linux driver ------ platform模型，通过杂项设备（主设备号是10）注册设备节点

注册完设备和驱动之后，就需要注册设备节点

Linux杂项设备出现的意义在于：有很多简单的外围字符设备，它们功能相对简单，一个设备占用一个主设备号对于内核资源来说太浪费。所以对于这些简单的字符设备它们共用一个主设备号，不同的设备使用不同的次设备号。

MISC_DYNAMIC_MINOR 表示由系统分配子设备号

生成helloword.ko文件后，执行 insmod helloworld，就可以在 dev/ 文件夹下看到 hello_device_node 文件，表明成功生成设备节点，执行 rmmod helloword，则节点消失。

helloworld.c

#include <linux/init.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/miscdevice.h>
#include <linux/fs.h>

#define DRIVER_NAME "hello"
#define NODE_NAME "hello_device_node"

MODULE_LICENSE("Dual BSD/GPL"); // required
MODULE_AUTHOR("liuShuiDeng");

static long hello_fs_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
    printk("cmd is %d, arg is %ld\n", cmd, arg);
    return ;
}
static int hello_fs_release(struct inode *inode, struct file *file)
{
    printk(KERN_EMERG "hello_fs_release");
    return ;
}
static int hello_fs_open(struct inode *inode, struct file *file)
{
    printk(KERN_EMERG "hello_fs_open");
    return ;
}
static struct file_operations hello_fops = {
    .owner = THIS_MODULE,
    .open = hello_fs_open,
    .release = hello_fs_release,
    .unlocked_ioctl = hello_fs_ioctl,
};
static struct miscdevice hello_miscdevice = {
    .minor = MISC_DYNAMIC_MINOR,
    .name = NODE_NAME,
    .fops = &hello_fops,
};
static int hello_probe(struct platform_device *p)
{
    printk(KERN_EMERG "\nhello_probe\n");
    misc_register(&hello_miscdevice);
    return ;
}

static int hello_remove(struct platform_device *p)
{
    printk(KERN_EMERG "\nhello_remove\n");
    misc_deregister(&hello_miscdevice);
    return ;
}

static void hello_shutdown(struct platform_device *p)
{
    printk(KERN_EMERG "\nhello_shutdown\n");
}

static int hello_suspend(struct platform_device *p, pm_message_t state)
{
    printk(KERN_EMERG "\nhello_suspend\n");

    return ;
}

static int hello_resume(struct platform_device *p)
{
    printk(KERN_EMERG "\nhello_resume\n");

    return ;
}

static struct platform_driver hello_driver={
    .probe = hello_probe,
    .remove = hello_remove,
    .shutdown = hello_shutdown,
    .suspend = hello_suspend,
    .resume = hello_resume,
    .driver = {
        .name = DRIVER_NAME,
        .owner = THIS_MODULE,
    },
};

static int hello_init(void) //insmod xxx.ko, execute it
{
    printk(KERN_EMERG "\nhello world enter~\n\n");
    platform_driver_register(&hello_driver);
    return ;
}

static void hello_exit(void) //rmmod xxx( note: not xxx.ko ), execute it
{
    printk(KERN_EMERG "\nhello world exit~\n\n");
    platform_driver_unregister(&hello_driver);
}

module_init(hello_init);
module_exit(hello_exit);

Makefile

obj-m += helloworld.o # source file is helloworld.c

#kernel root directory
KDIR := /home/god/Desktop/logicalVolume/iTop4412_Kernel_3.

# directory of source file and Makefile
PWD ?= $(shell pwd)

all:
    $(MAKE) -C $(KDIR) M=$(PWD) modules
    rm -rf *.o
    rm -rf Module.*
    rm -rf modules.order
    rm -rf *.mod.*
    rm -rf .*.cmd
    rm -rf .*versions
clean:
    make -C $(KDIR) M=$(PWD) clean