本文共 2404 字，大约阅读时间需要 8 分钟。

int irq_set_irq_type(unsigned int irq, unsigned int type)用于设置irq对应的中断的触发类型.其使用的例程如下：static void __init meta_intc_init_cpu(struct meta_intc_priv *priv, int cpu){	unsigned int thread = cpu_2_hwthread_id[cpu];	unsigned int signum = TBID_SIGNUM_TR2(thread);	int irq = tbisig_map(signum);	/* Register the multiplexed IRQ handler */	irq_set_chained_handler(irq, meta_intc_irq_demux);	irq_set_irq_type(irq, IRQ_TYPE_LEVEL_LOW);}这里就通过调用irq_set_irq_type 将中断类型设置为低电平触发.其源码分析如下：int irq_set_irq_type(unsigned int irq, unsigned int type){	unsigned long flags;	#通过irq number得到中断描述符，得到并操作中断描述符时需要通过irq_get_desc_buslock和irq_put_desc_busunlock的保护.	struct irq_desc *desc = irq_get_desc_buslock(irq, &flags, IRQ_GET_DESC_CHECK_GLOBAL);	int ret = 0;	#中断描述符为null，则退出	if (!desc)		return -EINVAL;	#通过中断描述符设置中断触发的类型.	ret = __irq_set_trigger(desc, type);	irq_put_desc_busunlock(desc, flags);	return ret;}int __irq_set_trigger(struct irq_desc *desc, unsigned long flags){	struct irq_chip *chip = desc->irq_data.chip;	int ret, unmask = 0;	#中断描述符中的chip 或者chip对应的irq_set_type 为null，则退出	#因为这里最终会调用chip->irq_set_type 来设置中断触发类型	if (!chip || !chip->irq_set_type) {		/*		 * IRQF_TRIGGER_* but the PIC does not support multiple		 * flow-types?		 */		pr_debug("No set_type function for IRQ %d (%s)\n",			 irq_desc_get_irq(desc),			 chip ? (chip->name ? : "unknown") : "unknown");		return 0;	}	if (chip->flags & IRQCHIP_SET_TYPE_MASKED) {		if (!irqd_irq_masked(&desc->irq_data))			mask_irq(desc);		if (!irqd_irq_disabled(&desc->irq_data))			unmask = 1;	}	/* Mask all flags except trigger mode */	flags &= IRQ_TYPE_SENSE_MASK;	#核心代码设置irq的中断触发类型	ret = chip->irq_set_type(&desc->irq_data, flags);		switch (ret) {	#注意这个case 没有break 语句，因此返回值IRQ_SET_MASK_OK/IRQ_SET_MASK_OK_DONE会比IRQ_SET_MASK_OK_NOCOPY 多调用两个函数.	case IRQ_SET_MASK_OK:	case IRQ_SET_MASK_OK_DONE:		irqd_clear(&desc->irq_data, IRQD_TRIGGER_MASK);		irqd_set(&desc->irq_data, flags);	case IRQ_SET_MASK_OK_NOCOPY:		flags = irqd_get_trigger_type(&desc->irq_data);		irq_settings_set_trigger_mask(desc, flags);		irqd_clear(&desc->irq_data, IRQD_LEVEL);		irq_settings_clr_level(desc);		if (flags & IRQ_TYPE_LEVEL_MASK) {			irq_settings_set_level(desc);			irqd_set(&desc->irq_data, IRQD_LEVEL);		}		ret = 0;		break;	default:		pr_err("Setting trigger mode %lu for irq %u failed (%pF)\n",		       flags, irq_desc_get_irq(desc), chip->irq_set_type);	}	if (unmask)		unmask_irq(desc);	return ret;}

转载地址：http://ygjmi.baihongyu.com/