting on the “select” for this ZLU.

QFDATA - Queue function data

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