opensolaris man page for qreply

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

CONTEXT
       The qreply() function can be called from user, interrupt, or kernel 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 qreply() function (line
       13). If the FLUSHR bit is off, then the message is freed (line 15). See the example for flushq(9F) for the canonical flushing code for mod-
       ules.

	 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 5.11							    16 Jan 2006 							qreply(9F)