BACKQ(9F) Kernel Functions for Drivers BACKQ(9F)

NAME

backq - get pointer to the queue behind the current queue

SYNOPSIS

#include <sys/stream.h>


queue_t *backq(queue_t *cq);

INTERFACE LEVEL

Architecture independent level 1 (DDI/DKI).

PARAMETERS

cq
The pointer to the current queue. queue_t is an alias for the
queue(9S) structure.

DESCRIPTION

The backq() function returns a pointer to the queue preceding cq (the
current queue). If cq is a read queue, backq() returns a pointer to
the queue downstream from cq, unless it is the stream end. If cq is a
write queue, backq() returns a pointer to the next queue upstream
from cq, unless it is the stream head.

RETURN VALUES

If successful, backq() returns a pointer to the queue preceding the
current queue. Otherwise, it returns NULL.

CONTEXT

The backq() function can be called from user, interrupt, or kernel
context.

SEE ALSO

queue(9S)


Writing Device Drivers


STREAMS Programming Guide

January 16, 2006 BACKQ(9F)