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)
