/*********************************************************************
 *
 *      sir_dev.c:      irda sir network device
 * 
 *      Copyright (c) 2002 Martin Diehl
 * 
 *      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.
 *
 ********************************************************************/    

#include <linux/hardirq.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/delay.h>

#include <net/irda/irda.h>
#include <net/irda/wrapper.h>
#include <net/irda/irda_device.h>

#include "sir-dev.h"


static struct workqueue_struct *irda_sir_wq;

/* STATE MACHINE */

/* substate handler of the config-fsm to handle the cases where we want
 * to wait for transmit completion before changing the port configuration
 */

static int sirdev_tx_complete_fsm(struct sir_dev *dev)
{
        struct sir_fsm *fsm = &dev->fsm;
        unsigned next_state, delay;
        unsigned bytes_left;

        do {
                next_state = fsm->substate;     /* default: stay in current substate */
                delay = 0;

                switch(fsm->substate) {

                case SIRDEV_STATE_WAIT_XMIT:
                        if (dev->drv->chars_in_buffer)
                                bytes_left = dev->drv->chars_in_buffer(dev);
                        else
                                bytes_left = 0;
                        if (!bytes_left) {
                                next_state = SIRDEV_STATE_WAIT_UNTIL_SENT;
                                break;
                        }

                        if (dev->speed > 115200)
                                delay = (bytes_left*8*10000) / (dev->speed/100);
                        else if (dev->speed > 0)
                                delay = (bytes_left*10*10000) / (dev->speed/100);
                        else
                                delay = 0;
                        /* expected delay (usec) until remaining bytes are sent */
                        if (delay < 100) {
                                udelay(delay);
                                delay = 0;
                                break;
                        }
                        /* sleep some longer delay (msec) */
                        delay = (delay+999) / 1000;
                        break;

                case SIRDEV_STATE_WAIT_UNTIL_SENT:
                        /* block until underlaying hardware buffer are empty */
                        if (dev->drv->wait_until_sent)
                                dev->drv->wait_until_sent(dev);
                        next_state = SIRDEV_STATE_TX_DONE;
                        break;

                case SIRDEV_STATE_TX_DONE:
                        return 0;

                default:
                        net_err_ratelimited("%s - undefined state\n", __func__);
                        return -EINVAL;
                }
                fsm->substate = next_state;
        } while (delay == 0);
        return delay;
}

/*
 * Function sirdev_config_fsm
 *
 * State machine to handle the configuration of the device (and attached dongle, if any).
 * This handler is scheduled for execution in kIrDAd context, so we can sleep.
 * however, kIrDAd is shared by all sir_dev devices so we better don't sleep there too
 * long. Instead, for longer delays we start a timer to reschedule us later.
 * On entry, fsm->sem is always locked and the netdev xmit queue stopped.
 * Both must be unlocked/restarted on completion - but only on final exit.
 */

static void sirdev_config_fsm(struct work_struct *work)
{
        struct sir_dev *dev = container_of(work, struct sir_dev, fsm.work.work);
        struct sir_fsm *fsm = &dev->fsm;
        int next_state;
        int ret = -1;
        unsigned delay;

        pr_debug("%s(), <%ld>\n", __func__, jiffies);

        do {
                pr_debug("%s - state=0x%04x / substate=0x%04x\n",
                         __func__, fsm->state, fsm->substate);

                next_state = fsm->state;
                delay = 0;

                switch(fsm->state) {

                case SIRDEV_STATE_DONGLE_OPEN:
                        if (dev->dongle_drv != NULL) {
                                ret = sirdev_put_dongle(dev);
                                if (ret) {
                                        fsm->result = -EINVAL;
                                        next_state = SIRDEV_STATE_ERROR;
                                        break;
                                }
                        }

                        /* Initialize dongle */
                        ret = sirdev_get_dongle(dev, fsm->param);
                        if (ret) {
                                fsm->result = ret;
                                next_state = SIRDEV_STATE_ERROR;
                                break;
                        }

                        /* Dongles are powered through the modem control lines which
                         * were just set during open. Before resetting, let's wait for
                         * the power to stabilize. This is what some dongle drivers did
                         * in open before, while others didn't - should be safe anyway.
                         */

                        delay = 50;
                        fsm->substate = SIRDEV_STATE_DONGLE_RESET;
                        next_state = SIRDEV_STATE_DONGLE_RESET;

                        fsm->param = 9600;

                        break;

                case SIRDEV_STATE_DONGLE_CLOSE:
                        /* shouldn't we just treat this as success=? */
                        if (dev->dongle_drv == NULL) {
                                fsm->result = -EINVAL;
                                next_state = SIRDEV_STATE_ERROR;
                                break;
                        }

                        ret = sirdev_put_dongle(dev);
                        if (ret) {
                                fsm->result = ret;
                                next_state = SIRDEV_STATE_ERROR;
                                break;
                        }
                        next_state = SIRDEV_STATE_DONE;
                        break;

                case SIRDEV_STATE_SET_DTR_RTS:
                        ret = sirdev_set_dtr_rts(dev,
                                (fsm->param&0x02) ? TRUE : FALSE,
                                (fsm->param&0x01) ? TRUE : FALSE);
                        next_state = SIRDEV_STATE_DONE;
                        break;

                case SIRDEV_STATE_SET_SPEED:
                        fsm->substate = SIRDEV_STATE_WAIT_XMIT;
                        next_state = SIRDEV_STATE_DONGLE_CHECK;
                        break;

                case SIRDEV_STATE_DONGLE_CHECK:
                        ret = sirdev_tx_complete_fsm(dev);
                        if (ret < 0) {
                                fsm->result = ret;
                                next_state = SIRDEV_STATE_ERROR;
                                break;
                        }
                        if ((delay=ret) != 0)
                                break;

                        if (dev->dongle_drv) {
                                fsm->substate = SIRDEV_STATE_DONGLE_RESET;
                                next_state = SIRDEV_STATE_DONGLE_RESET;
                        }
                        else {
                                dev->speed = fsm->param;
                                next_state = SIRDEV_STATE_PORT_SPEED;
                        }
                        break;

                case SIRDEV_STATE_DONGLE_RESET:
                        if (dev->dongle_drv->reset) {
                                ret = dev->dongle_drv->reset(dev);
                                if (ret < 0) {
                                        fsm->result = ret;
                                        next_state = SIRDEV_STATE_ERROR;
                                        break;
                                }
                        }
                        else
                                ret = 0;
                        if ((delay=ret) == 0) {
                                /* set serial port according to dongle default speed */
                                if (dev->drv->set_speed)
                                        dev->drv->set_speed(dev, dev->speed);
                                fsm->substate = SIRDEV_STATE_DONGLE_SPEED;
                                next_state = SIRDEV_STATE_DONGLE_SPEED;
                        }
                        break;

                case SIRDEV_STATE_DONGLE_SPEED:
                        if (dev->dongle_drv->set_speed) {
                                ret = dev->dongle_drv->set_speed(dev, fsm->param);
                                if (ret < 0) {
                                        fsm->result = ret;
                                        next_state = SIRDEV_STATE_ERROR;
                                        break;
                                }
                        }
                        else
                                ret = 0;
                        if ((delay=ret) == 0)
                                next_state = SIRDEV_STATE_PORT_SPEED;
                        break;

                case SIRDEV_STATE_PORT_SPEED:
                        /* Finally we are ready to change the serial port speed */
                        if (dev->drv->set_speed)
                                dev->drv->set_speed(dev, dev->speed);
                        dev->new_speed = 0;
                        next_state = SIRDEV_STATE_DONE;
                        break;

                case SIRDEV_STATE_DONE:
                        /* Signal network layer so it can send more frames */
                        netif_wake_queue(dev->netdev);
                        next_state = SIRDEV_STATE_COMPLETE;
                        break;

                default:
                        net_err_ratelimited("%s - undefined state\n", __func__);
                        fsm->result = -EINVAL;
                        /* fall thru */

                case SIRDEV_STATE_ERROR:
                        net_err_ratelimited("%s - error: %d\n",
                                            __func__, fsm->result);

#if 0   /* don't enable this before we have netdev->tx_timeout to recover */
                        netif_stop_queue(dev->netdev);
#else
                        netif_wake_queue(dev->netdev);
#endif
                        /* fall thru */

                case SIRDEV_STATE_COMPLETE:
                        /* config change finished, so we are not busy any longer */
                        sirdev_enable_rx(dev);
                        up(&fsm->sem);
                        return;
                }
                fsm->state = next_state;
        } while(!delay);

        queue_delayed_work(irda_sir_wq, &fsm->work, msecs_to_jiffies(delay));
}

/* schedule some device configuration task for execution by kIrDAd
 * on behalf of the above state machine.
 * can be called from process or interrupt/tasklet context.
 */

int sirdev_schedule_request(struct sir_dev *dev, int initial_state, unsigned param)
{
        struct sir_fsm *fsm = &dev->fsm;

        pr_debug("%s - state=0x%04x / param=%u\n", __func__,
                 initial_state, param);

        if (down_trylock(&fsm->sem)) {
                if (in_interrupt()  ||  in_atomic()  ||  irqs_disabled()) {
                        pr_debug("%s(), state machine busy!\n", __func__);
                        return -EWOULDBLOCK;
                } else
                        down(&fsm->sem);
        }

        if (fsm->state == SIRDEV_STATE_DEAD) {
                /* race with sirdev_close should never happen */
                net_err_ratelimited("%s(), instance staled!\n", __func__);
                up(&fsm->sem);
                return -ESTALE;         /* or better EPIPE? */
        }

        netif_stop_queue(dev->netdev);
        atomic_set(&dev->enable_rx, 0);

        fsm->state = initial_state;
        fsm->param = param;
        fsm->result = 0;

        INIT_DELAYED_WORK(&fsm->work, sirdev_config_fsm);
        queue_delayed_work(irda_sir_wq, &fsm->work, 0);
        return 0;
}


/***************************************************************************/

void sirdev_enable_rx(struct sir_dev *dev)
{
        if (unlikely(atomic_read(&dev->enable_rx)))
                return;

        /* flush rx-buffer - should also help in case of problems with echo cancelation */
        dev->rx_buff.data = dev->rx_buff.head;
        dev->rx_buff.len = 0;
        dev->rx_buff.in_frame = FALSE;
        dev->rx_buff.state = OUTSIDE_FRAME;
        atomic_set(&dev->enable_rx, 1);
}

static int sirdev_is_receiving(struct sir_dev *dev)
{
        if (!atomic_read(&dev->enable_rx))
                return 0;

        return dev->rx_buff.state != OUTSIDE_FRAME;
}

int sirdev_set_dongle(struct sir_dev *dev, IRDA_DONGLE type)
{
        int err;

        pr_debug("%s : requesting dongle %d.\n", __func__, type);

        err = sirdev_schedule_dongle_open(dev, type);
        if (unlikely(err))
                return err;
        down(&dev->fsm.sem);            /* block until config change completed */
        err = dev->fsm.result;
        up(&dev->fsm.sem);
        return err;
}
EXPORT_SYMBOL(sirdev_set_dongle);

/* used by dongle drivers for dongle programming */

int sirdev_raw_write(struct sir_dev *dev, const char *buf, int len)
{
        unsigned long flags;
        int ret;

        if (unlikely(len > dev->tx_buff.truesize))
                return -ENOSPC;

        spin_lock_irqsave(&dev->tx_lock, flags);        /* serialize with other tx operations */
        while (dev->tx_buff.len > 0) {                  /* wait until tx idle */
                spin_unlock_irqrestore(&dev->tx_lock, flags);
                msleep(10);
                spin_lock_irqsave(&dev->tx_lock, flags);
        }

        dev->tx_buff.data = dev->tx_buff.head;
        memcpy(dev->tx_buff.data, buf, len);    
        dev->tx_buff.len = len;

        ret = dev->drv->do_write(dev, dev->tx_buff.data, dev->tx_buff.len);
        if (ret > 0) {
                pr_debug("%s(), raw-tx started\n", __func__);

                dev->tx_buff.data += ret;
                dev->tx_buff.len -= ret;
                dev->raw_tx = 1;
                ret = len;              /* all data is going to be sent */
        }
        spin_unlock_irqrestore(&dev->tx_lock, flags);
        return ret;
}
EXPORT_SYMBOL(sirdev_raw_write);

/* seems some dongle drivers may need this */

int sirdev_raw_read(struct sir_dev *dev, char *buf, int len)
{
        int count;

        if (atomic_read(&dev->enable_rx))
                return -EIO;            /* fail if we expect irda-frames */

        count = (len < dev->rx_buff.len) ? len : dev->rx_buff.len;

        if (count > 0) {
                memcpy(buf, dev->rx_buff.data, count);
                dev->rx_buff.data += count;
                dev->rx_buff.len -= count;
        }

        /* remaining stuff gets flushed when re-enabling normal rx */

        return count;
}
EXPORT_SYMBOL(sirdev_raw_read);

int sirdev_set_dtr_rts(struct sir_dev *dev, int dtr, int rts)
{
        int ret = -ENXIO;
        if (dev->drv->set_dtr_rts)
                ret =  dev->drv->set_dtr_rts(dev, dtr, rts);
        return ret;
}
EXPORT_SYMBOL(sirdev_set_dtr_rts);

/**********************************************************************/

/* called from client driver - likely with bh-context - to indicate
 * it made some progress with transmission. Hence we send the next
 * chunk, if any, or complete the skb otherwise
 */

void sirdev_write_complete(struct sir_dev *dev)
{
        unsigned long flags;
        struct sk_buff *skb;
        int actual = 0;
        int err;
        
        spin_lock_irqsave(&dev->tx_lock, flags);

        pr_debug("%s() - dev->tx_buff.len = %d\n",
                 __func__, dev->tx_buff.len);

        if (likely(dev->tx_buff.len > 0))  {
                /* Write data left in transmit buffer */
                actual = dev->drv->do_write(dev, dev->tx_buff.data, dev->tx_buff.len);

                if (likely(actual>0)) {
                        dev->tx_buff.data += actual;
                        dev->tx_buff.len  -= actual;
                }
                else if (unlikely(actual<0)) {
                        /* could be dropped later when we have tx_timeout to recover */
                        net_err_ratelimited("%s: drv->do_write failed (%d)\n",
                                            __func__, actual);
                        if ((skb=dev->tx_skb) != NULL) {
                                dev->tx_skb = NULL;
                                dev_kfree_skb_any(skb);
                                dev->netdev->stats.tx_errors++;
                                dev->netdev->stats.tx_dropped++;
                        }
                        dev->tx_buff.len = 0;
                }
                if (dev->tx_buff.len > 0)
                        goto done;      /* more data to send later */
        }

        if (unlikely(dev->raw_tx != 0)) {
                /* in raw mode we are just done now after the buffer was sent
                 * completely. Since this was requested by some dongle driver
                 * running under the control of the irda-thread we must take
                 * care here not to re-enable the queue. The queue will be
                 * restarted when the irda-thread has completed the request.
                 */

                pr_debug("%s(), raw-tx done\n", __func__);
                dev->raw_tx = 0;
                goto done;      /* no post-frame handling in raw mode */
        }

        /* we have finished now sending this skb.
         * update statistics and free the skb.
         * finally we check and trigger a pending speed change, if any.
         * if not we switch to rx mode and wake the queue for further
         * packets.
         * note the scheduled speed request blocks until the lower
         * client driver and the corresponding hardware has really
         * finished sending all data (xmit fifo drained f.e.)
         * before the speed change gets finally done and the queue
         * re-activated.
         */

        pr_debug("%s(), finished with frame!\n", __func__);
                
        if ((skb=dev->tx_skb) != NULL) {
                dev->tx_skb = NULL;
                dev->netdev->stats.tx_packets++;
                dev->netdev->stats.tx_bytes += skb->len;
                dev_kfree_skb_any(skb);
        }

        if (unlikely(dev->new_speed > 0)) {
                pr_debug("%s(), Changing speed!\n", __func__);
                err = sirdev_schedule_speed(dev, dev->new_speed);
                if (unlikely(err)) {
                        /* should never happen
                         * forget the speed change and hope the stack recovers
                         */
                        net_err_ratelimited("%s - schedule speed change failed: %d\n",
                                            __func__, err);
                        netif_wake_queue(dev->netdev);
                }
                /* else: success
                 *      speed change in progress now
                 *      on completion dev->new_speed gets cleared,
                 *      rx-reenabled and the queue restarted
                 */
        }
        else {
                sirdev_enable_rx(dev);
                netif_wake_queue(dev->netdev);
        }

done:
        spin_unlock_irqrestore(&dev->tx_lock, flags);
}
EXPORT_SYMBOL(sirdev_write_complete);

/* called from client driver - likely with bh-context - to give us
 * some more received bytes. We put them into the rx-buffer,
 * normally unwrapping and building LAP-skb's (unless rx disabled)
 */

int sirdev_receive(struct sir_dev *dev, const unsigned char *cp, size_t count) 
{
        if (!dev || !dev->netdev) {
                net_warn_ratelimited("%s(), not ready yet!\n", __func__);
                return -1;
        }

        if (!dev->irlap) {
                net_warn_ratelimited("%s - too early: %p / %zd!\n",
                                     __func__, cp, count);
                return -1;
        }

        if (cp==NULL) {
                /* error already at lower level receive
                 * just update stats and set media busy
                 */
                irda_device_set_media_busy(dev->netdev, TRUE);
                dev->netdev->stats.rx_dropped++;
                pr_debug("%s; rx-drop: %zd\n", __func__, count);
                return 0;
        }

        /* Read the characters into the buffer */
        if (likely(atomic_read(&dev->enable_rx))) {
                while (count--)
                        /* Unwrap and destuff one byte */
                        async_unwrap_char(dev->netdev, &dev->netdev->stats,
                                          &dev->rx_buff, *cp++);
        } else {
                while (count--) {
                        /* rx not enabled: save the raw bytes and never
                         * trigger any netif_rx. The received bytes are flushed
                         * later when we re-enable rx but might be read meanwhile
                         * by the dongle driver.
                         */
                        dev->rx_buff.data[dev->rx_buff.len++] = *cp++;

                        /* What should we do when the buffer is full? */
                        if (unlikely(dev->rx_buff.len == dev->rx_buff.truesize))
                                dev->rx_buff.len = 0;
                }
        }

        return 0;
}
EXPORT_SYMBOL(sirdev_receive);

/**********************************************************************/

/* callbacks from network layer */

static netdev_tx_t sirdev_hard_xmit(struct sk_buff *skb,
                                          struct net_device *ndev)
{
        struct sir_dev *dev = netdev_priv(ndev);
        unsigned long flags;
        int actual = 0;
        int err;
        s32 speed;

        IRDA_ASSERT(dev != NULL, return NETDEV_TX_OK;);

        netif_stop_queue(ndev);

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

        speed = irda_get_next_speed(skb);
        if ((speed != dev->speed) && (speed != -1)) {
                if (!skb->len) {
                        err = sirdev_schedule_speed(dev, speed);
                        if (unlikely(err == -EWOULDBLOCK)) {
                                /* Failed to initiate the speed change, likely the fsm
                                 * is still busy (pretty unlikely, but...)
                                 * We refuse to accept the skb and return with the queue
                                 * stopped so the network layer will retry after the
                                 * fsm completes and wakes the queue.
                                 */
                                 return NETDEV_TX_BUSY;
                        }
                        else if (unlikely(err)) {
                                /* other fatal error - forget the speed change and
                                 * hope the stack will recover somehow
                                 */
                                 netif_start_queue(ndev);
                        }
                        /* else: success
                         *      speed change in progress now
                         *      on completion the queue gets restarted
                         */

                        dev_kfree_skb_any(skb);
                        return NETDEV_TX_OK;
                } else
                        dev->new_speed = speed;
        }

        /* Init tx buffer*/
        dev->tx_buff.data = dev->tx_buff.head;

        /* Check problems */
        if(spin_is_locked(&dev->tx_lock)) {
                pr_debug("%s(), write not completed\n", __func__);
        }

        /* serialize with write completion */
        spin_lock_irqsave(&dev->tx_lock, flags);

        /* Copy skb to tx_buff while wrapping, stuffing and making CRC */
        dev->tx_buff.len = async_wrap_skb(skb, dev->tx_buff.data, dev->tx_buff.truesize); 

        /* transmission will start now - disable receive.
         * if we are just in the middle of an incoming frame,
         * treat it as collision. probably it's a good idea to
         * reset the rx_buf OUTSIDE_FRAME in this case too?
         */
        atomic_set(&dev->enable_rx, 0);
        if (unlikely(sirdev_is_receiving(dev)))
                dev->netdev->stats.collisions++;

        actual = dev->drv->do_write(dev, dev->tx_buff.data, dev->tx_buff.len);

        if (likely(actual > 0)) {
                dev->tx_skb = skb;
                dev->tx_buff.data += actual;
                dev->tx_buff.len -= actual;
        }
        else if (unlikely(actual < 0)) {
                /* could be dropped later when we have tx_timeout to recover */
                net_err_ratelimited("%s: drv->do_write failed (%d)\n",
                                    __func__, actual);
                dev_kfree_skb_any(skb);
                dev->netdev->stats.tx_errors++;
                dev->netdev->stats.tx_dropped++;
                netif_wake_queue(ndev);
        }
        spin_unlock_irqrestore(&dev->tx_lock, flags);

        return NETDEV_TX_OK;
}

/* called from network layer with rtnl hold */

static int sirdev_ioctl(struct net_device *ndev, struct ifreq *rq, int cmd)
{
        struct if_irda_req *irq = (struct if_irda_req *) rq;
        struct sir_dev *dev = netdev_priv(ndev);
        int ret = 0;

        IRDA_ASSERT(dev != NULL, return -1;);

        pr_debug("%s(), %s, (cmd=0x%X)\n", __func__, ndev->name, cmd);
        
        switch (cmd) {
        case SIOCSBANDWIDTH: /* Set bandwidth */
                if (!capable(CAP_NET_ADMIN))
                        ret = -EPERM;
                else
                        ret = sirdev_schedule_speed(dev, irq->ifr_baudrate);
                /* cannot sleep here for completion
                 * we are called from network layer with rtnl hold
                 */
                break;

        case SIOCSDONGLE: /* Set dongle */
                if (!capable(CAP_NET_ADMIN))
                        ret = -EPERM;
                else
                        ret = sirdev_schedule_dongle_open(dev, irq->ifr_dongle);
                /* cannot sleep here for completion
                 * we are called from network layer with rtnl hold
                 */
                break;

        case SIOCSMEDIABUSY: /* Set media busy */
                if (!capable(CAP_NET_ADMIN))
                        ret = -EPERM;
                else
                        irda_device_set_media_busy(dev->netdev, TRUE);
                break;

        case SIOCGRECEIVING: /* Check if we are receiving right now */
                irq->ifr_receiving = sirdev_is_receiving(dev);
                break;

        case SIOCSDTRRTS:
                if (!capable(CAP_NET_ADMIN))
                        ret = -EPERM;
                else
                        ret = sirdev_schedule_dtr_rts(dev, irq->ifr_dtr, irq->ifr_rts);
                /* cannot sleep here for completion
                 * we are called from network layer with rtnl hold
                 */
                break;

        case SIOCSMODE:
#if 0
                if (!capable(CAP_NET_ADMIN))
                        ret = -EPERM;
                else
                        ret = sirdev_schedule_mode(dev, irq->ifr_mode);
                /* cannot sleep here for completion
                 * we are called from network layer with rtnl hold
                 */
                break;
#endif
        default:
                ret = -EOPNOTSUPP;
        }
        
        return ret;
}

/* ----------------------------------------------------------------------------- */

#define SIRBUF_ALLOCSIZE 4269   /* worst case size of a wrapped IrLAP frame */

static int sirdev_alloc_buffers(struct sir_dev *dev)
{
        dev->tx_buff.truesize = SIRBUF_ALLOCSIZE;
        dev->rx_buff.truesize = IRDA_SKB_MAX_MTU; 

        /* Bootstrap ZeroCopy Rx */
        dev->rx_buff.skb = __netdev_alloc_skb(dev->netdev, dev->rx_buff.truesize,
                                              GFP_KERNEL);
        if (dev->rx_buff.skb == NULL)
                return -ENOMEM;
        skb_reserve(dev->rx_buff.skb, 1);
        dev->rx_buff.head = dev->rx_buff.skb->data;

        dev->tx_buff.head = kmalloc(dev->tx_buff.truesize, GFP_KERNEL);
        if (dev->tx_buff.head == NULL) {
                kfree_skb(dev->rx_buff.skb);
                dev->rx_buff.skb = NULL;
                dev->rx_buff.head = NULL;
                return -ENOMEM;
        }

        dev->tx_buff.data = dev->tx_buff.head;
        dev->rx_buff.data = dev->rx_buff.head;
        dev->tx_buff.len = 0;
        dev->rx_buff.len = 0;

        dev->rx_buff.in_frame = FALSE;
        dev->rx_buff.state = OUTSIDE_FRAME;
        return 0;
};

static void sirdev_free_buffers(struct sir_dev *dev)
{
        kfree_skb(dev->rx_buff.skb);
        kfree(dev->tx_buff.head);
        dev->rx_buff.head = dev->tx_buff.head = NULL;
        dev->rx_buff.skb = NULL;
}

static int sirdev_open(struct net_device *ndev)
{
        struct sir_dev *dev = netdev_priv(ndev);
        const struct sir_driver *drv = dev->drv;

        if (!drv)
                return -ENODEV;

        /* increase the reference count of the driver module before doing serious stuff */
        if (!try_module_get(drv->owner))
                return -ESTALE;

        if (sirdev_alloc_buffers(dev))
                goto errout_dec;

        if (!dev->drv->start_dev  ||  dev->drv->start_dev(dev))
                goto errout_free;

        sirdev_enable_rx(dev);
        dev->raw_tx = 0;

        netif_start_queue(ndev);
        dev->irlap = irlap_open(ndev, &dev->qos, dev->hwname);
        if (!dev->irlap)
                goto errout_stop;

        netif_wake_queue(ndev);

        pr_debug("%s - done, speed = %d\n", __func__, dev->speed);

        return 0;

errout_stop:
        atomic_set(&dev->enable_rx, 0);
        if (dev->drv->stop_dev)
                dev->drv->stop_dev(dev);
errout_free:
        sirdev_free_buffers(dev);
errout_dec:
        module_put(drv->owner);
        return -EAGAIN;
}

static int sirdev_close(struct net_device *ndev)
{
        struct sir_dev *dev = netdev_priv(ndev);
        const struct sir_driver *drv;

/* pr_debug("%s\n", __func__); */

        netif_stop_queue(ndev);

        down(&dev->fsm.sem);            /* block on pending config completion */

        atomic_set(&dev->enable_rx, 0);

        if (unlikely(!dev->irlap))
                goto out;
        irlap_close(dev->irlap);
        dev->irlap = NULL;

        drv = dev->drv;
        if (unlikely(!drv  ||  !dev->priv))
                goto out;

        if (drv->stop_dev)
                drv->stop_dev(dev);

        sirdev_free_buffers(dev);
        module_put(drv->owner);

out:
        dev->speed = 0;
        up(&dev->fsm.sem);
        return 0;
}

static const struct net_device_ops sirdev_ops = {
        .ndo_start_xmit = sirdev_hard_xmit,
        .ndo_open       = sirdev_open,
        .ndo_stop       = sirdev_close,
        .ndo_do_ioctl   = sirdev_ioctl,
};
/* ----------------------------------------------------------------------------- */

struct sir_dev * sirdev_get_instance(const struct sir_driver *drv, const char *name)
{
        struct net_device *ndev;
        struct sir_dev *dev;

        pr_debug("%s - %s\n", __func__, name);

        /* instead of adding tests to protect against drv->do_write==NULL
         * at several places we refuse to create a sir_dev instance for
         * drivers which don't implement do_write.
         */
        if (!drv ||  !drv->do_write)
                return NULL;

        /*
         *  Allocate new instance of the device
         */
        ndev = alloc_irdadev(sizeof(*dev));
        if (ndev == NULL) {
                net_err_ratelimited("%s - Can't allocate memory for IrDA control block!\n",
                                    __func__);
                goto out;
        }
        dev = netdev_priv(ndev);

        irda_init_max_qos_capabilies(&dev->qos);
        dev->qos.baud_rate.bits = IR_9600|IR_19200|IR_38400|IR_57600|IR_115200;
        dev->qos.min_turn_time.bits = drv->qos_mtt_bits;
        irda_qos_bits_to_value(&dev->qos);

        strncpy(dev->hwname, name, sizeof(dev->hwname)-1);

        atomic_set(&dev->enable_rx, 0);
        dev->tx_skb = NULL;

        spin_lock_init(&dev->tx_lock);
        sema_init(&dev->fsm.sem, 1);

        dev->drv = drv;
        dev->netdev = ndev;

        /* Override the network functions we need to use */
        ndev->netdev_ops = &sirdev_ops;

        if (register_netdev(ndev)) {
                net_err_ratelimited("%s(), register_netdev() failed!\n",
                                    __func__);
                goto out_freenetdev;
        }

        return dev;

out_freenetdev:
        free_netdev(ndev);
out:
        return NULL;
}
EXPORT_SYMBOL(sirdev_get_instance);

int sirdev_put_instance(struct sir_dev *dev)
{
        int err = 0;

        pr_debug("%s\n", __func__);

        atomic_set(&dev->enable_rx, 0);

        netif_carrier_off(dev->netdev);
        netif_device_detach(dev->netdev);

        if (dev->dongle_drv)
                err = sirdev_schedule_dongle_close(dev);
        if (err)
                net_err_ratelimited("%s - error %d\n", __func__, err);

        sirdev_close(dev->netdev);

        down(&dev->fsm.sem);
        dev->fsm.state = SIRDEV_STATE_DEAD;     /* mark staled */
        dev->dongle_drv = NULL;
        dev->priv = NULL;
        up(&dev->fsm.sem);

        /* Remove netdevice */
        unregister_netdev(dev->netdev);

        free_netdev(dev->netdev);

        return 0;
}
EXPORT_SYMBOL(sirdev_put_instance);

static int __init sir_wq_init(void)
{
        irda_sir_wq = create_singlethread_workqueue("irda_sir_wq");
        if (!irda_sir_wq)
                return -ENOMEM;
        return 0;
}

static void __exit sir_wq_exit(void)
{
        destroy_workqueue(irda_sir_wq);
}

module_init(sir_wq_init);
module_exit(sir_wq_exit);

MODULE_AUTHOR("Martin Diehl <info@mdiehl.de>");
MODULE_DESCRIPTION("IrDA SIR core");
MODULE_LICENSE("GPL");