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

       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.

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  }

SEE ALSO

       put(9E), cmn_err(9F), datamsg(9F), putctl1(9F), putnextctl(9F)

       Writing Device Drivers

       STREAMS Programming Guide

SunOS 5.10							    11 Apr 1991 							putctl(9F)