US Patent 7565471 Message signaled interrupt extended (MSI-X) auto clear and failsafe lock

A method and apparatus is disclosed for improving the MSI and MSI-X specifications by implementing an efficient delivery and clearing mechanism for interrupt conditions to increase performance between the driver and hardware/firmware interface while ensuring that no interrupts are lost in the process. In particular, an auto clear function is employed to eliminate the need for drivers in the host to send writes over the PCI-based bus to deassert and assert attention enable register bits and clear down attention register bits, and a fail safe mechanism is utilized to prevent lost interrupts.