Domain Functions
User programs access HPI-based platform management by opening a Session with a Domain. The user program may open a Session with a specific Domain by specifying a Domain Identifier, or more commonly, it may open a Session with a default Domain. With a Session established, the user program may access various Domain-level functions, or it may access any of the Resources that are currently listed as members of the Domain. Because a Session will only allow access to Resources that are currently members of the Domain, user access control can be enforced by an HPI implementation by limiting which Resources are members of each Domain, and limiting which users are allowed to establish Sessions with those Domains.
One of the most important functions of the Domain is providing information, via the Resource Presence Table (RPT), about all the Resources that are members of the Domain. A second table, the Domain Reference Table (DRT) provides information about other HPI Domains that may be accessed by opening additional Sessions.
The HPI interface provides three services at the Domain level that a user program can use to stay informed of exceptional conditions in the hardware platform. The most important of these is the Event Management Service. A user may request events be forwarded from the Domain on any open Session. When significant events occur to the hardware Entities monitored by any of the Resources that are members of the Domain, Event messages are generated and queued to all open Sessions that have made such a request. Through this mechanism, user programs can stay informed of changes in the managed platform without needing to continually poll for status. Events may also be stored in the Domain Event Log and retrieved at a later time for historical analysis. Finally, the Domain Alarm Table is accessible by the user program and reports on current alarm conditions present in any of the Resources that are members of the Domain.
Read more about this topic: Hardware Platform Interface
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