BACKQ(9F) Kernel Functions for Drivers BACKQ(9F)
backq - get pointer to the queue behind the current queue
#include <sys/stream.h>
queue_t *backq(queue_t *cq);
Architecture independent level 1 (DDI/DKI).
cq
The pointer to the current queue. queue_t is an alias for the
queue(9S) structure.
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.
If successful, backq() returns a pointer to the queue preceding the
current queue. Otherwise, it returns NULL.
The backq() function can be called from user, interrupt, or kernel
context.
queue(9S)
Writing Device Drivers
STREAMS Programming Guide
January 16, 2006 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)