pkon(2) [v7 man page]

PKON(2) 							System Calls Manual							   PKON(2)

NAME

       pkon, pkoff - establish packet protocol

SYNOPSIS

       pkon(fd, size)

       pkoff(fd)

DESCRIPTION

       Pkon  establishes  packet  protocol  (see  pk(4)) on the open character special file whose file descriptor is fd.  Size is a desired packet
       size, a power of 2 in the range 32<=size<=4096.	The size is negotiated with a remote packet driver, and a possibly smaller  actual  packet
       size is returned.

       An asynchronous line used for packet communication should be in raw mode; see tty(4).

       Pkoff turns off the packet driver on the channel whose file descriptor is fd.

SEE ALSO

       pk(4), pkopen(3), tty(4), signal(2)

DIAGNOSTICS

       Pkon returns -1 if fd does not describe an open file, or if packet communication cannot be established.

       Pkoff returns -1 for an unknown file descriptor.

       Writing on a packet driver link that has been shut down by close or pkoff at the other end raises signal SIGPIPE in the writing process.

																	   PKON(2)

PK(4)							     Kernel Interfaces Manual							     PK(4)

NAME

       pk - packet driver

DESCRIPTION

       The  packet  driver implements a full-duplex end-to-end flow control strategy for machine-to-machine communication.  Packet driver protocol
       is established by calling pkon(2) with a character device file descriptor and a desired packet size in bytes.  The packet size  must  be  a
       power  of  2,  32<=size<=4096.  The file descriptor must represent an 8-bit data path.  This is normally obtained by  setting the device in
       raw mode (see ioctl(2)).

       The actual packet size, which may be smaller than the desired packet size, is arrived at by negotiation	with  the  packet  driver  at  the
       remote end of the data link.

       The  packet  driver  maintains  two data areas for incoming and outgoing packets.  The output area is needed to implement retransmission on
       errors, and arriving packets are queued in the input area.  Data arriving for a file not open for reading is discarded.	Initially the size
       of both areas is set to two packets.

       It  is not necessary that reads and writes be multiples of the packet size although there is less system overhead if they are.  Read opera-
       tions return the maximum amount of data available from the input area up to the number of bytes specified in the system call.   The  buffer
       sizes  in  write  operations  are  not  normally transmitted across the link.  However, writes of zero length are treated specially and are
       reflected at the remote end as a zero-length read.  This facilitates marking the serial byte stream, usually for delimiting files.

       When one side of a packet driver link is shut down by close(2)or pkoff (see pkon(2)), read(2) on the other side will return 0, and write on
       the other side will raise a SIGPIPE signal.

SEE ALSO

       pkon(2), pkopen(3)

								       local								     PK(4)