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
#include
#include
#include //含有iomap函数iounmap函数
#include //含有copy_from_user函数
#include
#include //含有S3C2410_GPF0等相关的
#include
#include //含有IRQT_BOTHEDGE触发类型
#include
//#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