SaaS和API(应用连接)的关系

蜂鸣器驱动原理

1、修改设备树文件

• 添加 pinctrl 节点

• 添加 BEEP 设备节点

beep {
     #address-cells = <1>;
     #size-cells = <1>;
     compatible = "atkalpha-beep";
     pinctrl-names = "default";
     pinctrl-0 = <&pinctrl_beep>;
     beep-gpio = <&gpio5 1 GPIO_ACTIVE_HIGH>;
     status = "okay";
 };

• 检查 PIN 是否被其他外设使用

蜂鸣器驱动程序编写

#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/delay.h>
#include <linux/ide.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/errno.h>
#include <linux/gpio.h>
#include <linux/cdev.h>
#include <linux/device.h>
#include <linux/of.h>
#include <linux/of_address.h>
#include <linux/of_gpio.h>
#include <asm/mach/map.h>
#include <asm/uaccess.h>
#include <asm/io.h>


#define BEEP_CNT		1		  	/* 设备号个数 */
#define BEEP_NAME	 "beep"	/* 名字 */

#define BEEPOFF   0  //关闭
#define BEEPON    1 //打开

/* gpiobeep设备结构体 */
struct beep_dev{
	dev_t devid;			/* 设备号 	 */
	struct cdev cdev;		/* cdev 	*/
	struct class *class;	/* 类 		*/
	struct device *device;	/* 设备 	 */
	int major;				/* 主设备号	  */
	int minor;				/* 次设备号   */
	struct device_node	*nd; /* 设备节点 */
	int beep_gpio;
	
};

struct beep_dev beep;	/* beep设备 */


static int beep_open(struct inode *inode, struct file *filp)
{
	filp->private_data = &beep; /* 设置私有数据 */
	return 0;
}


static ssize_t beep_read(struct file *filp, char __user *buf, size_t cnt, loff_t *offt)
{	

	return 0;
}


static ssize_t beep_write(struct file *filp, const char __user *buf, size_t cnt, loff_t *offt)
{
	int retval = 0;
	unsigned char databuf[1];
	unsigned char beepstat;
	struct beep_dev *dev = filp->private_data;

	retval = copy_from_user(databuf,buf,cnt);
	if(retval < 0)
	{
		printk("kernel write failed!\r\n");
		return -EFAULT;
	}

	beepstat = databuf[0];
	if(beepstat == BEEPON)
	{
		gpio_set_value(dev->beep_gpio,0);   //打开蜂鸣器	
	}else if (beepstat == BEEPOFF)
	{
		gpio_set_value(dev->beep_gpio,1);  //关闭蜂鸣器
	}

	return 0;
}


static int beep_release(struct inode *inode, struct file *filp)
{
	return 0;
}

/* 设备操作函数 */
static struct file_operations beep_fops = {
	.owner = THIS_MODULE,
	.open = beep_open,
	.read = beep_read,
	.write = beep_write,
	.release = 	beep_release,
};

/*
 * @description	: 驱动出口函数
 * @param 		: 无
 * @return 		: 无
 */
static int __init beep_init(void)
{
	int ret = 0;
	/* 注册字符设备驱动 */
	/* 1、创建设备号 */
	if (beep.major) {		/*  定义了设备号 */
		beep.devid = MKDEV(beep.major, 0);
		register_chrdev_region(beep.devid, BEEP_CNT, BEEP_NAME);
	} else {						/* 没有定义设备号 */
		alloc_chrdev_region(&beep.devid, 0, BEEP_CNT, BEEP_NAME);	/* 申请设备号 */
		beep.major = MAJOR(beep.devid);	/* 获取分配号的主设备号 */
		beep.minor = MINOR(beep.devid);	/* 获取分配号的次设备号 */
	}
	printk("gpiobeep major=%d,minor=%d\r\n",beep.major, beep.minor);	
	
	/* 2、初始化cdev */
	beep.cdev.owner = THIS_MODULE;
	cdev_init(&beep.cdev, &beep_fops);
	
	/* 3、添加一个cdev */
	cdev_add(&beep.cdev, beep.devid, BEEP_CNT);

	/* 4、创建类 */
	beep.class = class_create(THIS_MODULE, BEEP_NAME);
	if (IS_ERR(beep.class)) {
		return PTR_ERR(beep.class);
	}

	/* 5、创建设备 */
	beep.device = device_create(beep.class, NULL, beep.devid, NULL, BEEP_NAME);
	if (IS_ERR(beep.device)) {
		return PTR_ERR(beep.device);
	}

	/*初始化beep*/
	/*获取设备节点:beep*/
	beep.nd = of_find_node_by_path("/beep");
	if(beep.nd == NULL)
	{
		printk("beep node not find!\r\n");
		return -EINVAL;
	}else
	{
		printk("beep node find!\r\n");
	}

	/*获取设备树中的gpio属性，得到BEEP所使用的beep编号*/
	beep.beep_gpio  = of_get_named_gpio(beep.nd,"beep-gpio",0);
	if(beep.beep_gpio < 0)
	{
		printk("can not get beep-gpio\n");
		return -EINVAL;
	}
	
	printk("led-gpio num = %d\r\n",beep.beep_gpio);

	/*设置GPIO5_IO01为输出，并且输出高电平，默认关闭BEEP*/
	ret = gpio_direction_output(beep.beep_gpio,1);
	if (ret < 0)
	{
		printk("cant set gpio!\r\n");
	}
	

	return 0;
}

/*
 * @description	: 驱动出口函数
 * @param 		: 无
 * @return 		: 无
 */
static void __exit beep_exit(void)
{
	/* 注销字符设备驱动 */
	cdev_del(&beep.cdev);/*  删除cdev */
	unregister_chrdev_region(beep.devid, BEEP_CNT); /* 注销设备号 */

	device_destroy(beep.class, beep.devid);
	class_destroy(beep.class);
}

module_init(beep_init);
module_exit(beep_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("hsj");

编写测试 APP

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdio.h>
#include <unistd.h>
#include <string.h>

#define LEDOFF 0 
#define LEDON  1

int main(int argc,char *argv[])
{
   int fd,retvalue;
   char *filename;
   unsigned char databuf[1];

   if(argc != 3)
   {
       printf("error usage!\r\n");
       return -1;
   }

   filename = argv[1];
   fd = open(filename,O_RDWR);
   if(fd < 0)
   {
      printf("open failed\r\n");
      return -1;
   }
   
   databuf[0] = atoi(argv[2]);   //将字符转换为数字
   retvalue = write(fd,databuf,1);
   if (retvalue < 0)
    {
      printf("LED Control failed!\r\n");
      close(fd);
      return -1;   
    }


    close(fd);
    return 0;
}

运行测试