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

NAME

       qreply - send a message on a stream in the reverse direction

SYNOPSIS

       #include <sys/stream.h>

       void qreply(queue_t *q, mblk_t *mp);

INTERFACE LEVEL

       Architecture independent level 1 (DDI/DKI).

PARAMETERS

       q	Pointer to the queue.

       mp	Pointer to the message to be sent in the opposite direction.

DESCRIPTION

       qreply() sends messages in the reverse direction of normal flow. That is, qreply(q, mp) is equivalent to putnext(OTHERQ(q), mp).

CONTEXT

       qreply() can be called from user or interrupt context.

EXAMPLES

       Example 1: Canonical Flushing Code for STREAMS Drivers.

       This  example  depicts the canonical flushing code for STREAMS drivers.	Assume that the driver has service procedures so that there may be
       messages on its queues. See srv(9E). Its write-side put procedure handles M_FLUSH messages by first checking the FLUSHW bit  in	the  first
       byte of the message, then the write queue is flushed (line 8) and the  FLUSHW bit is turned off (line 9). See put(9E). If the
	FLUSHR	bit  is  on,  then  the read queue is flushed (line 12) and the message is sent back up the read side of the stream with the  qre-
       ply(9F) function (line 13). If the  FLUSHR bit is off, then the message is freed (line 15). See the example for	flushq(9F) for the canoni-
       cal flushing code for modules.

	1  xxxwput(q, mp)
	2    queue_t *q;
	3    mblk_t *mp;
	4  {
	5	switch(mp->b_datap->db_type) {
	6	case M_FLUSH:
	7	    if (*mp->b_rptr & FLUSHW) {
	8		   flushq(q, FLUSHALL);
	9		   *mp->b_rptr &= ~FLUSHW;
       10	      }
       11	    if (*mp->b_rptr & FLUSHR) {
       12		   flushq(RD(q), FLUSHALL);
       13		     qreply(q, mp);
       14	    } else {
       15		     freemsg(mp);
       16	      }
       17	    break;
		  . . .
       18     }
       19  }

SEE ALSO

       put(9E), srv(9E), flushq(9F), OTHERQ(9F), putnext(9F)

       Writing Device Drivers

	STREAMS Programming Guide

SunOS 5.10							    11 Apr 1991 							qreply(9F)