Hi all, First, I have to say sorry for my pool English , because I am not a native English speaker. I know this is too simple, but I have tried hours to get the definition (not declaration) of irq_desc array in the interrupt subsys. Actually, I have been troubled in finding the definition. Because the array name( irq_desc) is same as the name of struct irq_desc. I think the irq_desc array is the core of interrupt subsys, so I didn't describe it in details. I tried describing my question , if there is something not clear, please let me know ,and I will try .. Sorry for my pool English again....