Linux ioctl 从应用到驱动

示例代码

驱动

将示例代码中n76e003_driver复制到linux/drivers/misc目录下，修改相关Kconfig与Makefile文件

1. 头文件中定义ioctl命令

// ioctl cmd
#define N76E003_IOC_MAGIC  'k'

#define N76E003_IOC_HEARTBEAT   _IO(N76E003_IOC_MAGIC, 1)
#define N76E003_IOC_SET_UPTIME _IOW(N76E003_IOC_MAGIC, 2, int)

#define N76E003_IOC_MAXNR 2

struct n76e003_data {
    struct i2c_client *client;
    struct miscdevice n76e003_device;
};

2. 实现ioctl函数

static int n76e003_dev_open(struct inode *inode, struct file *filp)
{
    int ret = 0;

    struct n76e003_data *n76e003 = container_of(filp->private_data,
                               struct n76e003_data,
                               n76e003_device);
    filp->private_data = n76e003;
    dev_info(&n76e003->client->dev,
         "device node major=%d, minor=%d\n", imajor(inode), iminor(inode));

    return ret;
}


static long n76e003_dev_ioctl(struct file *pfile,
                     unsigned int cmd, unsigned long arg)
{
    int ret = 0;
    int data = 0;
    struct n76e003_data *n76e003 = pfile->private_data;

    if (_IOC_TYPE(cmd) != N76E003_IOC_MAGIC) 
        return -EINVAL;
    if (_IOC_NR(cmd) > N76E003_IOC_MAXNR) 
        return -EINVAL;

    if (_IOC_DIR(cmd) & _IOC_READ)
        ret = !access_ok(VERIFY_WRITE, (void *)arg, _IOC_SIZE(cmd));
    else if (_IOC_DIR(cmd) & _IOC_WRITE)
        ret = !access_ok(VERIFY_READ, (void *)arg, _IOC_SIZE(cmd));
    if (ret) 
        return -EFAULT;

    dev_info(&n76e003->client->dev,
                 "%s, (%x, %lx):\n", __func__, cmd,
                 arg);
    
    switch (cmd) {
        case N76E003_IOC_HEARTBEAT:
            n76e003_heartbeat(n76e003->client);
            break;
        
        case N76E003_IOC_SET_UPTIME:
            if (copy_from_user(&data, (int *)arg, sizeof(int))) {
                dev_err(&n76e003->client->dev, 
                    "%s, copy from user failed\n", __func__);
                return -EFAULT;
            }
            n76e003_set_uptime(n76e003->client, data);
            break;
            
        default:
            return -EINVAL;
    }

    return 0;
}

3. 定义file_operations

static const struct file_operations n76e003_dev_fops = {
    .owner = THIS_MODULE,
    .open = n76e003_dev_open,
    .unlocked_ioctl = n76e003_dev_ioctl
};

4. 注册设备

static int n76e003_probe(struct i2c_client * client, const struct i2c_device_id * id)
{
    ...
    
    n76e003->n76e003_device.minor = MISC_DYNAMIC_MINOR;
    n76e003->n76e003_device.name = "n76e003";
    n76e003->n76e003_device.fops = &n76e003_dev_fops;

    ret = misc_register(&n76e003->n76e003_device);
    if (ret) {
        dev_err(&client->dev, "Failed misc_register\n");
        goto exit_misc_register;
    }

    ...
}

应用程序

如果是Android工程，将示例代码中n76e003_app复制到external目录下，并在Android根目录执行：make n76e003

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

#define DEV_NAME "/dev/n76e003"

// ioctl cmd
#define N76E003_IOC_MAGIC  'k'

#define N76E003_IOC_HEARTBEAT   _IO(N76E003_IOC_MAGIC, 1)
#define N76E003_IOC_SET_UPTIME  _IOW(N76E003_IOC_MAGIC, 2, int)

int main(int argc, char const *argv[])
{
    int ret, fd, num, arg;

    fd = open(DEV_NAME, O_RDWR);
    if (fd < 0) {
        printf("Open device fail!\n");
        return -1;
    }

    /*
    read(fd, &num, sizeof(int));
    printf("The num is: %d\n", num);

    printf("Please input a number written to testdriver: \n");
    scanf("%d", &num);

    write(fd, &num, sizeof(int));

    read(fd, &num, sizeof(int));
    printf("The num is: %d\n", num);
    */
    
    arg = 0xff;
    ret = ioctl(fd, N76E003_IOC_HEARTBEAT, &arg);
    if (ret < 0) {
        printf("ioctl: %d\n", ret);
    }
    
    sleep(10);
    
    arg = 0x01020304;
    ret = ioctl(fd, N76E003_IOC_SET_UPTIME, &arg);
    if (ret < 0) {
        printf("ioctl: %d\n", ret);
    }

    close(fd);
    return 0;
}