getq(9F)

NAME

     getq - get the next message from a queue

SYNOPSIS

     #include <sys/stream.h>

     mblk_t *getq(queue_t *q);

INTERFACE LEVEL

     Architecture independent level 1 (DDI/DKI).

PARAMETERS

     q     Pointer to the queue from which the message is  to  be
           retrieved.

DESCRIPTION

     getq() is used by a service ( srv(9E)) routine  to  retrieve
     its enqueued messages.

     A module or driver may include a service routine to  process
     enqueued messages. Once the STREAMS scheduler calls srv() it
     must process all enqueued messages, unless prevented by flow
     control.  getq() obtains the next available message from the
     top of the queue pointed to by q. It should be called  in  a
     while  loop  that is exited only when there are no more mes-
     sages or flow control prevents further processing.

     If an attempt was made to write to the queue  while  it  was
     blocked  by flow control, getq() back-enables (restarts) the
     service routine once it falls below the low water mark.

RETURN VALUES

     If there is a message to retrieve, getq() returns a  pointer
     to  it.  If  no  message  is  queued,  getq() returns a NULL
     pointer.

CONTEXT

     getq() can be called from user or interrupt context.

EXAMPLES

     See dupb(9F).

SEE ALSO

     srv(9E),  bcanput(9F),  canput(9F),   dupb(9F),   putbq(9F),
     putq(9F), qenable(9F)

     Writing Device Drivers

     STREAMS Programming Guide