putnextctl(D3) putnextctl(D3)
NAME
putnextctl - send a control message to a queue
SYNOPSIS
#include <sys/stream.h>
#include <sys/ddi.h>
int putnextctl(queue_t *q, int type);
Arguments
q Pointer to the queue from which the message is to be
sent.
type Message type (must be a control type).
DESCRIPTION
putnextctl tests the type argument to make sure a data type
has not been specified, and then attempts to allocate a
message block. putnextctl fails if type is M_DATA, M_PROTO,
or M_PCPROTO, or if a message block cannot be allocated. If
successful, putnextctl calls the put(D2) procedure of the
queue pointed to by q->q_next, passing it the allocated
message.
Return Values
Upon successful completion, putnextctl returns 1. If type is
a data type, or if a message block cannot be allocated, 0 is
returned.
USAGE
In multithreaded drivers, the q argument to putctl(D3) and
putnextctl may not reference q_next (for example, an argument
of q->q_next is erroneous in a multithreaded driver and is
disallowed by the DDI/DKI). putnextctl(q, type) is provided
as a multiprocessor-safe equivalent to the common call
putctl(q->q_next, type), which is no longer allowed.
Level
Base or Interrupt.
Synchronization Constraints
Does not sleep.
Driver-defined basic locks, read/write locks, and sleep locks
may not be held across calls to this function.
Copyright 1994 Novell, Inc. Page 1
putnextctl(D3) putnextctl(D3)
The caller cannot have the stream frozen [see freezestr(D3)]
when calling this function.
Examples
The send_ctl routine is used to pass control messages
downstream. M_BREAK messages are handled with putnextctl
(line 9). putnextctl1 (line 11) is used for M_DELAY messages,
so that param can be used to specify the length of the delay.
If an invalid message type is detected, send_ctl returns 0,
indicating failure (line 13).
1 int
2 send_ctl(wrq, type, param)
3 queue_t *wrq;
4 uchar_t type;
5 uchar_t param;
6 {
7 switch (type) {
8 case M_BREAK:
9 return(putnextctl(wrq, M_BREAK));
10 case M_DELAY:
11 return(putnextctl1(wrq, M_DELAY, param));
12 default:
13 return(0);
14 }
15 }
REFERENCES
put(D2), put(D3), putctl(D3), putctl1(D3), putnextctl1(D3)
NOTICES
Portability
All processors
Applicability
ddi: 3, 5, 5mp, 6, 6mp, 7, 7mp
Copyright 1994 Novell, Inc. Page 2