NFC: basic NCI protocol implementation

The NFC Controller Interface (NCI) is a standard
communication protocol between an NFC Controller (NFCC)
and a Device Host (DH), defined by the NFC Forum.

Signed-off-by: Ilan Elias <ilane@ti.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 245 insertions, 0 deletions

diff --git a/net/nfc/nci/data.c b/net/nfc/nci/data.c
new file mode 100644
index 00000000000..141790ada4a
--- /dev/null
+++ b/net/nfc/nci/data.c
@@ -0,0 +1,245 @@
+/*
+ *  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
+ *
+ */
+
+#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;
+
+        nfc_dbg("entry, len %d, err %d", ((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) {
+                nfc_err("no rx callback, dropping rx data...");
+
+                /* no waiting callback, free skb */
+                kfree_skb(skb);
+        }
+}
+
+/* ----------------- 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;
+
+        nfc_dbg("entry, conn_id 0x%x, total_len %d", conn_id, total_len);
+
+        __skb_queue_head_init(&frags_q);
+
+        while (total_len) {
+                frag_len = min_t(int, total_len, ndev->max_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;
+
+                nfc_dbg("frag_len %d, remaining total_len %d",
+                        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;
+
+        nfc_dbg("entry, conn_id 0x%x, plen %d", conn_id, skb->len);
+
+        /* check if the packet need to be fragmented */
+        if (skb->len <= ndev->max_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) {
+                        nfc_err("failed to fragment tx data packet");
+                        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)) {
+                        nfc_err("error adding room for accumulated rx data");
+
+                        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);
+
+        nfc_dbg("entry, len %d", skb->len);
+
+        nfc_dbg("NCI RX: MT=data, PBF=%d, conn_id=%d, plen=%d",
+                        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 */
+                nfc_dbg("NFC_PROTO_MIFARE => remove the status byte");
+                skb_trim(skb, (skb->len - 1));
+        }
+
+        nci_add_rx_data_frag(ndev, skb, pbf);
+}