Writing Monitors for the Event Monitoring Service (December 1999)

80 Chapter3

Creating a Resource Monitor

Processing a Subclass Request Event

The Subclass Request is a message that a client sends to get the

deﬁnition of a particular resource class or instance.

The Subclass Request Event is speciﬁed by a return_type of

RM_SUBCLASS_REQUEST_EVENT from rm_get_next_event().

Include in the reply information that describes the resource, plus the

names of any subclasses that exist below the resource.

• If the subclass event is for a resource class, provide subclasses.

• If the subclass event is for a resource instance, provide the instance

type and other instance information. For example, if the resource

instance is an enumerated type, provide enumerations.

Replying to Subclass Events

To write a subclass event for your resource monitor, include the following

information.

• Check that the resource (class or instance) requested is one we

support.

If the monitor cannot respond immediately with its resource, it can

reply with RmResourceType=RM_NOT_READY. This should only be done

for temporary delays.

• Check the subclass ﬁlter. For example:

— If the request is for asynchronous resources but the monitor has

only state resources, no resources satisfy the ﬁltered request. Set

RmResourceType to RM_ERROR_TYPE, and send the reply.

— If the request allows for both asynchronous and state type

resources and the monitor only has state type resources, set the

RmStateType to RM_STATE.

• If the monitor is for a resource class, provide the subclasses.

• If the monitor is for a resource instance, set RmResourceType:

— If the type is enumerated, set the RmStateObject ﬁeld.

— If the type is enumerated and is an RM_OV_ENUMERATION, set the