DLPI Programmer's Guide

Chapter 2 141
DLPI Primitives
DLPI States
• The DLS provider may never generate a primitive that places the
interface out of state.
• If the DLS provider generates a STREAMS M_ERROR message
upstream, it should free any further primitives processed by its write
side put or service procedure.
• The close of a stream is considered an abortive action by the DLS
user, and may be executed from any state. The DLS provider must
issue appropriate indications to the remote DLS user when a close
occurs. For example, if the DLPI state is DL_DATAXFER, a
DL_DISCONNECT_IND should be sent to the remote DLS user. The
DLS provider should free any resources associated with that stream
and reset the stream to its unopened condition.
The following points clarify the state transition table.
• If the DLS provider supports connection-mode service, the value of
the outcnt state variable must be initialized to zero for each stream
when that stream is first opened.
• The initial and final state for a style 2 DLS provider is
DL_UNATTACHED. However, because a style 1 DLS provider
implicitly attaches a PPA to a stream when it is opened, the initial
and final DLPI state for a style 1 provider is DL_UNBOUND. The
DLS user should not issue DL_ATTACH_REQ or DL_DETACH_REQ
primitives to a style 1 DLS provider.
• A DLS provider may have multiple connect indications outstanding
(i.e. the DLS user has not responded to them) at one time. As the
state transition table points out, the stream on which those
indications are outstanding will remain in the
DL_INCON_PENDING state until the DLS provider receives a
response for all indications.
• The DLPI state associated with a given stream may be transferred to
another stream only when the DL_CONNECT_RES primitive
indicates this behavior. In this case, the responding stream (where
the connection will be established) must be in the DL_IDLE state.
• The labeling of the states DL_PROV_RESET_PENDING and
DL_USER_RESET_PENDING indicate the party that started the
local interaction, and does not necessarily indicate the originator of
the reset procedure.