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garmin_gps.c

/*
 * Garmin GPS driver
 *
 * Copyright (C) 2006,2007 Hermann Kneissel herkne@users.sourceforge.net
 *
 * The latest version of the driver can be found at
 * http://sourceforge.net/projects/garmin-gps/
 *
 * This driver has been derived from v2.1 of the visor driver.
 *
 * 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.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111 USA
 */

#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/timer.h>
#include <linux/tty.h>
#include <linux/tty_driver.h>
#include <linux/tty_flip.h>
#include <linux/module.h>
#include <linux/spinlock.h>
#include <asm/uaccess.h>
#include <asm/atomic.h>
#include <linux/usb.h>
#include <linux/usb/serial.h>

#include <linux/version.h>

/* the mode to be set when the port ist opened */
static int initial_mode = 1;

/* debug flag */
static int debug = 0;

#define GARMIN_VENDOR_ID             0x091E

/*
 * Version Information
 */

#define VERSION_MAJOR   0
#define VERSION_MINOR   31

#define _STR(s) #s
#define _DRIVER_VERSION(a,b) "v" _STR(a) "." _STR(b)
#define DRIVER_VERSION _DRIVER_VERSION(VERSION_MAJOR, VERSION_MINOR)
#define DRIVER_AUTHOR "hermann kneissel"
#define DRIVER_DESC "garmin gps driver"

/* error codes returned by the driver */
#define EINVPKT   1000  /* invalid packet structure */


// size of the header of a packet using the usb protocol
#define GARMIN_PKTHDR_LENGTH  12

// max. possible size of a packet using the serial protocol 
#define MAX_SERIAL_PKT_SIZ (3+255+3)

// max. possible size of a packet with worst case stuffing
#define MAX_SERIAL_PKT_SIZ_STUFFED MAX_SERIAL_PKT_SIZ+256

// size of a buffer able to hold a complete (no stuffing) packet
// (the document protocol does not contain packets with a larger
//  size, but in theory a packet may be 64k+12 bytes - if in
//  later protocol versions larger packet sizes occur, this value
//  should be increased accordingly, so the input buffer is always 
//  large enough the store a complete packet inclusive header)
#define GPS_IN_BUFSIZ  (GARMIN_PKTHDR_LENGTH+MAX_SERIAL_PKT_SIZ) 

// size of a buffer able to hold a complete (incl. stuffing) packet
#define GPS_OUT_BUFSIZ (GARMIN_PKTHDR_LENGTH+MAX_SERIAL_PKT_SIZ_STUFFED) 

// where to place the packet id of a serial packet, so we can
// prepend the usb-packet header without the need to move the
// packets data
#define GSP_INITIAL_OFFSET (GARMIN_PKTHDR_LENGTH-2)

// max. size of incoming private packets (header+1 param)
#define PRIVPKTSIZ (GARMIN_PKTHDR_LENGTH+4)

#define GARMIN_LAYERID_TRANSPORT  0
#define GARMIN_LAYERID_APPL      20
// our own layer-id to use for some control mechanisms
#define GARMIN_LAYERID_PRIVATE      0x01106E4B

#define GARMIN_PKTID_PVT_DATA 51
#define GARMIN_PKTID_L001_COMMAND_DATA 10

#define CMND_ABORT_TRANSFER 0

// packet ids used in private layer
#define PRIV_PKTID_SET_DEBUG  1
#define PRIV_PKTID_SET_MODE   2
#define PRIV_PKTID_INFO_REQ   3
#define PRIV_PKTID_INFO_RESP  4
#define PRIV_PKTID_RESET_REQ  5
#define PRIV_PKTID_SET_DEF_MODE     6


#define ETX 0x03
#define DLE 0x10
#define ACK 0x06
#define NAK 0x15

/* structure used to queue incoming packets */
struct garmin_packet {
      struct list_head  list;
      int               seq;
      int               size; // the real size of the data array, always > 0
      __u8              data[1];
};

/* structure used to keep the current state of the driver */
struct garmin_data {
      __u8   state;
      __u16  flags;
      __u8   mode;
      __u8   ignorePkts;
      __u8   count;
      __u8   pkt_id;
      __u32  serial_num;
      struct timer_list timer;
      struct usb_serial_port *port;
      int    seq_counter;
      int    insize;
      int    outsize;
      __u8   inbuffer [GPS_IN_BUFSIZ];  /* tty -> usb */
      __u8   outbuffer[GPS_OUT_BUFSIZ]; /* usb -> tty */
      __u8   privpkt[4*6];
      atomic_t req_count;
      atomic_t resp_count;
      spinlock_t lock;
      struct list_head pktlist;
};


#define STATE_NEW            0
#define STATE_INITIAL_DELAY  1
#define STATE_TIMEOUT        2
#define STATE_SESSION_REQ1   3
#define STATE_SESSION_REQ2   4
#define STATE_ACTIVE         5

#define STATE_RESET          8
#define STATE_DISCONNECTED   9
#define STATE_WAIT_TTY_ACK  10
#define STATE_GSP_WAIT_DATA 11

#define MODE_NATIVE          0
#define MODE_GARMIN_SERIAL   1

// Flags used in garmin_data.flags:
#define FLAGS_SESSION_REPLY_MASK  0x00C0
#define FLAGS_SESSION_REPLY1_SEEN 0x0080
#define FLAGS_SESSION_REPLY2_SEEN 0x0040
#define FLAGS_BULK_IN_ACTIVE      0x0020
#define FLAGS_BULK_IN_RESTART     0x0010
#define FLAGS_THROTTLED           0x0008
#define CLEAR_HALT_REQUIRED       0x0001

#define FLAGS_QUEUING             0x0100
#define FLAGS_DROP_DATA           0x0800

#define FLAGS_GSP_SKIP            0x1000
#define FLAGS_GSP_DLESEEN         0x2000






/* function prototypes */
static void gsp_next_packet(struct garmin_data * garmin_data_p);
static int  garmin_write_bulk(struct usb_serial_port *port,
                       const unsigned char *buf, int count,
                       int dismiss_ack);

/* some special packets to be send or received */
static unsigned char const GARMIN_START_SESSION_REQ[]
      = { 0, 0, 0, 0,  5, 0, 0, 0, 0, 0, 0, 0 };
static unsigned char const GARMIN_START_SESSION_REQ2[]
      = { 0, 0, 0, 0, 16, 0, 0, 0, 0, 0, 0, 0 };
static unsigned char const GARMIN_START_SESSION_REPLY[]
      = { 0, 0, 0, 0,  6, 0, 0, 0, 4, 0, 0, 0 };
static unsigned char const GARMIN_SESSION_ACTIVE_REPLY[]
      = { 0, 0, 0, 0, 17, 0, 0, 0, 4, 0, 0, 0, 0, 16, 0, 0 };
static unsigned char const GARMIN_BULK_IN_AVAIL_REPLY[]
      = { 0, 0, 0, 0,  2, 0, 0, 0, 0, 0, 0, 0 };
static unsigned char const GARMIN_APP_LAYER_REPLY[]
      = { 0x14, 0, 0, 0 };
static unsigned char const GARMIN_START_PVT_REQ[]
      = { 20, 0, 0, 0,  10, 0, 0, 0, 2, 0, 0, 0, 49, 0 };
static unsigned char const GARMIN_STOP_PVT_REQ[]
      = { 20, 0, 0, 0,  10, 0, 0, 0, 2, 0, 0, 0, 50, 0 };
static unsigned char const GARMIN_STOP_TRANSFER_REQ[]
      = { 20, 0, 0, 0,  10, 0, 0, 0, 2, 0, 0, 0, 0, 0 };
static unsigned char const GARMIN_STOP_TRANSFER_REQ_V2[]
      = { 20, 0, 0, 0,  10, 0, 0, 0, 1, 0, 0, 0, 0 };
static unsigned char const PRIVATE_REQ[]
      =    { 0x4B, 0x6E, 0x10, 0x01,  0xFF, 0, 0, 0, 0xFF, 0, 0, 0 };



static struct usb_device_id id_table [] = {
      /* the same device id seems to be used by all usb enabled gps devices */
      { USB_DEVICE(GARMIN_VENDOR_ID, 3 ) },
      { }                           /* Terminating entry */
};

MODULE_DEVICE_TABLE (usb, id_table);

static struct usb_driver garmin_driver = {
      .name =           "garmin_gps",
      .probe =    usb_serial_probe,
      .disconnect =     usb_serial_disconnect,
      .id_table = id_table,
      .no_dynamic_id = 1,
};


static inline int noResponseFromAppLayer(struct garmin_data * garmin_data_p)
{
      return atomic_read(&garmin_data_p->req_count) == atomic_read(&garmin_data_p->resp_count);
}


static inline int getLayerId(const __u8 *usbPacket)
{
      return __le32_to_cpup((__le32 *)(usbPacket));
}

static inline int getPacketId(const __u8 *usbPacket)
{
      return __le32_to_cpup((__le32 *)(usbPacket+4));
}

static inline int getDataLength(const __u8 *usbPacket)
{
      return __le32_to_cpup((__le32 *)(usbPacket+8));
}


/*
 * check if the usb-packet in buf contains an abort-transfer command.
 * (if yes, all queued data will be dropped)
 */
static inline int isAbortTrfCmnd(const unsigned char *buf)
{
      if (0 == memcmp(buf, GARMIN_STOP_TRANSFER_REQ, 
                      sizeof(GARMIN_STOP_TRANSFER_REQ)) ||
          0 == memcmp(buf, GARMIN_STOP_TRANSFER_REQ_V2, 
                      sizeof(GARMIN_STOP_TRANSFER_REQ_V2)))
            return 1;
      else
            return 0;
}



static void send_to_tty(struct usb_serial_port *port,
                  char *data, unsigned int actual_length)
{
      struct tty_struct *tty = port->tty;

      if (tty && actual_length) {

            usb_serial_debug_data(debug, &port->dev, 
                              __FUNCTION__, actual_length, data);

            tty_buffer_request_room(tty, actual_length);
            tty_insert_flip_string(tty, data, actual_length);
            tty_flip_buffer_push(tty);
      }
}


/******************************************************************************
 * packet queue handling
 ******************************************************************************/

/*
 * queue a received (usb-)packet for later processing
 */
static int pkt_add(struct garmin_data * garmin_data_p,
               unsigned char *data, unsigned int data_length)
{
      int state = 0;
      int result = 0;
      unsigned long flags;
      struct garmin_packet *pkt;

      /* process only packets containg data ... */
      if (data_length) {
            pkt = kmalloc(sizeof(struct garmin_packet)+data_length,
                          GFP_ATOMIC);
            if (pkt == NULL) {
                  dev_err(&garmin_data_p->port->dev, "out of memory\n");
                  return 0;
            }
            pkt->size = data_length;
            memcpy(pkt->data, data, data_length);

            spin_lock_irqsave(&garmin_data_p->lock, flags);
            garmin_data_p->flags |= FLAGS_QUEUING;
            result = list_empty(&garmin_data_p->pktlist);
            pkt->seq = garmin_data_p->seq_counter++;
            list_add_tail(&pkt->list, &garmin_data_p->pktlist);
            state = garmin_data_p->state;
            spin_unlock_irqrestore(&garmin_data_p->lock, flags);

            /* in serial mode, if someone is waiting for data from
               the device, iconvert and send the next packet to tty. */
            if (result && (state == STATE_GSP_WAIT_DATA)) {
                  gsp_next_packet(garmin_data_p);
            }
      }
      return result;
}


/* get the next pending packet */
static struct garmin_packet *pkt_pop(struct garmin_data * garmin_data_p)
{
      unsigned long flags;
      struct garmin_packet *result = NULL;

      spin_lock_irqsave(&garmin_data_p->lock, flags);
      if (!list_empty(&garmin_data_p->pktlist)) {
            result = (struct garmin_packet *)garmin_data_p->pktlist.next;
            list_del(&result->list);
      }
      spin_unlock_irqrestore(&garmin_data_p->lock, flags);
      return result;
}


/* free up all queued data */
static void pkt_clear(struct garmin_data * garmin_data_p)
{
      unsigned long flags;
      struct garmin_packet *result = NULL;

      dbg("%s", __FUNCTION__);

      spin_lock_irqsave(&garmin_data_p->lock, flags);
      while (!list_empty(&garmin_data_p->pktlist)) {
            result = (struct garmin_packet *)garmin_data_p->pktlist.next;
            list_del(&result->list);
            kfree(result);
      }
      spin_unlock_irqrestore(&garmin_data_p->lock, flags);
}


/******************************************************************************
 * garmin serial protocol handling handling
 ******************************************************************************/

/* send an ack packet back to the tty */
static int gsp_send_ack(struct garmin_data * garmin_data_p, __u8 pkt_id)
{
      __u8 pkt[10];
      __u8 cksum = 0;
      __u8 *ptr = pkt;
      unsigned  l = 0;

      dbg("%s - pkt-id: 0x%X.", __FUNCTION__, 0xFF & pkt_id);

      *ptr++ = DLE;
      *ptr++ = ACK;
      cksum += ACK;

      *ptr++ = 2;
      cksum += 2;

      *ptr++ = pkt_id;
      cksum += pkt_id;

      if (pkt_id == DLE) {
            *ptr++ = DLE;
      }

      *ptr++ = 0;
      *ptr++ = 0xFF & (-cksum);
      *ptr++ = DLE;
      *ptr++ = ETX;

      l = ptr-pkt;

      send_to_tty(garmin_data_p->port, pkt, l);
      return 0;
}



/*
 * called for a complete packet received from tty layer
 *
 * the complete packet (pkzid ... cksum) is in garmin_data_p->inbuf starting
 * at GSP_INITIAL_OFFSET.
 *
 * count - number of bytes in the input buffer including space reserved for
 *         the usb header: GSP_INITIAL_OFFSET + number of bytes in packet 
 *         (including pkt-id, data-length a. cksum)
 */
static int gsp_rec_packet(struct garmin_data * garmin_data_p, int count)
{
      const __u8* recpkt = garmin_data_p->inbuffer+GSP_INITIAL_OFFSET;
      __le32 *usbdata = (__le32 *) garmin_data_p->inbuffer;

      int cksum = 0;
      int n = 0;
      int pktid = recpkt[0];
      int size = recpkt[1];

      usb_serial_debug_data(debug, &garmin_data_p->port->dev,
                         __FUNCTION__, count-GSP_INITIAL_OFFSET, recpkt);

      if (size != (count-GSP_INITIAL_OFFSET-3)) {
            dbg("%s - invalid size, expected %d bytes, got %d",
                  __FUNCTION__, size, (count-GSP_INITIAL_OFFSET-3));
            return -EINVPKT;
      }

      cksum += *recpkt++;
      cksum += *recpkt++;

      // sanity check, remove after test ...
      if ((__u8*)&(usbdata[3]) != recpkt) {
            dbg("%s - ptr mismatch %p - %p",
                  __FUNCTION__, &(usbdata[4]), recpkt);
            return -EINVPKT;
      }

      while (n < size) {
            cksum += *recpkt++;
            n++;
      }

      if ((0xff & (cksum + *recpkt)) != 0) {
            dbg("%s - invalid checksum, expected %02x, got %02x",
                  __FUNCTION__, 0xff & -cksum, 0xff & *recpkt);
            return -EINVPKT;
      }

      usbdata[0] = __cpu_to_le32(GARMIN_LAYERID_APPL);
      usbdata[1] = __cpu_to_le32(pktid);
      usbdata[2] = __cpu_to_le32(size);

      garmin_write_bulk (garmin_data_p->port, garmin_data_p->inbuffer,
                     GARMIN_PKTHDR_LENGTH+size, 0);

      /* if this was an abort-transfer command, flush all
         queued data. */
      if (isAbortTrfCmnd(garmin_data_p->inbuffer)) {
            garmin_data_p->flags |= FLAGS_DROP_DATA;
            pkt_clear(garmin_data_p);
      }

      return count;
}



/*
 * Called for data received from tty
 *
 * buf contains the data read, it may span more than one packet or even
 * incomplete packets
 *
 * input record should be a serial-record, but it may not be complete.
 * Copy it into our local buffer, until an etx is seen (or an error
 * occurs).
 * Once the record is complete, convert into a usb packet and send it
 * to the bulk pipe, send an ack back to the tty.
 *
 * If the input is an ack, just send the last queued packet to the
 * tty layer.
 *
 * if the input is an abort command, drop all queued data.
 */

static int gsp_receive(struct garmin_data * garmin_data_p,
                   const unsigned char *buf, int count)
{
      unsigned long flags;
      int offs = 0;
      int ack_or_nak_seen = 0;
      int i = 0;
      __u8 *dest;
      int size;
      // dleSeen: set if last byte read was a DLE
      int dleSeen;
      // skip: if set, skip incoming data until possible start of
      //       new packet
      int skip;
      __u8 data;

      spin_lock_irqsave(&garmin_data_p->lock, flags);
      dest = garmin_data_p->inbuffer;
      size = garmin_data_p->insize;
      dleSeen = garmin_data_p->flags & FLAGS_GSP_DLESEEN;
      skip = garmin_data_p->flags & FLAGS_GSP_SKIP;
      spin_unlock_irqrestore(&garmin_data_p->lock, flags);

      dbg("%s - dle=%d skip=%d size=%d count=%d",
            __FUNCTION__, dleSeen, skip, size, count);

      if (size == 0) {
            size = GSP_INITIAL_OFFSET;
      }

      while (offs < count) {

            data = *(buf+offs);
            offs ++;

            if (data == DLE) {
                  if (skip) { /* start of a new pkt */
                        skip = 0;
                        size = GSP_INITIAL_OFFSET;
                        dleSeen = 1;
                  } else if (dleSeen) {
                        dest[size++] = data;
                        dleSeen = 0;
                  } else {
                        dleSeen = 1;
                  }
            } else if (data == ETX) {
                  if (dleSeen) {
                        /* packet complete */

                        data = dest[GSP_INITIAL_OFFSET];

                        if (data == ACK) {
                              ack_or_nak_seen = ACK;
                              dbg("ACK packet complete.");
                        } else if (data == NAK) {
                              ack_or_nak_seen = NAK;
                              dbg("NAK packet complete.");
                        } else {
                              dbg("packet complete "
                                            "- id=0x%X.",
                                            0xFF & data);
                              gsp_rec_packet(garmin_data_p, size);
                        }

                        skip = 1;
                        size = GSP_INITIAL_OFFSET;
                        dleSeen = 0;
                  } else {
                        dest[size++] = data;
                  }
            } else if (!skip) {

                  if (dleSeen) {
                        dbg("non-masked DLE at %d - restarting", i);
                        size = GSP_INITIAL_OFFSET;
                        dleSeen = 0;
                  }

                  dest[size++] = data;
            }

            if (size >= GPS_IN_BUFSIZ) {
                  dbg("%s - packet too large.", __FUNCTION__);
                  skip = 1;
                  size = GSP_INITIAL_OFFSET;
                  dleSeen = 0;
            }
      }

      spin_lock_irqsave(&garmin_data_p->lock, flags);

      garmin_data_p->insize = size;

      // copy flags back to structure
      if (skip)
            garmin_data_p->flags |= FLAGS_GSP_SKIP;
      else
            garmin_data_p->flags &= ~FLAGS_GSP_SKIP;

      if (dleSeen)
            garmin_data_p->flags |= FLAGS_GSP_DLESEEN;
      else
            garmin_data_p->flags &= ~FLAGS_GSP_DLESEEN;

      if (ack_or_nak_seen) {
            garmin_data_p->state = STATE_GSP_WAIT_DATA;
      }

      spin_unlock_irqrestore(&garmin_data_p->lock, flags);

      if (ack_or_nak_seen) {
            gsp_next_packet(garmin_data_p);
      }

      return count;
}




/*
 * Sends a usb packet to the tty
 *
 * Assumes, that all packages and at an usb-packet boundary.
 *
 * return <0 on error, 0 if packet is incomplete or > 0 if packet was sent
 */
static int gsp_send(struct garmin_data * garmin_data_p,
                const unsigned char *buf, int count)
{
      const unsigned char *src;
      unsigned char *dst;
      int pktid = 0;
      int datalen = 0;
      int cksum = 0;
      int i=0;
      int k;

      dbg("%s - state %d - %d bytes.", __FUNCTION__,
               garmin_data_p->state, count);

      k = garmin_data_p->outsize;
      if ((k+count) > GPS_OUT_BUFSIZ) {
            dbg("packet too large");
            garmin_data_p->outsize = 0;
            return -4;
      }

      memcpy(garmin_data_p->outbuffer+k, buf, count);
      k += count;
      garmin_data_p->outsize = k;

      if (k >= GARMIN_PKTHDR_LENGTH) {
            pktid  = getPacketId(garmin_data_p->outbuffer);
            datalen= getDataLength(garmin_data_p->outbuffer);
            i = GARMIN_PKTHDR_LENGTH + datalen;
            if (k < i)
                  return 0;
      } else {
            return 0;
      }

      dbg("%s - %d bytes in buffer, %d bytes in pkt.", __FUNCTION__,
               k, i);

      /* garmin_data_p->outbuffer now contains a complete packet */

      usb_serial_debug_data(debug, &garmin_data_p->port->dev,
                               __FUNCTION__, k, garmin_data_p->outbuffer);

      garmin_data_p->outsize = 0;

      if (GARMIN_LAYERID_APPL != getLayerId(garmin_data_p->outbuffer)) {
            dbg("not an application packet (%d)", 
                    getLayerId(garmin_data_p->outbuffer));
            return -1;
      }

      if (pktid > 255) {
            dbg("packet-id %d too large", pktid);
            return -2;
      }

      if (datalen > 255) {
            dbg("packet-size %d too large", datalen);
            return -3;
      }

      /* the serial protocol should be able to handle this packet */

      k = 0;
      src = garmin_data_p->outbuffer+GARMIN_PKTHDR_LENGTH;
      for (i=0; i<datalen; i++) {
            if (*src++ == DLE)
                  k++;
      }

      src = garmin_data_p->outbuffer+GARMIN_PKTHDR_LENGTH;
      if (k > (GARMIN_PKTHDR_LENGTH-2)) {
            /* can't add stuffing DLEs in place, move data to end 
               of buffer ... */
            dst = garmin_data_p->outbuffer+GPS_OUT_BUFSIZ-datalen;
            memcpy(dst, src, datalen);
            src = dst;
      }

      dst = garmin_data_p->outbuffer;

      *dst++ = DLE;
      *dst++ = pktid;
      cksum += pktid;
      *dst++ = datalen;
      cksum += datalen;
      if (datalen == DLE)
            *dst++ = DLE;

      for (i=0; i<datalen; i++) {
            __u8 c = *src++;
            *dst++ = c;
            cksum += c;
            if (c == DLE)
                  *dst++ = DLE;
      }
            
      cksum = 0xFF & -cksum;
      *dst++ = cksum;
      if (cksum == DLE)
            *dst++ = DLE;
      *dst++ = DLE;
      *dst++ = ETX;

      i = dst-garmin_data_p->outbuffer;

      send_to_tty(garmin_data_p->port, garmin_data_p->outbuffer, i);

      garmin_data_p->pkt_id = pktid;
      garmin_data_p->state  = STATE_WAIT_TTY_ACK;

      return i;
}





/*
 * Process the next pending data packet - if there is one
 */
static void gsp_next_packet(struct garmin_data * garmin_data_p)
{
      struct garmin_packet *pkt = NULL;

      while ((pkt = pkt_pop(garmin_data_p)) != NULL) {
            dbg("%s - next pkt: %d", __FUNCTION__, pkt->seq);
            if (gsp_send(garmin_data_p, pkt->data, pkt->size) > 0) {
                  kfree(pkt);
                  return;
            }
            kfree(pkt);
      }
}




/******************************************************************************
 * garmin native mode
 ******************************************************************************/


/*
 * Called for data received from tty
 *
 * The input data is expected to be in garmin usb-packet format.
 *
 * buf contains the data read, it may span more than one packet
 * or even incomplete packets
 */
static int nat_receive(struct garmin_data * garmin_data_p,
                   const unsigned char *buf, int count)
{
      unsigned long flags;
      __u8 * dest;
      int offs = 0;
      int result = count;
      int len;

      while (offs < count) {
            // if buffer contains header, copy rest of data
            if (garmin_data_p->insize >= GARMIN_PKTHDR_LENGTH)
                  len = GARMIN_PKTHDR_LENGTH
                        +getDataLength(garmin_data_p->inbuffer);
            else
                  len = GARMIN_PKTHDR_LENGTH;

            if (len >= GPS_IN_BUFSIZ) {
                  /* seem to be an invalid packet, ignore rest of input */
                  dbg("%s - packet size too large: %d",
                          __FUNCTION__, len);
                  garmin_data_p->insize = 0;
                  count = 0;
                  result = -EINVPKT;
            } else {
                  len -= garmin_data_p->insize;
                  if (len > (count-offs))
                        len = (count-offs);
                  if (len > 0) {
                        dest = garmin_data_p->inbuffer
                                    +garmin_data_p->insize;
                        memcpy(dest, buf+offs, len);
                        garmin_data_p->insize += len;
                        offs += len;
                  }
            }

            /* do we have a complete packet ? */
            if (garmin_data_p->insize >= GARMIN_PKTHDR_LENGTH) {
                  len = GARMIN_PKTHDR_LENGTH+
                     getDataLength(garmin_data_p->inbuffer);
                  if (garmin_data_p->insize >= len) {
                        garmin_write_bulk (garmin_data_p->port,
                                           garmin_data_p->inbuffer,
                                           len, 0);
                        garmin_data_p->insize = 0;

                        /* if this was an abort-transfer command,
                           flush all queued data. */
                        if (isAbortTrfCmnd(garmin_data_p->inbuffer)) {
                              spin_lock_irqsave(&garmin_data_p->lock, flags);
                              garmin_data_p->flags |= FLAGS_DROP_DATA;
                              spin_unlock_irqrestore(&garmin_data_p->lock, flags);
                              pkt_clear(garmin_data_p);
                        }
                  }
            }
      }
      return result;
}


/******************************************************************************
 * private packets
 ******************************************************************************/

static void priv_status_resp(struct usb_serial_port *port)
{
      struct garmin_data * garmin_data_p = usb_get_serial_port_data(port);
      __le32 *pkt = (__le32 *)garmin_data_p->privpkt;

      pkt[0] = __cpu_to_le32(GARMIN_LAYERID_PRIVATE);
      pkt[1] = __cpu_to_le32(PRIV_PKTID_INFO_RESP);
      pkt[2] = __cpu_to_le32(12);
      pkt[3] = __cpu_to_le32(VERSION_MAJOR << 16 | VERSION_MINOR);
      pkt[4] = __cpu_to_le32(garmin_data_p->mode);
      pkt[5] = __cpu_to_le32(garmin_data_p->serial_num);

      send_to_tty(port, (__u8*)pkt, 6*4);
}


/******************************************************************************
 * Garmin specific driver functions
 ******************************************************************************/

static int process_resetdev_request(struct usb_serial_port *port)
{
      unsigned long flags;
      int status;
      struct garmin_data * garmin_data_p = usb_get_serial_port_data(port);

      spin_lock_irqsave(&garmin_data_p->lock, flags);
      garmin_data_p->flags &= ~(CLEAR_HALT_REQUIRED);
      garmin_data_p->state = STATE_RESET;
      garmin_data_p->serial_num = 0;
      spin_unlock_irqrestore(&garmin_data_p->lock, flags);

      usb_kill_urb (port->interrupt_in_urb);
      dbg("%s - usb_reset_device", __FUNCTION__ );
      status = usb_reset_device(port->serial->dev);
      if (status)
            dbg("%s - usb_reset_device failed: %d",
                  __FUNCTION__, status);
      return status;
}



/*
 * clear all cached data
 */
static int garmin_clear(struct garmin_data * garmin_data_p)
{
      unsigned long flags;
      int status = 0;

      struct usb_serial_port *port = garmin_data_p->port;

      if (port != NULL && atomic_read(&garmin_data_p->resp_count)) {
            /* send a terminate command */
            status = garmin_write_bulk(port, GARMIN_STOP_TRANSFER_REQ,
                                       sizeof(GARMIN_STOP_TRANSFER_REQ),
                                 1);
      }

      /* flush all queued data */
      pkt_clear(garmin_data_p);

      spin_lock_irqsave(&garmin_data_p->lock, flags);
      garmin_data_p->insize = 0;
      garmin_data_p->outsize = 0;
      spin_unlock_irqrestore(&garmin_data_p->lock, flags);

      return status;
}






static int garmin_init_session(struct usb_serial_port *port)
{
      unsigned long flags;
      struct usb_serial *serial = port->serial;
      struct garmin_data * garmin_data_p = usb_get_serial_port_data(port);
      int status = 0;

      if (status == 0) {
            usb_kill_urb (port->interrupt_in_urb);

            dbg("%s - adding interrupt input", __FUNCTION__);
            port->interrupt_in_urb->dev = serial->dev;
            status = usb_submit_urb(port->interrupt_in_urb, GFP_KERNEL);
            if (status)
                  dev_err(&serial->dev->dev,
                          "%s - failed submitting interrupt urb,"
                        " error %d\n",
                          __FUNCTION__, status);
      }

      if (status == 0) {
            dbg("%s - starting session ...", __FUNCTION__);
            garmin_data_p->state = STATE_ACTIVE;
            status = garmin_write_bulk(port, GARMIN_START_SESSION_REQ,
                                       sizeof(GARMIN_START_SESSION_REQ),
                                 0);

            if (status >= 0) {

                  spin_lock_irqsave(&garmin_data_p->lock, flags);
                  garmin_data_p->ignorePkts++;
                  spin_unlock_irqrestore(&garmin_data_p->lock, flags);

                  /* not needed, but the win32 driver does it too ... */
                  status = garmin_write_bulk(port,
                                       GARMIN_START_SESSION_REQ2,
                                             sizeof(GARMIN_START_SESSION_REQ2),
                                       0);
                  if (status >= 0) {
                        status = 0;
                        spin_lock_irqsave(&garmin_data_p->lock, flags);
                        garmin_data_p->ignorePkts++;
                        spin_unlock_irqrestore(&garmin_data_p->lock, flags);
                  }
            }
      }

      return status;
}





static int garmin_open (struct usb_serial_port *port, struct file *filp)
{
      unsigned long flags;
      int status = 0;
      struct garmin_data * garmin_data_p = usb_get_serial_port_data(port);

      dbg("%s - port %d", __FUNCTION__, port->number);

      /*
       * Force low_latency on so that our tty_push actually forces the data
       * through, otherwise it is scheduled, and with high data rates (like
       * with OHCI) data can get lost.
       */
      if (port->tty)
            port->tty->low_latency = 1;

      spin_lock_irqsave(&garmin_data_p->lock, flags);
      garmin_data_p->mode  = initial_mode;
      garmin_data_p->count = 0;
      garmin_data_p->flags = 0;
      atomic_set(&garmin_data_p->req_count, 0);
      atomic_set(&garmin_data_p->resp_count, 0);
      spin_unlock_irqrestore(&garmin_data_p->lock, flags);

      /* shutdown any bulk reads that might be going on */
      usb_kill_urb (port->write_urb);
      usb_kill_urb (port->read_urb);

      if (garmin_data_p->state == STATE_RESET) {
            status = garmin_init_session(port);
      }

      garmin_data_p->state = STATE_ACTIVE;

      return status;
}


static void garmin_close (struct usb_serial_port *port, struct file * filp)
{
      struct usb_serial *serial = port->serial;
      struct garmin_data * garmin_data_p = usb_get_serial_port_data(port);

      dbg("%s - port %d - mode=%d state=%d flags=0x%X", __FUNCTION__,
            port->number, garmin_data_p->mode,
            garmin_data_p->state, garmin_data_p->flags);

      if (!serial)
            return;

      garmin_clear(garmin_data_p);

      /* shutdown our urbs */
      usb_kill_urb (port->read_urb);
      usb_kill_urb (port->write_urb);

      if (noResponseFromAppLayer(garmin_data_p) ||
          ((garmin_data_p->flags & CLEAR_HALT_REQUIRED) != 0)) {
            process_resetdev_request(port);
            garmin_data_p->state = STATE_RESET;
      } else {
            garmin_data_p->state = STATE_DISCONNECTED;
      }
}


static void garmin_write_bulk_callback (struct urb *urb)
{
      unsigned long flags;
      struct usb_serial_port *port = (struct usb_serial_port *)urb->context;
      int status = urb->status;

      if (port) {
            struct garmin_data * garmin_data_p = usb_get_serial_port_data(port);

            dbg("%s - port %d", __FUNCTION__, port->number);

            if (GARMIN_LAYERID_APPL == getLayerId(urb->transfer_buffer)
                && (garmin_data_p->mode == MODE_GARMIN_SERIAL))  {
                  gsp_send_ack(garmin_data_p, ((__u8 *)urb->transfer_buffer)[4]);
            }

            if (status) {
                  dbg("%s - nonzero write bulk status received: %d",
                      __FUNCTION__, urb->status);
                  spin_lock_irqsave(&garmin_data_p->lock, flags);
                  garmin_data_p->flags |= CLEAR_HALT_REQUIRED;
                  spin_unlock_irqrestore(&garmin_data_p->lock, flags);
            }

            usb_serial_port_softint(port);
      }

      /* Ignore errors that resulted from garmin_write_bulk with dismiss_ack=1 */

      /* free up the transfer buffer, as usb_free_urb() does not do this */
      kfree (urb->transfer_buffer);
}


static int garmin_write_bulk (struct usb_serial_port *port,
                        const unsigned char *buf, int count,
                        int dismiss_ack)
{
      unsigned long flags;
      struct usb_serial *serial = port->serial;
      struct garmin_data * garmin_data_p = usb_get_serial_port_data(port);
      struct urb *urb;
      unsigned char *buffer;
      int status;

      dbg("%s - port %d, state %d", __FUNCTION__, port->number,
            garmin_data_p->state);

      spin_lock_irqsave(&garmin_data_p->lock, flags);
      garmin_data_p->flags &= ~FLAGS_DROP_DATA;
      spin_unlock_irqrestore(&garmin_data_p->lock, flags);

      buffer = kmalloc (count, GFP_ATOMIC);
      if (!buffer) {
            dev_err(&port->dev, "out of memory\n");
            return -ENOMEM;
      }

      urb = usb_alloc_urb(0, GFP_ATOMIC);
      if (!urb) {
            dev_err(&port->dev, "no more free urbs\n");
            kfree (buffer);
            return -ENOMEM;
      }

      memcpy (buffer, buf, count);

      usb_serial_debug_data(debug, &port->dev, __FUNCTION__, count, buffer);

      usb_fill_bulk_urb (urb, serial->dev,
                        usb_sndbulkpipe (serial->dev,
                        port->bulk_out_endpointAddress),
                        buffer, count,
                        garmin_write_bulk_callback,
                        dismiss_ack ? NULL : port);
      urb->transfer_flags |= URB_ZERO_PACKET;

      if (GARMIN_LAYERID_APPL == getLayerId(buffer)) {
            atomic_inc(&garmin_data_p->req_count);
            if (garmin_data_p->mode == MODE_GARMIN_SERIAL)  {
                  pkt_clear(garmin_data_p);
                  garmin_data_p->state = STATE_GSP_WAIT_DATA;
            }
      }

      /* send it down the pipe */
      status = usb_submit_urb(urb, GFP_ATOMIC);
      if (status) {
            dev_err(&port->dev,
                    "%s - usb_submit_urb(write bulk) "
                    "failed with status = %d\n",
                        __FUNCTION__, status);
            count = status;
      }

      /* we are done with this urb, so let the host driver
       * really free it when it is finished with it */
      usb_free_urb (urb);

      return count;
}



static int garmin_write (struct usb_serial_port *port,
                   const unsigned char *buf, int count)
{
      int pktid, pktsiz, len;
      struct garmin_data * garmin_data_p = usb_get_serial_port_data(port);
      __le32 *privpkt = (__le32 *)garmin_data_p->privpkt;

      usb_serial_debug_data(debug, &port->dev, __FUNCTION__, count, buf);

      /* check for our private packets */
      if (count >= GARMIN_PKTHDR_LENGTH) {

            len = PRIVPKTSIZ;
            if (count < len)
                  len = count;

            memcpy(garmin_data_p->privpkt, buf, len);

            pktsiz = getDataLength(garmin_data_p->privpkt);
            pktid  = getPacketId(garmin_data_p->privpkt);

            if (count == (GARMIN_PKTHDR_LENGTH+pktsiz)
                && GARMIN_LAYERID_PRIVATE == getLayerId(garmin_data_p->privpkt)) {

                  dbg("%s - processing private request %d",
                        __FUNCTION__, pktid);

                  // drop all unfinished transfers
                  garmin_clear(garmin_data_p);

                  switch(pktid) {

                  case PRIV_PKTID_SET_DEBUG:
                        if (pktsiz != 4)
                              return -EINVPKT;
                        debug = __le32_to_cpu(privpkt[3]);
                        dbg("%s - debug level set to 0x%X",
                              __FUNCTION__, debug);
                        break;

                  case PRIV_PKTID_SET_MODE:
                        if (pktsiz != 4)
                              return -EINVPKT;
                        garmin_data_p->mode = __le32_to_cpu(privpkt[3]);
                        dbg("%s - mode set to %d",
                              __FUNCTION__, garmin_data_p->mode);
                        break;

                  case PRIV_PKTID_INFO_REQ:
                        priv_status_resp(port);
                        break;

                  case PRIV_PKTID_RESET_REQ:
                        atomic_inc(&garmin_data_p->req_count);
                        break;

                  case PRIV_PKTID_SET_DEF_MODE:
                        if (pktsiz != 4)
                              return -EINVPKT;
                        initial_mode = __le32_to_cpu(privpkt[3]);
                        dbg("%s - initial_mode set to %d",
                              __FUNCTION__,
                              garmin_data_p->mode);
                        break;
                  }
                  return count;
            }
      }

      garmin_data_p->ignorePkts = 0;

      if (garmin_data_p->mode == MODE_GARMIN_SERIAL) {
            return gsp_receive(garmin_data_p, buf, count);
      } else {    /* MODE_NATIVE */
            return nat_receive(garmin_data_p, buf, count);
      }
}


static int garmin_write_room (struct usb_serial_port *port)
{
      /*
       * Report back the bytes currently available in the output buffer.
       */
      struct garmin_data * garmin_data_p = usb_get_serial_port_data(port);
      return GPS_OUT_BUFSIZ-garmin_data_p->outsize;
}


static int garmin_chars_in_buffer (struct usb_serial_port *port)
{
      /*
       * Report back the number of bytes currently in our input buffer.
       * Will this lock up the driver - the buffer contains an incomplete
       * package which will not be written to the device until it
       * has been completed ?
       */
      //struct garmin_data * garmin_data_p = usb_get_serial_port_data(port);
      //return garmin_data_p->insize;
      return 0;
}


static void garmin_read_process(struct garmin_data * garmin_data_p,
                         unsigned char *data, unsigned data_length)
{
      if (garmin_data_p->flags & FLAGS_DROP_DATA) {
            /* abort-transfer cmd is actice */
            dbg("%s - pkt dropped", __FUNCTION__);
      } else if (garmin_data_p->state != STATE_DISCONNECTED &&
                 garmin_data_p->state != STATE_RESET ) {

            /* remember any appl.layer packets, so we know
               if a reset is required or not when closing
               the device */
            if (0 == memcmp(data, GARMIN_APP_LAYER_REPLY,
                            sizeof(GARMIN_APP_LAYER_REPLY))) {
                  atomic_inc(&garmin_data_p->resp_count);
            }

            /* if throttling is active or postprecessing is required
               put the received data in the input queue, otherwise
               send it directly to the tty port */
            if (garmin_data_p->flags & FLAGS_QUEUING) {
                  pkt_add(garmin_data_p, data, data_length);
            } else if (garmin_data_p->mode == MODE_GARMIN_SERIAL) {
                  if (getLayerId(data) == GARMIN_LAYERID_APPL) {
                        pkt_add(garmin_data_p, data, data_length);
                  }
            } else {
                  send_to_tty(garmin_data_p->port, data, data_length);
            }
      }
}


static void garmin_read_bulk_callback (struct urb *urb)
{
      unsigned long flags;
      struct usb_serial_port *port = (struct usb_serial_port *)urb->context;
      struct usb_serial *serial =  port->serial;
      struct garmin_data * garmin_data_p = usb_get_serial_port_data(port);
      unsigned char *data = urb->transfer_buffer;
      int status = urb->status;
      int retval;

      dbg("%s - port %d", __FUNCTION__, port->number);

      if (!serial) {
            dbg("%s - bad serial pointer, exiting", __FUNCTION__);
            return;
      }

      if (status) {
            dbg("%s - nonzero read bulk status received: %d",
                  __FUNCTION__, status);
            return;
      }

      usb_serial_debug_data(debug, &port->dev, 
                        __FUNCTION__, urb->actual_length, data);

      garmin_read_process(garmin_data_p, data, urb->actual_length);

      if (urb->actual_length == 0 &&
                  0 != (garmin_data_p->flags & FLAGS_BULK_IN_RESTART)) {
            spin_lock_irqsave(&garmin_data_p->lock, flags);
            garmin_data_p->flags &= ~FLAGS_BULK_IN_RESTART;
            spin_unlock_irqrestore(&garmin_data_p->lock, flags);
            retval = usb_submit_urb(port->read_urb, GFP_ATOMIC);
            if (retval)
                  dev_err(&port->dev,
                        "%s - failed resubmitting read urb, error %d\n",
                        __FUNCTION__, retval);
      } else if (urb->actual_length > 0) {
            /* Continue trying to read until nothing more is received  */
            if (0 == (garmin_data_p->flags & FLAGS_THROTTLED)) {
                  retval = usb_submit_urb(port->read_urb, GFP_ATOMIC);
                  if (retval)
                        dev_err(&port->dev,
                              "%s - failed resubmitting read urb, "
                              "error %d\n", __FUNCTION__, retval);
            }
      } else {
            dbg("%s - end of bulk data", __FUNCTION__);
            spin_lock_irqsave(&garmin_data_p->lock, flags);
            garmin_data_p->flags &= ~FLAGS_BULK_IN_ACTIVE;
            spin_unlock_irqrestore(&garmin_data_p->lock, flags);
      }
      return;
}


static void garmin_read_int_callback (struct urb *urb)
{
      unsigned long flags;
      int retval;
      struct usb_serial_port *port = (struct usb_serial_port *)urb->context;
      struct usb_serial *serial = port->serial;
      struct garmin_data * garmin_data_p = usb_get_serial_port_data(port);
      unsigned char *data = urb->transfer_buffer;
      int status = urb->status;

      switch (status) {
      case 0:
            /* success */
            break;
      case -ECONNRESET:
      case -ENOENT:
      case -ESHUTDOWN:
            /* this urb is terminated, clean up */
            dbg("%s - urb shutting down with status: %d",
                  __FUNCTION__, status);
            return;
      default:
            dbg("%s - nonzero urb status received: %d",
                  __FUNCTION__, status);
            return;
      }

      usb_serial_debug_data(debug, &port->dev, __FUNCTION__, 
                        urb->actual_length, urb->transfer_buffer);

      if (urb->actual_length == sizeof(GARMIN_BULK_IN_AVAIL_REPLY) &&
          0 == memcmp(data, GARMIN_BULK_IN_AVAIL_REPLY,
                    sizeof(GARMIN_BULK_IN_AVAIL_REPLY))) {

            dbg("%s - bulk data available.", __FUNCTION__);

            if (0 == (garmin_data_p->flags & FLAGS_BULK_IN_ACTIVE)) {

                  /* bulk data available */
                  usb_fill_bulk_urb (port->read_urb, serial->dev,
                              usb_rcvbulkpipe (serial->dev,
                              port->bulk_in_endpointAddress),
                              port->read_urb->transfer_buffer,
                              port->read_urb->transfer_buffer_length,
                              garmin_read_bulk_callback, port);
                  retval = usb_submit_urb(port->read_urb, GFP_ATOMIC);
                  if (retval) {
                        dev_err(&port->dev,
                              "%s - failed submitting read urb, error %d\n",
                        __FUNCTION__, retval);
                  } else {
                        spin_lock_irqsave(&garmin_data_p->lock, flags);
                        garmin_data_p->flags |= FLAGS_BULK_IN_ACTIVE;
                        /* do not send this packet to the user */
                        garmin_data_p->ignorePkts = 1;
                        spin_unlock_irqrestore(&garmin_data_p->lock, flags);
                  }
            } else {
                  /* bulk-in transfer still active */
                  spin_lock_irqsave(&garmin_data_p->lock, flags);
                  garmin_data_p->flags |= FLAGS_BULK_IN_RESTART;
                  spin_unlock_irqrestore(&garmin_data_p->lock, flags);
            }

      } else if (urb->actual_length == (4+sizeof(GARMIN_START_SESSION_REPLY))
                   && 0 == memcmp(data, GARMIN_START_SESSION_REPLY,
                                  sizeof(GARMIN_START_SESSION_REPLY))) {

            spin_lock_irqsave(&garmin_data_p->lock, flags);
            garmin_data_p->flags |= FLAGS_SESSION_REPLY1_SEEN;
            spin_unlock_irqrestore(&garmin_data_p->lock, flags);

            /* save the serial number */
            garmin_data_p->serial_num 
                  = __le32_to_cpup((__le32*)(data+GARMIN_PKTHDR_LENGTH));

            dbg("%s - start-of-session reply seen - serial %u.",
                  __FUNCTION__, garmin_data_p->serial_num);
      }

      if (garmin_data_p->ignorePkts) {
            /* this reply belongs to a request generated by the driver,
               ignore it. */
            dbg("%s - pkt ignored (%d)",
                  __FUNCTION__, garmin_data_p->ignorePkts);
            spin_lock_irqsave(&garmin_data_p->lock, flags);
            garmin_data_p->ignorePkts--;
            spin_unlock_irqrestore(&garmin_data_p->lock, flags);
      } else {
            garmin_read_process(garmin_data_p, data, urb->actual_length);
      }

      port->interrupt_in_urb->dev = port->serial->dev;
      retval = usb_submit_urb (urb, GFP_ATOMIC);
      if (retval)
            dev_err(&urb->dev->dev,
                  "%s - Error %d submitting interrupt urb\n",
                  __FUNCTION__, retval);
}


/*
 * Sends the next queued packt to the tty port (garmin native mode only)
 * and then sets a timer to call itself again until all queued data
 * is sent.
 */
static int garmin_flush_queue(struct garmin_data * garmin_data_p)
{
      unsigned long flags;
      struct garmin_packet *pkt;

      if ((garmin_data_p->flags & FLAGS_THROTTLED) == 0) {
            pkt = pkt_pop(garmin_data_p);
            if (pkt != NULL) {
                  send_to_tty(garmin_data_p->port, pkt->data, pkt->size);
                  kfree(pkt);
                  mod_timer(&garmin_data_p->timer, (1)+jiffies);

            } else {
                  spin_lock_irqsave(&garmin_data_p->lock, flags);
                  garmin_data_p->flags &= ~FLAGS_QUEUING;
                  spin_unlock_irqrestore(&garmin_data_p->lock, flags);
            }
      }
      return 0;
}


static void garmin_throttle (struct usb_serial_port *port)
{
      unsigned long flags;
      struct garmin_data * garmin_data_p = usb_get_serial_port_data(port);

      dbg("%s - port %d", __FUNCTION__, port->number);
      /* set flag, data received will be put into a queue
         for later processing */
      spin_lock_irqsave(&garmin_data_p->lock, flags);
      garmin_data_p->flags |= FLAGS_QUEUING|FLAGS_THROTTLED;
      spin_unlock_irqrestore(&garmin_data_p->lock, flags);
}


static void garmin_unthrottle (struct usb_serial_port *port)
{
      unsigned long flags;
      struct garmin_data * garmin_data_p = usb_get_serial_port_data(port);
      int status;

      dbg("%s - port %d", __FUNCTION__, port->number);
      spin_lock_irqsave(&garmin_data_p->lock, flags);
      garmin_data_p->flags &= ~FLAGS_THROTTLED;
      spin_unlock_irqrestore(&garmin_data_p->lock, flags);

      /* in native mode send queued data to tty, in
         serial mode nothing needs to be done here */
      if (garmin_data_p->mode == MODE_NATIVE)
            garmin_flush_queue(garmin_data_p);

      if (0 != (garmin_data_p->flags & FLAGS_BULK_IN_ACTIVE)) {
            status = usb_submit_urb(port->read_urb, GFP_ATOMIC);
            if (status)
                  dev_err(&port->dev,
                        "%s - failed resubmitting read urb, error %d\n",
                        __FUNCTION__, status);
      }
}



/*
 * The timer is currently only used to send queued packets to
 * the tty in cases where the protocol provides no own handshaking
 * to initiate the transfer.
 */
static void timeout_handler(unsigned long data)
{
      struct garmin_data *garmin_data_p = (struct garmin_data *) data;

      /* send the next queued packet to the tty port */
      if (garmin_data_p->mode == MODE_NATIVE)
            if (garmin_data_p->flags & FLAGS_QUEUING)
                  garmin_flush_queue(garmin_data_p);
}



static int garmin_attach (struct usb_serial *serial)
{
      int status = 0;
      struct usb_serial_port *port = serial->port[0];
      struct garmin_data * garmin_data_p = NULL;

      dbg("%s", __FUNCTION__);

      garmin_data_p = kzalloc(sizeof(struct garmin_data), GFP_KERNEL);
      if (garmin_data_p == NULL) {
            dev_err(&port->dev, "%s - Out of memory\n", __FUNCTION__);
            return -ENOMEM;
      }
      init_timer(&garmin_data_p->timer);
      spin_lock_init(&garmin_data_p->lock);
      INIT_LIST_HEAD(&garmin_data_p->pktlist);
      //garmin_data_p->timer.expires = jiffies + session_timeout;
      garmin_data_p->timer.data = (unsigned long)garmin_data_p;
      garmin_data_p->timer.function = timeout_handler;
      garmin_data_p->port = port;
      garmin_data_p->state = 0;
      garmin_data_p->count = 0;
      usb_set_serial_port_data(port, garmin_data_p);

      status = garmin_init_session(port);

      return status;
}


static void garmin_shutdown (struct usb_serial *serial)
{
      struct usb_serial_port *port = serial->port[0];
      struct garmin_data * garmin_data_p = usb_get_serial_port_data(port);

      dbg("%s", __FUNCTION__);

      usb_kill_urb (port->interrupt_in_urb);
      del_timer_sync(&garmin_data_p->timer);
      kfree (garmin_data_p);
      usb_set_serial_port_data(port, NULL);
}


/* All of the device info needed */
static struct usb_serial_driver garmin_device = {
      .driver = {
            .owner       = THIS_MODULE,
            .name        = "garmin_gps",
      },
      .description         = "Garmin GPS usb/tty",
      .usb_driver          = &garmin_driver,
      .id_table            = id_table,
      .num_interrupt_in    = 1,
      .num_bulk_in         = 1,
      .num_bulk_out        = 1,
      .num_ports           = 1,
      .open                = garmin_open,
      .close               = garmin_close,
      .throttle            = garmin_throttle,
      .unthrottle          = garmin_unthrottle,
      .attach              = garmin_attach,
      .shutdown            = garmin_shutdown,
      .write               = garmin_write,
      .write_room          = garmin_write_room,
      .chars_in_buffer     = garmin_chars_in_buffer,
      .write_bulk_callback = garmin_write_bulk_callback,
      .read_bulk_callback  = garmin_read_bulk_callback,
      .read_int_callback   = garmin_read_int_callback,
};



static int __init garmin_init (void)
{
      int retval;

      retval = usb_serial_register(&garmin_device);
      if (retval)
            goto failed_garmin_register;
      retval = usb_register(&garmin_driver);
      if (retval)
            goto failed_usb_register;
      info(DRIVER_DESC " " DRIVER_VERSION);

      return 0;
failed_usb_register:
      usb_serial_deregister(&garmin_device);
failed_garmin_register:
      return retval;
}


static void __exit garmin_exit (void)
{
      usb_deregister (&garmin_driver);
      usb_serial_deregister (&garmin_device);
}




module_init(garmin_init);
module_exit(garmin_exit);

MODULE_AUTHOR( DRIVER_AUTHOR );
MODULE_DESCRIPTION( DRIVER_DESC );
MODULE_LICENSE("GPL");

module_param(debug, bool, S_IWUSR | S_IRUGO);
MODULE_PARM_DESC(debug, "Debug enabled or not");
module_param(initial_mode, int, S_IRUGO);
MODULE_PARM_DESC(initial_mode, "Initial mode");


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