Linux内核驱动基础框架

Linux内核驱动基础框架

驱动代码

#include <linux/fs.h>      //file_operations 声明
#include <linux/module.h>  //module_init module_exit 声明
#include <linux/init.h>    // __init __exit 宏定义声明
#include <linux/device.h>  //class device 声明
#include <linux/uaccess.h> //copy_from_user 头文件
#include <linux/types.h>   //设备号 dev_t 声明 
#include <asm/io.h>	   //ioremap iounmap 头文件

static struct class *pin_class;
static struct device *pin_class_dev;

static dev_t devno; 			  //设备号
static int major = 231;			  //主设备号
static int minjor = 0;			  //次设备号
static char *module_name = "pin"; //模块名

volatile unsigned int* GPFSEL0 = NULL;
volatile unsigned int* GPSET0 = NULL;
volatile unsigned int* GPCLR0 = NULL;

static int pin_open (struct inode *inode, struct file *file)
{
    
    
	printk("pin_open\n");
	*GPFSEL0 &= ~(0x6 << 12);
	*GPFSEL0 |= (0x1 << 12);
	return 0;
}

static int pin_read (struct file *file1, char __user *buf, size_t count, loff_t *ppos)
{
    
    
	printk("pin_read\n");
	return 0;
}

static int pin_write (struct file *file1, char __user *buf, size_t count, loff_t *ppos)
{
    
    
	int userCmd;

	printk("pin_write\n");
	
	copy_from_user(&userCmd,buf,count);
	if(userCmd == 1){
    
    
		printk("set 1\n");
	}else if(userCmd == 0){
    
    
                printk("set 0\n");
                *GPCLR0 |= 0x1 << 4;
        }else {
    
    
		printk("undo\n");
	}
	return 0;
}
static struct file_operations pin_fops = {
    
    
	.owner = THIS_MODULE,
	.open  = pin_open,
	.write = pin_write,
	.read  = pin_read,
};
int __init pin_drv_init(void)
{
    
    
	int ret;
	printk("insmod driver pin success\n");
	devno = MKDEV(major,minor);		//创建设备号
	ret = register_chrdev( major, module_name, &pin_fops);	//注册驱动
	
	pin_class = class_create( THIS_MODULE, "myfirstdemo");	//让代码在dev下自动生成设备
	pin_class_dev = device_create(pin_class, NULL, devno, NULL, module_name);	//创建设备文件

	GPFSEL0 = (volatile unsigned int *)ioremap(0x3f200000,4);		//物理地址转换成虚拟地址
	GPSET0  = (volatile unsigned int *)ioremap(0x3f20001c,4);
	GPCLR0  = (volatile unsigned int *)ioremap(0x3f200028,4);
	return 0;
}
void __exit pin_dev_exit(void)
{
    
    
	iounmap(GPFSEL0);
	iounmap(GPSET0);
	iounmap(GPCLR0);
	device_destroy(pin_class,devno);
	class_destroy(pin_class);
	unregister_chrdev(major, module_name);		//卸载驱动
}

module_init(pin_drv_init);		//入口
module_exit(pin_drv_exit);
MODULE_LICENSE("GPL v2");

• IO口属于字符设备目录，所以进入到源码目录树的字符设备下

cd /home/whao/linux-rpi-4.14.y/drivers/char/

• 将桌面的pin4driver.c驱动代码黏贴进入源码目录树的字符设备下

cp ~/pin4driver.c .

• ~/代表桌面
  打开Makefile修改配置文件（模块形式）

vi Makefile

加入

obj-m                           += pindriver.o

• 回到源码目录树下进行编译

cd /home/whao/linux-rpi-4.14.y/

ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- KERNEL=kernel7 make modules

• 将生成的 pindriver.ko 发送到开发板

scp drivers/char/pin4driver.ko pi@192.168.1.7:/home/pi

开发板端

• 加载驱动

sudo insmod pindriver.ko 

• 给 /dev/pin 可读可写权限

chmod 666 /dev/pin

上层代码

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

void main()
{
    
    
	int fd,data;
	fd = open("/dev/pin",O_RDWR);
	if(fd<0){
    
    
	printf("open failed\n");
	perror("reson");
}else{
    
    
	printf("open succeed")
		write(fd,1,1);
	}
}

arm-linux-gnueabihf-gcc pintest.c -o pintest

将pintest发送到开发板

scp pintest pi@192.168.1.7:/home/pi

查看内核打印信息

dmesg