struct irq_data — per irq and irq chip data passed down to chip functions
struct irq_data {
unsigned int irq;
unsigned int node;
struct irq_chip * chip;
void * handler_data;
void * chip_data;
struct msi_desc * msi_desc;
#ifdef CONFIG_SMP
cpumask_var_t affinity;
#endif
}; interrupt number
node index useful for balancing
low level interrupt hardware access
per-IRQ data for the irq_chip methods
platform-specific per-chip private data for the chip methods, to allow shared chip implementations
MSI descriptor
IRQ affinity on SMP