/**
 * @file    demo_misc.c
 * @author  your name (you@domain.com)
 * @brief 
 * @version 0.1
 * @date    2019-10-15
 * 
 * @copyright Copyright (c) 2019
 * 
 */
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/miscdevice.h>
#include <linux/uaccess.h>

MODULE_AUTHOR("Rick Chan");
MODULE_LICENSE("GPL");

#define IOCTL_IOC_SIZE 8
#define IOCTL_IOC   _IOC(_IOC_READ|_IOC_WRITE, 0, 0, IOCTL_IOC_SIZE)
#define IOCTL_IO    _IO(0, 1)
#define IOCTL_IOR   _IOR(0, 2, uint16_t)
#define IOCTL_IOW   _IOW(0, 3, int32_t)
#define IOCTL_IOWR  _IOWR(0, 4, uint32_t)

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

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

static loff_t demo_llseek(struct file *filp, loff_t offset, int origin)
{
    return filp->f_pos;
}

static ssize_t demo_read(struct file *filp, char __user *buffer, size_t count, loff_t *offset)
{
    const char __user *p = buffer;
    return p-buffer;
}

static ssize_t demo_write(struct file *filp, const char __user *buffer, size_t count, loff_t *offset)
{
    const char __user *p = buffer;
    return p-buffer;
}

static long demo_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
{
    switch(cmd)
    {
    case IOCTL_IOC:
    {
        uint8_t tmp[IOCTL_IOC_SIZE];
        copy_from_user(&tmp, (void*)arg, _IOC_SIZE(cmd));
        copy_to_user((void*)arg, &tmp, _IOC_SIZE(cmd));
    }
        break;
    case IOCTL_IO:
        break;
    case IOCTL_IOR:
    {
        uint16_t tmp = 0x55AA;
        copy_to_user((void*)arg, &tmp, _IOC_SIZE(cmd));
    }
        break;
    case IOCTL_IOW:
    {
        int32_t tmp = 0;
        copy_from_user(&tmp, (void*)arg, _IOC_SIZE(cmd));
    }
        break;
    case IOCTL_IOWR:
    {
        uint32_t tmp = 0;
        copy_from_user(&tmp, (void*)arg, _IOC_SIZE(cmd));
        copy_to_user((void*)arg, &tmp, _IOC_SIZE(cmd));
    }
        break;
    default:
        return -ENOIOCTLCMD;
    }
    return 0;
}

static int demo_mmap(struct file* filp, struct vm_area_struct* vma)
{
    return 0;
}

static struct file_operations demo_fops = {
    .owner          = THIS_MODULE,
    .open           = demo_open,
    .release        = demo_release,
    .llseek         = demo_llseek,
    .read           = demo_read,
    .write          = demo_write,
    .unlocked_ioctl = demo_ioctl,
    .mmap           = demo_mmap
};

static struct miscdevice demo_dev = {
    .minor  = MISC_DYNAMIC_MINOR,   // Dynamically allocate minor.
    .name   = "demo_misc",
    .fops   = &demo_fops,
};

static int __init demo_init(void)
{
    misc_register(&demo_dev);
    return 0;
}

static void __exit demo_exit(void)
{
    misc_deregister(&demo_dev);
}

module_init(demo_init);
module_exit(demo_exit);