第一个ubuntu驱动实现

环境确认

因为驱动程序是调用的内核头文件，所以首先需要确认头文件有没有，下面第一条命令是确认有没有，没有的话，使用第二条进行下载。

apt-cache search linux-headers-$(uname -r)
sudo apt-get install linux-headers-$(uname -r)

代码实现

目录结构

其中test_driver.c是驱动程序，编译结果是test.ko文件。app.c 是使用驱动, 通过`gcc app.c -o app`编译成可执行程序。

test_driver.c

#include <linux/module.h>
#include <linux/fs.h>
#include <linux/device.h>

static int major = 0;
static struct class *hello_for_class;

#define KMAX_LEN 32 
char kbuf[KMAX_LEN+1] = "kernel_data"; 
static size_t count = strlen("kernel_data");

static ssize_t hello_read(struct file *file, char __user *buf, size_t size, loff_t *offset)
{
    printk("%s %s line %d size %d\n",__FILE__,__FUNCTION__, __LINE__, size);
    if(size > count) 
    {
        size = count;
    }
    if(copy_to_user(buf,kbuf, size)) //内核空间拷贝数据到用户空间
    {
        return -EFAULT;
    }
    return size;
}

static ssize_t hello_write(struct file *file, const char __user *buf, size_t size, loff_t *offset)
{
    printk("%s %s line %d size %d\n", __FILE__, __FUNCTION__, __LINE__, size);

    if(size > KMAX_LEN) 
    {
        size = KMAX_LEN;
    }
    count = size;
    memset(kbuf,0,sizeof(kbuf));
    if(copy_from_user(kbuf, buf, size)) //用户空间拷贝数据到内核空间
    {
        return -EFAULT;
    }
    printk("%s\n",kbuf);
    return size;
}

static struct file_operations hello_linux_fops = {
    .owner = THIS_MODULE,
    .read = hello_read,
    .write = hello_write,
};

int __init hello_init(void)
{
    printk("hello_linux_dri init\n");
    major = register_chrdev(0,"hello_linux_dri", &hello_linux_fops);
    hello_for_class = class_create(THIS_MODULE, "hello_class");
    device_create(hello_for_class, NULL, MKDEV(major, 0), NULL, "hello_linux_dri");
    return 0;
}

void __exit hello_exit(void)
{
    printk("hello_linux_dri exit\n");

    device_destroy(hello_for_class, MKDEV(major, 0));
    class_destroy(hello_for_class);
    unregister_chrdev(major, "hello_linux_dri");
    return;
}

module_init(hello_init);
module_exit(hello_exit);
MODULE_LICENSE("GPL");

Makefile

CONFIG_MODULE_SIG=n
KDIR := /lib/modules/$(shell uname -r)/build
PWD := $(shell pwd)
MOD_NAME := test

obj-m := ${MOD_NAME}.o
${MOD_NAME}-objs += test_driver.o

modules:
  $(MAKE) -C $(KDIR) M=$(PWD) modules

.PHONEY:clean
clean :
  $(MAKE) -C $(KDIR) M=$(PWD) clean

app.c

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

int main(int argc, char **argv)
{
    int fd;
    char buf[1024];
    int len;
    int ret;

    if (argc < 2) {
        printf("Usage: %s -w <string>\n", argv[0]);
        printf("       %s -r\n",argv[0]);
        return -1;
    }

    fd = open("/dev/hello_linux_dri", O_RDWR);
    if (fd == -1)
    {
        printf("can not open file /dev/hello_linux_dri\n");
        return -1;
    }
    printf("open /dev/hello_linux_dri success\n");
    if ((0 == strcmp(argv[1], "-w")) && (argc  == 3))
    {
        len = strlen(argv[2]) + 1;
        len = len < 1024 ? len : 1024;
        ret = write(fd, argv[2], len);
        printf("write driver : %d\n", ret);
    } else {
        len = read(fd, buf, 1024);
        printf("read driver : %d\n", len);
        buf[1023] = '\0';
        printf("APP read : %s\n", buf);
    }

    close(fd);

    return 0;
}

编译

驱动编译

make

生成: test.ko

app编译

gcc app.c -o app

生成: app

测试

驱动安装卸载：

驱动安装: sudo insmod test.ko
查看驱动安装和卸载信息：dmesg
卸载驱动：sudo rmmod test.ko

运行驱动测试程序

需要驱动安装后测试，驱动卸载后使用会报错

参考：​​https://harmonyos.51cto.com/posts/9195​​