3.字符设备创建class，自动创建设备

Posted 2022-02-26 我爱一次性

#include <linux/module.h>
#include <linux/init.h>

#include <linux/cdev.h>
#include <linux/fs.h>

#include <linux/device.h>

static dev_t fan_num;
static struct cdev fan_cdev;
static int status;
static struct class *fan_class;
static struct device *fan_device;


static int Odin_fan_open(struct inode *ip, struct file *fp)
	printk("led_open status:%d\\n fan_num:%d",status,fan_num);
	return 0;

 
static int Odin_fan_close(struct inode *ip, struct file *fp)
	printk("led_close\\n");
	return 0;  


static struct file_operations fan_fops=
    .owner = THIS_MODULE,
    .open = Odin_fan_open,
    .release = Odin_fan_close,
;

static int __init Odin_fan_init(void)
    int ret;
    status = 0;
    ret = alloc_chrdev_region(&fan_num,0,1,"Odin_fan");

    if(ret < 0)
        printk("register_chrdev_region \\n");
		goto dev_number_error;
    
    printk("major:%d min:%d\\n",MAJOR(fan_num),MINOR(fan_num));
 
    cdev_init(&fan_cdev,&fan_fops);
    ret = cdev_add(&fan_cdev,fan_num,1);
    //成功后 cat /proc/device/ -> 有显示Odin_fan的设备号
    if(ret < 0)
		printk("cdev_add \\n");
		goto err_cdev_add;
    

    fan_class = class_create(THIS_MODULE, "Odin_fan_class");
    //创建完后  /sys/class/Odin_fan_class 就会出现
    if(IS_ERR(fan_class))
        ret = PTR_ERR(fan_class);
        printk("fan class create fail \\n");
        goto class_error;
    

    fan_device = device_create(fan_class, NULL, fan_num, NULL, "odin_fan_device");
    //创建完后 /dev/odin_fan_device 就会出现，不用再手动mknod设备节点了
    if(IS_ERR(fan_device))
        ret = PTR_ERR(fan_device);
        printk("fan devices create fail \\n");
        goto device_error;
    

    return 0;

    //和初始化的顺序相反
    device_error:
        device_destroy(fan_class, fan_num);
    class_error:
        class_destroy(fan_class);
    err_cdev_add:	
	    cdev_del(&fan_cdev);
    dev_number_error:
        unregister_chrdev_region(fan_num,1);

    return ret;


static void __exit Odin_fan_exit(void)
    device_destroy(fan_class, fan_num);
    class_destroy(fan_class);
    cdev_del(&fan_cdev);
    unregister_chrdev_region(fan_num, 1);
    printk("Odin_fan_ exit\\n");


module_init(Odin_fan_init);
module_exit(Odin_fan_exit);
 
MODULE_AUTHOR("oncethings");
MODULE_DESCRIPTION("Odin PI fan driver");
MODULE_LICENSE("GPL");

解析：

1.class_create

创建类，完成后 /sys/class/Odin_fan_class

2.device_create

再类创建完成后，在创建设备。通过这个函数不用再mknod设备节点了。每次开机都会自己创建好。 /dev/odin_fan_device