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1. MISC设备

1. MISC设备的主设备号为10.
2. MISC设备会自动创建cdev，不需要再手动创建。
3. MISC设备是基于platform的.

MISC驱动的编写的核心就是初始化miscdevice结构体变量，然后用misc_register函数向内核注册，然后使用misc_deregister函数删除注册.

1. 如果设置MISC结构体中的minor是255的话是自动分配设备号。

2. MISC蜂鸣器实验

1. 设备树添加

beep{compatible = "alientek,beep";pinctrl-names = "default";pinctrl-0 =  <&pinctrl_beep>;beep-gpios=<&gpio5 1 GPIO_ACTIVE_HIGH>;status = "okay";};

2. 驱动文件编写

 驱动编写的思路就是先写paltform平台模板，随后就是关于MISC设备模板流程，最后就是自己设备信息的添加，例如节点信息，gpio号等等.

#define MISCBEEP_NAME "miscbeep"
#define MISCBEEP_MINOR  144
#define BEEPON  1
#define BEEPOFF 0
//添加设备的信息，注意这里是用户自定义的结构体，里面的信息是自主要添加的
struct miscbeep_dev {struct device_node *nd;int beep_gpio;
};
struct miscbeep_dev miscbeep;
//fops文件操作函数
static int miscbeep_release(struct inode *inode, struct file *file)
{printk("Close ok\r\n");return 0;
}
//fops文件操作函数
static int miscbeep_open(struct inode *inode, struct file *file)
{printk("Open ok\r\n");file->private_data = &miscbeep;return 0;
}
//fops文件操作函数
static ssize_t miscbeep_write(struct file *file, const char __user *buffer,size_t count, loff_t *pos)
{int ret = 0;unsigned char databuf[1];struct miscbeep_dev *dev=file->private_data;ret = copy_from_user(databuf,buffer,count);if(ret<0){return -EINVAL;}if(databuf[0]==BEEPON){gpio_set_value(dev->beep_gpio,0);}if(databuf[0]==BEEPOFF){gpio_set_value(dev->beep_gpio,1);}return 0;
}
//fops文件操作函数集
static struct file_operations miscbeep_fops = {.owner = THIS_MODULE,.open = miscbeep_open,.write = miscbeep_write,.release = miscbeep_release,};
//将要注册的设备，包含必要的信息例如设备号，名字，文件操作合集，
//注意这里的结构体是内核定义的
static struct miscdevice beep_miscdev = {.minor = MISCBEEP_MINOR,.name = MISCBEEP_NAME,.fops = &miscbeep_fops,
};
//paltform平台设备与驱动匹配成功后执行的函数
static int  miscbeep_probe(struct platform_device *dev)
{int ret = 0;/*1.初始化蜂鸣器IO*/miscbeep.nd = dev->dev.of_node;miscbeep.beep_gpio = of_get_named_gpio(miscbeep.nd,"beep-gpios",0);if(miscbeep.beep_gpio < 0){ret = -EINVAL;goto fail_findgpio;}ret = gpio_request(miscbeep.beep_gpio,"beep-gpio");if(ret){printk("cant't request %d gpio",miscbeep.beep_gpio);ret = -EINVAL;goto fail_findgpio;}ret = gpio_direction_output(miscbeep.beep_gpio,1);/*输出高电平*/if(ret<0){goto fail_setoutput;}/*2.MISC驱动注册*/ret = misc_register(&beep_miscdev);if(ret<0){goto fail_setoutput;}return 0;
fail_setoutput:gpio_free(miscbeep.beep_gpio);
fail_findgpio:return ret;
}//paltform平台设备与驱动匹配成功后，移除驱动后要执行的函数
static int miscbeep_remove(struct platform_device *dev)
{gpio_set_value(miscbeep.beep_gpio,1);gpio_free(miscbeep.beep_gpio);misc_deregister(&beep_miscdev);return 0;
}
/*paltform匹配表*/
static const struct of_device_id beep_of_match[]={{.compatible = "alientek,beep",},{/**/}
};
//paltform平台设备驱动定义结构体
static struct platform_driver miscbeep_driver = {.driver = {.name = "imx6ull-beep",.of_match_table = beep_of_match,/*设备树匹配表*/},.probe = miscbeep_probe,.remove = miscbeep_remove,
};
/*驱动入口和出口函数*/
static int __init miscbeep_init(void)
{return platform_driver_register(&miscbeep_driver);
}
static void __exit miscbeep_exit(void)
{platform_driver_unregister(&miscbeep_driver);
}
module_init(miscbeep_init);
module_exit(miscbeep_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("WYJ");