前言
内核驱动:运行在内核态的动态模块,遵循内核模块框架接口,更倾向于插件。
应用程序:运行在用户态的进程。
应用程序与内核驱动交互通过既定接口,内核态和用户态访问依然遵循内核既定接口。
环境搭建
系统:openEuler-20.03-LTS-SP3
yum install gcc kernel-devel
编写源码
- char_module.c
c
#include <linux/module.h>
#include <linux/init.h>
#include <linux/fs.h>
#include <asm/uaccess.h>
#include <asm/device.h> //下面这三个头文件是由于动态创建需要加的
#include <linux/device.h>
#include <linux/cdev.h>
MODULE_LICENSE("GPL");
#define DEVICE_NAME "char_module"
#define BUF_SIZE 32
static struct class *cdev_class;
dev_t dev_num = 0; // 这里是动态分配设备号和动态创建设备结点需要用到的
struct cdev dev_c;
static char context_buf[BUF_SIZE]={"this a test context buffer\0"};
static ssize_t read(struct file *, char *, size_t, loff_t *);
static ssize_t write(struct file *, const char *, size_t, loff_t *);
static int open(struct inode *, struct file *);
static int release(struct inode *, struct file *);
// 初始化字符设备驱动的 file_operations 结构体
struct file_operations fops = {
.read = read,
.write = write,
.open = open,
.release = release
};
static int __init demo_init(void)
{
int ret, err;
printk(KERN_INFO "%s: %s", DEVICE_NAME , __func__);
// 注册设备驱动
ret = alloc_chrdev_region(&dev_num, 0, 1, DEVICE_NAME); // 动态分配设备号
if (ret)
{
printk("demo_init register failure\n");
unregister_chrdev_region(dev_num, 1);
return ret;
}
printk("demo_init register success\n");
// 初始化设备操作
cdev_init(&dev_c, &fops);
err = cdev_add(&dev_c, dev_num, 1);
if (err)
{
printk(KERN_NOTICE "error %d adding cdev\n", err);
unregister_chrdev_region(dev_num, 1);
return err;
}
// 动态创建设备结点
cdev_class = class_create(THIS_MODULE, DEVICE_NAME);
if (IS_ERR(cdev_class))
{
printk("ERR:cannot create a cdev_class\n");
unregister_chrdev_region(dev_num, 1);
return -1;
}
device_create(cdev_class, NULL, dev_num, 0, DEVICE_NAME);
return ret;
}
static void __exit demo_exit(void)
{
printk(KERN_INFO "%s: %s", DEVICE_NAME , __func__);
// 注销设备驱动
device_destroy(cdev_class, dev_num);
class_destroy(cdev_class);
unregister_chrdev_region(dev_num, 1);
}
static ssize_t read(struct file *filp, char *buf, size_t len, loff_t *off)
{
// 内核空间到用户空间copy
printk(KERN_INFO "%s: %s", DEVICE_NAME , __func__);
if (raw_copy_to_user(buf, &context_buf, sizeof(context_buf)))
{
return -EFAULT;
}
printk(KERN_INFO "user space: %pF", buf);
printk(KERN_INFO "read: %pF; size: %ld; data: %s", &context_buf, sizeof(context_buf), context_buf);
return BUF_SIZE;
}
static ssize_t write (struct file *filp, const char __user *buf, size_t len, loff_t *off)
{
// 用户空间到内核空间copy
printk(KERN_INFO "%s: %s", DEVICE_NAME , __func__);
if (raw_copy_from_user(&context_buf, buf, sizeof(context_buf)))
{
return -EFAULT;
}
printk(KERN_INFO "user space: %pF", buf);
printk(KERN_INFO "write: %pF; size: %ld; data: %s", &context_buf, sizeof(context_buf), context_buf);
return BUF_SIZE;
}
static int open(struct inode *inodp, struct file *filp)
{
printk(KERN_INFO "%s: %s", DEVICE_NAME , __func__);
return 0;
}
static int release(struct inode *inodp, struct file *filp)
{
printk(KERN_INFO "%s: %s", DEVICE_NAME, __func__);
return 0;
}
module_init(demo_init);
module_exit(demo_exit);
- Makefile
c
ifneq ($(KERNELRELEASE),)
obj-m := char_module.o
else
PWD := $(shell pwd)
KVER := $(shell uname -r)
KDIR := /lib/modules/$(KVER)/build
all:
$(MAKE) -C $(KDIR) M=$(PWD) modules modules_install
clean:
rm -rf .*.cmd *.o *.mod.c *.ko .tmp_versions modules.* Module.*
endif
app.c
c
#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>
#include <string.h>
#define CHAR_DEV_NAME "/dev/char_module"
int main()
{
int ret;
int fd;
char buf[32];
fd = open(CHAR_DEV_NAME, O_RDWR | O_NDELAY);
if(fd < 0)
{
printf("open failed!\n");
return -1;
}
int size = read(fd, buf, 32);
printf("read size: %d;\nbuffer:[%s]\n", size, buf);
char *write_buf = "use a application wirte to driver buffer";
int w_size = write(fd, write_buf, strlen(write_buf));
printf("write size: %d;\nbuffer:[%s]\n", w_size, write_buf);
close(fd);
return 0;
}
构建并测试
-
驱动构建
bashmake && insmod char_module.ko
-
驱动信息确认
-
应用程序构建
bashgcc app.c -o app ./app
-
应用程序运行结果
-
查看驱动日志
bashdmesg