Gadgets are necessary to follow a protocol so the interrupt-ask for (IRQ) traces might be shared. The PCI bus features four interrupt lines, INTA# by means of INTD#, all of which can be found to each system. Approximately eight PCI devices share exactly the same IRQ line (INTINA# via INTINH#) https://nathanlabsadvisory.com/iot-security-testing/