1.中断处理体系结构
Linux内核将所有中断统一编号，使用一个irq_desc结构数组来描述这些中断。
数组声明在/linux/kernel/irq/handle.c中，其中#define NR_IRQS 128，定义在/linux/include/asm/irq.h中
/*
* Linux has a controller-independent interrupt architecture.
* Every controller has a 'controller-template', that is used
* by the main code to do the right thing. Each driver-visible
* interrupt source is transparently wired to the appropriate
* controller. Thus drivers need not be aware of the
* interrupt-controller.
*
* The code is designed to be easily extended with new/different
* interrupt controllers, without having to do assembly magic or
* having to touch the generic code.
*
* Controller mappings for all interrupt sources:
*/
struct irq_desc irq_desc[NR_IRQS] __cacheline_aligned_in_smp = {
[0 ... NR_IRQS-1] = {
.status = IRQ_DISABLED,
.chip = &no_irq_chip,
.handle_irq = handle_bad_irq,
.depth = 1,
.lock = __SPIN_LOCK_UNLOCKED(irq_desc->lock),
#ifdef CONFIG_SMP
.affinity = CPU_MASK_ALL
#endif
}
};
irq_desc结构的数据类型在/linuxinclude/linux/irq.h中定义，
struct irq_desc {
irq_flow_handler_t handle_irq;
struct irq_chip *chip;
struct msi_desc *msi_desc;
void *handler_data;
void *chip_data;
struct irqaction *action; /* IRQ action list */
unsigned int status; /* IRQ status */
unsigned int depth; /* nested irq disables */
unsigned int wake_depth; /* nested wake enables */
unsigned int irq_count; /* For detecting broken IRQs */
unsigned int irqs_unhandled;
spinlock_t lock;
#ifdef CONFIG_SMP
cpumask_t affinity;
unsigned int cpu;
#endif
#if defined(CONFIG_GENERIC_PENDING_IRQ) || defined(CONFIG_IRQBALANCE)
cpumask_t pending_mask;
#endif
#ifdef CONFIG_PROC_FS
struct proc_dir_entry *dir;
#endif
const char *name;
} ____cacheline_internodealigned_in_smp;
handle_irq是这个或这组中断的处理函数入口。发生中断时，总入口函数asm_do_IRQ将根据中断号调用相应irq_desc数组项中handle_irq.
typedef void fastcall (*irq_flow_handler_t)(unsigned int irq, struct irq_desc *desc);
handle_irq使用chip结构中的函数清除、屏蔽或者重新使能中断，还要调用用户在action链表中注册的中断处理函数。irq_chip结构类型也是在include/linux/irq.h中定义，其中的成员大多用于操作底层硬件，比如设置寄存器以屏蔽中断，使能中断，清除中断等。注意这里的成员name会出现在/proc/interrupts中。
struct irq_chip {
const char *name;
unsigned int (*startup)(unsigned int irq);
void (*shutdown)(unsigned int irq);
void (*enable)(unsigned int irq);
void (*disable)(unsigned int irq);
void (*ack)(unsigned int irq);
void (*mask)(unsigned int irq);
void (*mask_ack)(unsigned int irq);
void (*unmask)(unsigned int irq);
void (*eoi)(unsigned int irq);
void (*end)(unsigned int irq);
void (*set_affinity)(unsigned int irq, cpumask_t dest);
int (*retrigger)(unsigned int irq);
int (*set_type)(unsigned int irq, unsigned int flow_type);
int (*set_wake)(unsigned int irq, unsigned int on);
/* Currently used only by UML, might disappear one day.*/
#ifdef CONFIG_IRQ_RELEASE_METHOD
void (*release)(unsigned int irq, void *dev_id);
#endif
/*
* For compatibility, ->typename is copied into ->name.
* Will disappear.
*/
const char *typename;
};