// SPDX-License-Identifier: GPL-2.0
/* Copyright (c) 2018, Linaro Ltd */

#include <linux/miscdevice.h>
#include <linux/module.h>
#include <linux/poll.h>
#include <linux/skbuff.h>
#include <linux/uaccess.h>

#include "qrtr.h"

struct qrtr_tun {
        struct qrtr_endpoint ep;

        struct sk_buff_head queue;
        wait_queue_head_t readq;
};

static int qrtr_tun_send(struct qrtr_endpoint *ep, struct sk_buff *skb)
{
        struct qrtr_tun *tun = container_of(ep, struct qrtr_tun, ep);

        skb_queue_tail(&tun->queue, skb);

        /* wake up any blocking processes, waiting for new data */
        wake_up_interruptible(&tun->readq);

        return 0;
}

static int qrtr_tun_open(struct inode *inode, struct file *filp)
{
        struct qrtr_tun *tun;
        int ret;

        tun = kzalloc_obj(*tun);
        if (!tun)
                return -ENOMEM;

        skb_queue_head_init(&tun->queue);
        init_waitqueue_head(&tun->readq);

        tun->ep.xmit = qrtr_tun_send;

        filp->private_data = tun;

        ret = qrtr_endpoint_register(&tun->ep, QRTR_EP_NID_AUTO);
        if (ret)
                goto out;

        return 0;

out:
        filp->private_data = NULL;
        kfree(tun);
        return ret;
}

static ssize_t qrtr_tun_read_iter(struct kiocb *iocb, struct iov_iter *to)
{
        struct file *filp = iocb->ki_filp;
        struct qrtr_tun *tun = filp->private_data;
        struct sk_buff *skb;
        int count;

        while (!(skb = skb_dequeue(&tun->queue))) {
                if (filp->f_flags & O_NONBLOCK)
                        return -EAGAIN;

                /* Wait until we get data or the endpoint goes away */
                if (wait_event_interruptible(tun->readq,
                                             !skb_queue_empty(&tun->queue)))
                        return -ERESTARTSYS;
        }

        count = min_t(size_t, iov_iter_count(to), skb->len);
        if (copy_to_iter(skb->data, count, to) != count)
                count = -EFAULT;

        kfree_skb(skb);

        return count;
}

static ssize_t qrtr_tun_write_iter(struct kiocb *iocb, struct iov_iter *from)
{
        struct file *filp = iocb->ki_filp;
        struct qrtr_tun *tun = filp->private_data;
        size_t len = iov_iter_count(from);
        ssize_t ret;
        void *kbuf;

        if (!len)
                return -EINVAL;

        if (len > KMALLOC_MAX_SIZE)
                return -ENOMEM;

        kbuf = kzalloc(len, GFP_KERNEL);
        if (!kbuf)
                return -ENOMEM;

        if (!copy_from_iter_full(kbuf, len, from)) {
                kfree(kbuf);
                return -EFAULT;
        }

        ret = qrtr_endpoint_post(&tun->ep, kbuf, len);

        kfree(kbuf);
        return ret < 0 ? ret : len;
}

static __poll_t qrtr_tun_poll(struct file *filp, poll_table *wait)
{
        struct qrtr_tun *tun = filp->private_data;
        __poll_t mask = 0;

        poll_wait(filp, &tun->readq, wait);

        if (!skb_queue_empty(&tun->queue))
                mask |= EPOLLIN | EPOLLRDNORM;

        return mask;
}

static int qrtr_tun_release(struct inode *inode, struct file *filp)
{
        struct qrtr_tun *tun = filp->private_data;

        qrtr_endpoint_unregister(&tun->ep);

        /* Discard all SKBs */
        skb_queue_purge(&tun->queue);

        kfree(tun);

        return 0;
}

static const struct file_operations qrtr_tun_ops = {
        .owner = THIS_MODULE,
        .open = qrtr_tun_open,
        .poll = qrtr_tun_poll,
        .read_iter = qrtr_tun_read_iter,
        .write_iter = qrtr_tun_write_iter,
        .release = qrtr_tun_release,
};

static struct miscdevice qrtr_tun_miscdev = {
        MISC_DYNAMIC_MINOR,
        "qrtr-tun",
        &qrtr_tun_ops,
};

static int __init qrtr_tun_init(void)
{
        int ret;

        ret = misc_register(&qrtr_tun_miscdev);
        if (ret)
                pr_err("failed to register Qualcomm IPC Router tun device\n");

        return ret;
}

static void __exit qrtr_tun_exit(void)
{
        misc_deregister(&qrtr_tun_miscdev);
}

module_init(qrtr_tun_init);
module_exit(qrtr_tun_exit);

MODULE_DESCRIPTION("Qualcomm IPC Router TUN device");
MODULE_LICENSE("GPL v2");