Kernel Functions for Drivers                            backq(9F)



NAME
     backq - get pointer to the queue behind the current queue

SYNOPSIS
     #include 



     queuet *backq(queuet *cq);


INTERFACE LEVEL
     Architecture independent level 1 (DI/DKI).

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


DESCRIPTION
     The backq() function returns a pointer to the queue  preced-
     ing  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 NUL.

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

SEE ALSO
     queue(9S)


     Writing Device Drivers


     STREAMS Programming Guide












SunOS 5.11          Last change: 16 Jan 2006                    1