上一节讲到的字符设备注册与销毁是通过cdev_init、cdev_add、cdev_del等函数分步执行的，本小节用一种更简单的方式，来注册字符设备

register_chrdev

•  如果major为0，该函数将动态的分配一个主设备号并且返回对应的值
• 如果major > 0，该函数尝试获取该制定的设备号，并且申请成功，返回0

__register_chrdev函数原型：

 unregister_chrdev

实验

操作截图

 查看设备

 代码

/*
 *hello.c
 *Original Author: luoyunheng, 2025-02-25
 *
 * Linux驱动之字符设备注册-register_chrdev
*/

#include <linux/init.h>
#include <linux/module.h>
#include <linux/kdev_t.h>
#include <linux/fs.h>
#include <linux/cdev.h>

MODULE_LICENSE("GPL");

unsigned int major = 237;

int hello_open(struct inode *node, struct file *file)
{
    printk("hello_open()\n");
    return 0;
}

int hello_release(struct inode *node, struct file *file)
{
    printk("hello_release()\n");
    return 0;
}

static struct file_operations fops = {
    .open = hello_open,
    .release = hello_release,
};


static int hello_init(void)
{
    int ret;

    printk("hello_init()\n");

    ret = register_chrdev(major, "loh", &fops);
    if (ret < 0) {
        printk("Major number allocated: %d\n", major);
        return ret;
    }

    return 0;
}

static void hello_exit(void)
{
    printk("hello_exit()\n");
    unregister_chrdev(major, "loh");

    return;
}

module_init(hello_init);
module_exit(hello_exit);

makefile

ifneq ($(KERNELRELEASE),)
obj-m:=hello.o
else
KDIR :=/lib/modules/$(shell uname -r)/build
PWD  :=$(shell pwd)
all:
	make -C $(KDIR) M=$(PWD) modules
clean:
	rm -f *.ko *.o *.mod.o *.symvers *.cmd *.mod.c *.order
endif

应用程序

代码

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

int main(int argc, char **argv)
{
	int fd;

	fd = open("/dev/loh", O_RDWR);
	if(fd < 0) {
		perror("");
		return 0;
	}	
	
	sleep(10);

	close(fd);

	return 0;
}

字符设备驱动编写步骤总结