Hardware Platform Interface - Hot-swap Management

Hot-swap Management

A key feature of the HPI specification is the way it handles dynamic reconfiguration, or hot-swap actions in the managed platform. Hot-swap refers to the ability to add or remove hardware components in a running platform. HPI terms a hardware Entity that can be hot-swapped as a Field Replaceable Unit, or FRU. Often, especially in system architectures like AdvancedTCA, FRUs include their own platform management controllers. Thus, hot-swapping a FRU can simultaneously modify both the set of hardware Entities to be managed and the infrastructure available for that management.

The HPI approach to hot-swap management reflects this by modeling the addition or removal of a hardware Entity by adding or removing a Resource in a Domain. If the FRU does not include its own management controller, the Resource may not have any management capabilities assigned to it, but it is still used to report the presence of the FRU in the system. On the other hand, if the FRU does include a management controller, then the Resource that is added to the Domain can host new Management Instruments or other capabilities and make them available to the HPI user.

The Resource associated with a FRU will always be in one of five Hot-swap States, which are readable by the HPI user: Not Present, Inactive, Insertion Pending, Active, Extraction Pending. The Not Present state is never actually reported by a Resource, because when the FRU is not present in the system, the Resource should not exist as a member of any Domain. The other four states are applicable for FRUs that are physically present in the system, whether or not they are fully operational. When a Resource changes to a new Hot-swap State, an HPI event is sent to user programs that have requested event notifications.

HPI Resources that model hot-swappable FRUs may be configured to support either Unmanaged Hot-swap or Managed Hot-swap. A Resource that supports Unmanaged Hot-swap will report its current Hot-swap State, but the user has no control over the Hot-swap operations of the FRU. When a Resource supports Managed Hot-swap, then a user program can interact with the HPI implementation and the underlying platform management infrastructure to coordinate the actions required to integrate newly added FRUs or to deactivate FRUs being removed from the system.