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字符设备驱动程序按键驱动---中断方式

字符设备驱动程序按键驱动---中断方式

发布时间:2023-09-25

中断函数：包含#include

request_irq(irq,handle,irqflag,name,dev_id)

{

1,分配一个irqaction结构体

2、把这个结构体放到irq_desc[irq]（action链表）中

3、设置引脚

4、使能中断

}

free_irq(irq,dev_id)

{

1、irqaciton出链

2、禁止中断

}

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1、open函数里，配置中断引脚，中断方式irqflags,中断号irq(如外部中断,用于表明哪个引脚)，处理函数handle，中断名name,设备号dev_id

调用request_irq(irq,handle,irqflag,name,dev_id)

static int third_drv_open(struct inode *inode, struct file *file)
{
/* 配置GPF0,2为输入引脚 */
/* 配置GPG3,11为输入引脚 */
request_irq(IRQ_EINT0, buttons_irq, IRQT_BOTHEDGE, "S2", &pins_desc[0]);
request_irq(IRQ_EINT2, buttons_irq, IRQT_BOTHEDGE, "S3", &pins_desc[1]);
request_irq(IRQ_EINT11, buttons_irq, IRQT_BOTHEDGE, "S4", &pins_desc[2]);
request_irq(IRQ_EINT19, buttons_irq, IRQT_BOTHEDGE, "S5", &pins_desc[3]);

return 0;
}

2、在file_operation结构体添加

.release = third_drv_close,
用于关闭中断函数

int third_drv_close(struct inode *inode, struct file *file)
{
free_irq(IRQ_EINT0, &pins_desc[0]);
free_irq(IRQ_EINT2, &pins_desc[1]);
free_irq(IRQ_EINT11, &pins_desc[2]);
free_irq(IRQ_EINT19, &pins_desc[3]);
return 0;
}

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中断处理函数Button_irq对中断发生时需要处理的事件，本次主要时对按键中断函数处理

/* 键值: 按下时, 0x01, 0x02, 0x03, 0x04 */
/* 键值: 松开时, 0x81, 0x82, 0x83, 0x84 */
static unsigned char key_val;

struct pin_desc pins_desc[4] = {
{S3C2410_GPF0, 0x01},
{S3C2410_GPF2, 0x02},
{S3C2410_GPG3, 0x03},
{S3C2410_GPG11, 0x04},
};

/*
* 确定按键值
*/
static irqreturn_t buttons_irq(int irq, void *dev_id)
{

/* 引脚描述结构体 */
struct pin_desc * pindesc = (struct pin_desc *)dev_id;
unsigned int pinval;

/* 系统函数读出引脚值 */
pinval = s3c2410_gpio_getpin(pindesc->pin);

if (pinval)
{
/* 松开 */
key_val = 0x80 | pindesc->key_val;
}
else
{
/* 按下 */
key_val = pindesc->key_val;
}

ev_press = 1; /* 表示中断发生了 */
wake_up_interruptible(&button_waitq); /* 唤醒休眠的进程 */

return IRQ_RETVAL(IRQ_HANDLED);
}

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读函数需要处理的事件

1、判断按键发生事件，没有就休眠，让出CPU

2、有按键事件发生，返回按键值

/* 中断事件标志, 中断服务程序将它置1，third_drv_read将它清0 */
static volatile int ev_press = 0;

struct pin_desc{
unsigned int pin;
unsigned int key_val;
};

ssize_t third_drv_read(struct file *file, char __user *buf, size_t size, loff_t *ppos)
{
if (size != 1)
return -EINVAL;

/* 如果没有按键动作, 休眠 */
wait_event_interruptible(button_waitq, ev_press);

/* 如果有按键动作, 返回键值 */
copy_to_user(buf, &key_val, 1);
ev_press = 0;

return 1;
}

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