NAME    [Toc]    [Back]

       pckt  - STREAMS module for constructing message packets on
       a pty

DESCRIPTION    [Toc]    [Back]

       The pckt module is a STREAMS module that can be used  with
       a  pseudoterminal to transfer messages in packet mode. The
       packet mode feature of pty devices allows the user process
       on  the  master side of the device to be informed of state
       changes.

       For packet mode to be enabled in the pty device, the  user
       process  must push the pckt module onto the master side of
       the pty with a call to the STREAMS  I_PUSH  ioctl()  function.


       When  the user process writes data, the pckt module passes
       the message on to the next  module  or  driver  unchanged.
       When  the  user process reads data or when the pckt module
       receives certain STREAMS message types,  it  constructs  a
       packet out of the message for forwarding upstream.

       To  construct  a  message  packet,  the  module creates an
       M_PROTO message. This M_PROTO message contains the  original
  message type in the first data block and the original
       message in as many data blocks as needed. The user process
       can  then  retrieve the M_PROTO message with a call to the
       getmsg() function.

       The STREAMS message types that the pckt module  places  in
       packets, are the following:

       M_DATA
       M_IOCTL
       M_PROTO
       M_PCPROTO
       M_FLUSH
       M_START
       M_STOP
       M_STARTI
       M_STOPI
       M_READ

       All other messages are passed unchanged upstream.

       If  the  message  is  an  M_FLUSH message, the pckt module
       looks at the flag and takes the following actions: If  the
       flag  is  FLUSHW,  the  module changes it to FLUSHR before
       creating the  M_PROTO  message,  and  passes  the  message
       upstream.  The  module  also sends an M_FLUSH message with
       the FLUSHW flag set.  If the flag is  FLUSHR,  the  module
       changes  it to FLUSHW before creating the M_PROTO message,
       and passes the message upstream.  If the flag is  FLUSHRW,
       the  module  changes  it  to  FLUSHW  before  creating the
       M_PROTO message, and passes the message upstream. The module
  also  sends  an  M_FLUSH message with the FLUSHW flag
       set.

SEE ALSO    [Toc]    [Back]

       Functions: getmsg(2), ioctl(2)

       Interfaces: ldterm(7), ptem(7), streamio(7)



                                                          pckt(7)