// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Virtual NCI device simulation driver
 *
 * Copyright (C) 2020 Samsung Electronics
 * Bongsu Jeon <bongsu.jeon@samsung.com>
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/miscdevice.h>
#include <linux/mutex.h>
#include <linux/wait.h>
#include <net/nfc/nci_core.h>

#define IOCTL_GET_NCIDEV_IDX    0
#define VIRTUAL_NFC_PROTOCOLS   (NFC_PROTO_JEWEL_MASK | \
                                 NFC_PROTO_MIFARE_MASK | \
                                 NFC_PROTO_FELICA_MASK | \
                                 NFC_PROTO_ISO14443_MASK | \
                                 NFC_PROTO_ISO14443_B_MASK | \
                                 NFC_PROTO_ISO15693_MASK)

struct virtual_nci_dev {
        struct nci_dev *ndev;
        struct mutex mtx;
        struct sk_buff *send_buff;
        struct wait_queue_head wq;
        bool running;
};

static int virtual_nci_open(struct nci_dev *ndev)
{
        struct virtual_nci_dev *vdev = nci_get_drvdata(ndev);

        vdev->running = true;
        return 0;
}

static int virtual_nci_close(struct nci_dev *ndev)
{
        struct virtual_nci_dev *vdev = nci_get_drvdata(ndev);

        mutex_lock(&vdev->mtx);
        kfree_skb(vdev->send_buff);
        vdev->send_buff = NULL;
        vdev->running = false;
        mutex_unlock(&vdev->mtx);

        return 0;
}

static int virtual_nci_send(struct nci_dev *ndev, struct sk_buff *skb)
{
        struct virtual_nci_dev *vdev = nci_get_drvdata(ndev);

        mutex_lock(&vdev->mtx);
        if (vdev->send_buff || !vdev->running) {
                mutex_unlock(&vdev->mtx);
                kfree_skb(skb);
                return -1;
        }
        vdev->send_buff = skb_copy(skb, GFP_KERNEL);
        if (!vdev->send_buff) {
                mutex_unlock(&vdev->mtx);
                kfree_skb(skb);
                return -1;
        }
        mutex_unlock(&vdev->mtx);
        wake_up_interruptible(&vdev->wq);
        consume_skb(skb);

        return 0;
}

static const struct nci_ops virtual_nci_ops = {
        .open = virtual_nci_open,
        .close = virtual_nci_close,
        .send = virtual_nci_send
};

static ssize_t virtual_ncidev_read(struct file *file, char __user *buf,
                                   size_t count, loff_t *ppos)
{
        struct virtual_nci_dev *vdev = file->private_data;
        size_t actual_len;

        mutex_lock(&vdev->mtx);
        while (!vdev->send_buff) {
                mutex_unlock(&vdev->mtx);
                if (wait_event_interruptible(vdev->wq, vdev->send_buff))
                        return -EFAULT;
                mutex_lock(&vdev->mtx);
        }

        actual_len = min_t(size_t, count, vdev->send_buff->len);

        if (copy_to_user(buf, vdev->send_buff->data, actual_len)) {
                mutex_unlock(&vdev->mtx);
                return -EFAULT;
        }

        skb_pull(vdev->send_buff, actual_len);
        if (vdev->send_buff->len == 0) {
                consume_skb(vdev->send_buff);
                vdev->send_buff = NULL;
        }
        mutex_unlock(&vdev->mtx);

        return actual_len;
}

static ssize_t virtual_ncidev_write(struct file *file,
                                    const char __user *buf,
                                    size_t count, loff_t *ppos)
{
        struct virtual_nci_dev *vdev = file->private_data;
        struct sk_buff *skb;

        skb = alloc_skb(count, GFP_KERNEL);
        if (!skb)
                return -ENOMEM;

        if (copy_from_user(skb_put(skb, count), buf, count)) {
                kfree_skb(skb);
                return -EFAULT;
        }

        nci_recv_frame(vdev->ndev, skb);
        return count;
}

static int virtual_ncidev_open(struct inode *inode, struct file *file)
{
        int ret = 0;
        struct virtual_nci_dev *vdev;

        vdev = kzalloc_obj(*vdev);
        if (!vdev)
                return -ENOMEM;
        vdev->ndev = nci_allocate_device(&virtual_nci_ops,
                VIRTUAL_NFC_PROTOCOLS, 0, 0);
        if (!vdev->ndev) {
                kfree(vdev);
                return -ENOMEM;
        }

        mutex_init(&vdev->mtx);
        init_waitqueue_head(&vdev->wq);
        file->private_data = vdev;
        nci_set_drvdata(vdev->ndev, vdev);

        ret = nci_register_device(vdev->ndev);
        if (ret < 0) {
                nci_free_device(vdev->ndev);
                mutex_destroy(&vdev->mtx);
                kfree(vdev);
                return ret;
        }

        return 0;
}

static int virtual_ncidev_close(struct inode *inode, struct file *file)
{
        struct virtual_nci_dev *vdev = file->private_data;

        nci_unregister_device(vdev->ndev);
        nci_free_device(vdev->ndev);
        mutex_destroy(&vdev->mtx);
        kfree(vdev);

        return 0;
}

static long virtual_ncidev_ioctl(struct file *file, unsigned int cmd,
                                 unsigned long arg)
{
        struct virtual_nci_dev *vdev = file->private_data;
        const struct nfc_dev *nfc_dev = vdev->ndev->nfc_dev;
        void __user *p = (void __user *)arg;

        if (cmd != IOCTL_GET_NCIDEV_IDX)
                return -ENOTTY;

        if (copy_to_user(p, &nfc_dev->idx, sizeof(nfc_dev->idx)))
                return -EFAULT;

        return 0;
}

static const struct file_operations virtual_ncidev_fops = {
        .owner = THIS_MODULE,
        .read = virtual_ncidev_read,
        .write = virtual_ncidev_write,
        .open = virtual_ncidev_open,
        .release = virtual_ncidev_close,
        .unlocked_ioctl = virtual_ncidev_ioctl
};

static struct miscdevice miscdev = {
        .minor = MISC_DYNAMIC_MINOR,
        .name = "virtual_nci",
        .fops = &virtual_ncidev_fops,
        .mode = 0600,
};

module_misc_device(miscdev);

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("Virtual NCI device simulation driver");
MODULE_AUTHOR("Bongsu Jeon <bongsu.jeon@samsung.com>");