illumos: manual page: putctl.9f

PUTCTL(9F) Kernel Functions for Drivers 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).

PARAMETERS

q
Queue to which the message is to be sent.

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

DESCRIPTION

The putctl() function 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

The putctl() function can be called from user, interrupt, or kernel
context.

EXAMPLES

Example 1: Using putctl()

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