Interrupt handling for a computing system with logical devices and

Abstract

A computing system including a host processor and at least one intelligent subsystem having attached devices, has two interrupt ports. The one intelligent subsystem and the attached devices are each viewed as a logical device by the host processor, and each is assigned a device identification number. The host processor provides direct and indirect commands to the logical devices. For direct commands, first physical interrupts are provided to the host processor serially from the logical devices through an Interrupt Status Port. For indirect commands, logical interrupts are stored in predetermined bit positions in a Device Interrupt Indentifier Port (DIIP) in accordance with the device identification numbers. A second single physical interrupt is provided to the host processor as long as there is at least one logical interrupt pending from at least one logical device as the result of an indirect command. The host processor reads the DIIP to determine which logical devices have at least one logical interrupt pending for an indirect command. A plurality of logical interrupts for a single logical device may be cleared with a single reset interrupt command from the host processor.