putctl(9f) - osol9

1putctl(9F)               Kernel Functions for Drivers               putctl(9F)
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NAME

6       putctl - send a control message to a queue
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SYNOPSIS

9       #include <sys/stream.h>
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13       int putctl(queue_t *q, int type);
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INTERFACE LEVEL

17       Architecture independent level 1 (DDI/DKI).
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PARAMETERS

20       q       Queue to which the message is to be sent.
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23       type    Message type (must be control, not data type).
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DESCRIPTION

27       The  putctl() function tests the type argument to make sure a data type
28       has not been specified, and then attempts to allocate a message  block.
29       putctl()  fails  if type is M_DATA, M_PROTO, or M_PCPROTO, or if a mes‐
30       sage block cannot be allocated.  If  successful,   putctl()  calls  the
31       put(9E)  routine  of the queue pointed to by q with the newly allocated
32       and initialized messages.
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RETURN VALUES

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

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

43       Example 1 Using putctl()
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46       The send_ctl() routine is used to  pass  control  messages  downstream.
47       M_BREAK messages are handled with putctl() (line 11). putctl1(9F) (line
48       16) is used for M_DELAY messages, so that parm can be used  to  specify
49       the  length  of the delay. In either case, if a message block cannot be
50       allocated a variable recording the number  of  allocation  failures  is
51       incremented  (lines  12,  17).  If an invalid message type is detected,
52       cmn_err(9F) panics the system (line 21).
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55         1  void
56          2  send_ctl(wrq, type, parm)
57          3      queue_t *wrq;
58          4      uchar_t type;
59          5      uchar_t parm;
60          6  {
61          7         extern int num_alloc_fail;
62          8
63          9       switch (type) {
64         10         case M_BREAK:
65         11             if (!putctl(wrq->q_next, M_BREAK))
66         12                      num_alloc_fail++;
67         13               break;
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69         15       case M_DELAY:
70         16             if (!putctl1(wrq->q_next, M_DELAY, parm))
71         17                      num_alloc_fail++;
72         18             break;
73         19
74         20       default:
75         21             cmn_err(CE_PANIC, "send_ctl: bad message type passed");
76         22               break;
77         23         }
78         24  }
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