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.

SEE ALSO


srv(9E), putctl(9F), putctl1(9F), putnext(9F), putnextctl(9F),
putnextctl1(9F), putq(9F), qreply(9F), queue(9S), streamtab(9S)


Writing Device Drivers


STREAMS Programming Guide


November 12, 1992 PUT(9E)