/******************************************************************************
 *
 *  Copyright (C) 2010-2013 Broadcom Corporation
 *
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at:
 *
 *  http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 *
 ******************************************************************************/


/******************************************************************************
 *
 *  This file contains the LLCP Link Management
 *
 ******************************************************************************/

#include <string.h>
#include "gki.h"
#include "nfc_target.h"
#include "bt_types.h"
#include "trace_api.h"
#include "llcp_int.h"
#include "llcp_defs.h"
#include "nfc_int.h"

const UINT16 llcp_link_rwt[15] =  /* RWT = (302us)*2**WT; 302us = 256*16/fc; fc = 13.56MHz */
{
       1, /* WT=0,     302us */
       1, /* WT=1,     604us */
       2, /* WT=2,    1208us */
       3, /* WT=3,     2.4ms */
       5, /* WT=4,     4.8ms */
      10, /* WT=5,     9.7ms */
      20, /* WT=6,    19.3ms */
      39, /* WT=7,    38.7ms */
      78, /* WT=8,    77.3ms */
     155, /* WT=9,   154.6ms */
     310, /* WT=10,  309.2ms */
     619, /* WT=11,  618.5ms */
    1237, /* WT=12, 1237.0ms */
    2474, /* WT=13, 2474.0ms */
    4948, /* WT=14, 4948.0ms */
};

static BOOLEAN llcp_link_parse_gen_bytes (UINT8 gen_bytes_len, UINT8 *p_gen_bytes);
static BOOLEAN llcp_link_version_agreement (void);

static void    llcp_link_send_SYMM (void);
static void    llcp_link_update_status (BOOLEAN is_activated);
static void    llcp_link_check_congestion (void);
static void    llcp_link_check_uncongested (void);
static void    llcp_link_proc_ui_pdu (UINT8 local_sap, UINT8 remote_sap, UINT16 ui_pdu_length, UINT8 *p_ui_pdu, BT_HDR *p_msg);
static void    llcp_link_proc_agf_pdu (BT_HDR *p_msg);
static void    llcp_link_proc_rx_pdu (UINT8 dsap, UINT8 ptype, UINT8 ssap, BT_HDR *p_msg);
static void    llcp_link_proc_rx_data (BT_HDR *p_msg);

static BT_HDR *llcp_link_get_next_pdu (BOOLEAN length_only, UINT16 *p_next_pdu_length);
static BT_HDR *llcp_link_build_next_pdu (BT_HDR *p_agf);
static void    llcp_link_send_to_lower (BT_HDR *p_msg);

#if (LLCP_TEST_INCLUDED == TRUE) /* this is for LLCP testing */
extern tLLCP_TEST_PARAMS llcp_test_params;
#endif

/* debug functions type */
#if (BT_TRACE_VERBOSE == TRUE)
static char *llcp_pdu_type (UINT8 ptype);
#endif

/*******************************************************************************
**
** Function         llcp_link_start_inactivity_timer
**
** Description      This function start LLCP link inactivity timer.
**
** Returns          void
**
*******************************************************************************/
static void llcp_link_start_inactivity_timer (void)
{
    if (  (llcp_cb.lcb.inact_timer.in_use == FALSE)
        &&(llcp_cb.lcb.inact_timeout > 0)  )
    {
        LLCP_TRACE_DEBUG1 ("Start inactivity_timer: %d ms", llcp_cb.lcb.inact_timeout);

        nfc_start_quick_timer (&llcp_cb.lcb.inact_timer, NFC_TTYPE_LLCP_LINK_INACT,
                               ((UINT32) llcp_cb.lcb.inact_timeout) * QUICK_TIMER_TICKS_PER_SEC / 1000);
    }
}

/*******************************************************************************
**
** Function         llcp_link_stop_inactivity_timer
**
** Description      This function stop LLCP link inactivity timer.
**
** Returns          void
**
*******************************************************************************/
static void llcp_link_stop_inactivity_timer (void)
{
    if (llcp_cb.lcb.inact_timer.in_use)
    {
        LLCP_TRACE_DEBUG0 ("Stop inactivity_timer");

        nfc_stop_quick_timer (&llcp_cb.lcb.inact_timer);
    }
}

/*******************************************************************************
**
** Function         llcp_link_start_link_timer
**
** Description      This function starts LLCP link timer (LTO or delay response).
**
** Returns          void
**
*******************************************************************************/
static void llcp_link_start_link_timer (void)
{
    if (llcp_cb.lcb.symm_state == LLCP_LINK_SYMM_LOCAL_XMIT_NEXT)
    {
        /* wait for application layer sending data */
        nfc_start_quick_timer (&llcp_cb.lcb.timer, NFC_TTYPE_LLCP_LINK_MANAGER,
                               (((UINT32) llcp_cb.lcb.symm_delay) * QUICK_TIMER_TICKS_PER_SEC) / 1000);
    }
    else
    {
        /* wait for data to receive from remote */
        nfc_start_quick_timer (&llcp_cb.lcb.timer, NFC_TTYPE_LLCP_LINK_MANAGER,
                               ((UINT32) llcp_cb.lcb.peer_lto) * QUICK_TIMER_TICKS_PER_SEC / 1000);
    }
}

/*******************************************************************************
**
** Function         llcp_link_stop_link_timer
**
** Description      This function stop LLCP link timer (LTO or delay response).
**
** Returns          void
**
*******************************************************************************/
static void llcp_link_stop_link_timer (void)
{
    nfc_stop_quick_timer (&llcp_cb.lcb.timer);
}

/*******************************************************************************
**
** Function         llcp_link_activate
**
** Description      Activate LLCP link
**
** Returns          tLLCP_STATUS
**
*******************************************************************************/
tLLCP_STATUS llcp_link_activate (tLLCP_ACTIVATE_CONFIG *p_config)
{
    LLCP_TRACE_DEBUG0 ("llcp_link_activate ()");

    /* At this point, MAC link activation procedure has been successfully completed */

    /* The Length Reduction values LRi and LRt MUST be 11b. (254bytes) */
    if (p_config->max_payload_size != LLCP_NCI_MAX_PAYL_SIZE)
    {
        LLCP_TRACE_WARNING2 ("llcp_link_activate (): max payload size (%d) must be %d bytes",
                             p_config->max_payload_size, LLCP_NCI_MAX_PAYL_SIZE);
    }

    /* Processing the parametes that have been received with the MAC link activation */
    if (llcp_link_parse_gen_bytes (p_config->gen_bytes_len,
                                   p_config->p_gen_bytes ) == FALSE)
    {
        LLCP_TRACE_ERROR0 ("llcp_link_activate (): Failed to parse general bytes");
        (*llcp_cb.lcb.p_link_cback) (LLCP_LINK_ACTIVATION_FAILED_EVT, LLCP_LINK_BAD_GEN_BYTES);
        return LLCP_STATUS_FAIL;
    }

    /*
    ** For the Target device, the scaled value of RWT MUST be less than or equal to the
    ** scaled value of the LLC Link Timeout (LTO).
    */
    if ((p_config->is_initiator) && (llcp_link_rwt[p_config->waiting_time] > llcp_cb.lcb.peer_lto))
    {
        LLCP_TRACE_WARNING3 ("llcp_link_activate (): WT (%d, %dms) must be less than or equal to LTO (%dms)",
                             p_config->waiting_time,
                             llcp_link_rwt[p_config->waiting_time],
                             llcp_cb.lcb.peer_lto);
    }

    /* extend LTO as much as internally required processing time and propagation delays */
    llcp_cb.lcb.peer_lto += LLCP_INTERNAL_TX_DELAY + LLCP_INTERNAL_RX_DELAY;

    /* LLCP version number agreement */
    if (llcp_link_version_agreement () == FALSE)
    {
        LLCP_TRACE_ERROR0 ("llcp_link_activate (): Failed to agree version");
        (*llcp_cb.lcb.p_link_cback) (LLCP_LINK_ACTIVATION_FAILED_EVT, LLCP_LINK_VERSION_FAILED);
        return LLCP_STATUS_FAIL;
    }

    llcp_cb.lcb.received_first_packet = FALSE;
    llcp_cb.lcb.is_initiator = p_config->is_initiator;

    /* reset internal flags */
    llcp_cb.lcb.flags = 0x00;

    /* set tx MIU to MIN (MIU of local LLCP, MIU of peer LLCP) */

    if (llcp_cb.lcb.local_link_miu >= llcp_cb.lcb.peer_miu)
        llcp_cb.lcb.effective_miu = llcp_cb.lcb.peer_miu;
    else
        llcp_cb.lcb.effective_miu = llcp_cb.lcb.local_link_miu;

    /*
    ** When entering the normal operation phase, LLCP shall initialize the symmetry
    ** procedure.
    */
    if (llcp_cb.lcb.is_initiator)
    {
        LLCP_TRACE_DEBUG0 ("llcp_link_activate (): Connected as Initiator");

        llcp_cb.lcb.inact_timeout = llcp_cb.lcb.inact_timeout_init;
        llcp_cb.lcb.symm_state    = LLCP_LINK_SYMM_LOCAL_XMIT_NEXT;

        if (llcp_cb.lcb.delay_first_pdu_timeout > 0)
        {
            /* give a chance to upper layer to send PDU if need */
            nfc_start_quick_timer (&llcp_cb.lcb.timer, NFC_TTYPE_LLCP_DELAY_FIRST_PDU,
                                   (((UINT32) llcp_cb.lcb.delay_first_pdu_timeout) * QUICK_TIMER_TICKS_PER_SEC) / 1000);
        }
        else
        {
            llcp_link_send_SYMM ();
        }
    }
    else
    {
        LLCP_TRACE_DEBUG0 ("llcp_link_activate (): Connected as Target");
        llcp_cb.lcb.inact_timeout = llcp_cb.lcb.inact_timeout_target;
        llcp_cb.lcb.symm_state    = LLCP_LINK_SYMM_REMOTE_XMIT_NEXT;

        /* wait for data to receive from remote */
        llcp_link_start_link_timer ();
    }


    /*
    ** Set state to LLCP_LINK_STATE_ACTIVATED and notify activation before set data callback
    ** because LLCP PDU could be in NCI queue.
    */
    llcp_cb.lcb.link_state = LLCP_LINK_STATE_ACTIVATED;

    /* LLCP Link Activation completed */
    (*llcp_cb.lcb.p_link_cback) (LLCP_LINK_ACTIVATION_COMPLETE_EVT, LLCP_LINK_SUCCESS);

    /* Update link status to service layer */
    llcp_link_update_status (TRUE);

    NFC_SetStaticRfCback (llcp_link_connection_cback);

    return (LLCP_STATUS_SUCCESS);
}

/*******************************************************************************
**
** Function         llcp_deactivate_cleanup
**
** Description      Clean up for link deactivation
**
** Returns          void
**
*******************************************************************************/
static void llcp_deactivate_cleanup  (UINT8 reason)
{
    /* report SDP failure for any pending request */
    llcp_sdp_proc_deactivation ();

    /* Update link status to service layer */
    llcp_link_update_status (FALSE);

    /* We had sent out DISC */
    llcp_cb.lcb.link_state = LLCP_LINK_STATE_DEACTIVATED;

    llcp_link_stop_link_timer ();

    /* stop inactivity timer */
    llcp_link_stop_inactivity_timer ();

    /* Let upper layer deactivate local link */
    (*llcp_cb.lcb.p_link_cback) (LLCP_LINK_DEACTIVATED_EVT, reason);
}

/*******************************************************************************
**
** Function         llcp_link_process_link_timeout
**
** Description      Process timeout events for LTO, SYMM and deactivating
**
** Returns          void
**
*******************************************************************************/
void llcp_link_process_link_timeout (void)
{
    if (llcp_cb.lcb.link_state == LLCP_LINK_STATE_ACTIVATED)
    {
        if ((llcp_cb.lcb.symm_delay > 0) && (llcp_cb.lcb.symm_state == LLCP_LINK_SYMM_LOCAL_XMIT_NEXT))
        {
            /* upper layer doesn't have anything to send */
            LLCP_TRACE_DEBUG0 ("llcp_link_process_link_timeout (): LEVT_TIMEOUT in state of LLCP_LINK_SYMM_LOCAL_XMIT_NEXT");
            llcp_link_send_SYMM ();

            /* wait for data to receive from remote */
            llcp_link_start_link_timer ();

            /* start inactivity timer */
            if (llcp_cb.num_data_link_connection == 0)
            {
                llcp_link_start_inactivity_timer ();
            }
        }
        else
        {
            LLCP_TRACE_ERROR0 ("llcp_link_process_link_timeout (): LEVT_TIMEOUT in state of LLCP_LINK_SYMM_REMOTE_XMIT_NEXT");
            llcp_link_deactivate (LLCP_LINK_TIMEOUT);
        }
    }
    else if (llcp_cb.lcb.link_state == LLCP_LINK_STATE_DEACTIVATING)
    {
        llcp_deactivate_cleanup (llcp_cb.lcb.link_deact_reason);

        NFC_SetStaticRfCback (NULL);
    }
}

/*******************************************************************************
**
** Function         llcp_link_deactivate
**
** Description      Deactivate LLCP link
**
** Returns          void
**
*******************************************************************************/
void llcp_link_deactivate (UINT8 reason)
{
    UINT8        local_sap, idx;
    tLLCP_DLCB   *p_dlcb;
    tLLCP_APP_CB *p_app_cb;

    LLCP_TRACE_DEBUG1 ("llcp_link_deactivate () reason = 0x%x", reason);

    /* Release any held buffers in signaling PDU queue */
    while (llcp_cb.lcb.sig_xmit_q.p_first)
        GKI_freebuf (GKI_dequeue (&llcp_cb.lcb.sig_xmit_q));

    /* Release any held buffers in UI PDU queue */
    for (local_sap = LLCP_SAP_SDP + 1; local_sap < LLCP_NUM_SAPS; local_sap++)
    {
        p_app_cb = llcp_util_get_app_cb (local_sap);

        if (  (p_app_cb)
            &&(p_app_cb->p_app_cback)  )
        {
            while (p_app_cb->ui_xmit_q.p_first)
                GKI_freebuf (GKI_dequeue (&p_app_cb->ui_xmit_q));

            p_app_cb->is_ui_tx_congested = FALSE;

            while (p_app_cb->ui_rx_q.p_first)
                GKI_freebuf (GKI_dequeue (&p_app_cb->ui_rx_q));
        }
    }

    llcp_cb.total_tx_ui_pdu = 0;
    llcp_cb.total_rx_ui_pdu = 0;

    /* Notify all of data link */
    for (idx = 0; idx < LLCP_MAX_DATA_LINK; idx++)
    {
        if (llcp_cb.dlcb[idx].state != LLCP_DLC_STATE_IDLE)
        {
            p_dlcb = &(llcp_cb.dlcb[idx]);

            llcp_dlsm_execute (p_dlcb, LLCP_DLC_EVENT_LINK_ERROR, NULL);
        }
    }
    llcp_cb.total_tx_i_pdu = 0;
    llcp_cb.total_rx_i_pdu = 0;

    llcp_cb.overall_tx_congested = FALSE;
    llcp_cb.overall_rx_congested = FALSE;

    if (  (reason == LLCP_LINK_FRAME_ERROR)
        ||(reason == LLCP_LINK_LOCAL_INITIATED)  )
    {
        /* get rid of the data pending in NFC tx queue, so DISC PDU can be sent ASAP */
        NFC_FlushData (NFC_RF_CONN_ID);

        llcp_util_send_disc (LLCP_SAP_LM, LLCP_SAP_LM);

        /* Wait until DISC is sent to peer */
        LLCP_TRACE_DEBUG0 ("llcp_link_deactivate (): Wait until DISC is sent to peer");

        llcp_cb.lcb.link_state = LLCP_LINK_STATE_DEACTIVATING;

        if (llcp_cb.lcb.sig_xmit_q.count == 0)
        {
            /* if DISC is sent to NFCC, wait for short period for NFCC to send it to peer */
            nfc_start_quick_timer (&llcp_cb.lcb.timer, NFC_TTYPE_LLCP_LINK_MANAGER,
                                   ((UINT32) 50) * QUICK_TIMER_TICKS_PER_SEC / 1000);
        }

        llcp_cb.lcb.link_deact_reason = reason;
        return;
    }
    else if (  (reason == LLCP_LINK_REMOTE_INITIATED)
             &&(!llcp_cb.lcb.is_initiator)  )
    {
        /* if received DISC to deactivate LLCP link as target role, send SYMM PDU */
        llcp_link_send_SYMM ();
    }
    else /*  for link timeout and interface error */
    {
        /* if got RF link loss receiving no LLC PDU from peer */
        NFC_FlushData (NFC_RF_CONN_ID);
    }

    llcp_deactivate_cleanup (reason);
}

/*******************************************************************************
**
** Function         llcp_link_parse_gen_bytes
**
** Description      Check LLCP magic number and get parameters in general bytes
**
** Returns          TRUE if success
**
*******************************************************************************/
static BOOLEAN llcp_link_parse_gen_bytes (UINT8 gen_bytes_len, UINT8 *p_gen_bytes)
{
    UINT8 *p = p_gen_bytes + LLCP_MAGIC_NUMBER_LEN;
    UINT8 length = gen_bytes_len - LLCP_MAGIC_NUMBER_LEN;

    if (  (gen_bytes_len >= LLCP_MAGIC_NUMBER_LEN)
        &&(*(p_gen_bytes) == LLCP_MAGIC_NUMBER_BYTE0)
        &&(*(p_gen_bytes + 1) == LLCP_MAGIC_NUMBER_BYTE1)
        &&(*(p_gen_bytes + 2) == LLCP_MAGIC_NUMBER_BYTE2)  )
    {
        /* in case peer didn't include these */
        llcp_cb.lcb.peer_miu = LLCP_DEFAULT_MIU;
        llcp_cb.lcb.peer_lto = LLCP_DEFAULT_LTO_IN_MS;

        return (llcp_util_parse_link_params (length, p));
    }
    else /* if this is not LLCP */
    {
        return (FALSE);
    }

    return (TRUE);
}

/*******************************************************************************
**
** Function         llcp_link_version_agreement
**
** Description      LLCP version number agreement
**
** Returns          TRUE if success
**
*******************************************************************************/
static BOOLEAN llcp_link_version_agreement (void)
{
    UINT8 peer_major_version, peer_minor_version;

    peer_major_version = LLCP_GET_MAJOR_VERSION (llcp_cb.lcb.peer_version);
    peer_minor_version = LLCP_GET_MINOR_VERSION (llcp_cb.lcb.peer_version);

    if (peer_major_version < LLCP_MIN_MAJOR_VERSION)
    {
        LLCP_TRACE_ERROR1("llcp_link_version_agreement(): unsupported peer version number. Peer Major Version:%d", peer_major_version);
        return FALSE;
    }
    else
    {
        if (peer_major_version == LLCP_VERSION_MAJOR)
        {
            llcp_cb.lcb.agreed_major_version = LLCP_VERSION_MAJOR;
            if (peer_minor_version >= LLCP_VERSION_MINOR)
            {
                llcp_cb.lcb.agreed_minor_version = LLCP_VERSION_MINOR;
            }
            else
            {
                llcp_cb.lcb.agreed_minor_version = peer_minor_version;
            }
        }
        else if (peer_major_version < LLCP_VERSION_MAJOR)
        {
            /* so far we can support backward compatibility */
            llcp_cb.lcb.agreed_major_version = peer_major_version;
            llcp_cb.lcb.agreed_minor_version = peer_minor_version;
        }
        else
        {
            /* let peer (higher major version) decide it */
            llcp_cb.lcb.agreed_major_version = LLCP_VERSION_MAJOR;
            llcp_cb.lcb.agreed_minor_version = LLCP_VERSION_MINOR;
        }

        LLCP_TRACE_DEBUG6 ("local version:%d.%d, remote version:%d.%d, agreed version:%d.%d",
                            LLCP_VERSION_MAJOR, LLCP_VERSION_MINOR,
                            peer_major_version, peer_minor_version,
                            llcp_cb.lcb.agreed_major_version, llcp_cb.lcb.agreed_minor_version);

        return (TRUE);
    }
}

/*******************************************************************************
**
** Function         llcp_link_update_status
**
** Description      Notify all of service layer client link status change
**
** Returns          void
**
*******************************************************************************/
static void llcp_link_update_status (BOOLEAN is_activated)
{
    tLLCP_SAP_CBACK_DATA data;
    tLLCP_APP_CB *p_app_cb;
    UINT8 sap;

    data.link_status.event        = LLCP_SAP_EVT_LINK_STATUS;
    data.link_status.is_activated = is_activated;
    data.link_status.is_initiator = llcp_cb.lcb.is_initiator;

    /* notify all SAP so they can create connection while link is activated */
    for (sap = LLCP_SAP_SDP + 1; sap < LLCP_NUM_SAPS; sap++)
    {
        p_app_cb = llcp_util_get_app_cb (sap);

        if (  (p_app_cb)
            &&(p_app_cb->p_app_cback)  )
        {
            data.link_status.local_sap = sap;
            p_app_cb->p_app_cback (&data);
        }
    }
}

/*******************************************************************************
**
** Function         llcp_link_check_congestion
**
** Description      Check overall congestion status
**                  Notify to all of upper layer if congested
**
** Returns          void
**
*******************************************************************************/
static void llcp_link_check_congestion (void)
{
    tLLCP_SAP_CBACK_DATA data;
    tLLCP_APP_CB *p_app_cb;
    UINT8 sap, idx;

    if (llcp_cb.overall_tx_congested)
    {
        /* already congested so no need to check again */
        return;
    }

    if (llcp_cb.total_tx_ui_pdu + llcp_cb.total_tx_i_pdu >= llcp_cb.max_num_tx_buff)
    {
        /* overall buffer usage is high */
        llcp_cb.overall_tx_congested = TRUE;

        LLCP_TRACE_WARNING2 ("overall tx congestion start: total_tx_ui_pdu=%d, total_tx_i_pdu=%d",
                              llcp_cb.total_tx_ui_pdu, llcp_cb.total_tx_i_pdu);

        data.congest.event        = LLCP_SAP_EVT_CONGEST;
        data.congest.is_congested = TRUE;

        /* notify logical data link congestion status */
        data.congest.remote_sap = LLCP_INVALID_SAP;
        data.congest.link_type  = LLCP_LINK_TYPE_LOGICAL_DATA_LINK;

        for (sap = LLCP_SAP_SDP + 1; sap < LLCP_NUM_SAPS; sap++)
        {
            p_app_cb = llcp_util_get_app_cb (sap);

            if (  (p_app_cb)
                &&(p_app_cb->p_app_cback)
                &&(p_app_cb->link_type & LLCP_LINK_TYPE_LOGICAL_DATA_LINK)  )
            {
                /* if already congested then no need to notify again */
                if (!p_app_cb->is_ui_tx_congested)
                {
                    p_app_cb->is_ui_tx_congested = TRUE;

                    LLCP_TRACE_WARNING2 ("Logical link (SAP=0x%X) congestion start: count=%d",
                                          sap, p_app_cb->ui_xmit_q.count);

                    data.congest.local_sap = sap;
                    p_app_cb->p_app_cback (&data);
                }
            }
        }

        /* notify data link connection congestion status */
        data.congest.link_type  = LLCP_LINK_TYPE_DATA_LINK_CONNECTION;

        for (idx = 0; idx < LLCP_MAX_DATA_LINK; idx++ )
        {
            if (  (llcp_cb.dlcb[idx].state == LLCP_DLC_STATE_CONNECTED)
                &&(llcp_cb.dlcb[idx].remote_busy == FALSE)
                &&(llcp_cb.dlcb[idx].is_tx_congested == FALSE)  )
            {
                llcp_cb.dlcb[idx].is_tx_congested = TRUE;

                LLCP_TRACE_WARNING3 ("Data link (SSAP:DSAP=0x%X:0x%X) congestion start: count=%d",
                                      llcp_cb.dlcb[idx].local_sap, llcp_cb.dlcb[idx].remote_sap,
                                      llcp_cb.dlcb[idx].i_xmit_q.count);

                data.congest.local_sap  = llcp_cb.dlcb[idx].local_sap;
                data.congest.remote_sap = llcp_cb.dlcb[idx].remote_sap;

                (*llcp_cb.dlcb[idx].p_app_cb->p_app_cback) (&data);
            }
        }
    }
}

/*******************************************************************************
**
** Function         llcp_link_check_uncongested
**
** Description      Check overall congestion status, logical data link and
**                  data link connection congestion status
**                  Notify to each upper layer if uncongested
**
** Returns          void
**
*******************************************************************************/
static void llcp_link_check_uncongested (void)
{
    tLLCP_SAP_CBACK_DATA data;
    tLLCP_APP_CB *p_app_cb;
    UINT8 xx, sap, idx;

    if (llcp_cb.overall_tx_congested)
    {
        if (llcp_cb.total_tx_ui_pdu + llcp_cb.total_tx_i_pdu <= llcp_cb.max_num_tx_buff / 2)
        {
            /* overall congestion is cleared */
            llcp_cb.overall_tx_congested = FALSE;

            LLCP_TRACE_WARNING2 ("overall tx congestion end: total_tx_ui_pdu=%d, total_tx_i_pdu=%d",
                                  llcp_cb.total_tx_ui_pdu, llcp_cb.total_tx_i_pdu);
        }
        else
        {
            /* wait until more data packets are sent out */
            return;
        }
    }

    data.congest.event        = LLCP_SAP_EVT_CONGEST;
    data.congest.is_congested = FALSE;

    /* if total number of UI PDU is below threshold */
    if (llcp_cb.total_tx_ui_pdu < llcp_cb.max_num_ll_tx_buff)
    {
        /* check and notify logical data link congestion status */
        data.congest.remote_sap = LLCP_INVALID_SAP;
        data.congest.link_type  = LLCP_LINK_TYPE_LOGICAL_DATA_LINK;

        /*
        ** start point of uncongested status notification is in round robin
        ** so each logical data link has equal chance of transmitting.
        */
        sap = llcp_cb.ll_tx_uncongest_ntf_start_sap;

        for (xx = LLCP_SAP_SDP + 1; xx < LLCP_NUM_SAPS; xx++)
        {
            /* no logical data link on LM and SDP */
            if (sap > LLCP_SAP_SDP)
            {
                p_app_cb = llcp_util_get_app_cb (sap);

                if (  (p_app_cb)
                    &&(p_app_cb->p_app_cback)
                    &&(p_app_cb->link_type & LLCP_LINK_TYPE_LOGICAL_DATA_LINK)
                    &&(p_app_cb->is_ui_tx_congested)
                    &&(p_app_cb->ui_xmit_q.count <= llcp_cb.ll_tx_congest_end)  )
                {
                    /* if it was congested but now tx queue count is below threshold */
                    p_app_cb->is_ui_tx_congested = FALSE;

                    LLCP_TRACE_DEBUG2 ("Logical link (SAP=0x%X) congestion end: count=%d",
                                        sap, p_app_cb->ui_xmit_q.count);

                    data.congest.local_sap = sap;
                    p_app_cb->p_app_cback (&data);
                }
            }

            sap = (sap + 1) % LLCP_NUM_SAPS;
        }

        /* move start point for next logical data link */
        for (xx = 0; xx < LLCP_NUM_SAPS; xx++)
        {
            sap = (llcp_cb.ll_tx_uncongest_ntf_start_sap + 1) % LLCP_NUM_SAPS;

            if (sap > LLCP_SAP_SDP)
            {
                p_app_cb = llcp_util_get_app_cb (sap);

                if (  (p_app_cb)
                    &&(p_app_cb->p_app_cback)
                    &&(p_app_cb->link_type & LLCP_LINK_TYPE_LOGICAL_DATA_LINK)  )
                {
                    llcp_cb.ll_tx_uncongest_ntf_start_sap = sap;
                    break;
                }
            }
        }
    }

    /* notify data link connection congestion status */
    data.congest.link_type  = LLCP_LINK_TYPE_DATA_LINK_CONNECTION;

    /*
    ** start point of uncongested status notification is in round robin
    ** so each data link connection has equal chance of transmitting.
    */
    idx = llcp_cb.dl_tx_uncongest_ntf_start_idx;

    for (xx = 0; xx < LLCP_MAX_DATA_LINK; xx++ )
    {
        /* if it was congested but now tx queue is below threshold (receiving window) */
        if (  (llcp_cb.dlcb[idx].state == LLCP_DLC_STATE_CONNECTED)
            &&(llcp_cb.dlcb[idx].is_tx_congested)
            &&(llcp_cb.dlcb[idx].i_xmit_q.count <= llcp_cb.dlcb[idx].remote_rw / 2)  )
        {
            llcp_cb.dlcb[idx].is_tx_congested = FALSE;

            if (llcp_cb.dlcb[idx].remote_busy == FALSE)
            {
                LLCP_TRACE_DEBUG3 ("Data link (SSAP:DSAP=0x%X:0x%X) congestion end: count=%d",
                                    llcp_cb.dlcb[idx].local_sap, llcp_cb.dlcb[idx].remote_sap,
                                    llcp_cb.dlcb[idx].i_xmit_q.count);

                data.congest.local_sap  = llcp_cb.dlcb[idx].local_sap;
                data.congest.remote_sap = llcp_cb.dlcb[idx].remote_sap;

                (*llcp_cb.dlcb[idx].p_app_cb->p_app_cback) (&data);
            }
        }
        idx = (idx + 1) % LLCP_MAX_DATA_LINK;
    }

    /* move start point for next data link connection */
    for (xx = 0; xx < LLCP_MAX_DATA_LINK; xx++ )
    {
        idx = (llcp_cb.dl_tx_uncongest_ntf_start_idx + 1) % LLCP_MAX_DATA_LINK;
        if (llcp_cb.dlcb[idx].state == LLCP_DLC_STATE_CONNECTED)
        {
            llcp_cb.dl_tx_uncongest_ntf_start_idx = idx;
            break;
        }
    }
}

/*******************************************************************************
**
** Function         llcp_link_send_SYMM
**
** Description      Send SYMM PDU
**
** Returns          void
**
*******************************************************************************/
static void llcp_link_send_SYMM (void)
{
    BT_HDR *p_msg;
    UINT8  *p;

    p_msg = (BT_HDR*) GKI_getpoolbuf (LLCP_POOL_ID);

    if (p_msg)
    {
        p_msg->len    = LLCP_PDU_SYMM_SIZE;
        p_msg->offset = NCI_MSG_OFFSET_SIZE + NCI_DATA_HDR_SIZE;

        p = (UINT8 *) (p_msg + 1) + p_msg->offset;
        UINT16_TO_BE_STREAM (p, LLCP_GET_PDU_HEADER (LLCP_SAP_LM, LLCP_PDU_SYMM_TYPE, LLCP_SAP_LM ));

        llcp_link_send_to_lower (p_msg);
    }
}

/*******************************************************************************
**
** Function         llcp_link_check_send_data
**
** Description      Send PDU to peer
**
** Returns          void
**
*******************************************************************************/
void llcp_link_check_send_data (void)
{
    BT_HDR *p_pdu;

    /* don't re-enter while processing to prevent out of sequence */
    if (llcp_cb.lcb.is_sending_data)
        return;
    else
        llcp_cb.lcb.is_sending_data = TRUE;

    /*
    ** check overall congestion due to high usage of buffer pool
    ** if congested then notify all of upper layers not to send any more data
    */
    llcp_link_check_congestion ();

    if (llcp_cb.lcb.symm_state == LLCP_LINK_SYMM_LOCAL_XMIT_NEXT)
    {
        LLCP_TRACE_DEBUG0 ("llcp_link_check_send_data () in state of LLCP_LINK_SYMM_LOCAL_XMIT_NEXT");

        p_pdu = llcp_link_build_next_pdu (NULL);

        /*
        ** For data link connection,
        ** V(RA) was updated and N(R) was set to V(RA), if I PDU was added in this transmission.
        ** If there was no I PDU to carry V(RA) and V(RA) is not V(R) and it's not congested,
        ** then RR PDU will be sent.
        ** If there was no I PDU to carry V(RA) and V(RA) is not V(R) and it's congested,
        ** then RNR PDU will be sent.
        ** If local busy state has been changed then RR or RNR PDU may be sent.
        */
        llcp_dlc_check_to_send_rr_rnr ();

        /* add RR/RNR PDU to be sent if any */
        p_pdu = llcp_link_build_next_pdu (p_pdu);

        if (p_pdu != NULL)
        {
            llcp_link_send_to_lower (p_pdu);

            /* stop inactivity timer */
            llcp_link_stop_inactivity_timer ();

            /* check congestion status after sending out some data */
            llcp_link_check_uncongested ();
        }
        else
        {
            /* There is no data to send, so send SYMM */
            if (llcp_cb.lcb.link_state == LLCP_LINK_STATE_ACTIVATED)
            {
                if (llcp_cb.lcb.symm_delay > 0)
                {
                    /* wait for application layer sending data */
                    llcp_link_start_link_timer ();
                    llcp_cb.lcb.is_sending_data = FALSE;
                    return;
                }
                else
                {
                    llcp_link_send_SYMM ();

                    /* start inactivity timer */
                    if (llcp_cb.num_data_link_connection == 0)
                    {
                        llcp_link_start_inactivity_timer ();
                    }
                }
            }
            else
            {
                llcp_cb.lcb.is_sending_data = FALSE;
                return;
            }
        }

        if (llcp_cb.lcb.link_state == LLCP_LINK_STATE_DEACTIVATING)
        {
            /* wait for short period for NFCC to send DISC */
            nfc_start_quick_timer (&llcp_cb.lcb.timer, NFC_TTYPE_LLCP_LINK_MANAGER,
                                   ((UINT32) 50) * QUICK_TIMER_TICKS_PER_SEC / 1000);
        }
        else
        {
            /* wait for data to receive from remote */
            llcp_link_start_link_timer ();
        }
    }

    llcp_cb.lcb.is_sending_data = FALSE;
}

/*******************************************************************************
**
** Function         llcp_link_proc_ui_pdu
**
** Description      Process UI PDU from peer device
**
** Returns          None
**
*******************************************************************************/
static void llcp_link_proc_ui_pdu (UINT8  local_sap,
                                   UINT8  remote_sap,
                                   UINT16 ui_pdu_length,
                                   UINT8  *p_ui_pdu,
                                   BT_HDR *p_msg)
{
    BOOLEAN      appended;
    BT_HDR       *p_last_buf;
    UINT16       available_bytes;
    UINT8        *p_dst;
    tLLCP_APP_CB *p_app_cb;
    tLLCP_SAP_CBACK_DATA data;
    tLLCP_DLCB   *p_dlcb;

    p_app_cb = llcp_util_get_app_cb (local_sap);
        /*if UI PDU sent to SAP with data link connection*/
    if ((p_dlcb = llcp_dlc_find_dlcb_by_sap (local_sap, remote_sap)))
    {
        llcp_util_send_frmr (p_dlcb, LLCP_FRMR_W_ERROR_FLAG, LLCP_PDU_UI_TYPE, 0);
        llcp_dlsm_execute (p_dlcb, LLCP_DLC_EVENT_FRAME_ERROR, NULL);
        if (p_msg)
        {
            GKI_freebuf (p_msg);
        }
        return;
    }

    /* if application is registered and expecting UI PDU on logical data link */
    if (  (p_app_cb)
        &&(p_app_cb->p_app_cback)
        &&(p_app_cb->link_type & LLCP_LINK_TYPE_LOGICAL_DATA_LINK)  )
    {
        LLCP_TRACE_DEBUG2 ("llcp_link_proc_ui_pdu () Local SAP:0x%x, Remote SAP:0x%x", local_sap, remote_sap);

        /* if this is not from AGF PDU */
        if (p_msg)
        {
            ui_pdu_length = p_msg->len; /* including LLCP header */
            p_ui_pdu      = (UINT8*) (p_msg + 1) + p_msg->offset;
        }

        appended = FALSE;

        /* get last buffer in rx queue */
        p_last_buf = (BT_HDR *) GKI_getlast (&p_app_cb->ui_rx_q);

        if (p_last_buf)
        {
            /* get max length to append at the end of buffer */
            available_bytes = GKI_get_buf_size (p_last_buf) - BT_HDR_SIZE - p_last_buf->offset - p_last_buf->len;

            /* if new UI PDU with length can be attached at the end of buffer */
            if (available_bytes >= LLCP_PDU_AGF_LEN_SIZE + ui_pdu_length)
            {
                p_dst = (UINT8*) (p_last_buf + 1) + p_last_buf->offset + p_last_buf->len;

                /* add length of UI PDU */
                UINT16_TO_BE_STREAM (p_dst, ui_pdu_length);

                /* copy UI PDU with LLCP header */
                memcpy (p_dst, p_ui_pdu, ui_pdu_length);

                p_last_buf->len += LLCP_PDU_AGF_LEN_SIZE + ui_pdu_length;

                if (p_msg)
                    GKI_freebuf (p_msg);

                appended = TRUE;
            }
        }

        /* if it is not available to append */
        if (!appended)
        {
            /* if it's not from AGF PDU */
            if (p_msg)
            {
                /* add length of PDU in front of UI PDU (reuse room for NCI header) */
                p_ui_pdu -= LLCP_PDU_AGF_LEN_SIZE;
                UINT16_TO_BE_STREAM (p_ui_pdu, ui_pdu_length);

                p_msg->offset -= LLCP_PDU_AGF_LEN_SIZE;
                p_msg->len    += LLCP_PDU_AGF_LEN_SIZE;
                p_msg->layer_specific = 0;
            }
            else
            {
                p_msg = (BT_HDR *) GKI_getpoolbuf (LLCP_POOL_ID);

                if (p_msg)
                {
                    p_dst = (UINT8*) (p_msg + 1);

                    /* add length of PDU in front of UI PDU */
                    UINT16_TO_BE_STREAM (p_dst, ui_pdu_length);

                    memcpy (p_dst, p_ui_pdu, ui_pdu_length);

                    p_msg->offset = 0;
                    p_msg->len    = LLCP_PDU_AGF_LEN_SIZE + ui_pdu_length;
                    p_msg->layer_specific = 0;
                }
                else
                {
                    LLCP_TRACE_ERROR0 ("llcp_link_proc_ui_pdu (): out of buffer");
                }
            }

            /* insert UI PDU in rx queue */
            if (p_msg)
            {
                GKI_enqueue (&p_app_cb->ui_rx_q, p_msg);
                llcp_cb.total_rx_ui_pdu++;
            }
        }

        if (p_app_cb->ui_rx_q.count > llcp_cb.ll_rx_congest_start)
        {
            LLCP_TRACE_WARNING2 ("llcp_link_proc_ui_pdu (): SAP:0x%x, rx link is congested (%d), discard oldest UI PDU",
                                 local_sap, p_app_cb->ui_rx_q.count);

            GKI_freebuf (GKI_dequeue (&p_app_cb->ui_rx_q));
            llcp_cb.total_rx_ui_pdu--;
        }

        if ((p_app_cb->ui_rx_q.count == 1) && (appended == FALSE))
        {
            data.data_ind.event         = LLCP_SAP_EVT_DATA_IND;
            data.data_ind.local_sap     = local_sap;
            data.data_ind.remote_sap    = remote_sap;
            data.data_ind.link_type     = LLCP_LINK_TYPE_LOGICAL_DATA_LINK;
            (*p_app_cb->p_app_cback) (&data);
        }
    }
    else
    {
        LLCP_TRACE_ERROR1 ("llcp_link_proc_ui_pdu (): Unregistered SAP:0x%x", local_sap);

        if (p_msg)
        {
            GKI_freebuf (p_msg);
        }
    }
}

/*******************************************************************************
**
** Function         llcp_link_proc_agf_pdu
**
** Description      Process AGF PDU from peer device
**
** Returns          void
**
*******************************************************************************/
static void llcp_link_proc_agf_pdu (BT_HDR *p_agf)
{
    UINT16 agf_length;
    UINT8 *p, *p_info, *p_pdu_length;
    UINT16 pdu_hdr, pdu_length;
    UINT8  dsap, ptype, ssap;

    p_agf->len    -= LLCP_PDU_HEADER_SIZE;
    p_agf->offset += LLCP_PDU_HEADER_SIZE;

    /*
    ** check integrity of AGF PDU and get number of PDUs in AGF PDU
    */
    agf_length = p_agf->len;
    p = (UINT8 *) (p_agf + 1) + p_agf->offset;

    while (agf_length > 0)
    {
        if (agf_length > LLCP_PDU_AGF_LEN_SIZE)
        {
            BE_STREAM_TO_UINT16 (pdu_length, p);
            agf_length -= LLCP_PDU_AGF_LEN_SIZE;
        }
        else
        {
            break;
        }

        if (pdu_length <= agf_length)
        {
            p += pdu_length;
            agf_length -= pdu_length;
        }
        else
        {
            break;
        }
    }

    if (agf_length != 0)
    {
        LLCP_TRACE_ERROR0 ("llcp_link_proc_agf_pdu (): Received invalid AGF PDU");
        GKI_freebuf (p_agf);
        return;
    }

    /*
    ** Process PDUs in AGF
    */
    agf_length = p_agf->len;
    p = (UINT8 *) (p_agf + 1) + p_agf->offset;

    while (agf_length > 0)
    {
        /* get length of PDU */
        p_pdu_length = p;
        BE_STREAM_TO_UINT16 (pdu_length, p);
        agf_length -= LLCP_PDU_AGF_LEN_SIZE;

        /* get DSAP/PTYPE/SSAP */
        p_info = p;
        BE_STREAM_TO_UINT16 (pdu_hdr, p_info );

        dsap  = LLCP_GET_DSAP (pdu_hdr);
        ptype = (UINT8) (LLCP_GET_PTYPE (pdu_hdr));
        ssap  = LLCP_GET_SSAP (pdu_hdr);

#if (BT_TRACE_VERBOSE == TRUE)
        LLCP_TRACE_DEBUG4 ("llcp_link_proc_agf_pdu (): Rx DSAP:0x%x, PTYPE:%s (0x%x), SSAP:0x%x in AGF",
                           dsap, llcp_pdu_type (ptype), ptype, ssap);
#endif

        if (  (ptype == LLCP_PDU_DISC_TYPE)
            &&(dsap == LLCP_SAP_LM)
            &&(ssap == LLCP_SAP_LM)  )
        {
            GKI_freebuf (p_agf);
            llcp_link_deactivate (LLCP_LINK_REMOTE_INITIATED);
            return;
        }
        else if (ptype == LLCP_PDU_SYMM_TYPE)
        {
            LLCP_TRACE_ERROR0 ("llcp_link_proc_agf_pdu (): SYMM PDU exchange shall not be in AGF");
        }
        else if (ptype == LLCP_PDU_PAX_TYPE)
        {
            LLCP_TRACE_ERROR0 ("llcp_link_proc_agf_pdu (): PAX PDU exchange shall not be used");
        }
        else if (ptype == LLCP_PDU_SNL_TYPE)
        {
            llcp_sdp_proc_snl ((UINT16) (pdu_length - LLCP_PDU_HEADER_SIZE), p_info);
        }
        else if ((ptype == LLCP_PDU_UI_TYPE) && (pdu_length > LLCP_PDU_HEADER_SIZE))
        {
            llcp_link_proc_ui_pdu (dsap, ssap, pdu_length, p, NULL);
        }
        else if (ptype == LLCP_PDU_I_TYPE)
        {
            llcp_dlc_proc_i_pdu (dsap, ssap, pdu_length, p, NULL);
        }
        else /* let data link connection handle PDU */
        {
            llcp_dlc_proc_rx_pdu (dsap, ptype, ssap, (UINT16) (pdu_length - LLCP_PDU_HEADER_SIZE), p_info);
        }

        p += pdu_length;
        agf_length -= pdu_length;
    }

    GKI_freebuf (p_agf);
}

/*******************************************************************************
**
** Function         llcp_link_proc_rx_pdu
**
** Description      Process received PDU from peer device
**
** Returns          void
**
*******************************************************************************/
static void llcp_link_proc_rx_pdu (UINT8 dsap, UINT8 ptype, UINT8 ssap, BT_HDR *p_msg)
{
    BOOLEAN free_buffer = TRUE;
    UINT8   *p_data;

    switch (ptype)
    {
    case LLCP_PDU_PAX_TYPE:
        LLCP_TRACE_ERROR0 ("llcp_link_proc_rx_pdu (); PAX PDU exchange shall not be used");
        break;

    case LLCP_PDU_DISC_TYPE:
        if ((dsap == LLCP_SAP_LM) && (ssap == LLCP_SAP_LM))
        {
            llcp_link_deactivate (LLCP_LINK_REMOTE_INITIATED);
        }
        else
        {
            p_data = (UINT8 *) (p_msg + 1) + p_msg->offset + LLCP_PDU_HEADER_SIZE;
            llcp_dlc_proc_rx_pdu (dsap, ptype, ssap, (UINT16) (p_msg->len - LLCP_PDU_HEADER_SIZE), p_data);
        }
        break;

    case LLCP_PDU_SNL_TYPE:
        p_data = (UINT8 *) (p_msg + 1) + p_msg->offset + LLCP_PDU_HEADER_SIZE;
        llcp_sdp_proc_snl ((UINT16) (p_msg->len - LLCP_PDU_HEADER_SIZE), p_data);
        break;

    case LLCP_PDU_AGF_TYPE:
        llcp_link_proc_agf_pdu (p_msg);
        free_buffer = FALSE;
        break;

    case LLCP_PDU_UI_TYPE:
        llcp_link_proc_ui_pdu (dsap, ssap, 0, NULL, p_msg);
        free_buffer = FALSE;
        break;

    case LLCP_PDU_I_TYPE:
        llcp_dlc_proc_i_pdu (dsap, ssap, 0, NULL, p_msg);
        free_buffer = FALSE;
        break;

    default:
        p_data = (UINT8 *) (p_msg + 1) + p_msg->offset + LLCP_PDU_HEADER_SIZE;
        llcp_dlc_proc_rx_pdu (dsap, ptype, ssap, (UINT16) (p_msg->len - LLCP_PDU_HEADER_SIZE), p_data);
        break;
    }

    if (free_buffer)
        GKI_freebuf (p_msg);
}

/*******************************************************************************
**
** Function         llcp_link_proc_rx_data
**
** Description      Process received data from NFCC and maintain symmetry state
**
** Returns          void
**
*******************************************************************************/
static void llcp_link_proc_rx_data (BT_HDR *p_msg)
{
    UINT8  *p;
    UINT16  pdu_hdr, info_length = 0;
    UINT8   dsap, ptype, ssap;
    BOOLEAN free_buffer = TRUE;
    BOOLEAN frame_error = FALSE;

    if (llcp_cb.lcb.symm_state == LLCP_LINK_SYMM_REMOTE_XMIT_NEXT)
    {
        llcp_link_stop_link_timer ();

        if (llcp_cb.lcb.received_first_packet == FALSE)
        {
            llcp_cb.lcb.received_first_packet = TRUE;
            (*llcp_cb.lcb.p_link_cback) (LLCP_LINK_FIRST_PACKET_RECEIVED_EVT, LLCP_LINK_SUCCESS);
        }
        if (  (llcp_cb.lcb.link_state == LLCP_LINK_STATE_DEACTIVATING)
            &&(llcp_cb.lcb.sig_xmit_q.count == 0)  )
        {
            /* this indicates that DISC PDU had been sent out to peer */
            /* initiator may wait for SYMM PDU */
            llcp_link_process_link_timeout ();
        }
        else
        {
            if (p_msg->len < LLCP_PDU_HEADER_SIZE)
            {
                LLCP_TRACE_ERROR1 ("Received too small PDU: got %d bytes", p_msg->len);
                frame_error = TRUE;
            }
            else
            {
                p = (UINT8 *) (p_msg + 1) + p_msg->offset;
                BE_STREAM_TO_UINT16 (pdu_hdr, p );

                dsap  = LLCP_GET_DSAP (pdu_hdr);
                ptype = (UINT8) (LLCP_GET_PTYPE (pdu_hdr));
                ssap  = LLCP_GET_SSAP (pdu_hdr);

                /* get length of information per PDU type */
                if (  (ptype == LLCP_PDU_I_TYPE)
                    ||(ptype == LLCP_PDU_RR_TYPE)
                    ||(ptype == LLCP_PDU_RNR_TYPE)  )
                {
                    if (p_msg->len >= LLCP_PDU_HEADER_SIZE + LLCP_SEQUENCE_SIZE)
                    {
                        info_length = p_msg->len - LLCP_PDU_HEADER_SIZE - LLCP_SEQUENCE_SIZE;
                    }
                    else
                    {
                        LLCP_TRACE_ERROR0 ("Received I/RR/RNR PDU without sequence");
                        frame_error = TRUE;
                    }
                }
                else
                {
                    info_length = p_msg->len - LLCP_PDU_HEADER_SIZE;
                }

                /* check if length of information is bigger than link MIU */
                if ((!frame_error) && (info_length > llcp_cb.lcb.local_link_miu))
                {
                    LLCP_TRACE_ERROR2 ("Received exceeding MIU (%d): got %d bytes SDU",
                                       llcp_cb.lcb.local_link_miu, info_length);

                    frame_error = TRUE;
                }
                else
                {
#if (BT_TRACE_VERBOSE == TRUE)
                    LLCP_TRACE_DEBUG4 ("llcp_link_proc_rx_data (): DSAP:0x%x, PTYPE:%s (0x%x), SSAP:0x%x",
                                       dsap, llcp_pdu_type (ptype), ptype, ssap);
#endif

                    if (ptype == LLCP_PDU_SYMM_TYPE)
                    {
                        if (info_length > 0)
                        {
                            LLCP_TRACE_ERROR1 ("Received extra data (%d bytes) in SYMM PDU", info_length);
                            frame_error = TRUE;
                        }
                    }
                    else
                    {
                        /* received other than SYMM */
                        llcp_link_stop_inactivity_timer ();

                        llcp_link_proc_rx_pdu (dsap, ptype, ssap, p_msg);
                        free_buffer = FALSE;
                    }
                }
            }

            llcp_cb.lcb.symm_state = LLCP_LINK_SYMM_LOCAL_XMIT_NEXT;

            /* check if any pending packet */
            llcp_link_check_send_data ();
        }
    }
    else
    {
        LLCP_TRACE_ERROR0 ("Received PDU in state of SYMM_MUST_XMIT_NEXT");
    }

    if (free_buffer)
        GKI_freebuf (p_msg);
}

/*******************************************************************************
**
** Function         llcp_link_get_next_pdu
**
** Description      Get next PDU from link manager or data links w/wo dequeue
**
** Returns          pointer of a PDU to send if length_only is FALSE
**                  NULL otherwise
**
*******************************************************************************/
static BT_HDR *llcp_link_get_next_pdu (BOOLEAN length_only, UINT16 *p_next_pdu_length)
{
    BT_HDR *p_msg;
    int     count, xx;
    tLLCP_APP_CB *p_app_cb;

    /* processing signalling PDU first */
    if (llcp_cb.lcb.sig_xmit_q.p_first)
    {
        if (length_only)
        {
            p_msg = (BT_HDR*) llcp_cb.lcb.sig_xmit_q.p_first;
            *p_next_pdu_length = p_msg->len;
            return NULL;
        }
        else
            p_msg = (BT_HDR*) GKI_dequeue (&llcp_cb.lcb.sig_xmit_q);

        return p_msg;
    }
    else
    {
        /* transmitting logical data link and data link connection equaly */
        for (xx = 0; xx < 2; xx++)
        {
            if (!llcp_cb.lcb.ll_served)
            {
                /* Get one from logical link connection */
                for (count = 0; count < LLCP_NUM_SAPS; count++)
                {
                    /* round robin schedule without priority  */
                    p_app_cb = llcp_util_get_app_cb (llcp_cb.lcb.ll_idx);

                    if (  (p_app_cb)
                        &&(p_app_cb->p_app_cback)
                        &&(p_app_cb->ui_xmit_q.count)  )
                    {
                        if (length_only)
                        {
                            /* don't alternate next data link to return the same length of PDU */
                            p_msg = (BT_HDR *) p_app_cb->ui_xmit_q.p_first;
                            *p_next_pdu_length = p_msg->len;
                            return NULL;
                        }
                        else
                        {
                            /* check data link connection first in next time */
                            llcp_cb.lcb.ll_served = !llcp_cb.lcb.ll_served;

                            p_msg = (BT_HDR*) GKI_dequeue (&p_app_cb->ui_xmit_q);
                            llcp_cb.total_tx_ui_pdu--;

                            /* this logical link has been served, so start from next logical link next time */
                            llcp_cb.lcb.ll_idx = (llcp_cb.lcb.ll_idx + 1) % LLCP_NUM_SAPS;

                            return p_msg;
                        }
                    }
                    else
                    {
                        /* check next logical link connection */
                        llcp_cb.lcb.ll_idx = (llcp_cb.lcb.ll_idx + 1) % LLCP_NUM_SAPS;
                    }
                }

                /* no data, so check data link connection if not checked yet */
                llcp_cb.lcb.ll_served = !llcp_cb.lcb.ll_served;
            }
            else
            {
                /* Get one from data link connection */
                for (count = 0; count < LLCP_MAX_DATA_LINK; count++)
                {
                    /* round robin schedule without priority  */
                    if (llcp_cb.dlcb[llcp_cb.lcb.dl_idx].state != LLCP_DLC_STATE_IDLE)
                    {
                        if (length_only)
                        {
                            *p_next_pdu_length = llcp_dlc_get_next_pdu_length (&llcp_cb.dlcb[llcp_cb.lcb.dl_idx]);

                            if (*p_next_pdu_length > 0 )
                            {
                                /* don't change data link connection to return the same length of PDU */
                                return NULL;
                            }
                            else
                            {
                                /* no data, so check next data link connection */
                                llcp_cb.lcb.dl_idx = (llcp_cb.lcb.dl_idx + 1) % LLCP_MAX_DATA_LINK;
                            }
                        }
                        else
                        {
                            p_msg = llcp_dlc_get_next_pdu (&llcp_cb.dlcb[llcp_cb.lcb.dl_idx]);

                            /* this data link has been served, so start from next data link next time */
                            llcp_cb.lcb.dl_idx = (llcp_cb.lcb.dl_idx + 1) % LLCP_MAX_DATA_LINK;

                            if (p_msg)
                            {
                                /* serve logical data link next time */
                                llcp_cb.lcb.ll_served = !llcp_cb.lcb.ll_served;
                                return p_msg;
                            }
                        }
                    }
                    else
                    {
                        /* check next data link connection */
                        llcp_cb.lcb.dl_idx = (llcp_cb.lcb.dl_idx + 1) % LLCP_MAX_DATA_LINK;
                    }
                }

                /* if all of data link connection doesn't have data to send */
                if (count >= LLCP_MAX_DATA_LINK)
                {
                    llcp_cb.lcb.ll_served = !llcp_cb.lcb.ll_served;
                }
            }
        }
    }

    /* nothing to send */
    *p_next_pdu_length = 0;
    return NULL;
}

/*******************************************************************************
**
** Function         llcp_link_build_next_pdu
**
** Description      Build a PDU from Link Manager and Data Link
**                  Perform aggregation procedure if necessary
**
** Returns          BT_HDR* if sent any PDU
**
*******************************************************************************/
static BT_HDR *llcp_link_build_next_pdu (BT_HDR *p_pdu)
{
    BT_HDR *p_agf = NULL, *p_msg = NULL, *p_next_pdu;
    UINT8  *p, ptype;
    UINT16  next_pdu_length, pdu_hdr;

    LLCP_TRACE_DEBUG0 ("llcp_link_build_next_pdu ()");

    /* add any pending SNL PDU into sig_xmit_q for transmitting */
    llcp_sdp_check_send_snl ();

    if (p_pdu)
    {
        /* get PDU type */
        p = (UINT8 *) (p_pdu + 1) + p_pdu->offset;
        BE_STREAM_TO_UINT16 (pdu_hdr, p);

        ptype = (UINT8) (LLCP_GET_PTYPE (pdu_hdr));

        if (ptype == LLCP_PDU_AGF_TYPE)
        {
            /* add more PDU into this AGF PDU */
            p_agf = p_pdu;
        }
        else
        {
            p_msg = p_pdu;
        }
    }
    else
    {
        /* Get a PDU from link manager or data links */
        p_msg = llcp_link_get_next_pdu (FALSE, &next_pdu_length);

        if (!p_msg)
        {
            return NULL;
        }
    }

    /* Get length of next PDU from link manager or data links without dequeue */
    llcp_link_get_next_pdu (TRUE, &next_pdu_length);
    while (next_pdu_length > 0)
    {
        /* if it's first visit */
        if (!p_agf)
        {
            /* if next PDU fits into MIU, allocate AGF PDU and copy the first PDU */
            if (2 + p_msg->len + 2 + next_pdu_length <= llcp_cb.lcb.effective_miu)
            {
                p_agf = (BT_HDR*) GKI_getpoolbuf (LLCP_POOL_ID);
                if (p_agf)
                {
                    p_agf->offset = NCI_MSG_OFFSET_SIZE + NCI_DATA_HDR_SIZE;

                    p = (UINT8 *) (p_agf + 1) + p_agf->offset;

                    UINT16_TO_BE_STREAM (p, LLCP_GET_PDU_HEADER (LLCP_SAP_LM, LLCP_PDU_AGF_TYPE, LLCP_SAP_LM ));
                    UINT16_TO_BE_STREAM (p, p_msg->len);
                    memcpy(p, (UINT8 *) (p_msg + 1) + p_msg->offset, p_msg->len);

                    p_agf->len      = LLCP_PDU_HEADER_SIZE + 2 + p_msg->len;

                    GKI_freebuf (p_msg);
                    p_msg = p_agf;
                }
                else
                {
                    LLCP_TRACE_ERROR0 ("llcp_link_build_next_pdu (): Out of buffer");
                    return p_msg;
                }
            }
            else
            {
                break;
            }
        }

        /* if next PDU fits into MIU, copy the next PDU into AGF */
        if (p_agf->len - LLCP_PDU_HEADER_SIZE + 2 + next_pdu_length <= llcp_cb.lcb.effective_miu)
        {
            /* Get a next PDU from link manager or data links */
            p_next_pdu = llcp_link_get_next_pdu (FALSE, &next_pdu_length);

            p = (UINT8 *) (p_agf + 1) + p_agf->offset + p_agf->len;

            UINT16_TO_BE_STREAM (p, p_next_pdu->len);
            memcpy (p, (UINT8 *) (p_next_pdu + 1) + p_next_pdu->offset, p_next_pdu->len);

            p_agf->len += 2 + p_next_pdu->len;

            GKI_freebuf (p_next_pdu);

            /* Get next PDU length from link manager or data links without dequeue */
            llcp_link_get_next_pdu (TRUE, &next_pdu_length);
        }
        else
        {
            break;
        }
    }

    if (p_agf)
        return p_agf;
    else
        return p_msg;
}

/*******************************************************************************
**
** Function         llcp_link_send_to_lower
**
** Description      Send PDU to lower layer
**
** Returns          void
**
*******************************************************************************/
static void llcp_link_send_to_lower (BT_HDR *p_pdu)
{
#if (BT_TRACE_PROTOCOL == TRUE)
    DispLLCP (p_pdu, FALSE);
#endif

    llcp_cb.lcb.symm_state = LLCP_LINK_SYMM_REMOTE_XMIT_NEXT;

    NFC_SendData (NFC_RF_CONN_ID, p_pdu);
}

/*******************************************************************************
**
** Function         llcp_link_connection_cback
**
** Description      processing incoming data
**
** Returns          void
**
*******************************************************************************/
void llcp_link_connection_cback (UINT8 conn_id, tNFC_CONN_EVT event, tNFC_CONN *p_data)
{
    if (event == NFC_DATA_CEVT)
    {
#if (BT_TRACE_PROTOCOL == TRUE)
        DispLLCP ((BT_HDR *)p_data->data.p_data, TRUE);
#endif
        if (llcp_cb.lcb.link_state == LLCP_LINK_STATE_DEACTIVATED)
        {
            /* respoding SYMM while LLCP is deactivated but RF link is not deactivated yet */
            llcp_link_send_SYMM ();
            GKI_freebuf ((BT_HDR *) p_data->data.p_data);
        }
        else
        {
            llcp_cb.lcb.flags |= LLCP_LINK_FLAGS_RX_ANY_LLC_PDU;
            llcp_link_proc_rx_data ((BT_HDR *) p_data->data.p_data);
        }
    }
    else if (event == NFC_ERROR_CEVT)
    {
        /* RF interface specific status code */
        llcp_link_deactivate (*(UINT8*) p_data);
    }
    else if (event == NFC_DEACTIVATE_CEVT)
    {
        if (  (llcp_cb.lcb.link_state == LLCP_LINK_STATE_DEACTIVATING)
            &&(!llcp_cb.lcb.is_initiator)  )
        {
            /* peer initiates NFC link deactivation before timeout */
            llcp_link_stop_link_timer ();
            llcp_link_process_link_timeout ();
        }
        else if (llcp_cb.lcb.link_state != LLCP_LINK_STATE_DEACTIVATED)
        {
            llcp_link_deactivate (LLCP_LINK_RF_LINK_LOSS_ERR);
        }
        NFC_SetStaticRfCback (NULL);
    }

    /* LLCP ignores the following events

        NFC_CONN_CREATE_CEVT
        NFC_CONN_CLOSE_CEVT
    */
}

#if (BT_TRACE_VERBOSE == TRUE)
/*******************************************************************************
**
** Function         llcp_pdu_type
**
** Description
**
** Returns          string of PDU type
**
*******************************************************************************/
static char *llcp_pdu_type (UINT8 ptype)
{
    switch(ptype)
    {
    case LLCP_PDU_SYMM_TYPE:
        return "SYMM";
    case LLCP_PDU_PAX_TYPE:
        return "PAX";
    case LLCP_PDU_AGF_TYPE:
        return "AGF";
    case LLCP_PDU_UI_TYPE:
        return "UI";
    case LLCP_PDU_CONNECT_TYPE:
        return "CONNECT";
    case LLCP_PDU_DISC_TYPE:
        return "DISC";
    case LLCP_PDU_CC_TYPE:
        return "CC";
    case LLCP_PDU_DM_TYPE:
        return "DM";
    case LLCP_PDU_FRMR_TYPE:
        return "FRMR";
    case LLCP_PDU_SNL_TYPE:
        return "SNL";
    case LLCP_PDU_I_TYPE:
        return "I";
    case LLCP_PDU_RR_TYPE:
        return "RR";
    case LLCP_PDU_RNR_TYPE:
        return "RNR";

    default:
        return "RESERVED";
    }
}

#endif