中断驱动分析

中断驱动程序加载和卸载过程分析：箭头代表进入该函数内部  部分代码省略

//1.注册中断服务程序
>>int request_irq(unsigned int irq, irq_handler_t handler,
        unsigned long irqflags, const char *devname, void *dev_id)
    //1.1分配irqaction结构体
        action = kmalloc(sizeof(struct irqaction), GFP_ATOMIC);
    //1.2设置irq
      >>retval = setup_irq(irq, action);
        //1.2.a 找到中断号对应的irq_desc结构体 irq_desc[irq]

            struct irq_desc *desc = irq_desc + irq;
            struct irqaction *old, **p;
            const char *old_name = NULL;
            unsigned long flags;
            int shared = 0;
            p = &desc->action;
            old = *p;
         //    判断是否有链入action结构体，如果有，
        //    则判断是否为IRQF_SHARED，IRQF_TRIGGER_MASK才能链入action
            if (old) {
                            /*
                             * Can't share interrupts unless both agree to and are
                             * the same type (level, edge, polarity). So both flag
                             * fields must have IRQF_SHARED set and the bits which
                             * set the trigger type must match.
                             */
                            if (!((old->flags & new->flags) & IRQF_SHARED) ||
                                ((old->flags ^ new->flags) & IRQF_TRIGGER_MASK)) {
                                old_name = old->name;
                                goto mismatch;        //跳到出错处理
                            }
                            //将action添加到链表
                            do {
                            p = &old->next;
                            old = *p;
                            } while (old);
                }

        //chip结构体中set_type,starup,enable等操作
            desc->chip->set_type(irq,new->flags & IRQF_TRIGGER_MASK);
            if (desc->chip->startup)
                desc->chip->startup(irq);
            else
                desc->chip->enable(irq);


//2 卸载中断服务程序
>>void free_irq(unsigned int irq, void *dev_id)
        //2.1找到对应的irq_desc结构体，释放action结构体
            desc = irq_desc + irq;
            if (desc->chip->shutdown)
                    desc->chip->shutdown(irq);
            else
                    desc->chip->disable(irq);
            kfree(action);