Service request system using an activity indicator to reduce processing overhead

Abstract

A service request system for a subsystem of a computer including a processor, a driver, and inhibit logic. The inhibit logic detects requests for service by the subsystem and asserts an interrupt unless the driver is executing and servicing the subsystem. The driver is executed by the processor in response to the interrupt to service the subsystem, where the driver controls the inhibit logic to prevent interrupts associated with the subsystem from being asserted while the driver is being executed by the processor. In this manner, redundant interrupts or service requests initiated by the subsystem are eliminated. The service request system may include an activity indicator that indicates whether the driver is being executed. Th inhibit logic asserts an interrupt in response to a service request from the subsystem unless the activity indicator indicates that the driver is in control of the processor. The subsystem may further detect the activity indicator and inhibit requesting service while the activity indicator indicates that the driver is active. In this manner, the subsystem avoids wasting time associated with requesting service. Also, the subsystem may be operated in a more streamlined mode while the driver is in control of the processor. In one embodiment, the activity indicator is a logic bit, where the driver changes the state of the logic bit upon execution to a first state and changes the state of the logic bit to a second state upon exiting.