/*
 *  The NFC Controller Interface is the communication protocol between an
 *  NFC Controller (NFCC) and a Device Host (DH).
 *
 *  Copyright (C) 2011 Texas Instruments, Inc.
 *
 *  Written by Ilan Elias <ilane@ti.com>
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License version 2
 *  as published by the Free Software Foundation
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": %s: " fmt, __func__

#include <linux/types.h>
#include <linux/interrupt.h>
#include <linux/wait.h>
#include <linux/bitops.h>
#include <linux/skbuff.h>

#include "../nfc.h"
#include <net/nfc/nci.h>
#include <net/nfc/nci_core.h>
#include <linux/nfc.h>

/* Complete data exchange transaction and forward skb to nfc core */
void nci_data_exchange_complete(struct nci_dev *ndev,
                                struct sk_buff *skb,
                                int err)
{
        data_exchange_cb_t cb = ndev->data_exchange_cb;
        void *cb_context = ndev->data_exchange_cb_context;

        pr_debug("len %d, err %d\n", skb ? skb->len : 0, err);

        if (cb) {
                ndev->data_exchange_cb = NULL;
                ndev->data_exchange_cb_context = 0;

                /* forward skb to nfc core */
                cb(cb_context, skb, err);
        } else if (skb) {
                pr_err("no rx callback, dropping rx data...\n");

                /* no waiting callback, free skb */
                kfree_skb(skb);
        }

        clear_bit(NCI_DATA_EXCHANGE, &ndev->flags);
}

/* ----------------- NCI TX Data ----------------- */

static inline void nci_push_data_hdr(struct nci_dev *ndev,
                                        __u8 conn_id,
                                        struct sk_buff *skb,
                                        __u8 pbf)
{
        struct nci_data_hdr *hdr;
        int plen = skb->len;

        hdr = (struct nci_data_hdr *) skb_push(skb, NCI_DATA_HDR_SIZE);
        hdr->conn_id = conn_id;
        hdr->rfu = 0;
        hdr->plen = plen;

        nci_mt_set((__u8 *)hdr, NCI_MT_DATA_PKT);
        nci_pbf_set((__u8 *)hdr, pbf);

        skb->dev = (void *) ndev;
}

static int nci_queue_tx_data_frags(struct nci_dev *ndev,
                                        __u8 conn_id,
                                        struct sk_buff *skb) {
        int total_len = skb->len;
        unsigned char *data = skb->data;
        unsigned long flags;
        struct sk_buff_head frags_q;
        struct sk_buff *skb_frag;
        int frag_len;
        int rc = 0;

        pr_debug("conn_id 0x%x, total_len %d\n", conn_id, total_len);

        __skb_queue_head_init(&frags_q);

        while (total_len) {
                frag_len =
                        min_t(int, total_len, ndev->max_data_pkt_payload_size);

                skb_frag = nci_skb_alloc(ndev,
                                        (NCI_DATA_HDR_SIZE + frag_len),
                                        GFP_KERNEL);
                if (skb_frag == NULL) {
                        rc = -ENOMEM;
                        goto free_exit;
                }
                skb_reserve(skb_frag, NCI_DATA_HDR_SIZE);

                /* first, copy the data */
                memcpy(skb_put(skb_frag, frag_len), data, frag_len);

                /* second, set the header */
                nci_push_data_hdr(ndev, conn_id, skb_frag,
                ((total_len == frag_len) ? (NCI_PBF_LAST) : (NCI_PBF_CONT)));

                __skb_queue_tail(&frags_q, skb_frag);

                data += frag_len;
                total_len -= frag_len;

                pr_debug("frag_len %d, remaining total_len %d\n",
                         frag_len, total_len);
        }

        /* queue all fragments atomically */
        spin_lock_irqsave(&ndev->tx_q.lock, flags);

        while ((skb_frag = __skb_dequeue(&frags_q)) != NULL)
                __skb_queue_tail(&ndev->tx_q, skb_frag);

        spin_unlock_irqrestore(&ndev->tx_q.lock, flags);

        /* free the original skb */
        kfree_skb(skb);

        goto exit;

free_exit:
        while ((skb_frag = __skb_dequeue(&frags_q)) != NULL)
                kfree_skb(skb_frag);

exit:
        return rc;
}

/* Send NCI data */
int nci_send_data(struct nci_dev *ndev, __u8 conn_id, struct sk_buff *skb)
{
        int rc = 0;

        pr_debug("conn_id 0x%x, plen %d\n", conn_id, skb->len);

        /* check if the packet need to be fragmented */
        if (skb->len <= ndev->max_data_pkt_payload_size) {
                /* no need to fragment packet */
                nci_push_data_hdr(ndev, conn_id, skb, NCI_PBF_LAST);

                skb_queue_tail(&ndev->tx_q, skb);
        } else {
                /* fragment packet and queue the fragments */
                rc = nci_queue_tx_data_frags(ndev, conn_id, skb);
                if (rc) {
                        pr_err("failed to fragment tx data packet\n");
                        goto free_exit;
                }
        }

        queue_work(ndev->tx_wq, &ndev->tx_work);

        goto exit;

free_exit:
        kfree_skb(skb);

exit:
        return rc;
}

/* ----------------- NCI RX Data ----------------- */

static void nci_add_rx_data_frag(struct nci_dev *ndev,
                                struct sk_buff *skb,
                                __u8 pbf)
{
        int reassembly_len;
        int err = 0;

        if (ndev->rx_data_reassembly) {
                reassembly_len = ndev->rx_data_reassembly->len;

                /* first, make enough room for the already accumulated data */
                if (skb_cow_head(skb, reassembly_len)) {
                        pr_err("error adding room for accumulated rx data\n");

                        kfree_skb(skb);
                        skb = 0;

                        kfree_skb(ndev->rx_data_reassembly);
                        ndev->rx_data_reassembly = 0;

                        err = -ENOMEM;
                        goto exit;
                }

                /* second, combine the two fragments */
                memcpy(skb_push(skb, reassembly_len),
                                ndev->rx_data_reassembly->data,
                                reassembly_len);

                /* third, free old reassembly */
                kfree_skb(ndev->rx_data_reassembly);
                ndev->rx_data_reassembly = 0;
        }

        if (pbf == NCI_PBF_CONT) {
                /* need to wait for next fragment, store skb and exit */
                ndev->rx_data_reassembly = skb;
                return;
        }

exit:
        nci_data_exchange_complete(ndev, skb, err);
}

/* Rx Data packet */
void nci_rx_data_packet(struct nci_dev *ndev, struct sk_buff *skb)
{
        __u8 pbf = nci_pbf(skb->data);

        pr_debug("len %d\n", skb->len);

        pr_debug("NCI RX: MT=data, PBF=%d, conn_id=%d, plen=%d\n",
                 nci_pbf(skb->data),
                 nci_conn_id(skb->data),
                 nci_plen(skb->data));

        /* strip the nci data header */
        skb_pull(skb, NCI_DATA_HDR_SIZE);

        if (ndev->target_active_prot == NFC_PROTO_MIFARE) {
                /* frame I/F => remove the status byte */
                pr_debug("NFC_PROTO_MIFARE => remove the status byte\n");
                skb_trim(skb, (skb->len - 1));
        }

        nci_add_rx_data_frag(ndev, skb, pbf);
}