putctl(9F)

NAME

putctl − send a control message to a queue

SYNOPSIS

#include <sys/stream.h>
int putctl(queue_t ∗q, int type);

INTERFACE LEVEL

Architecture independent level 1 (DDI/DKI).

ARGUMENTS

q Queue to which the message is to be sent.

type Message type (must be control, not data type).

DESCRIPTION

putctl() tests the type argument to make sure a data type has not been specified, and then attempts to allocate a message block. putctl fails if type is M_DATA, M_PROTO, or M_PCPROTO, or if a message block cannot be allocated. If successful, putctl() calls the put(9E) routine of the queue pointed to by q with the newly allocated and initialized messages.

RETURN VALUES

On success, 1 is returned. If type is a data type, or if a message block cannot be allocated, 0 is returned.

CONTEXT

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

EXAMPLE

The send_ctl routine is used to pass control messages downstream. M_BREAK messages are handled with putctl() (line 11). putctl1(9F) (line 16) is used for M_DELAY messages, so that parm can be used to specify the length of the delay. In either case, if a message block cannot be allocated a variable recording the number of allocation failures is incremented (lines 12, 17). If an invalid message type is detected, cmn_err(9F) panics the system (line 21).

1 void
2 send_ctl(wrq, type, parm)
3      queue_t ∗wrq;
4      unchar type;
5      unchar parm;
6 {
7extern int num_alloc_fail;
8
9switch (type) {
10case M_BREAK:
11if (!putctl(wrq->q_next, M_BREAK))
12num_alloc_fail++;
13break;
14
15case M_DELAY:
16if (!putctl1(wrq->q_next, M_DELAY, parm))
17num_alloc_fail++;
18break;
19
20default:
21cmn_err(CE_PANIC, "send_ctl: bad message type passed");
22break;
23}
24 }

Museum

Related Articles