irttp.c

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/*********************************************************************
 *
 * Filename:      irttp.c
 * Version:       1.2
 * Description:   Tiny Transport Protocol (TTP) implementation
 * Status:        Stable
 * Author:        Dag Brattli <[email protected]>
 * Created at:    Sun Aug 31 20:14:31 1997
 * Modified at:   Wed Jan  5 11:31:27 2000
 * Modified by:   Dag Brattli <[email protected]>
 *
 *     Copyright (c) 1998-2000 Dag Brattli <[email protected]>,
 *     All Rights Reserved.
 *     Copyright (c) 2000-2003 Jean Tourrilhes <[email protected]>
 *
 *     This program is free software; you can redistribute it and/or
 *     modify it under the terms of the GNU General Public License as
 *     published by the Free Software Foundation; either version 2 of
 *     the License, or (at your option) any later version.
 *
 *     Neither Dag Brattli nor University of Tromsø admit liability nor
 *     provide warranty for any of this software. This material is
 *     provided "AS-IS" and at no charge.
 *
 ********************************************************************/

#include <linux/skbuff.h>
#include <linux/init.h>
#include <linux/fs.h>
#include <linux/seq_file.h>
#include <linux/slab.h>
#include <linux/export.h>

#include <asm/byteorder.h>
#include <asm/unaligned.h>

#include <net/irda/irda.h>
#include <net/irda/irlap.h>
#include <net/irda/irlmp.h>
#include <net/irda/parameters.h>
#include <net/irda/irttp.h>

static struct irttp_cb *irttp;

static void __irttp_close_tsap(struct tsap_cb *self);

static int irttp_data_indication(void *instance, void *sap,
                 struct sk_buff *skb);
static int irttp_udata_indication(void *instance, void *sap,
                  struct sk_buff *skb);
static void irttp_disconnect_indication(void *instance, void *sap,
                    LM_REASON reason, struct sk_buff *);
static void irttp_connect_indication(void *instance, void *sap,
                     struct qos_info *qos, __u32 max_sdu_size,
                     __u8 header_size, struct sk_buff *skb);
static void irttp_connect_confirm(void *instance, void *sap,
                  struct qos_info *qos, __u32 max_sdu_size,
                  __u8 header_size, struct sk_buff *skb);
static void irttp_run_tx_queue(struct tsap_cb *self);
static void irttp_run_rx_queue(struct tsap_cb *self);

static void irttp_flush_queues(struct tsap_cb *self);
static void irttp_fragment_skb(struct tsap_cb *self, struct sk_buff *skb);
static struct sk_buff *irttp_reassemble_skb(struct tsap_cb *self);
static void irttp_todo_expired(unsigned long data);
static int irttp_param_max_sdu_size(void *instance, irda_param_t *param,
                    int get);

static void irttp_flow_indication(void *instance, void *sap, LOCAL_FLOW flow);
static void irttp_status_indication(void *instance,
                    LINK_STATUS link, LOCK_STATUS lock);

/* Information for parsing parameters in IrTTP */
static pi_minor_info_t pi_minor_call_table[] = {
    { NULL, 0 },                                             /* 0x00 */
    { irttp_param_max_sdu_size, PV_INTEGER | PV_BIG_ENDIAN } /* 0x01 */
};
static pi_major_info_t pi_major_call_table[] = {{ pi_minor_call_table, 2 }};
static pi_param_info_t param_info = { pi_major_call_table, 1, 0x0f, 4 };

/************************ GLOBAL PROCEDURES ************************/

/*
 * Function irttp_init (void)
 *
 *    Initialize the IrTTP layer. Called by module initialization code
 *
 */
int __init irttp_init(void)
{
    irttp = kzalloc(sizeof(struct irttp_cb), GFP_KERNEL);
    if (irttp == NULL)
        return -ENOMEM;

    irttp->magic = TTP_MAGIC;

    irttp->tsaps = hashbin_new(HB_LOCK);
    if (!irttp->tsaps) {
        IRDA_ERROR("%s: can't allocate IrTTP hashbin!\n",
               __func__);
        kfree(irttp);
        return -ENOMEM;
    }

    return 0;
}

/*
 * Function irttp_cleanup (void)
 *
 *    Called by module destruction/cleanup code
 *
 */
void irttp_cleanup(void)
{
    /* Check for main structure */
    IRDA_ASSERT(irttp->magic == TTP_MAGIC, return;);

    /*
     *  Delete hashbin and close all TSAP instances in it
     */
    hashbin_delete(irttp->tsaps, (FREE_FUNC) __irttp_close_tsap);

    irttp->magic = 0;

    /* De-allocate main structure */
    kfree(irttp);

    irttp = NULL;
}

/*************************** SUBROUTINES ***************************/

/*
 * Function irttp_start_todo_timer (self, timeout)
 *
 *    Start todo timer.
 *
 * Made it more effient and unsensitive to race conditions - Jean II
 */
static inline void irttp_start_todo_timer(struct tsap_cb *self, int timeout)
{
    /* Set new value for timer */
    mod_timer(&self->todo_timer, jiffies + timeout);
}

/*
 * Function irttp_todo_expired (data)
 *
 *    Todo timer has expired!
 *
 * One of the restriction of the timer is that it is run only on the timer
 * interrupt which run every 10ms. This mean that even if you set the timer
 * with a delay of 0, it may take up to 10ms before it's run.
 * So, to minimise latency and keep cache fresh, we try to avoid using
 * it as much as possible.
 * Note : we can't use tasklets, because they can't be asynchronously
 * killed (need user context), and we can't guarantee that here...
 * Jean II
 */
static void irttp_todo_expired(unsigned long data)
{
    struct tsap_cb *self = (struct tsap_cb *) data;

    /* Check that we still exist */
    if (!self || self->magic != TTP_TSAP_MAGIC)
        return;

    IRDA_DEBUG(4, "%s(instance=%p)\n", __func__, self);

    /* Try to make some progress, especially on Tx side - Jean II */
    irttp_run_rx_queue(self);
    irttp_run_tx_queue(self);

    /* Check if time for disconnect */
    if (test_bit(0, &self->disconnect_pend)) {
        /* Check if it's possible to disconnect yet */
        if (skb_queue_empty(&self->tx_queue)) {
            /* Make sure disconnect is not pending anymore */
            clear_bit(0, &self->disconnect_pend);   /* FALSE */

            /* Note : self->disconnect_skb may be NULL */
            irttp_disconnect_request(self, self->disconnect_skb,
                         P_NORMAL);
            self->disconnect_skb = NULL;
        } else {
            /* Try again later */
            irttp_start_todo_timer(self, HZ/10);

            /* No reason to try and close now */
            return;
        }
    }

    /* Check if it's closing time */
    if (self->close_pend)
        /* Finish cleanup */
        irttp_close_tsap(self);
}

/*
 * Function irttp_flush_queues (self)
 *
 *     Flushes (removes all frames) in transitt-buffer (tx_list)
 */
static void irttp_flush_queues(struct tsap_cb *self)
{
    struct sk_buff* skb;

    IRDA_DEBUG(4, "%s()\n", __func__);

    IRDA_ASSERT(self != NULL, return;);
    IRDA_ASSERT(self->magic == TTP_TSAP_MAGIC, return;);

    /* Deallocate frames waiting to be sent */
    while ((skb = skb_dequeue(&self->tx_queue)) != NULL)
        dev_kfree_skb(skb);

    /* Deallocate received frames */
    while ((skb = skb_dequeue(&self->rx_queue)) != NULL)
        dev_kfree_skb(skb);

    /* Deallocate received fragments */
    while ((skb = skb_dequeue(&self->rx_fragments)) != NULL)
        dev_kfree_skb(skb);
}

/*
 * Function irttp_reassemble (self)
 *
 *    Makes a new (continuous) skb of all the fragments in the fragment
 *    queue
 *
 */
static struct sk_buff *irttp_reassemble_skb(struct tsap_cb *self)
{
    struct sk_buff *skb, *frag;
    int n = 0;  /* Fragment index */

    IRDA_ASSERT(self != NULL, return NULL;);
    IRDA_ASSERT(self->magic == TTP_TSAP_MAGIC, return NULL;);

    IRDA_DEBUG(2, "%s(), self->rx_sdu_size=%d\n", __func__,
           self->rx_sdu_size);

    skb = dev_alloc_skb(TTP_HEADER + self->rx_sdu_size);
    if (!skb)
        return NULL;

    /*
     * Need to reserve space for TTP header in case this skb needs to
     * be requeued in case delivery failes
     */
    skb_reserve(skb, TTP_HEADER);
    skb_put(skb, self->rx_sdu_size);

    /*
     *  Copy all fragments to a new buffer
     */
    while ((frag = skb_dequeue(&self->rx_fragments)) != NULL) {
        skb_copy_to_linear_data_offset(skb, n, frag->data, frag->len);
        n += frag->len;

        dev_kfree_skb(frag);
    }

    IRDA_DEBUG(2,
           "%s(), frame len=%d, rx_sdu_size=%d, rx_max_sdu_size=%d\n",
           __func__, n, self->rx_sdu_size, self->rx_max_sdu_size);
    /* Note : irttp_run_rx_queue() calculate self->rx_sdu_size
     * by summing the size of all fragments, so we should always
     * have n == self->rx_sdu_size, except in cases where we
     * droped the last fragment (when self->rx_sdu_size exceed
     * self->rx_max_sdu_size), where n < self->rx_sdu_size.
     * Jean II */
    IRDA_ASSERT(n <= self->rx_sdu_size, n = self->rx_sdu_size;);

    /* Set the new length */
    skb_trim(skb, n);

    self->rx_sdu_size = 0;

    return skb;
}

/*
 * Function irttp_fragment_skb (skb)
 *
 *    Fragments a frame and queues all the fragments for transmission
 *
 */
static inline void irttp_fragment_skb(struct tsap_cb *self,
                      struct sk_buff *skb)
{
    struct sk_buff *frag;
    __u8 *frame;

    IRDA_DEBUG(2, "%s()\n", __func__);

    IRDA_ASSERT(self != NULL, return;);
    IRDA_ASSERT(self->magic == TTP_TSAP_MAGIC, return;);
    IRDA_ASSERT(skb != NULL, return;);

    /*
     *  Split frame into a number of segments
     */
    while (skb->len > self->max_seg_size) {
        IRDA_DEBUG(2, "%s(), fragmenting ...\n", __func__);

        /* Make new segment */
        frag = alloc_skb(self->max_seg_size+self->max_header_size,
                 GFP_ATOMIC);
        if (!frag)
            return;

        skb_reserve(frag, self->max_header_size);

        /* Copy data from the original skb into this fragment. */
        skb_copy_from_linear_data(skb, skb_put(frag, self->max_seg_size),
                  self->max_seg_size);

        /* Insert TTP header, with the more bit set */
        frame = skb_push(frag, TTP_HEADER);
        frame[0] = TTP_MORE;

        /* Hide the copied data from the original skb */
        skb_pull(skb, self->max_seg_size);

        /* Queue fragment */
        skb_queue_tail(&self->tx_queue, frag);
    }
    /* Queue what is left of the original skb */
    IRDA_DEBUG(2, "%s(), queuing last segment\n", __func__);

    frame = skb_push(skb, TTP_HEADER);
    frame[0] = 0x00; /* Clear more bit */

    /* Queue fragment */
    skb_queue_tail(&self->tx_queue, skb);
}

/*
 * Function irttp_param_max_sdu_size (self, param)
 *
 *    Handle the MaxSduSize parameter in the connect frames, this function
 *    will be called both when this parameter needs to be inserted into, and
 *    extracted from the connect frames
 */
static int irttp_param_max_sdu_size(void *instance, irda_param_t *param,
                    int get)
{
    struct tsap_cb *self;

    self = instance;

    IRDA_ASSERT(self != NULL, return -1;);
    IRDA_ASSERT(self->magic == TTP_TSAP_MAGIC, return -1;);

    if (get)
        param->pv.i = self->tx_max_sdu_size;
    else
        self->tx_max_sdu_size = param->pv.i;

    IRDA_DEBUG(1, "%s(), MaxSduSize=%d\n", __func__, param->pv.i);

    return 0;
}

/*************************** CLIENT CALLS ***************************/
/************************** LMP CALLBACKS **************************/
/* Everything is happily mixed up. Waiting for next clean up - Jean II */

/*
 * Initialization, that has to be done on new tsap
 * instance allocation and on duplication
 */
static void irttp_init_tsap(struct tsap_cb *tsap)
{
    spin_lock_init(&tsap->lock);
    init_timer(&tsap->todo_timer);

    skb_queue_head_init(&tsap->rx_queue);
    skb_queue_head_init(&tsap->tx_queue);
    skb_queue_head_init(&tsap->rx_fragments);
}

/*
 * Function irttp_open_tsap (stsap, notify)
 *
 *    Create TSAP connection endpoint,
 */
struct tsap_cb *irttp_open_tsap(__u8 stsap_sel, int credit, notify_t *notify)
{
    struct tsap_cb *self;
    struct lsap_cb *lsap;
    notify_t ttp_notify;

    IRDA_ASSERT(irttp->magic == TTP_MAGIC, return NULL;);

    /* The IrLMP spec (IrLMP 1.1 p10) says that we have the right to
     * use only 0x01-0x6F. Of course, we can use LSAP_ANY as well.
     * JeanII */
    if((stsap_sel != LSAP_ANY) &&
       ((stsap_sel < 0x01) || (stsap_sel >= 0x70))) {
        IRDA_DEBUG(0, "%s(), invalid tsap!\n", __func__);
        return NULL;
    }

    self = kzalloc(sizeof(struct tsap_cb), GFP_ATOMIC);
    if (self == NULL) {
        IRDA_DEBUG(0, "%s(), unable to kmalloc!\n", __func__);
        return NULL;
    }

    /* Initialize internal objects */
    irttp_init_tsap(self);

    /* Initialise todo timer */
    self->todo_timer.data     = (unsigned long) self;
    self->todo_timer.function = &irttp_todo_expired;

    /* Initialize callbacks for IrLMP to use */
    irda_notify_init(&ttp_notify);
    ttp_notify.connect_confirm = irttp_connect_confirm;
    ttp_notify.connect_indication = irttp_connect_indication;
    ttp_notify.disconnect_indication = irttp_disconnect_indication;
    ttp_notify.data_indication = irttp_data_indication;
    ttp_notify.udata_indication = irttp_udata_indication;
    ttp_notify.flow_indication = irttp_flow_indication;
    if(notify->status_indication != NULL)
        ttp_notify.status_indication = irttp_status_indication;
    ttp_notify.instance = self;
    strncpy(ttp_notify.name, notify->name, NOTIFY_MAX_NAME);

    self->magic = TTP_TSAP_MAGIC;
    self->connected = FALSE;

    /*
     *  Create LSAP at IrLMP layer
     */
    lsap = irlmp_open_lsap(stsap_sel, &ttp_notify, 0);
    if (lsap == NULL) {
        IRDA_DEBUG(0, "%s: unable to allocate LSAP!!\n", __func__);
        __irttp_close_tsap(self);
        return NULL;
    }

    /*
     *  If user specified LSAP_ANY as source TSAP selector, then IrLMP
     *  will replace it with whatever source selector which is free, so
     *  the stsap_sel we have might not be valid anymore
     */
    self->stsap_sel = lsap->slsap_sel;
    IRDA_DEBUG(4, "%s(), stsap_sel=%02x\n", __func__, self->stsap_sel);

    self->notify = *notify;
    self->lsap = lsap;

    hashbin_insert(irttp->tsaps, (irda_queue_t *) self, (long) self, NULL);

    if (credit > TTP_RX_MAX_CREDIT)
        self->initial_credit = TTP_RX_MAX_CREDIT;
    else
        self->initial_credit = credit;

    return self;
}
EXPORT_SYMBOL(irttp_open_tsap);

/*
 * Function irttp_close (handle)
 *
 *    Remove an instance of a TSAP. This function should only deal with the
 *    deallocation of the TSAP, and resetting of the TSAPs values;
 *
 */
static void __irttp_close_tsap(struct tsap_cb *self)
{
    /* First make sure we're connected. */
    IRDA_ASSERT(self != NULL, return;);
    IRDA_ASSERT(self->magic == TTP_TSAP_MAGIC, return;);

    irttp_flush_queues(self);

    del_timer(&self->todo_timer);

    /* This one won't be cleaned up if we are disconnect_pend + close_pend
     * and we receive a disconnect_indication */
    if (self->disconnect_skb)
        dev_kfree_skb(self->disconnect_skb);

    self->connected = FALSE;
    self->magic = ~TTP_TSAP_MAGIC;

    kfree(self);
}

/*
 * Function irttp_close (self)
 *
 *    Remove TSAP from list of all TSAPs and then deallocate all resources
 *    associated with this TSAP
 *
 * Note : because we *free* the tsap structure, it is the responsibility
 * of the caller to make sure we are called only once and to deal with
 * possible race conditions. - Jean II
 */
int irttp_close_tsap(struct tsap_cb *self)
{
    struct tsap_cb *tsap;

    IRDA_DEBUG(4, "%s()\n", __func__);

    IRDA_ASSERT(self != NULL, return -1;);
    IRDA_ASSERT(self->magic == TTP_TSAP_MAGIC, return -1;);

    /* Make sure tsap has been disconnected */
    if (self->connected) {
        /* Check if disconnect is not pending */
        if (!test_bit(0, &self->disconnect_pend)) {
            IRDA_WARNING("%s: TSAP still connected!\n",
                     __func__);
            irttp_disconnect_request(self, NULL, P_NORMAL);
        }
        self->close_pend = TRUE;
        irttp_start_todo_timer(self, HZ/10);

        return 0; /* Will be back! */
    }

    tsap = hashbin_remove(irttp->tsaps, (long) self, NULL);

    IRDA_ASSERT(tsap == self, return -1;);

    /* Close corresponding LSAP */
    if (self->lsap) {
        irlmp_close_lsap(self->lsap);
        self->lsap = NULL;
    }

    __irttp_close_tsap(self);

    return 0;
}
EXPORT_SYMBOL(irttp_close_tsap);

/*
 * Function irttp_udata_request (self, skb)
 *
 *    Send unreliable data on this TSAP
 *
 */
int irttp_udata_request(struct tsap_cb *self, struct sk_buff *skb)
{
    int ret;

    IRDA_ASSERT(self != NULL, return -1;);
    IRDA_ASSERT(self->magic == TTP_TSAP_MAGIC, return -1;);
    IRDA_ASSERT(skb != NULL, return -1;);

    IRDA_DEBUG(4, "%s()\n", __func__);

    /* Take shortcut on zero byte packets */
    if (skb->len == 0) {
        ret = 0;
        goto err;
    }

    /* Check that nothing bad happens */
    if (!self->connected) {
        IRDA_WARNING("%s(), Not connected\n", __func__);
        ret = -ENOTCONN;
        goto err;
    }

    if (skb->len > self->max_seg_size) {
        IRDA_ERROR("%s(), UData is too large for IrLAP!\n", __func__);
        ret = -EMSGSIZE;
        goto err;
    }

    irlmp_udata_request(self->lsap, skb);
    self->stats.tx_packets++;

    return 0;

err:
    dev_kfree_skb(skb);
    return ret;
}
EXPORT_SYMBOL(irttp_udata_request);


/*
 * Function irttp_data_request (handle, skb)
 *
 *    Queue frame for transmission. If SAR is enabled, fragement the frame
 *    and queue the fragments for transmission
 */
int irttp_data_request(struct tsap_cb *self, struct sk_buff *skb)
{
    __u8 *frame;
    int ret;

    IRDA_ASSERT(self != NULL, return -1;);
    IRDA_ASSERT(self->magic == TTP_TSAP_MAGIC, return -1;);
    IRDA_ASSERT(skb != NULL, return -1;);

    IRDA_DEBUG(2, "%s() : queue len = %d\n", __func__,
           skb_queue_len(&self->tx_queue));

    /* Take shortcut on zero byte packets */
    if (skb->len == 0) {
        ret = 0;
        goto err;
    }

    /* Check that nothing bad happens */
    if (!self->connected) {
        IRDA_WARNING("%s: Not connected\n", __func__);
        ret = -ENOTCONN;
        goto err;
    }

    /*
     *  Check if SAR is disabled, and the frame is larger than what fits
     *  inside an IrLAP frame
     */
    if ((self->tx_max_sdu_size == 0) && (skb->len > self->max_seg_size)) {
        IRDA_ERROR("%s: SAR disabled, and data is too large for IrLAP!\n",
               __func__);
        ret = -EMSGSIZE;
        goto err;
    }

    /*
     *  Check if SAR is enabled, and the frame is larger than the
     *  TxMaxSduSize
     */
    if ((self->tx_max_sdu_size != 0) &&
        (self->tx_max_sdu_size != TTP_SAR_UNBOUND) &&
        (skb->len > self->tx_max_sdu_size))
    {
        IRDA_ERROR("%s: SAR enabled, but data is larger than TxMaxSduSize!\n",
               __func__);
        ret = -EMSGSIZE;
        goto err;
    }
    /*
     *  Check if transmit queue is full
     */
    if (skb_queue_len(&self->tx_queue) >= TTP_TX_MAX_QUEUE) {
        /*
         *  Give it a chance to empty itself
         */
        irttp_run_tx_queue(self);

        /* Drop packet. This error code should trigger the caller
         * to resend the data in the client code - Jean II */
        ret = -ENOBUFS;
        goto err;
    }

    /* Queue frame, or queue frame segments */
    if ((self->tx_max_sdu_size == 0) || (skb->len < self->max_seg_size)) {
        /* Queue frame */
        IRDA_ASSERT(skb_headroom(skb) >= TTP_HEADER, return -1;);
        frame = skb_push(skb, TTP_HEADER);
        frame[0] = 0x00; /* Clear more bit */

        skb_queue_tail(&self->tx_queue, skb);
    } else {
        /*
         *  Fragment the frame, this function will also queue the
         *  fragments, we don't care about the fact the transmit
         *  queue may be overfilled by all the segments for a little
         *  while
         */
        irttp_fragment_skb(self, skb);
    }

    /* Check if we can accept more data from client */
    if ((!self->tx_sdu_busy) &&
        (skb_queue_len(&self->tx_queue) > TTP_TX_HIGH_THRESHOLD)) {
        /* Tx queue filling up, so stop client. */
        if (self->notify.flow_indication) {
            self->notify.flow_indication(self->notify.instance,
                             self, FLOW_STOP);
        }
        /* self->tx_sdu_busy is the state of the client.
         * Update state after notifying client to avoid
         * race condition with irttp_flow_indication().
         * If the queue empty itself after our test but before
         * we set the flag, we will fix ourselves below in
         * irttp_run_tx_queue().
         * Jean II */
        self->tx_sdu_busy = TRUE;
    }

    /* Try to make some progress */
    irttp_run_tx_queue(self);

    return 0;

err:
    dev_kfree_skb(skb);
    return ret;
}
EXPORT_SYMBOL(irttp_data_request);

/*
 * Function irttp_run_tx_queue (self)
 *
 *    Transmit packets queued for transmission (if possible)
 *
 */
static void irttp_run_tx_queue(struct tsap_cb *self)
{
    struct sk_buff *skb;
    unsigned long flags;
    int n;

    IRDA_DEBUG(2, "%s() : send_credit = %d, queue_len = %d\n",
           __func__,
           self->send_credit, skb_queue_len(&self->tx_queue));

    /* Get exclusive access to the tx queue, otherwise don't touch it */
    if (irda_lock(&self->tx_queue_lock) == FALSE)
        return;

    /* Try to send out frames as long as we have credits
     * and as long as LAP is not full. If LAP is full, it will
     * poll us through irttp_flow_indication() - Jean II */
    while ((self->send_credit > 0) &&
           (!irlmp_lap_tx_queue_full(self->lsap)) &&
           (skb = skb_dequeue(&self->tx_queue)))
    {
        /*
         *  Since we can transmit and receive frames concurrently,
         *  the code below is a critical region and we must assure that
         *  nobody messes with the credits while we update them.
         */
        spin_lock_irqsave(&self->lock, flags);

        n = self->avail_credit;
        self->avail_credit = 0;

        /* Only room for 127 credits in frame */
        if (n > 127) {
            self->avail_credit = n-127;
            n = 127;
        }
        self->remote_credit += n;
        self->send_credit--;

        spin_unlock_irqrestore(&self->lock, flags);

        /*
         *  More bit must be set by the data_request() or fragment()
         *  functions
         */
        skb->data[0] |= (n & 0x7f);

        /* Detach from socket.
         * The current skb has a reference to the socket that sent
         * it (skb->sk). When we pass it to IrLMP, the skb will be
         * stored in in IrLAP (self->wx_list). When we are within
         * IrLAP, we lose the notion of socket, so we should not
         * have a reference to a socket. So, we drop it here.
         *
         * Why does it matter ?
         * When the skb is freed (kfree_skb), if it is associated
         * with a socket, it release buffer space on the socket
         * (through sock_wfree() and sock_def_write_space()).
         * If the socket no longer exist, we may crash. Hard.
         * When we close a socket, we make sure that associated packets
         * in IrTTP are freed. However, we have no way to cancel
         * the packet that we have passed to IrLAP. So, if a packet
         * remains in IrLAP (retry on the link or else) after we
         * close the socket, we are dead !
         * Jean II */
        if (skb->sk != NULL) {
            /* IrSOCK application, IrOBEX, ... */
            skb_orphan(skb);
        }
            /* IrCOMM over IrTTP, IrLAN, ... */

        /* Pass the skb to IrLMP - done */
        irlmp_data_request(self->lsap, skb);
        self->stats.tx_packets++;
    }

    /* Check if we can accept more frames from client.
     * We don't want to wait until the todo timer to do that, and we
     * can't use tasklets (grr...), so we are obliged to give control
     * to client. That's ok, this test will be true not too often
     * (max once per LAP window) and we are called from places
     * where we can spend a bit of time doing stuff. - Jean II */
    if ((self->tx_sdu_busy) &&
        (skb_queue_len(&self->tx_queue) < TTP_TX_LOW_THRESHOLD) &&
        (!self->close_pend))
    {
        if (self->notify.flow_indication)
            self->notify.flow_indication(self->notify.instance,
                             self, FLOW_START);

        /* self->tx_sdu_busy is the state of the client.
         * We don't really have a race here, but it's always safer
         * to update our state after the client - Jean II */
        self->tx_sdu_busy = FALSE;
    }

    /* Reset lock */
    self->tx_queue_lock = 0;
}

/*
 * Function irttp_give_credit (self)
 *
 *    Send a dataless flowdata TTP-PDU and give available credit to peer
 *    TSAP
 */
static inline void irttp_give_credit(struct tsap_cb *self)
{
    struct sk_buff *tx_skb = NULL;
    unsigned long flags;
    int n;

    IRDA_ASSERT(self != NULL, return;);
    IRDA_ASSERT(self->magic == TTP_TSAP_MAGIC, return;);

    IRDA_DEBUG(4, "%s() send=%d,avail=%d,remote=%d\n",
           __func__,
           self->send_credit, self->avail_credit, self->remote_credit);

    /* Give credit to peer */
    tx_skb = alloc_skb(TTP_MAX_HEADER, GFP_ATOMIC);
    if (!tx_skb)
        return;

    /* Reserve space for LMP, and LAP header */
    skb_reserve(tx_skb, LMP_MAX_HEADER);

    /*
     *  Since we can transmit and receive frames concurrently,
     *  the code below is a critical region and we must assure that
     *  nobody messes with the credits while we update them.
     */
    spin_lock_irqsave(&self->lock, flags);

    n = self->avail_credit;
    self->avail_credit = 0;

    /* Only space for 127 credits in frame */
    if (n > 127) {
        self->avail_credit = n - 127;
        n = 127;
    }
    self->remote_credit += n;

    spin_unlock_irqrestore(&self->lock, flags);

    skb_put(tx_skb, 1);
    tx_skb->data[0] = (__u8) (n & 0x7f);

    irlmp_data_request(self->lsap, tx_skb);
    self->stats.tx_packets++;
}

/*
 * Function irttp_udata_indication (instance, sap, skb)
 *
 *    Received some unit-data (unreliable)
 *
 */
static int irttp_udata_indication(void *instance, void *sap,
                  struct sk_buff *skb)
{
    struct tsap_cb *self;
    int err;

    IRDA_DEBUG(4, "%s()\n", __func__);

    self = instance;

    IRDA_ASSERT(self != NULL, return -1;);
    IRDA_ASSERT(self->magic == TTP_TSAP_MAGIC, return -1;);
    IRDA_ASSERT(skb != NULL, return -1;);

    self->stats.rx_packets++;

    /* Just pass data to layer above */
    if (self->notify.udata_indication) {
        err = self->notify.udata_indication(self->notify.instance,
                            self,skb);
        /* Same comment as in irttp_do_data_indication() */
        if (!err)
            return 0;
    }
    /* Either no handler, or handler returns an error */
    dev_kfree_skb(skb);

    return 0;
}

/*
 * Function irttp_data_indication (instance, sap, skb)
 *
 *    Receive segment from IrLMP.
 *
 */
static int irttp_data_indication(void *instance, void *sap,
                 struct sk_buff *skb)
{
    struct tsap_cb *self;
    unsigned long flags;
    int n;

    self = instance;

    n = skb->data[0] & 0x7f;     /* Extract the credits */

    self->stats.rx_packets++;

    /*  Deal with inbound credit
     *  Since we can transmit and receive frames concurrently,
     *  the code below is a critical region and we must assure that
     *  nobody messes with the credits while we update them.
     */
    spin_lock_irqsave(&self->lock, flags);
    self->send_credit += n;
    if (skb->len > 1)
        self->remote_credit--;
    spin_unlock_irqrestore(&self->lock, flags);

    /*
     *  Data or dataless packet? Dataless frames contains only the
     *  TTP_HEADER.
     */
    if (skb->len > 1) {
        /*
         *  We don't remove the TTP header, since we must preserve the
         *  more bit, so the defragment routing knows what to do
         */
        skb_queue_tail(&self->rx_queue, skb);
    } else {
        /* Dataless flowdata TTP-PDU */
        dev_kfree_skb(skb);
    }


    /* Push data to the higher layer.
     * We do it synchronously because running the todo timer for each
     * receive packet would be too much overhead and latency.
     * By passing control to the higher layer, we run the risk that
     * it may take time or grab a lock. Most often, the higher layer
     * will only put packet in a queue.
     * Anyway, packets are only dripping through the IrDA, so we can
     * have time before the next packet.
     * Further, we are run from NET_BH, so the worse that can happen is
     * us missing the optimal time to send back the PF bit in LAP.
     * Jean II */
    irttp_run_rx_queue(self);

    /* We now give credits to peer in irttp_run_rx_queue().
     * We need to send credit *NOW*, otherwise we are going
     * to miss the next Tx window. The todo timer may take
     * a while before it's run... - Jean II */

    /*
     * If the peer device has given us some credits and we didn't have
     * anyone from before, then we need to shedule the tx queue.
     * We need to do that because our Tx have stopped (so we may not
     * get any LAP flow indication) and the user may be stopped as
     * well. - Jean II
     */
    if (self->send_credit == n) {
        /* Restart pushing stuff to LAP */
        irttp_run_tx_queue(self);
        /* Note : we don't want to schedule the todo timer
         * because it has horrible latency. No tasklets
         * because the tasklet API is broken. - Jean II */
    }

    return 0;
}

/*
 * Function irttp_status_indication (self, reason)
 *
 *    Status_indication, just pass to the higher layer...
 *
 */
static void irttp_status_indication(void *instance,
                    LINK_STATUS link, LOCK_STATUS lock)
{
    struct tsap_cb *self;

    IRDA_DEBUG(4, "%s()\n", __func__);

    self = instance;

    IRDA_ASSERT(self != NULL, return;);
    IRDA_ASSERT(self->magic == TTP_TSAP_MAGIC, return;);

    /* Check if client has already closed the TSAP and gone away */
    if (self->close_pend)
        return;

    /*
     *  Inform service user if he has requested it
     */
    if (self->notify.status_indication != NULL)
        self->notify.status_indication(self->notify.instance,
                           link, lock);
    else
        IRDA_DEBUG(2, "%s(), no handler\n", __func__);
}

/*
 * Function irttp_flow_indication (self, reason)
 *
 *    Flow_indication : IrLAP tells us to send more data.
 *
 */
static void irttp_flow_indication(void *instance, void *sap, LOCAL_FLOW flow)
{
    struct tsap_cb *self;

    self = instance;

    IRDA_ASSERT(self != NULL, return;);
    IRDA_ASSERT(self->magic == TTP_TSAP_MAGIC, return;);

    IRDA_DEBUG(4, "%s(instance=%p)\n", __func__, self);

    /* We are "polled" directly from LAP, and the LAP want to fill
     * its Tx window. We want to do our best to send it data, so that
     * we maximise the window. On the other hand, we want to limit the
     * amount of work here so that LAP doesn't hang forever waiting
     * for packets. - Jean II */

    /* Try to send some packets. Currently, LAP calls us every time
     * there is one free slot, so we will send only one packet.
     * This allow the scheduler to do its round robin - Jean II */
    irttp_run_tx_queue(self);

    /* Note regarding the interraction with higher layer.
     * irttp_run_tx_queue() may call the client when its queue
     * start to empty, via notify.flow_indication(). Initially.
     * I wanted this to happen in a tasklet, to avoid client
     * grabbing the CPU, but we can't use tasklets safely. And timer
     * is definitely too slow.
     * This will happen only once per LAP window, and usually at
     * the third packet (unless window is smaller). LAP is still
     * doing mtt and sending first packet so it's sort of OK
     * to do that. Jean II */

    /* If we need to send disconnect. try to do it now */
    if(self->disconnect_pend)
        irttp_start_todo_timer(self, 0);
}

/*
 * Function irttp_flow_request (self, command)
 *
 *    This function could be used by the upper layers to tell IrTTP to stop
 *    delivering frames if the receive queues are starting to get full, or
 *    to tell IrTTP to start delivering frames again.
 */
void irttp_flow_request(struct tsap_cb *self, LOCAL_FLOW flow)
{
    IRDA_DEBUG(1, "%s()\n", __func__);

    IRDA_ASSERT(self != NULL, return;);
    IRDA_ASSERT(self->magic == TTP_TSAP_MAGIC, return;);

    switch (flow) {
    case FLOW_STOP:
        IRDA_DEBUG(1, "%s(), flow stop\n", __func__);
        self->rx_sdu_busy = TRUE;
        break;
    case FLOW_START:
        IRDA_DEBUG(1, "%s(), flow start\n", __func__);
        self->rx_sdu_busy = FALSE;

        /* Client say he can accept more data, try to free our
         * queues ASAP - Jean II */
        irttp_run_rx_queue(self);

        break;
    default:
        IRDA_DEBUG(1, "%s(), Unknown flow command!\n", __func__);
    }
}
EXPORT_SYMBOL(irttp_flow_request);

/*
 * Function irttp_connect_request (self, dtsap_sel, daddr, qos)
 *
 *    Try to connect to remote destination TSAP selector
 *
 */
int irttp_connect_request(struct tsap_cb *self, __u8 dtsap_sel,
              __u32 saddr, __u32 daddr,
              struct qos_info *qos, __u32 max_sdu_size,
              struct sk_buff *userdata)
{
    struct sk_buff *tx_skb;
    __u8 *frame;
    __u8 n;

    IRDA_DEBUG(4, "%s(), max_sdu_size=%d\n", __func__, max_sdu_size);

    IRDA_ASSERT(self != NULL, return -EBADR;);
    IRDA_ASSERT(self->magic == TTP_TSAP_MAGIC, return -EBADR;);

    if (self->connected) {
        if(userdata)
            dev_kfree_skb(userdata);
        return -EISCONN;
    }

    /* Any userdata supplied? */
    if (userdata == NULL) {
        tx_skb = alloc_skb(TTP_MAX_HEADER + TTP_SAR_HEADER,
                   GFP_ATOMIC);
        if (!tx_skb)
            return -ENOMEM;

        /* Reserve space for MUX_CONTROL and LAP header */
        skb_reserve(tx_skb, TTP_MAX_HEADER + TTP_SAR_HEADER);
    } else {
        tx_skb = userdata;
        /*
         *  Check that the client has reserved enough space for
         *  headers
         */
        IRDA_ASSERT(skb_headroom(userdata) >= TTP_MAX_HEADER,
            { dev_kfree_skb(userdata); return -1; } );
    }

    /* Initialize connection parameters */
    self->connected = FALSE;
    self->avail_credit = 0;
    self->rx_max_sdu_size = max_sdu_size;
    self->rx_sdu_size = 0;
    self->rx_sdu_busy = FALSE;
    self->dtsap_sel = dtsap_sel;

    n = self->initial_credit;

    self->remote_credit = 0;
    self->send_credit = 0;

    /*
     *  Give away max 127 credits for now
     */
    if (n > 127) {
        self->avail_credit=n-127;
        n = 127;
    }

    self->remote_credit = n;

    /* SAR enabled? */
    if (max_sdu_size > 0) {
        IRDA_ASSERT(skb_headroom(tx_skb) >= (TTP_MAX_HEADER + TTP_SAR_HEADER),
            { dev_kfree_skb(tx_skb); return -1; } );

        /* Insert SAR parameters */
        frame = skb_push(tx_skb, TTP_HEADER+TTP_SAR_HEADER);

        frame[0] = TTP_PARAMETERS | n;
        frame[1] = 0x04; /* Length */
        frame[2] = 0x01; /* MaxSduSize */
        frame[3] = 0x02; /* Value length */

        put_unaligned(cpu_to_be16((__u16) max_sdu_size),
                  (__be16 *)(frame+4));
    } else {
        /* Insert plain TTP header */
        frame = skb_push(tx_skb, TTP_HEADER);

        /* Insert initial credit in frame */
        frame[0] = n & 0x7f;
    }

    /* Connect with IrLMP. No QoS parameters for now */
    return irlmp_connect_request(self->lsap, dtsap_sel, saddr, daddr, qos,
                     tx_skb);
}
EXPORT_SYMBOL(irttp_connect_request);

/*
 * Function irttp_connect_confirm (handle, qos, skb)
 *
 *    Service user confirms TSAP connection with peer.
 *
 */
static void irttp_connect_confirm(void *instance, void *sap,
                  struct qos_info *qos, __u32 max_seg_size,
                  __u8 max_header_size, struct sk_buff *skb)
{
    struct tsap_cb *self;
    int parameters;
    int ret;
    __u8 plen;
    __u8 n;

    IRDA_DEBUG(4, "%s()\n", __func__);

    self = instance;

    IRDA_ASSERT(self != NULL, return;);
    IRDA_ASSERT(self->magic == TTP_TSAP_MAGIC, return;);
    IRDA_ASSERT(skb != NULL, return;);

    self->max_seg_size = max_seg_size - TTP_HEADER;
    self->max_header_size = max_header_size + TTP_HEADER;

    /*
     *  Check if we have got some QoS parameters back! This should be the
     *  negotiated QoS for the link.
     */
    if (qos) {
        IRDA_DEBUG(4, "IrTTP, Negotiated BAUD_RATE: %02x\n",
               qos->baud_rate.bits);
        IRDA_DEBUG(4, "IrTTP, Negotiated BAUD_RATE: %d bps.\n",
               qos->baud_rate.value);
    }

    n = skb->data[0] & 0x7f;

    IRDA_DEBUG(4, "%s(), Initial send_credit=%d\n", __func__, n);

    self->send_credit = n;
    self->tx_max_sdu_size = 0;
    self->connected = TRUE;

    parameters = skb->data[0] & 0x80;

    IRDA_ASSERT(skb->len >= TTP_HEADER, return;);
    skb_pull(skb, TTP_HEADER);

    if (parameters) {
        plen = skb->data[0];

        ret = irda_param_extract_all(self, skb->data+1,
                         IRDA_MIN(skb->len-1, plen),
                         &param_info);

        /* Any errors in the parameter list? */
        if (ret < 0) {
            IRDA_WARNING("%s: error extracting parameters\n",
                     __func__);
            dev_kfree_skb(skb);

            /* Do not accept this connection attempt */
            return;
        }
        /* Remove parameters */
        skb_pull(skb, IRDA_MIN(skb->len, plen+1));
    }

    IRDA_DEBUG(4, "%s() send=%d,avail=%d,remote=%d\n", __func__,
          self->send_credit, self->avail_credit, self->remote_credit);

    IRDA_DEBUG(2, "%s(), MaxSduSize=%d\n", __func__,
           self->tx_max_sdu_size);

    if (self->notify.connect_confirm) {
        self->notify.connect_confirm(self->notify.instance, self, qos,
                         self->tx_max_sdu_size,
                         self->max_header_size, skb);
    } else
        dev_kfree_skb(skb);
}

/*
 * Function irttp_connect_indication (handle, skb)
 *
 *    Some other device is connecting to this TSAP
 *
 */
static void irttp_connect_indication(void *instance, void *sap,
        struct qos_info *qos, __u32 max_seg_size, __u8 max_header_size,
        struct sk_buff *skb)
{
    struct tsap_cb *self;
    struct lsap_cb *lsap;
    int parameters;
    int ret;
    __u8 plen;
    __u8 n;

    self = instance;

    IRDA_ASSERT(self != NULL, return;);
    IRDA_ASSERT(self->magic == TTP_TSAP_MAGIC, return;);
    IRDA_ASSERT(skb != NULL, return;);

    lsap = sap;

    self->max_seg_size = max_seg_size - TTP_HEADER;
    self->max_header_size = max_header_size+TTP_HEADER;

    IRDA_DEBUG(4, "%s(), TSAP sel=%02x\n", __func__, self->stsap_sel);

    /* Need to update dtsap_sel if its equal to LSAP_ANY */
    self->dtsap_sel = lsap->dlsap_sel;

    n = skb->data[0] & 0x7f;

    self->send_credit = n;
    self->tx_max_sdu_size = 0;

    parameters = skb->data[0] & 0x80;

    IRDA_ASSERT(skb->len >= TTP_HEADER, return;);
    skb_pull(skb, TTP_HEADER);

    if (parameters) {
        plen = skb->data[0];

        ret = irda_param_extract_all(self, skb->data+1,
                         IRDA_MIN(skb->len-1, plen),
                         &param_info);

        /* Any errors in the parameter list? */
        if (ret < 0) {
            IRDA_WARNING("%s: error extracting parameters\n",
                     __func__);
            dev_kfree_skb(skb);

            /* Do not accept this connection attempt */
            return;
        }

        /* Remove parameters */
        skb_pull(skb, IRDA_MIN(skb->len, plen+1));
    }

    if (self->notify.connect_indication) {
        self->notify.connect_indication(self->notify.instance, self,
                        qos, self->tx_max_sdu_size,
                        self->max_header_size, skb);
    } else
        dev_kfree_skb(skb);
}

/*
 * Function irttp_connect_response (handle, userdata)
 *
 *    Service user is accepting the connection, just pass it down to
 *    IrLMP!
 *
 */
int irttp_connect_response(struct tsap_cb *self, __u32 max_sdu_size,
               struct sk_buff *userdata)
{
    struct sk_buff *tx_skb;
    __u8 *frame;
    int ret;
    __u8 n;

    IRDA_ASSERT(self != NULL, return -1;);
    IRDA_ASSERT(self->magic == TTP_TSAP_MAGIC, return -1;);

    IRDA_DEBUG(4, "%s(), Source TSAP selector=%02x\n", __func__,
           self->stsap_sel);

    /* Any userdata supplied? */
    if (userdata == NULL) {
        tx_skb = alloc_skb(TTP_MAX_HEADER + TTP_SAR_HEADER,
                   GFP_ATOMIC);
        if (!tx_skb)
            return -ENOMEM;

        /* Reserve space for MUX_CONTROL and LAP header */
        skb_reserve(tx_skb, TTP_MAX_HEADER + TTP_SAR_HEADER);
    } else {
        tx_skb = userdata;
        /*
         *  Check that the client has reserved enough space for
         *  headers
         */
        IRDA_ASSERT(skb_headroom(userdata) >= TTP_MAX_HEADER,
            { dev_kfree_skb(userdata); return -1; } );
    }

    self->avail_credit = 0;
    self->remote_credit = 0;
    self->rx_max_sdu_size = max_sdu_size;
    self->rx_sdu_size = 0;
    self->rx_sdu_busy = FALSE;

    n = self->initial_credit;

    /* Frame has only space for max 127 credits (7 bits) */
    if (n > 127) {
        self->avail_credit = n - 127;
        n = 127;
    }

    self->remote_credit = n;
    self->connected = TRUE;

    /* SAR enabled? */
    if (max_sdu_size > 0) {
        IRDA_ASSERT(skb_headroom(tx_skb) >= (TTP_MAX_HEADER + TTP_SAR_HEADER),
            { dev_kfree_skb(tx_skb); return -1; } );

        /* Insert TTP header with SAR parameters */
        frame = skb_push(tx_skb, TTP_HEADER+TTP_SAR_HEADER);

        frame[0] = TTP_PARAMETERS | n;
        frame[1] = 0x04; /* Length */

        /* irda_param_insert(self, IRTTP_MAX_SDU_SIZE, frame+1,  */
/*                TTP_SAR_HEADER, &param_info) */

        frame[2] = 0x01; /* MaxSduSize */
        frame[3] = 0x02; /* Value length */

        put_unaligned(cpu_to_be16((__u16) max_sdu_size),
                  (__be16 *)(frame+4));
    } else {
        /* Insert TTP header */
        frame = skb_push(tx_skb, TTP_HEADER);

        frame[0] = n & 0x7f;
    }

    ret = irlmp_connect_response(self->lsap, tx_skb);

    return ret;
}
EXPORT_SYMBOL(irttp_connect_response);

/*
 * Function irttp_dup (self, instance)
 *
 *    Duplicate TSAP, can be used by servers to confirm a connection on a
 *    new TSAP so it can keep listening on the old one.
 */
struct tsap_cb *irttp_dup(struct tsap_cb *orig, void *instance)
{
    struct tsap_cb *new;
    unsigned long flags;

    IRDA_DEBUG(1, "%s()\n", __func__);

    /* Protect our access to the old tsap instance */
    spin_lock_irqsave(&irttp->tsaps->hb_spinlock, flags);

    /* Find the old instance */
    if (!hashbin_find(irttp->tsaps, (long) orig, NULL)) {
        IRDA_DEBUG(0, "%s(), unable to find TSAP\n", __func__);
        spin_unlock_irqrestore(&irttp->tsaps->hb_spinlock, flags);
        return NULL;
    }

    /* Allocate a new instance */
    new = kmemdup(orig, sizeof(struct tsap_cb), GFP_ATOMIC);
    if (!new) {
        IRDA_DEBUG(0, "%s(), unable to kmalloc\n", __func__);
        spin_unlock_irqrestore(&irttp->tsaps->hb_spinlock, flags);
        return NULL;
    }
    spin_lock_init(&new->lock);

    /* We don't need the old instance any more */
    spin_unlock_irqrestore(&irttp->tsaps->hb_spinlock, flags);

    /* Try to dup the LSAP (may fail if we were too slow) */
    new->lsap = irlmp_dup(orig->lsap, new);
    if (!new->lsap) {
        IRDA_DEBUG(0, "%s(), dup failed!\n", __func__);
        kfree(new);
        return NULL;
    }

    /* Not everything should be copied */
    new->notify.instance = instance;

    /* Initialize internal objects */
    irttp_init_tsap(new);

    /* This is locked */
    hashbin_insert(irttp->tsaps, (irda_queue_t *) new, (long) new, NULL);

    return new;
}
EXPORT_SYMBOL(irttp_dup);

/*
 * Function irttp_disconnect_request (self)
 *
 *    Close this connection please! If priority is high, the queued data
 *    segments, if any, will be deallocated first
 *
 */
int irttp_disconnect_request(struct tsap_cb *self, struct sk_buff *userdata,
                 int priority)
{
    int ret;

    IRDA_ASSERT(self != NULL, return -1;);
    IRDA_ASSERT(self->magic == TTP_TSAP_MAGIC, return -1;);

    /* Already disconnected? */
    if (!self->connected) {
        IRDA_DEBUG(4, "%s(), already disconnected!\n", __func__);
        if (userdata)
            dev_kfree_skb(userdata);
        return -1;
    }

    /* Disconnect already pending ?
     * We need to use an atomic operation to prevent reentry. This
     * function may be called from various context, like user, timer
     * for following a disconnect_indication() (i.e. net_bh).
     * Jean II */
    if(test_and_set_bit(0, &self->disconnect_pend)) {
        IRDA_DEBUG(0, "%s(), disconnect already pending\n",
               __func__);
        if (userdata)
            dev_kfree_skb(userdata);

        /* Try to make some progress */
        irttp_run_tx_queue(self);
        return -1;
    }

    /*
     *  Check if there is still data segments in the transmit queue
     */
    if (!skb_queue_empty(&self->tx_queue)) {
        if (priority == P_HIGH) {
            /*
             *  No need to send the queued data, if we are
             *  disconnecting right now since the data will
             *  not have any usable connection to be sent on
             */
            IRDA_DEBUG(1, "%s(): High priority!!()\n", __func__);
            irttp_flush_queues(self);
        } else if (priority == P_NORMAL) {
            /*
             *  Must delay disconnect until after all data segments
             *  have been sent and the tx_queue is empty
             */
            /* We'll reuse this one later for the disconnect */
            self->disconnect_skb = userdata;  /* May be NULL */

            irttp_run_tx_queue(self);

            irttp_start_todo_timer(self, HZ/10);
            return -1;
        }
    }
    /* Note : we don't need to check if self->rx_queue is full and the
     * state of self->rx_sdu_busy because the disconnect response will
     * be sent at the LMP level (so even if the peer has its Tx queue
     * full of data). - Jean II */

    IRDA_DEBUG(1, "%s(), Disconnecting ...\n", __func__);
    self->connected = FALSE;

    if (!userdata) {
        struct sk_buff *tx_skb;
        tx_skb = alloc_skb(LMP_MAX_HEADER, GFP_ATOMIC);
        if (!tx_skb)
            return -ENOMEM;

        /*
         *  Reserve space for MUX and LAP header
         */
        skb_reserve(tx_skb, LMP_MAX_HEADER);

        userdata = tx_skb;
    }
    ret = irlmp_disconnect_request(self->lsap, userdata);

    /* The disconnect is no longer pending */
    clear_bit(0, &self->disconnect_pend);   /* FALSE */

    return ret;
}
EXPORT_SYMBOL(irttp_disconnect_request);

/*
 * Function irttp_disconnect_indication (self, reason)
 *
 *    Disconnect indication, TSAP disconnected by peer?
 *
 */
static void irttp_disconnect_indication(void *instance, void *sap,
        LM_REASON reason, struct sk_buff *skb)
{
    struct tsap_cb *self;

    IRDA_DEBUG(4, "%s()\n", __func__);

    self = instance;

    IRDA_ASSERT(self != NULL, return;);
    IRDA_ASSERT(self->magic == TTP_TSAP_MAGIC, return;);

    /* Prevent higher layer to send more data */
    self->connected = FALSE;

    /* Check if client has already tried to close the TSAP */
    if (self->close_pend) {
        /* In this case, the higher layer is probably gone. Don't
         * bother it and clean up the remains - Jean II */
        if (skb)
            dev_kfree_skb(skb);
        irttp_close_tsap(self);
        return;
    }

    /* If we are here, we assume that is the higher layer is still
     * waiting for the disconnect notification and able to process it,
     * even if he tried to disconnect. Otherwise, it would have already
     * attempted to close the tsap and self->close_pend would be TRUE.
     * Jean II */

    /* No need to notify the client if has already tried to disconnect */
    if(self->notify.disconnect_indication)
        self->notify.disconnect_indication(self->notify.instance, self,
                           reason, skb);
    else
        if (skb)
            dev_kfree_skb(skb);
}

/*
 * Function irttp_do_data_indication (self, skb)
 *
 *    Try to deliver reassembled skb to layer above, and requeue it if that
 *    for some reason should fail. We mark rx sdu as busy to apply back
 *    pressure is necessary.
 */
static void irttp_do_data_indication(struct tsap_cb *self, struct sk_buff *skb)
{
    int err;

    /* Check if client has already closed the TSAP and gone away */
    if (self->close_pend) {
        dev_kfree_skb(skb);
        return;
    }

    err = self->notify.data_indication(self->notify.instance, self, skb);

    /* Usually the layer above will notify that it's input queue is
     * starting to get filled by using the flow request, but this may
     * be difficult, so it can instead just refuse to eat it and just
     * give an error back
     */
    if (err) {
        IRDA_DEBUG(0, "%s() requeueing skb!\n", __func__);

        /* Make sure we take a break */
        self->rx_sdu_busy = TRUE;

        /* Need to push the header in again */
        skb_push(skb, TTP_HEADER);
        skb->data[0] = 0x00; /* Make sure MORE bit is cleared */

        /* Put skb back on queue */
        skb_queue_head(&self->rx_queue, skb);
    }
}

/*
 * Function irttp_run_rx_queue (self)
 *
 *     Check if we have any frames to be transmitted, or if we have any
 *     available credit to give away.
 */
static void irttp_run_rx_queue(struct tsap_cb *self)
{
    struct sk_buff *skb;
    int more = 0;

    IRDA_DEBUG(2, "%s() send=%d,avail=%d,remote=%d\n", __func__,
           self->send_credit, self->avail_credit, self->remote_credit);

    /* Get exclusive access to the rx queue, otherwise don't touch it */
    if (irda_lock(&self->rx_queue_lock) == FALSE)
        return;

    /*
     *  Reassemble all frames in receive queue and deliver them
     */
    while (!self->rx_sdu_busy && (skb = skb_dequeue(&self->rx_queue))) {
        /* This bit will tell us if it's the last fragment or not */
        more = skb->data[0] & 0x80;

        /* Remove TTP header */
        skb_pull(skb, TTP_HEADER);

        /* Add the length of the remaining data */
        self->rx_sdu_size += skb->len;

        /*
         * If SAR is disabled, or user has requested no reassembly
         * of received fragments then we just deliver them
         * immediately. This can be requested by clients that
         * implements byte streams without any message boundaries
         */
        if (self->rx_max_sdu_size == TTP_SAR_DISABLE) {
            irttp_do_data_indication(self, skb);
            self->rx_sdu_size = 0;

            continue;
        }

        /* Check if this is a fragment, and not the last fragment */
        if (more) {
            /*
             *  Queue the fragment if we still are within the
             *  limits of the maximum size of the rx_sdu
             */
            if (self->rx_sdu_size <= self->rx_max_sdu_size) {
                IRDA_DEBUG(4, "%s(), queueing frag\n",
                       __func__);
                skb_queue_tail(&self->rx_fragments, skb);
            } else {
                /* Free the part of the SDU that is too big */
                dev_kfree_skb(skb);
            }
            continue;
        }
        /*
         *  This is the last fragment, so time to reassemble!
         */
        if ((self->rx_sdu_size <= self->rx_max_sdu_size) ||
            (self->rx_max_sdu_size == TTP_SAR_UNBOUND))
        {
            /*
             * A little optimizing. Only queue the fragment if
             * there are other fragments. Since if this is the
             * last and only fragment, there is no need to
             * reassemble :-)
             */
            if (!skb_queue_empty(&self->rx_fragments)) {
                skb_queue_tail(&self->rx_fragments,
                           skb);

                skb = irttp_reassemble_skb(self);
            }

            /* Now we can deliver the reassembled skb */
            irttp_do_data_indication(self, skb);
        } else {
            IRDA_DEBUG(1, "%s(), Truncated frame\n", __func__);

            /* Free the part of the SDU that is too big */
            dev_kfree_skb(skb);

            /* Deliver only the valid but truncated part of SDU */
            skb = irttp_reassemble_skb(self);

            irttp_do_data_indication(self, skb);
        }
        self->rx_sdu_size = 0;
    }

    /*
     * It's not trivial to keep track of how many credits are available
     * by incrementing at each packet, because delivery may fail
     * (irttp_do_data_indication() may requeue the frame) and because
     * we need to take care of fragmentation.
     * We want the other side to send up to initial_credit packets.
     * We have some frames in our queues, and we have already allowed it
     * to send remote_credit.
     * No need to spinlock, write is atomic and self correcting...
     * Jean II
     */
    self->avail_credit = (self->initial_credit -
                  (self->remote_credit +
                   skb_queue_len(&self->rx_queue) +
                   skb_queue_len(&self->rx_fragments)));

    /* Do we have too much credits to send to peer ? */
    if ((self->remote_credit <= TTP_RX_MIN_CREDIT) &&
        (self->avail_credit > 0)) {
        /* Send explicit credit frame */
        irttp_give_credit(self);
        /* Note : do *NOT* check if tx_queue is non-empty, that
         * will produce deadlocks. I repeat : send a credit frame
         * even if we have something to send in our Tx queue.
         * If we have credits, it means that our Tx queue is blocked.
         *
         * Let's suppose the peer can't keep up with our Tx. He will
         * flow control us by not sending us any credits, and we
         * will stop Tx and start accumulating credits here.
         * Up to the point where the peer will stop its Tx queue,
         * for lack of credits.
         * Let's assume the peer application is single threaded.
         * It will block on Tx and never consume any Rx buffer.
         * Deadlock. Guaranteed. - Jean II
         */
    }

    /* Reset lock */
    self->rx_queue_lock = 0;
}

#ifdef CONFIG_PROC_FS
struct irttp_iter_state {
    int id;
};

static void *irttp_seq_start(struct seq_file *seq, loff_t *pos)
{
    struct irttp_iter_state *iter = seq->private;
    struct tsap_cb *self;

    /* Protect our access to the tsap list */
    spin_lock_irq(&irttp->tsaps->hb_spinlock);
    iter->id = 0;

    for (self = (struct tsap_cb *) hashbin_get_first(irttp->tsaps);
         self != NULL;
         self = (struct tsap_cb *) hashbin_get_next(irttp->tsaps)) {
        if (iter->id == *pos)
            break;
        ++iter->id;
    }

    return self;
}

static void *irttp_seq_next(struct seq_file *seq, void *v, loff_t *pos)
{
    struct irttp_iter_state *iter = seq->private;

    ++*pos;
    ++iter->id;
    return (void *) hashbin_get_next(irttp->tsaps);
}

static void irttp_seq_stop(struct seq_file *seq, void *v)
{
    spin_unlock_irq(&irttp->tsaps->hb_spinlock);
}

static int irttp_seq_show(struct seq_file *seq, void *v)
{
    const struct irttp_iter_state *iter = seq->private;
    const struct tsap_cb *self = v;

    seq_printf(seq, "TSAP %d, ", iter->id);
    seq_printf(seq, "stsap_sel: %02x, ",
           self->stsap_sel);
    seq_printf(seq, "dtsap_sel: %02x\n",
           self->dtsap_sel);
    seq_printf(seq, "  connected: %s, ",
           self->connected? "TRUE":"FALSE");
    seq_printf(seq, "avail credit: %d, ",
           self->avail_credit);
    seq_printf(seq, "remote credit: %d, ",
           self->remote_credit);
    seq_printf(seq, "send credit: %d\n",
           self->send_credit);
    seq_printf(seq, "  tx packets: %lu, ",
           self->stats.tx_packets);
    seq_printf(seq, "rx packets: %lu, ",
           self->stats.rx_packets);
    seq_printf(seq, "tx_queue len: %u ",
           skb_queue_len(&self->tx_queue));
    seq_printf(seq, "rx_queue len: %u\n",
           skb_queue_len(&self->rx_queue));
    seq_printf(seq, "  tx_sdu_busy: %s, ",
           self->tx_sdu_busy? "TRUE":"FALSE");
    seq_printf(seq, "rx_sdu_busy: %s\n",
           self->rx_sdu_busy? "TRUE":"FALSE");
    seq_printf(seq, "  max_seg_size: %u, ",
           self->max_seg_size);
    seq_printf(seq, "tx_max_sdu_size: %u, ",
           self->tx_max_sdu_size);
    seq_printf(seq, "rx_max_sdu_size: %u\n",
           self->rx_max_sdu_size);

    seq_printf(seq, "  Used by (%s)\n\n",
           self->notify.name);
    return 0;
}

static const struct seq_operations irttp_seq_ops = {
    .start  = irttp_seq_start,
    .next   = irttp_seq_next,
    .stop   = irttp_seq_stop,
    .show   = irttp_seq_show,
};

static int irttp_seq_open(struct inode *inode, struct file *file)
{
    return seq_open_private(file, &irttp_seq_ops,
            sizeof(struct irttp_iter_state));
}

const struct file_operations irttp_seq_fops = {
    .owner      = THIS_MODULE,
    .open           = irttp_seq_open,
    .read           = seq_read,
    .llseek         = seq_lseek,
    .release    = seq_release_private,
};

#endif /* PROC_FS */