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| Kernel Functions for Drivers | putctl(9F) |
| | putctl - send a control message to a queue |
SYNOPSIS
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#include <sys/stream.h>
int putctl(queue_t *q, int type); |
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Architecture independent level 1 (DDI/DKI).
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q
- Queue to which the message is to be sent.
-
type
- Message type (must be control, not data type).
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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.
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On success, 1 is returned. If type is a data type, or if a message block cannot be allocated, 0 is returned.
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putctl() can be called from user or interrupt context.
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| | Example 1. Using putctl
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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).
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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 }
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