Linux字符設備-自動創建設備號和設備節點

Linux字符設備-自動創建設備號和設備節點

先寫一個自動分配字符設備號和設備節點的例子及APP

手動安裝步驟：

Insmod my_char_dev.ko

不需要再安裝設備節點

然後是測試app

./my_char_dev_app 1

#include <linux/module.h>
#include <linux/init.h>
#include <linux/io.h>
#include <linux/fs.h>
#include <asm/device.h>  //下面這三個頭文件是由於動態創建需要加的
#include <linux/device.h>
#include <linux/cdev.h>
#include "my_cdev.h"
struct cdev cdev;
dev_t devno;//這裡是動態分配設備號和動態創建設備結點需要用到的
struct class *cdev_class;

int my_cdev_open(struct inode *node,struct file *filp)
{
    printk("my_cdev_open sucess!\n");
    return 0;
}

long my_cdev_ioctl(struct file *filp ,unsigned int cmd ,unsigned long arg)
{
    switch(cmd)
    {
        case LED_ON:
            printk("LED_ON is set!\n");
            return 0;
        case LED_OFF:
            printk("LED_OFF is set!\n");
            return 0;
        default :
            return -EINVAL;
    }
}

struct file_operations my_cdev_fops=
{
    .open = my_cdev_open,
    .unlocked_ioctl = my_cdev_ioctl,

};

static int my_cdev_init(void)
{
    int ret;
    /**動態分配設備號*/
    ret = alloc_chrdev_region(&devno,0,1,"my_chardev");
    if(ret)
    {
        printk("alloc_chrdev_region fail!\n");
        unregister_chrdev_region(devno,1);
        return ret;
    }
    else
    {
        printk("alloc_chrdev_region sucess!\n");
    }
    /**描述結構初始化*/
    cdev_init(&cdev,&my_cdev_fops);
    /**描述結構注冊*/
    ret = cdev_add(&cdev,devno,1);
    if(ret)
    {
        printk("cdev add fail.\n");
        unregister_chrdev_region(devno,1);
        return ret;
    }
    else
    {
        printk("cdev add sucess!\n");
    }

    cdev_class = class_create(THIS_MODULE,"my_chardev");
    if(IS_ERR(cdev_class))
    {
        printk("Create class fail!\n");
        unregister_chrdev_region(devno,1);
        return -1;
    }
    else
    {
        printk("Create class sucess!\n");
    }

    device_create(cdev_class,NULL,devno,0,"my_chardev");
   
    return 0;
}
static void my_cdev_exit(void)
{
    device_destroy(cdev_class,devno);
    class_destroy(cdev_class);
    cdev_del(&cdev);
    unregister_chrdev_region(devno,1);
    printk("my_cdev_exit sucess!\n");
}
module_init(my_cdev_init);
module_exit(my_cdev_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("YEFEI");
MODULE_DESCRIPTION("YEFEI Driver");

---------------------------------------

#ifndef __MY_CDEV_H__
#define __MY_CDEV_H__

#define LED_MAGIC 'L'
#define LED_ON _IO(LED_MAGIC,0)
#define LED_OFF _IO(LED_MAGIC,1)

#endif

---------------------------------------

#include <sys/stat.h>
#include <sys/types.h>
#include <sys/ioctl.h>
#include <fcntl.h>
#include <stdio.h>
#include "my_cdev.h"

int main(int argc,char *argv[])
{
    int fd;
    int cmd;
    if(argc < 2)
    {
        printf("Please enter secend param!\n");
        return 0;
    }
    cmd = atoi(argv[1]);
    fd = open("/dev/my_chardev",O_RDWR);
    if(fd < 0)
    {
        printf("Open dev/my_chardev fail!\n");
        close(fd);
        return 0;
    }
    switch(cmd)
    {
        case 1:
            ioctl(fd,LED_ON);
            break;
        case 2:
            ioctl(fd,LED_OFF);
            break;
        default:
            break;
    }
    close(fd);
    return 0;
}

-------------------------------

1 obj-m := my_char_dev.o
2 KDIR := /home/win/dn377org/trunk/bcm7252/linux/
3 all:
4    make -C $(KDIR) M=$(PWD) modules CROSS_COMPILE=arm-linux- ARCH=arm
5 clean:
6    rm -f *.ko *.o *.mod.o *.mod.c *.symvers *.bak *.order