data.c

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/*
 *  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 <[email protected]>
 *
 *  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);

    /* data exchange is complete, stop the data timer */
    del_timer_sync(&ndev->data_timer);
    clear_bit(NCI_DATA_EXCHANGE_TO, &ndev->flags);

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

        /* 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 = NULL;

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

            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 = NULL;
    }

    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);
}