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Linux驱动之按键驱动编写（中断方式）

Linux驱动之按键驱动编写（中断方式）

2024-08-20

1、查看原理图，确定需要控制的IO端口

打开原理图，确定需要控制的IO端口为GPF0、GPF2、GPG3、GPG11。可以看到它的中断号为IRQ_EINT0、IRQ_EINT2、IRQ_EINT11、IRQ_EINT19

2、查看芯片手册，确定IO端口的寄存器地址，可以看到因为用了两组GPIO端口，所以它的基地址分别为0x56000050、0x56000060。中断方式的寄存器基地址为0x56000088、0x5600008c、0x56000090

3、编写驱动代码，编写驱动代码的步骤如下：

1）、编写出口、入口函数。代码如下，具体说明参考Linux驱动之LED驱动编写

static int second_drv_init(void)

{

Secondmajor = register_chrdev(0, 'buttons', &second_drv_ops);//注册驱动程序

if(Secondmajor < 0)

printk('failes 1 buttons_drv registern');

second_drv_class = class_create(THIS_MODULE, 'buttons');//创建类

if(second_drv_class < 0)

printk('failes 2 buttons_drv registern');

second_drv_class_dev = class_device_create(second_drv_class, NULL, MKDEV(Secondmajor,0), NULL,'buttons');//创建设备节点

if(second_drv_class_dev < 0)

printk('failes 3 buttons_drv registern');

gpfcon = ioremap(0x56000050, 16);//重映射

gpfdat = gpfcon + 1;

gpgcon = ioremap(0x56000060, 16);//重映射

gpgdat = gpgcon + 1;

printk('register buttons_drvn');

return 0;

}

static void second_drv_exit(void)

{

unregister_chrdev(Secondmajor,'buttons');

class_device_unregister(second_drv_class_dev);

class_destroy(second_drv_class);

iounmap(gpfcon);

iounmap(gpgcon);

printk('unregister buttons_drvn');

}

module_init(second_drv_init);

module_exit(second_drv_exit);

2）、添加file_operations 结构体，这个是字符设备驱动的核心结构，所有的应用层调用的函数最终都会调用这个结构下面定义的函数

static struct file_operations third_drv_ops =

{

.owner = THIS_MODULE,

.open = third_drv_open,

.read = third_drv_read,

.release = third_drv_close,//增加关闭函数

};

3）、分别编写file_operations 结构体下的open、read、release 函数。其中open函数主要将相应的IO端口配置成中断功能，并且向内核注册中断；read函数主要是在按键引脚电平未改变时休眠，然后按键引脚电平改变后，将按键值传给应用程序处理。（按键值的处理在中断处理程序中）；relase函数的功能主要是从内核释放掉open函数注册的中断。程序如下：

static int third_drv_open (struct inode * inode, struct file * file)

{

int ret;

ret = request_irq(IRQ_EINT0, buttons_irq, IRQT_BOTHEDGE, 's1', (void * )&pins_desc[0]);//注册一个外部中断S1，双边沿触发，dev_id为&pins_desc[0]

if(ret)

{

printk('open failed 1n');

return -1;

}

ret = request_irq(IRQ_EINT2, buttons_irq, IRQT_BOTHEDGE, 's2', (void * )& pins_desc[1]);//注册一个外部中断S2，双边沿触发，dev_id为&pins_desc[1]

if(ret)

{

printk('open failed 2n');

return -1;

}

ret = request_irq(IRQ_EINT11, buttons_irq, IRQT_BOTHEDGE, 's3', (void * )&pins_desc[2]);//注册一个外部中断S3，双边沿触发，dev_id为&pins_desc[2]

if(ret)

{

printk('open failed 3n');

return -1;

}

ret = request_irq(IRQ_EINT19, buttons_irq, IRQT_BOTHEDGE, 's4', (void * )&pins_desc[3]);//注册一个外部中断S4，双边沿触发，dev_id为&pins_desc[3]

if(ret)

{

printk('open failed 4n');

return -1;

}

return 0;

}

static int third_drv_close(struct inode * inode, struct file * file)

{

free_irq(IRQ_EINT0 ,(void * )&pins_desc[0]);//释放中断，根据IRQ_EINT0找到irq_desc结构。根据pins_desc[0]找到irq_desc->action结构

free_irq(IRQ_EINT2 ,(void * )& pins_desc[1]);//释放中断，根据IRQ_EINT2找到irq_desc结构。根据pins_desc[2]找到irq_desc->action结构

free_irq(IRQ_EINT11 ,(void * )&pins_desc[2]);//释放中断，根据IRQ_EINT11找到irq_desc结构。根据pins_desc[3]找到irq_desc->action结构

free_irq(IRQ_EINT19 ,(void * )&pins_desc[3]);//释放中断，根据IRQ_EINT19找到irq_desc结构。根据pins_desc[4]找到irq_desc->action结构

return 0;

}

static ssize_t third_drv_read(struct file * file, char __user * userbuf, size_t count, loff_t * off)

{

int ret;

if(count != 1)

{

printk('read errorn');

return -1;

}

wait_event_interruptible(button_waitq, ev_press);//将当前进程放入等待队列button_waitq中,并且释放CPU进入睡眠状态

ret = copy_to_user(userbuf, &key_val, 1);//将取得的按键值传给上层应用

ev_press = 0;//按键已经处理可以继续睡眠

if(ret)

{

printk('copy errorn');

return -1;

}

return 1;

}

4）、中断处理函数的编写，中断处理函数利用注册中断时传入的dev_id这个值来判断是哪个按键发生了中断，dev_iq被赋值为pin_desc结构，如下：

struct pin_desc

{

unsigned int pin; //是哪个按键

unsigned int key_val; //按键的按键值

};

static struct pin_desc pins_desc[4] =

{

{S3C2410_GPF0,0x01},

{S3C2410_GPF2,0x02},

{S3C2410_GPG3,0x03},

{S3C2410_GPG11,0x04}

};

取得哪个引脚发生的中断信息后，取得相应的引脚电平，然后确定按键值。接着将值传给key_val，再唤醒调用read的进程，将值直接拷贝给应用程序。具体函数如下

static unsigned int key_val;//全局变量

*0x01、0x02、0x03、0x04表示按键被按下

*0x81、0x82、0x83、0x84表示按键被松开

*利用dev_id的值为pins_desc来判断是哪一个按键被按下或松开

static irqreturn_t buttons_irq(int irq, void *dev_id)

{

unsigned int pin_val;

struct pin_desc * pin_desc = (struct pin_desc *)dev_id;//取得哪个按键被按下的状态，dev_id是action->dev_id，即在注册中断时传入的&pin_desc[num]

pin_val = s3c2410_gpio_getpin(pin_desc->pin); //取得按键对应的IO口的电平状态

if(pin_val) //按键松开

key_val = 0x80 | pin_desc->key_val;

else

key_val = pin_desc->key_val;

wake_up_interruptible(&button_waitq); /* 唤醒休眠的进程，即调用read函数的进程 */

ev_press = 1;

return IRQ_HANDLED;

}

5）、整体代码

#include

#include //含有iomap函数iounmap函数

#include //含有copy_from_user函数

#include //含有类相关的处理函数

#include //含有S3C2410_GPF0等相关的

#include //含有IRQ_HANDLEDIRQ_TYPE_EDGE_RISING

#include //含有IRQT_BOTHEDGE触发类型

#include //含有request_irq、free_irq函数

//#include

static struct class *third_drv_class;//类

static struct class_device *third_drv_class_dev;//类下面的设备

static int thirdmajor;

static unsigned long *gpfcon = NULL;

static unsigned long *gpfdat = NULL;

static unsigned long *gpgcon = NULL;

static unsigned long *gpgdat = NULL;

struct pin_desc

{

unsigned int pin; //是哪个按键

unsigned int key_val; //按键的按键值

};

static struct pin_desc pins_desc[4] =

{

{S3C2410_GPF0,0x01},

{S3C2410_GPF2,0x02},

{S3C2410_GPG3,0x03},

{S3C2410_GPG11,0x04}

};

unsigned int ev_press;

DECLARE_WAIT_QUEUE_HEAD(button_waitq);//注册一个等待队列button_waitq

static unsigned int key_val;//全局变量

*0x01、0x02、0x03、0x04表示按键被按下

*0x81、0x82、0x83、0x84表示按键被松开

*利用dev_id的值为pins_desc来判断是哪一个按键被按下或松开

static irqreturn_t buttons_irq(int irq, void *dev_id)

{

unsigned int pin_val;

struct pin_desc * pin_desc = (struct pin_desc *)dev_id;//取得哪个按键被按下的状态，dev_id是action->dev_id，即在注册中断时传入的&pin_desc[num]

pin_val = s3c2410_gpio_getpin(pin_desc->pin); //取得按键对应的IO口的电平状态

if(pin_val) //按键松开

key_val = 0x80 | pin_desc->key_val;

else

key_val = pin_desc->key_val;

wake_up_interruptible(&button_waitq); /* 唤醒休眠的进程，即调用read函数的进程 */

ev_press = 1;

return IRQ_HANDLED;

}

static int third_drv_open (struct inode * inode, struct file * file)

{

int ret;

ret = request_irq(IRQ_EINT0, buttons_irq, IRQT_BOTHEDGE, 's1', (void * )&pins_desc[0]);//注册一个外部中断S1，双边沿触发，dev_id为&pins_desc[0]

if(ret)

{

printk('open failed 1n');

return -1;

}

ret = request_irq(IRQ_EINT2, buttons_irq, IRQT_BOTHEDGE, 's2', (void * )& pins_desc[1]);//注册一个外部中断S2，双边沿触发，dev_id为&pins_desc[1]

if(ret)

{

printk('open failed 2n');

return -1;

}

ret = request_irq(IRQ_EINT11, buttons_irq, IRQT_BOTHEDGE, 's3', (void * )&pins_desc[2]);//注册一个外部中断S3，双边沿触发，dev_id为&pins_desc[2]

if(ret)

{

printk('open failed 3n');

return -1;

}

ret = request_irq(IRQ_EINT19, buttons_irq, IRQT_BOTHEDGE, 's4', (void * )&pins_desc[3]);//注册一个外部中断S4，双边沿触发，dev_id为&pins_desc[3]

if(ret)

{

printk('open failed 4n');

return -1;

}

return 0;

}

static int third_drv_close(struct inode * inode, struct file * file)

{

free_irq(IRQ_EINT0 ,(void * )&pins_desc[0]);//释放中断，根据IRQ_EINT0找到irq_desc结构。根据pins_desc[0]找到irq_desc->action结构

free_irq(IRQ_EINT2 ,(void * )& pins_desc[1]);//释放中断，根据IRQ_EINT2找到irq_desc结构。根据pins_desc[2]找到irq_desc->action结构

free_irq(IRQ_EINT11 ,(void * )&pins_desc[2]);//释放中断，根据IRQ_EINT11找到irq_desc结构。根据pins_desc[3]找到irq_desc->action结构

文章来源于:电子工程世界原文链接

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