putnextctl1

- send a control message with a one-byte parameter to a queue

Synopsis

#include <sys/stream.h>

int putnextctl1(queue_t *q, int type, int p);

Interface Level

Architecture independent level 1 (DDI/DKI).

Parameters

q

Queue to which the message is to be sent.

type

Type of message.

p

One-byte parameter.

Description

The putnextctl1() function, like putctl1(9F), tests the type argument to make sure a data type has not been specified, and attempts to allocate a message block. The p parameter can be used, for example, to specify how long the delay will be when an M_DELAY message is being sent. putnextctl1() fails if type is M_DATA, M_PROTO, or M_PCPROTO, or if a message block cannot be allocated. If successful, putnextctl1() calls the put(9E) routine of the queue pointed to by q with the newly allocated and initialized message.

A call to putnextctl1(q,type, p) is an atomic equivalent of putctl1(q->q_next, type, p). The STREAMS framework provides whatever mutual exclusion is necessary to insure that dereferencing q through its q_next field and then invoking putctl1(9F) proceeds without interference from other threads.

The putnextctl1() function should always be used in preference to putctl1(9F)

Return Values

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

Context

The putnextctl1() function can be called from user, interrupt, or kernel context.

Examples

See the putnextctl(9F) function page for an example of putnextctl1().

See Also

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

Writing Device Drivers

STREAMS Programming Guide