Manual Pages for UNIX Operating System command usage for man qreply

Kernel Functions for Drivers                           qreply(9F)



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

SYNOPSIS
     #include 



     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  direc-
     tion 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  qre-
     ply() 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 modules.


       1  xxxwput(q, mp)
        2    queue_t *q;
        3    mblk_t *mp;



SunOS 5.11          Last change: 16 Jan 2006                    1






Kernel Functions for Drivers                           qreply(9F)



        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          Last change: 16 Jan 2006                    2