Tribblix: manual page: put.9e

PUT(9E) Driver Entry Points PUT(9E)

NAME

put - receive messages from the preceding queue

SYNOPSIS

#include <sys/types.h>
#include <sys/stream.h>
#include <sys/stropts.h>
#include <sys/ddi.h>
#include <sys/sunddi.h>

int prefixrput(queue_t *q, mblk_t *mp); /* read side */

int prefixwput(queue_t *q, mblk_t *mp); /* write side */

INTERFACE LEVEL

Architecture independent level 1 (DDI/DKI). This entry point is
required for STREAMS.

ARGUMENTS

q
Pointer to the queue(9S) structure.

mp
Pointer to the message block.

DESCRIPTION

The primary task of the put() routine is to coordinate the passing of
messages from one queue to the next in a stream. The put() routine is
called by the preceding stream component (stream module, driver, or
stream head). put() routines are designated ``write'' or ``read''
depending on the direction of message flow.

With few exceptions, a streams module or driver must have a put()
routine. One exception is the read side of a driver, which does not
need a put() routine because there is no component downstream to call
it. The put() routine is always called before the component's
corresponding srv(9E) (service) routine, and so put() should be used
for the immediate processing of messages.

A put() routine must do at least one of the following when it
receives a message:

o pass the message to the next component on the stream by
calling the putnext(9F) function;

o process the message, if immediate processing is required
(for example, to handle high priority messages); or

o enqueue the message (with the putq(9F) function) for
deferred processing by the service srv(9E) routine.

Typically, a put() routine will switch on message type, which is
contained in the db_type member of the datab structure pointed to by
mp. The action taken by the put() routine depends on the message
type. For example, a put() routine might process high priority
messages, enqueue normal messages, and handle an unrecognized M_IOCTL
message by changing its type to M_IOCNAK (negative acknowledgement)
and sending it back to the stream head using the qreply(9F) function.

The putq(9F) function can be used as a module's put() routine when no
special processing is required and all messages are to be enqueued
for the srv(9E) routine.

RETURN VALUES

Ignored.

CONTEXT

put() routines do not have user context.