编写字符设备驱动实现简单功能,用户层调用ioctl接口，使用动态库测试与驱动通信的代码

以下是一个简单的字符设备驱动程序的示例代码，实现了读取和写入设备数据的功能，以及处理ioctl接口：

#include <linux/module.h>
#include <linux/fs.h>
#include <linux/uaccess.h>
#include <linux/cdev.h>
#include <linux/ioctl.h>

#define DEVICE_NAME "my_device"

struct my_device_data {
    char data[100];
    int len;
};

struct my_device {
    struct cdev cdev;
    struct my_device_data data;
};

static int my_device_open(struct inode *inode, struct file *filp)
{
    struct my_device *dev = container_of(inode->i_cdev, struct my_device, cdev);
    filp->private_data = dev;
    return 0;
}

static int my_device_release(struct inode *inode, struct file *filp)
{
    return 0;
}

static ssize_t my_device_read(struct file *filp, char __user *buf, size_t count, loff_t *f_pos)
{
    struct my_device *dev = filp->private_data;
    int len = min_t(int, count, dev->data.len - *f_pos);
    if (len <= 0)
        return 0;
    if (copy_to_user(buf, dev->data.data + *f_pos, len))
        return -EFAULT;
    *f_pos += len;
    return len;
}

static ssize_t my_device_write(struct file *filp, const char __user *buf, size_t count, loff_t *f_pos)
{
    struct my_device *dev = filp->private_data;
    int len = min_t(int, count, sizeof(dev->data.data) - *f_pos);
    if (len <= 0)
        return 0;
    if (copy_from_user(dev->data.data + *f_pos, buf, len))
        return -EFAULT;
    *f_pos += len;
    dev->data.len = *f_pos;
    return len;
}

static long my_device_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
{
    struct my_device *dev = filp->private_data;
    int err = 0;
    switch (cmd) {
        case 0:
            // do something
            break;
        case 1:
            // do something else
            break;
        default:
            err = -EINVAL;
            break;
    }
    return err;
}

static const struct file_operations my_device_fops = {
    .owner = THIS_MODULE,
    .open = my_device_open,
    .release = my_device_release,
    .read = my_device_read,
    .write = my_device_write,
    .unlocked_ioctl = my_device_ioctl,
};

static struct my_device my_device_data;

static dev_t devno;

static int __init my_device_init(void)
{
    int err;
    err = alloc_chrdev_region(&devno, 0, 1, DEVICE_NAME);
    if (err < 0)
        return err;
    cdev_init(&my_device_data.cdev, &my_device_fops);
    my_device_data.cdev.owner = THIS_MODULE;
    err = cdev_add(&my_device_data.cdev, devno, 1);
    if (err < 0) {
        unregister_chrdev_region(devno, 1);
        return err;
    }
    return 0;
}

static void __exit my_device_exit(void)
{
    cdev_del(&my_device_data.cdev);
    unregister_chrdev_region(devno, 1);
}

module_init(my_device_init);
module_exit(my_device_exit);
MODULE_LICENSE("GPL");

以下是一个简单的动态库的示例代码，用于测试与驱动程序的通信，其中包含了测试读取和写入设备数据的函数，以及测试ioctl接口的函数：

#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/ioctl.h>

#define DEVICE_NAME "/dev/my_device"

struct my_device_data {
    char data[100];
    int len;
};

#define MY_DEVICE_IOCTL_CMD0 _IO('M', 0)
#define MY_DEVICE_IOCTL_CMD1 _IO('M', 1)

int my_device_read(struct my_device_data *data)
{
    int fd = open(DEVICE_NAME, O_RDONLY);
    if (fd < 0)
        return fd;
    int ret = read(fd, data->data, sizeof(data->data));
    if (ret >= 0)
        data->len = ret;
    close(fd);
    return ret;
}

int my_device_write(struct my_device_data *data)
{
    int fd = open(DEVICE_NAME, O_WRONLY);
    if (fd < 0)
        return fd;
    int ret = write(fd, data->data, data->len);
    close(fd);
    return ret;
}

int my_device_ioctl(int cmd)
{
    int fd = open(DEVICE_NAME, O_RDWR);
    if (fd < 0)
        return fd;
    int ret = ioctl(fd, cmd);
    close(fd);
    return ret;
}

最后，以下是一个简单的用户层程序的示例代码，用于调用动态库中的测试函数，测试驱动程序的功能：

#include <stdio.h>
#include "my_device.h"

int main()
{
    struct my_device_data data = {{0}, 0};
    int ret;

    // test read and write
    strcpy(data.data, "hello, world!");
    data.len = strlen(data.data) + 1;
    ret = my_device_write(&data);
    if (ret < 0) {
        fprintf(stderr, "my_device_write failed: %d\n", ret);
        return 1;
    }
    memset(&data, 0, sizeof(data));
    ret = my_device_read(&data);
    if (ret < 0) {
        fprintf(stderr, "my_device_read failed: %d\n", ret);
        return 1;
    }
    printf("read data: %s\n", data.data);

    // test ioctl
    ret = my_device_ioctl(MY_DEVICE_IOCTL_CMD0);
    if (ret < 0) {
        fprintf(stderr, "my_device_ioctl failed: %d\n", ret);
        return 1;
    }

    return 0;
}