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