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The routines described in this section generate interrupt acknowledge cycles on the PCI bus. All interrupt acknowledge routines use the type RegEntryIDPtr to identify device nodes in the device tree, as described in Name Registry Using RegEntryIDPtr lets the system software and the PCI bridge generate the correct PCI interrupt acknowledge cycle for the target device.
Mac OS does not use PCI interrupt acknowledge cycles. The functionality is provided so that if a PCI device needs an interrupt acknowledge cycle the driver has a way to create the required cycle on the PCI bus.
Interrupt acknowledge cycles for PCI are always read actions. The target node chosen for the functions described in this section should be the single node in the system capable of responding to interrupt acknowledge cycles.