/*****************************************************************************
*
* Filename:      stir4200.c
* Version:       0.4
* Description:   Irda SigmaTel USB Dongle
* Status:        Experimental
* Author:        Stephen Hemminger <shemminger@osdl.org>
*
*       Based on earlier driver by Paul Stewart <stewart@parc.com>
*
*       Copyright (C) 2000, Roman Weissgaerber <weissg@vienna.at>
*       Copyright (C) 2001, Dag Brattli <dag@brattli.net>
*       Copyright (C) 2001, Jean Tourrilhes <jt@hpl.hp.com>
*       Copyright (C) 2004, Stephen Hemminger <shemminger@osdl.org>
*
*       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.
*
*       This program is distributed in the hope that it will be useful,
*       but WITHOUT ANY WARRANTY; without even the implied warranty of
*       MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
*       GNU General Public License for more details.
*
*       You should have received a copy of the GNU General Public License
*       along with this program; if not, write to the Free Software
*       Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*
*****************************************************************************/

/*
 * This dongle does no framing, and requires polling to receive the
 * data.  The STIr4200 has bulk in and out endpoints just like
 * usr-irda devices, but the data it sends and receives is raw; like
 * irtty, it needs to call the wrap and unwrap functions to add and
 * remove SOF/BOF and escape characters to/from the frame.
 */

#include <linux/module.h>
#include <linux/moduleparam.h>

#include <linux/kernel.h>
#include <linux/ktime.h>
#include <linux/types.h>
#include <linux/time.h>
#include <linux/skbuff.h>
#include <linux/netdevice.h>
#include <linux/slab.h>
#include <linux/delay.h>
#include <linux/usb.h>
#include <linux/crc32.h>
#include <linux/kthread.h>
#include <linux/freezer.h>
#include <net/irda/irda.h>
#include <net/irda/irda_device.h>
#include <net/irda/wrapper.h>
#include <net/irda/crc.h>
#include <asm/byteorder.h>
#include <asm/unaligned.h>

MODULE_AUTHOR("Stephen Hemminger <shemminger@linux-foundation.org>");
MODULE_DESCRIPTION("IrDA-USB Dongle Driver for SigmaTel STIr4200");
MODULE_LICENSE("GPL");

static int qos_mtt_bits = 0x07; /* 1 ms or more */
module_param(qos_mtt_bits, int, 0);
MODULE_PARM_DESC(qos_mtt_bits, "Minimum Turn Time");

static int rx_sensitivity = 1;  /* FIR 0..4, SIR 0..6 */
module_param(rx_sensitivity, int, 0);
MODULE_PARM_DESC(rx_sensitivity, "Set Receiver sensitivity (0-6, 0 is most sensitive)");

static int tx_power = 0;        /* 0 = highest ... 3 = lowest */
module_param(tx_power, int, 0);
MODULE_PARM_DESC(tx_power, "Set Transmitter power (0-3, 0 is highest power)");

#define STIR_IRDA_HEADER        4
#define CTRL_TIMEOUT            100        /* milliseconds */
#define TRANSMIT_TIMEOUT        200        /* milliseconds */
#define STIR_FIFO_SIZE          4096
#define FIFO_REGS_SIZE          3

enum FirChars {
        FIR_CE   = 0x7d,
        FIR_XBOF = 0x7f,
        FIR_EOF  = 0x7e,
};

enum StirRequests {
        REQ_WRITE_REG =         0x00,
        REQ_READ_REG =          0x01,
        REQ_READ_ROM =          0x02,
        REQ_WRITE_SINGLE =      0x03,
};

/* Register offsets */
enum StirRegs {
        REG_RSVD=0,
        REG_MODE,
        REG_PDCLK,
        REG_CTRL1,
        REG_CTRL2,
        REG_FIFOCTL,
        REG_FIFOLSB,
        REG_FIFOMSB,
        REG_DPLL,
        REG_IRDIG,
        REG_TEST=15,
};

enum StirModeMask {
        MODE_FIR = 0x80,
        MODE_SIR = 0x20,
        MODE_ASK = 0x10,
        MODE_FASTRX = 0x08,
        MODE_FFRSTEN = 0x04,
        MODE_NRESET = 0x02,
        MODE_2400 = 0x01,
};

enum StirPdclkMask {
        PDCLK_4000000 = 0x02,
        PDCLK_115200 = 0x09,
        PDCLK_57600 = 0x13,
        PDCLK_38400 = 0x1D,
        PDCLK_19200 = 0x3B,
        PDCLK_9600 = 0x77,
        PDCLK_2400 = 0xDF,
};

enum StirCtrl1Mask {
        CTRL1_SDMODE = 0x80,
        CTRL1_RXSLOW = 0x40,
        CTRL1_TXPWD = 0x10,
        CTRL1_RXPWD = 0x08,
        CTRL1_SRESET = 0x01,
};

enum StirCtrl2Mask {
        CTRL2_SPWIDTH = 0x08,
        CTRL2_REVID = 0x03,
};

enum StirFifoCtlMask {
        FIFOCTL_DIR = 0x10,
        FIFOCTL_CLR = 0x08,
        FIFOCTL_EMPTY = 0x04,
};

enum StirDiagMask {
        IRDIG_RXHIGH = 0x80,
        IRDIG_RXLOW = 0x40,
};

enum StirTestMask {
        TEST_PLLDOWN = 0x80,
        TEST_LOOPIR = 0x40,
        TEST_LOOPUSB = 0x20,
        TEST_TSTENA = 0x10,
        TEST_TSTOSC = 0x0F,
};

struct stir_cb {
        struct usb_device *usbdev;      /* init: probe_irda */
        struct net_device *netdev;      /* network layer */
        struct irlap_cb   *irlap;       /* The link layer we are binded to */

        struct qos_info   qos;
        unsigned          speed;        /* Current speed */

        struct task_struct *thread;     /* transmit thread */

        struct sk_buff    *tx_pending;
        void              *io_buf;      /* transmit/receive buffer */
        __u8              *fifo_status;

        iobuff_t          rx_buff;      /* receive unwrap state machine */
        ktime_t         rx_time;
        int               receiving;
        struct urb       *rx_urb;
};


/* These are the currently known USB ids */
static struct usb_device_id dongles[] = {
    /* SigmaTel, Inc,  STIr4200 IrDA/USB Bridge */
    { USB_DEVICE(0x066f, 0x4200) },
    { }
};

MODULE_DEVICE_TABLE(usb, dongles);

/* Send control message to set dongle register */
static int write_reg(struct stir_cb *stir, __u16 reg, __u8 value)
{
        struct usb_device *dev = stir->usbdev;

        pr_debug("%s: write reg %d = 0x%x\n",
                 stir->netdev->name, reg, value);
        return usb_control_msg(dev, usb_sndctrlpipe(dev, 0),
                               REQ_WRITE_SINGLE,
                               USB_DIR_OUT|USB_TYPE_VENDOR|USB_RECIP_DEVICE,
                               value, reg, NULL, 0,
                               CTRL_TIMEOUT);
}

/* Send control message to read multiple registers */
static inline int read_reg(struct stir_cb *stir, __u16 reg,
                    __u8 *data, __u16 count)
{
        struct usb_device *dev = stir->usbdev;

        return usb_control_msg(dev, usb_rcvctrlpipe(dev, 0),
                               REQ_READ_REG,
                               USB_DIR_IN | USB_TYPE_VENDOR | USB_RECIP_DEVICE,
                               0, reg, data, count,
                               CTRL_TIMEOUT);
}

static inline int isfir(u32 speed)
{
        return speed == 4000000;
}

/*
 * Prepare a FIR IrDA frame for transmission to the USB dongle.  The
 * FIR transmit frame is documented in the datasheet.  It consists of
 * a two byte 0x55 0xAA sequence, two little-endian length bytes, a
 * sequence of exactly 16 XBOF bytes of 0x7E, two BOF bytes of 0x7E,
 * then the data escaped as follows:
 *
 *    0x7D -> 0x7D 0x5D
 *    0x7E -> 0x7D 0x5E
 *    0x7F -> 0x7D 0x5F
 *
 * Then, 4 bytes of little endian (stuffed) FCS follow, then two
 * trailing EOF bytes of 0x7E.
 */
static inline __u8 *stuff_fir(__u8 *p, __u8 c)
{
        switch(c) {
        case 0x7d:
        case 0x7e:
        case 0x7f:
                *p++ = 0x7d;
                c ^= IRDA_TRANS;
                /* fall through */
        default:
                *p++ = c;
        }
        return p;
}

/* Take raw data in skb and put it wrapped into buf */
static unsigned wrap_fir_skb(const struct sk_buff *skb, __u8 *buf)
{
        __u8 *ptr = buf;
        __u32 fcs = ~(crc32_le(~0, skb->data, skb->len));
        __u16 wraplen;
        int i;

        /* Header */
        buf[0] = 0x55;
        buf[1] = 0xAA;

        ptr = buf + STIR_IRDA_HEADER;
        memset(ptr, 0x7f, 16);
        ptr += 16;

        /* BOF */
        *ptr++  = 0x7e;
        *ptr++  = 0x7e;

        /* Address / Control / Information */
        for (i = 0; i < skb->len; i++)
                ptr = stuff_fir(ptr, skb->data[i]);

        /* FCS */
        ptr = stuff_fir(ptr, fcs & 0xff);
        ptr = stuff_fir(ptr, (fcs >> 8) & 0xff);
        ptr = stuff_fir(ptr, (fcs >> 16) & 0xff);
        ptr = stuff_fir(ptr, (fcs >> 24) & 0xff);

        /* EOFs */
        *ptr++ = 0x7e;
        *ptr++ = 0x7e;

        /* Total length, minus the header */
        wraplen = (ptr - buf) - STIR_IRDA_HEADER;
        buf[2] = wraplen & 0xff;
        buf[3] = (wraplen >> 8) & 0xff;

        return wraplen + STIR_IRDA_HEADER;
}

static unsigned wrap_sir_skb(struct sk_buff *skb, __u8 *buf)
{
        __u16 wraplen;

        wraplen = async_wrap_skb(skb, buf + STIR_IRDA_HEADER,
                                 STIR_FIFO_SIZE - STIR_IRDA_HEADER);
        buf[0] = 0x55;
        buf[1] = 0xAA;
        buf[2] = wraplen & 0xff;
        buf[3] = (wraplen >> 8) & 0xff;

        return wraplen + STIR_IRDA_HEADER;
}

/*
 * Frame is fully formed in the rx_buff so check crc
 * and pass up to irlap
 * setup for next receive
 */
static void fir_eof(struct stir_cb *stir)
{
        iobuff_t *rx_buff = &stir->rx_buff;
        int len = rx_buff->len - 4;
        struct sk_buff *skb, *nskb;
        __u32 fcs;

        if (unlikely(len <= 0)) {
                pr_debug("%s: short frame len %d\n",
                         stir->netdev->name, len);

                ++stir->netdev->stats.rx_errors;
                ++stir->netdev->stats.rx_length_errors;
                return;
        }

        fcs = ~(crc32_le(~0, rx_buff->data, len));
        if (fcs != get_unaligned_le32(rx_buff->data + len)) {
                pr_debug("crc error calc 0x%x len %d\n", fcs, len);
                stir->netdev->stats.rx_errors++;
                stir->netdev->stats.rx_crc_errors++;
                return;
        }

        /* if frame is short then just copy it */
        if (len < IRDA_RX_COPY_THRESHOLD) {
                nskb = dev_alloc_skb(len + 1);
                if (unlikely(!nskb)) {
                        ++stir->netdev->stats.rx_dropped;
                        return;
                }
                skb_reserve(nskb, 1);
                skb = nskb;
                skb_copy_to_linear_data(nskb, rx_buff->data, len);
        } else {
                nskb = dev_alloc_skb(rx_buff->truesize);
                if (unlikely(!nskb)) {
                        ++stir->netdev->stats.rx_dropped;
                        return;
                }
                skb_reserve(nskb, 1);
                skb = rx_buff->skb;
                rx_buff->skb = nskb;
                rx_buff->head = nskb->data;
        }

        skb_put(skb, len);

        skb_reset_mac_header(skb);
        skb->protocol = htons(ETH_P_IRDA);
        skb->dev = stir->netdev;

        netif_rx(skb);

        stir->netdev->stats.rx_packets++;
        stir->netdev->stats.rx_bytes += len;

        rx_buff->data = rx_buff->head;
        rx_buff->len = 0;
}

/* Unwrap FIR stuffed data and bump it to IrLAP */
static void stir_fir_chars(struct stir_cb *stir,
                            const __u8 *bytes, int len)
{
        iobuff_t *rx_buff = &stir->rx_buff;
        int     i;

        for (i = 0; i < len; i++) {
                __u8    byte = bytes[i];

                switch(rx_buff->state) {
                case OUTSIDE_FRAME:
                        /* ignore garbage till start of frame */
                        if (unlikely(byte != FIR_EOF))
                                continue;
                        /* Now receiving frame */
                        rx_buff->state = BEGIN_FRAME;

                        /* Time to initialize receive buffer */
                        rx_buff->data = rx_buff->head;
                        rx_buff->len = 0;
                        continue;

                case LINK_ESCAPE:
                        if (byte == FIR_EOF) {
                                pr_debug("%s: got EOF after escape\n",
                                         stir->netdev->name);
                                goto frame_error;
                        }
                        rx_buff->state = INSIDE_FRAME;
                        byte ^= IRDA_TRANS;
                        break;

                case BEGIN_FRAME:
                        /* ignore multiple BOF/EOF */
                        if (byte == FIR_EOF)
                                continue;
                        rx_buff->state = INSIDE_FRAME;
                        rx_buff->in_frame = TRUE;

                        /* fall through */
                case INSIDE_FRAME:
                        switch(byte) {
                        case FIR_CE:
                                rx_buff->state = LINK_ESCAPE;
                                continue;
                        case FIR_XBOF:
                                /* 0x7f is not used in this framing */
                                pr_debug("%s: got XBOF without escape\n",
                                         stir->netdev->name);
                                goto frame_error;
                        case FIR_EOF:
                                rx_buff->state = OUTSIDE_FRAME;
                                rx_buff->in_frame = FALSE;
                                fir_eof(stir);
                                continue;
                        }
                        break;
                }

                /* add byte to rx buffer */
                if (unlikely(rx_buff->len >= rx_buff->truesize)) {
                        pr_debug("%s: fir frame exceeds %d\n",
                                 stir->netdev->name, rx_buff->truesize);
                        ++stir->netdev->stats.rx_over_errors;
                        goto error_recovery;
                }

                rx_buff->data[rx_buff->len++] = byte;
                continue;

        frame_error:
                ++stir->netdev->stats.rx_frame_errors;

        error_recovery:
                ++stir->netdev->stats.rx_errors;
                rx_buff->state = OUTSIDE_FRAME;
                rx_buff->in_frame = FALSE;
        }
}

/* Unwrap SIR stuffed data and bump it up to IrLAP */
static void stir_sir_chars(struct stir_cb *stir,
                            const __u8 *bytes, int len)
{
        int i;

        for (i = 0; i < len; i++)
                async_unwrap_char(stir->netdev, &stir->netdev->stats,
                                  &stir->rx_buff, bytes[i]);
}

static inline void unwrap_chars(struct stir_cb *stir,
                                const __u8 *bytes, int length)
{
        if (isfir(stir->speed))
                stir_fir_chars(stir, bytes, length);
        else
                stir_sir_chars(stir, bytes, length);
}

/* Mode parameters for each speed */
static const struct {
        unsigned speed;
        __u8 pdclk;
} stir_modes[] = {
        { 2400,    PDCLK_2400 },
        { 9600,    PDCLK_9600 },
        { 19200,   PDCLK_19200 },
        { 38400,   PDCLK_38400 },
        { 57600,   PDCLK_57600 },
        { 115200,  PDCLK_115200 },
        { 4000000, PDCLK_4000000 },
};


/*
 * Setup chip for speed.
 *  Called at startup to initialize the chip
 *  and on speed changes.
 *
 * Note: Write multiple registers doesn't appear to work
 */
static int change_speed(struct stir_cb *stir, unsigned speed)
{
        int i, err;
        __u8 mode;

        for (i = 0; i < ARRAY_SIZE(stir_modes); ++i) {
                if (speed == stir_modes[i].speed)
                        goto found;
        }

        dev_warn(&stir->netdev->dev, "invalid speed %d\n", speed);
        return -EINVAL;

 found:
        pr_debug("speed change from %d to %d\n", stir->speed, speed);

        /* Reset modulator */
        err = write_reg(stir, REG_CTRL1, CTRL1_SRESET);
        if (err)
                goto out;

        /* Undocumented magic to tweak the DPLL */
        err = write_reg(stir, REG_DPLL, 0x15);
        if (err)
                goto out;

        /* Set clock */
        err = write_reg(stir, REG_PDCLK, stir_modes[i].pdclk);
        if (err)
                goto out;

        mode = MODE_NRESET | MODE_FASTRX;
        if (isfir(speed))
                mode |= MODE_FIR | MODE_FFRSTEN;
        else
                mode |= MODE_SIR;

        if (speed == 2400)
                mode |= MODE_2400;

        err = write_reg(stir, REG_MODE, mode);
        if (err)
                goto out;

        /* This resets TEMIC style transceiver if any. */
        err = write_reg(stir, REG_CTRL1,
                        CTRL1_SDMODE | (tx_power & 3) << 1);
        if (err)
                goto out;

        err = write_reg(stir, REG_CTRL1, (tx_power & 3) << 1);
        if (err)
                goto out;

        /* Reset sensitivity */
        err = write_reg(stir, REG_CTRL2, (rx_sensitivity & 7) << 5);
 out:
        stir->speed = speed;
        return err;
}

/*
 * Called from net/core when new frame is available.
 */
static netdev_tx_t stir_hard_xmit(struct sk_buff *skb,
                                        struct net_device *netdev)
{
        struct stir_cb *stir = netdev_priv(netdev);

        netif_stop_queue(netdev);

        /* the IRDA wrapping routines don't deal with non linear skb */
        SKB_LINEAR_ASSERT(skb);

        skb = xchg(&stir->tx_pending, skb);
        wake_up_process(stir->thread);
        
        /* this should never happen unless stop/wakeup problem */
        if (unlikely(skb)) {
                WARN_ON(1);
                dev_kfree_skb(skb);
        }

        return NETDEV_TX_OK;
}

/*
 * Wait for the transmit FIFO to have space for next data
 *
 * If space < 0 then wait till FIFO completely drains.
 * FYI: can take up to 13 seconds at 2400baud.
 */
static int fifo_txwait(struct stir_cb *stir, int space)
{
        int err;
        unsigned long count, status;
        unsigned long prev_count = 0x1fff;

        /* Read FIFO status and count */
        for (;; prev_count = count) {
                err = read_reg(stir, REG_FIFOCTL, stir->fifo_status, 
                                   FIFO_REGS_SIZE);
                if (unlikely(err != FIFO_REGS_SIZE)) {
                        dev_warn(&stir->netdev->dev,
                                 "FIFO register read error: %d\n", err);

                        return err;
                }

                status = stir->fifo_status[0];
                count = (unsigned)(stir->fifo_status[2] & 0x1f) << 8 
                        | stir->fifo_status[1];

                pr_debug("fifo status 0x%lx count %lu\n", status, count);

                /* is fifo receiving already, or empty */
                if (!(status & FIFOCTL_DIR) ||
                    (status & FIFOCTL_EMPTY))
                        return 0;

                if (signal_pending(current))
                        return -EINTR;

                /* shutting down? */
                if (!netif_running(stir->netdev) ||
                    !netif_device_present(stir->netdev))
                        return -ESHUTDOWN;

                /* only waiting for some space */
                if (space >= 0 && STIR_FIFO_SIZE - 4 > space + count)
                        return 0;

                /* queue confused */
                if (prev_count < count)
                        break;

                /* estimate transfer time for remaining chars */
                msleep((count * 8000) / stir->speed);
        }
                        
        err = write_reg(stir, REG_FIFOCTL, FIFOCTL_CLR);
        if (err) 
                return err;
        err = write_reg(stir, REG_FIFOCTL, 0);
        if (err)
                return err;

        return 0;
}


/* Wait for turnaround delay before starting transmit.  */
static void turnaround_delay(const struct stir_cb *stir, long us)
{
        long ticks;

        if (us <= 0)
                return;

        us -= ktime_us_delta(ktime_get(), stir->rx_time);

        if (us < 10)
                return;

        ticks = us / (1000000 / HZ);
        if (ticks > 0)
                schedule_timeout_interruptible(1 + ticks);
        else
                udelay(us);
}

/*
 * Start receiver by submitting a request to the receive pipe.
 * If nothing is available it will return after rx_interval.
 */
static int receive_start(struct stir_cb *stir)
{
        /* reset state */
        stir->receiving = 1;

        stir->rx_buff.in_frame = FALSE;
        stir->rx_buff.state = OUTSIDE_FRAME;

        stir->rx_urb->status = 0;
        return usb_submit_urb(stir->rx_urb, GFP_KERNEL);
}

/* Stop all pending receive Urb's */
static void receive_stop(struct stir_cb *stir)
{
        stir->receiving = 0;
        usb_kill_urb(stir->rx_urb);

        if (stir->rx_buff.in_frame) 
                stir->netdev->stats.collisions++;
}
/*
 * Wrap data in socket buffer and send it.
 */
static void stir_send(struct stir_cb *stir, struct sk_buff *skb)
{
        unsigned wraplen;
        int first_frame = 0;

        /* if receiving, need to turnaround */
        if (stir->receiving) {
                receive_stop(stir);
                turnaround_delay(stir, irda_get_mtt(skb));
                first_frame = 1;
        }

        if (isfir(stir->speed))
                wraplen = wrap_fir_skb(skb, stir->io_buf);
        else
                wraplen = wrap_sir_skb(skb, stir->io_buf);
                
        /* check for space available in fifo */
        if (!first_frame)
                fifo_txwait(stir, wraplen);

        stir->netdev->stats.tx_packets++;
        stir->netdev->stats.tx_bytes += skb->len;
        stir->netdev->trans_start = jiffies;
        pr_debug("send %d (%d)\n", skb->len, wraplen);

        if (usb_bulk_msg(stir->usbdev, usb_sndbulkpipe(stir->usbdev, 1),
                         stir->io_buf, wraplen,
                         NULL, TRANSMIT_TIMEOUT))
                stir->netdev->stats.tx_errors++;
}

/*
 * Transmit state machine thread
 */
static int stir_transmit_thread(void *arg)
{
        struct stir_cb *stir = arg;
        struct net_device *dev = stir->netdev;
        struct sk_buff *skb;

        while (!kthread_should_stop()) {
#ifdef CONFIG_PM
                /* if suspending, then power off and wait */
                if (unlikely(freezing(current))) {
                        if (stir->receiving)
                                receive_stop(stir);
                        else
                                fifo_txwait(stir, -1);

                        write_reg(stir, REG_CTRL1, CTRL1_TXPWD|CTRL1_RXPWD);

                        try_to_freeze();

                        if (change_speed(stir, stir->speed))
                                break;
                }
#endif

                /* if something to send? */
                skb = xchg(&stir->tx_pending, NULL);
                if (skb) {
                        unsigned new_speed = irda_get_next_speed(skb);
                        netif_wake_queue(dev);

                        if (skb->len > 0)
                                stir_send(stir, skb);
                        dev_kfree_skb(skb);

                        if ((new_speed != -1) && (stir->speed != new_speed)) {
                                if (fifo_txwait(stir, -1) ||
                                    change_speed(stir, new_speed))
                                        break;
                        }
                        continue;
                }

                /* nothing to send? start receiving */
                if (!stir->receiving &&
                    irda_device_txqueue_empty(dev)) {
                        /* Wait otherwise chip gets confused. */
                        if (fifo_txwait(stir, -1))
                                break;

                        if (unlikely(receive_start(stir))) {
                                if (net_ratelimit())
                                        dev_info(&dev->dev,
                                                 "%s: receive usb submit failed\n",
                                                 stir->netdev->name);
                                stir->receiving = 0;
                                msleep(10);
                                continue;
                        }
                }

                /* sleep if nothing to send */
                set_current_state(TASK_INTERRUPTIBLE);
                schedule();

        }
        return 0;
}


/*
 * USB bulk receive completion callback.
 * Wakes up every ms (usb round trip) with wrapped 
 * data.
 */
static void stir_rcv_irq(struct urb *urb)
{
        struct stir_cb *stir = urb->context;
        int err;

        /* in process of stopping, just drop data */
        if (!netif_running(stir->netdev))
                return;

        /* unlink, shutdown, unplug, other nasties */
        if (urb->status != 0) 
                return;

        if (urb->actual_length > 0) {
                pr_debug("receive %d\n", urb->actual_length);
                unwrap_chars(stir, urb->transfer_buffer,
                             urb->actual_length);

                stir->rx_time = ktime_get();
        }

        /* kernel thread is stopping receiver don't resubmit */
        if (!stir->receiving)
                return;

        /* resubmit existing urb */
        err = usb_submit_urb(urb, GFP_ATOMIC);

        /* in case of error, the kernel thread will restart us */
        if (err) {
                dev_warn(&stir->netdev->dev, "usb receive submit error: %d\n",
                         err);
                stir->receiving = 0;
                wake_up_process(stir->thread);
        }
}

/*
 * Function stir_net_open (dev)
 *
 *    Network device is taken up. Usually this is done by "ifconfig irda0 up"
 */
static int stir_net_open(struct net_device *netdev)
{
        struct stir_cb *stir = netdev_priv(netdev);
        int err;
        char hwname[16];

        err = usb_clear_halt(stir->usbdev, usb_sndbulkpipe(stir->usbdev, 1));
        if (err)
                goto err_out1;
        err = usb_clear_halt(stir->usbdev, usb_rcvbulkpipe(stir->usbdev, 2));
        if (err)
                goto err_out1;

        err = change_speed(stir, 9600);
        if (err)
                goto err_out1;

        err = -ENOMEM;

        /* Initialize for SIR/FIR to copy data directly into skb.  */
        stir->receiving = 0;
        stir->rx_buff.truesize = IRDA_SKB_MAX_MTU;
        stir->rx_buff.skb = dev_alloc_skb(IRDA_SKB_MAX_MTU);
        if (!stir->rx_buff.skb) 
                goto err_out1;

        skb_reserve(stir->rx_buff.skb, 1);
        stir->rx_buff.head = stir->rx_buff.skb->data;
        stir->rx_time = ktime_get();

        stir->rx_urb = usb_alloc_urb(0, GFP_KERNEL);
        if (!stir->rx_urb) 
                goto err_out2;

        stir->io_buf = kmalloc(STIR_FIFO_SIZE, GFP_KERNEL);
        if (!stir->io_buf)
                goto err_out3;

        usb_fill_bulk_urb(stir->rx_urb, stir->usbdev,
                          usb_rcvbulkpipe(stir->usbdev, 2),
                          stir->io_buf, STIR_FIFO_SIZE,
                          stir_rcv_irq, stir);

        stir->fifo_status = kmalloc(FIFO_REGS_SIZE, GFP_KERNEL);
        if (!stir->fifo_status) 
                goto err_out4;
                
        /*
         * Now that everything should be initialized properly,
         * Open new IrLAP layer instance to take care of us...
         * Note : will send immediately a speed change...
         */
        sprintf(hwname, "usb#%d", stir->usbdev->devnum);
        stir->irlap = irlap_open(netdev, &stir->qos, hwname);
        if (!stir->irlap) {
                dev_err(&stir->usbdev->dev, "irlap_open failed\n");
                goto err_out5;
        }

        /** Start kernel thread for transmit.  */
        stir->thread = kthread_run(stir_transmit_thread, stir,
                                   "%s", stir->netdev->name);
        if (IS_ERR(stir->thread)) {
                err = PTR_ERR(stir->thread);
                dev_err(&stir->usbdev->dev, "unable to start kernel thread\n");
                goto err_out6;
        }

        netif_start_queue(netdev);

        return 0;

 err_out6:
        irlap_close(stir->irlap);
 err_out5:
        kfree(stir->fifo_status);
 err_out4:
        kfree(stir->io_buf);
 err_out3:
        usb_free_urb(stir->rx_urb);
 err_out2:
        kfree_skb(stir->rx_buff.skb);
 err_out1:
        return err;
}

/*
 * Function stir_net_close (stir)
 *
 *    Network device is taken down. Usually this is done by
 *    "ifconfig irda0 down"
 */
static int stir_net_close(struct net_device *netdev)
{
        struct stir_cb *stir = netdev_priv(netdev);

        /* Stop transmit processing */
        netif_stop_queue(netdev);

        /* Kill transmit thread */
        kthread_stop(stir->thread);
        kfree(stir->fifo_status);

        /* Mop up receive urb's */
        usb_kill_urb(stir->rx_urb);
        
        kfree(stir->io_buf);
        usb_free_urb(stir->rx_urb);
        kfree_skb(stir->rx_buff.skb);

        /* Stop and remove instance of IrLAP */
        if (stir->irlap)
                irlap_close(stir->irlap);

        stir->irlap = NULL;

        return 0;
}

/*
 * IOCTLs : Extra out-of-band network commands...
 */
static int stir_net_ioctl(struct net_device *netdev, struct ifreq *rq, int cmd)
{
        struct if_irda_req *irq = (struct if_irda_req *) rq;
        struct stir_cb *stir = netdev_priv(netdev);
        int ret = 0;

        switch (cmd) {
        case SIOCSBANDWIDTH: /* Set bandwidth */
                if (!capable(CAP_NET_ADMIN))
                        return -EPERM;

                /* Check if the device is still there */
                if (netif_device_present(stir->netdev))
                        ret = change_speed(stir, irq->ifr_baudrate);
                break;

        case SIOCSMEDIABUSY: /* Set media busy */
                if (!capable(CAP_NET_ADMIN))
                        return -EPERM;

                /* Check if the IrDA stack is still there */
                if (netif_running(stir->netdev))
                        irda_device_set_media_busy(stir->netdev, TRUE);
                break;

        case SIOCGRECEIVING:
                /* Only approximately true */
                irq->ifr_receiving = stir->receiving;
                break;

        default:
                ret = -EOPNOTSUPP;
        }

        return ret;
}

static const struct net_device_ops stir_netdev_ops = {
        .ndo_open       = stir_net_open,
        .ndo_stop       = stir_net_close,
        .ndo_start_xmit = stir_hard_xmit,
        .ndo_do_ioctl   = stir_net_ioctl,
};

/*
 * This routine is called by the USB subsystem for each new device
 * in the system. We need to check if the device is ours, and in
 * this case start handling it.
 * Note : it might be worth protecting this function by a global
 * spinlock... Or not, because maybe USB already deal with that...
 */
static int stir_probe(struct usb_interface *intf,
                      const struct usb_device_id *id)
{
        struct usb_device *dev = interface_to_usbdev(intf);
        struct stir_cb *stir = NULL;
        struct net_device *net;
        int ret = -ENOMEM;

        /* Allocate network device container. */
        net = alloc_irdadev(sizeof(*stir));
        if(!net)
                goto err_out1;

        SET_NETDEV_DEV(net, &intf->dev);
        stir = netdev_priv(net);
        stir->netdev = net;
        stir->usbdev = dev;

        ret = usb_reset_configuration(dev);
        if (ret != 0) {
                dev_err(&intf->dev, "usb reset configuration failed\n");
                goto err_out2;
        }

        printk(KERN_INFO "SigmaTel STIr4200 IRDA/USB found at address %d, "
                "Vendor: %x, Product: %x\n",
               dev->devnum, le16_to_cpu(dev->descriptor.idVendor),
               le16_to_cpu(dev->descriptor.idProduct));

        /* Initialize QoS for this device */
        irda_init_max_qos_capabilies(&stir->qos);

        /* That's the Rx capability. */
        stir->qos.baud_rate.bits       &= IR_2400 | IR_9600 | IR_19200 |
                                         IR_38400 | IR_57600 | IR_115200 |
                                         (IR_4000000 << 8);
        stir->qos.min_turn_time.bits   &= qos_mtt_bits;
        irda_qos_bits_to_value(&stir->qos);

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

        ret = register_netdev(net);
        if (ret != 0)
                goto err_out2;

        dev_info(&intf->dev, "IrDA: Registered SigmaTel device %s\n",
                 net->name);

        usb_set_intfdata(intf, stir);

        return 0;

err_out2:
        free_netdev(net);
err_out1:
        return ret;
}

/*
 * The current device is removed, the USB layer tell us to shut it down...
 */
static void stir_disconnect(struct usb_interface *intf)
{
        struct stir_cb *stir = usb_get_intfdata(intf);

        if (!stir)
                return;

        unregister_netdev(stir->netdev);
        free_netdev(stir->netdev);

        usb_set_intfdata(intf, NULL);
}

#ifdef CONFIG_PM
/* USB suspend, so power off the transmitter/receiver */
static int stir_suspend(struct usb_interface *intf, pm_message_t message)
{
        struct stir_cb *stir = usb_get_intfdata(intf);

        netif_device_detach(stir->netdev);
        return 0;
}

/* Coming out of suspend, so reset hardware */
static int stir_resume(struct usb_interface *intf)
{
        struct stir_cb *stir = usb_get_intfdata(intf);

        netif_device_attach(stir->netdev);

        /* receiver restarted when send thread wakes up */
        return 0;
}
#endif

/*
 * USB device callbacks
 */
static struct usb_driver irda_driver = {
        .name           = "stir4200",
        .probe          = stir_probe,
        .disconnect     = stir_disconnect,
        .id_table       = dongles,
#ifdef CONFIG_PM
        .suspend        = stir_suspend,
        .resume         = stir_resume,
#endif
};

module_usb_driver(irda_driver);