// SPDX-License-Identifier: GPL-2.0+
/*
 * Garmin GPS driver
 *
 * Copyright (C) 2006-2011 Hermann Kneissel herkne@gmx.de
 *
 * 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.
 */

#include <linux/kernel.h>
#include <linux/errno.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 <linux/uaccess.h>
#include <linux/atomic.h>
#include <linux/usb.h>
#include <linux/usb/serial.h>

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

#define GARMIN_VENDOR_ID             0x091E

/*
 * Version Information
 */

#define VERSION_MAJOR   0
#define VERSION_MINOR   36

#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;
        /* the real size of the data array, always > 0 */
        int               size;
        __u8              data[] __counted_by(size);
};

/* structure used to keep the current state of the driver */
struct garmin_data {
        __u8   state;
        __u16  flags;
        __u8   mode;
        __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];
        spinlock_t lock;
        struct list_head pktlist;
        struct usb_anchor write_urbs;
};


#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 APP_REQ_SEEN              0x0004
#define APP_RESP_SEEN             0x0002
#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 int 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_REPLY[]
        = { 0, 0, 0, 0,  6, 0, 0, 0, 4, 0, 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_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 };

/* packets currently unused, left as documentation */
#if 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 PRIVATE_REQ[]
        =    { 0x4B, 0x6E, 0x10, 0x01,  0xFF, 0, 0, 0, 0xFF, 0, 0, 0 };
#endif


static const 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 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 (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)) == 0)
                return 1;
        else
                return 0;
}



static void send_to_tty(struct usb_serial_port *port,
                        char *data, unsigned int actual_length)
{
        if (actual_length) {
                usb_serial_debug_data(&port->dev, __func__, actual_length, data);
                tty_insert_flip_string(&port->port, data, actual_length);
                tty_flip_buffer_push(&port->port);
        }
}


/******************************************************************************
 * 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 containing data ... */
        if (data_length) {
                pkt = kmalloc_flex(*pkt, data, data_length, GFP_ATOMIC);
                if (!pkt)
                        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);

                dev_dbg(&garmin_data_p->port->dev,
                        "%s - added: pkt: %d - %d bytes\n", __func__,
                        pkt->seq, data_length);

                /* in serial mode, if someone is waiting for data from
                   the device, convert 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;

        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;

        dev_dbg(&garmin_data_p->port->dev, "%s - pkt-id: 0x%X.\n", __func__,
                        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++ = (-cksum) & 0xFF;
        *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 (pktid ... 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)
{
        struct device *dev = &garmin_data_p->port->dev;
        unsigned long flags;
        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(&garmin_data_p->port->dev, __func__,
                              count-GSP_INITIAL_OFFSET, recpkt);

        if (size != (count-GSP_INITIAL_OFFSET-3)) {
                dev_dbg(dev, "%s - invalid size, expected %d bytes, got %d\n",
                        __func__, size, (count-GSP_INITIAL_OFFSET-3));
                return -EINVPKT;
        }

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

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

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

        if (((cksum + *recpkt) & 0xff) != 0) {
                dev_dbg(dev, "%s - invalid checksum, expected %02x, got %02x\n",
                        __func__, -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)) {
                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 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)
{
        struct device *dev = &garmin_data_p->port->dev;
        unsigned long flags;
        int offs = 0;
        int ack_or_nak_seen = 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);

        /* dev_dbg(dev, "%s - dle=%d skip=%d size=%d count=%d\n",
                __func__, 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;
                                        dev_dbg(dev, "ACK packet complete.\n");
                                } else if (data == NAK) {
                                        ack_or_nak_seen = NAK;
                                        dev_dbg(dev, "NAK packet complete.\n");
                                } else {
                                        dev_dbg(dev, "packet complete - id=0x%X.\n",
                                                        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) {
                                size = GSP_INITIAL_OFFSET;
                                dleSeen = 0;
                        }

                        dest[size++] = data;
                }

                if (size >= GPS_IN_BUFSIZ) {
                        dev_dbg(dev, "%s - packet too large.\n", __func__);
                        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;

        spin_unlock_irqrestore(&garmin_data_p->lock, flags);

        if (ack_or_nak_seen) {
                if (gsp_next_packet(garmin_data_p) > 0)
                        garmin_data_p->state = STATE_ACTIVE;
                else
                        garmin_data_p->state = STATE_GSP_WAIT_DATA;
        }
        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)
{
        struct device *dev = &garmin_data_p->port->dev;
        const unsigned char *src;
        unsigned char *dst;
        int pktid = 0;
        int datalen = 0;
        int cksum = 0;
        int i = 0;
        int k;

        dev_dbg(dev, "%s - state %d - %d bytes.\n", __func__,
                garmin_data_p->state, count);

        k = garmin_data_p->outsize;
        if ((k+count) > GPS_OUT_BUFSIZ) {
                dev_dbg(dev, "packet too large\n");
                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;
        }

        dev_dbg(dev, "%s - %d bytes in buffer, %d bytes in pkt.\n", __func__, k, i);

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

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

        garmin_data_p->outsize = 0;

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

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

        if (datalen > 255) {
                dev_dbg(dev, "packet-size %d too large\n", 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 = -cksum & 0xFF;
        *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 int gsp_next_packet(struct garmin_data *garmin_data_p)
{
        int result = 0;
        struct garmin_packet *pkt = NULL;

        while ((pkt = pkt_pop(garmin_data_p)) != NULL) {
                dev_dbg(&garmin_data_p->port->dev, "%s - next pkt: %d\n", __func__, pkt->seq);
                result = gsp_send(garmin_data_p, pkt->data, pkt->size);
                if (result > 0) {
                        kfree(pkt);
                        return result;
                }
                kfree(pkt);
        }
        return result;
}



/******************************************************************************
 * 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) {
                        /* seems to be an invalid packet, ignore rest
                           of input */
                        dev_dbg(&garmin_data_p->port->dev,
                                "%s - packet size too large: %d\n",
                                __func__, 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);
        dev_dbg(&port->dev, "%s - usb_reset_device\n", __func__);
        status = usb_reset_device(port->serial->dev);
        if (status)
                dev_dbg(&port->dev, "%s - usb_reset_device failed: %d\n",
                        __func__, status);
        return status;
}



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

        /* 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 0;
}


static int garmin_init_session(struct usb_serial_port *port)
{
        struct garmin_data *garmin_data_p = usb_get_serial_port_data(port);
        int status;
        int i;

        usb_kill_urb(port->interrupt_in_urb);

        status = usb_submit_urb(port->interrupt_in_urb, GFP_KERNEL);
        if (status) {
                dev_err(&port->dev, "failed to submit interrupt urb: %d\n",
                                status);
                return status;
        }

        /*
         * using the initialization method from gpsbabel. See comments in
         * gpsbabel/jeeps/gpslibusb.c gusb_reset_toggles()
         */
        dev_dbg(&port->dev, "%s - starting session ...\n", __func__);
        garmin_data_p->state = STATE_ACTIVE;

        for (i = 0; i < 3; i++) {
                status = garmin_write_bulk(port, GARMIN_START_SESSION_REQ,
                                sizeof(GARMIN_START_SESSION_REQ), 0);
                if (status < 0)
                        goto err_kill_urbs;
        }

        return 0;

err_kill_urbs:
        usb_kill_anchored_urbs(&garmin_data_p->write_urbs);
        usb_kill_urb(port->interrupt_in_urb);

        return status;
}



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

        spin_lock_irqsave(&garmin_data_p->lock, flags);
        garmin_data_p->mode  = initial_mode;
        garmin_data_p->count = 0;
        garmin_data_p->flags &= FLAGS_SESSION_REPLY1_SEEN;
        spin_unlock_irqrestore(&garmin_data_p->lock, flags);

        /* shutdown any bulk reads that might be going on */
        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 garmin_data *garmin_data_p = usb_get_serial_port_data(port);

        dev_dbg(&port->dev, "%s - mode=%d state=%d flags=0x%X\n",
                __func__, garmin_data_p->mode, garmin_data_p->state,
                garmin_data_p->flags);

        garmin_clear(garmin_data_p);

        /* shutdown our urbs */
        usb_kill_urb(port->read_urb);
        usb_kill_anchored_urbs(&garmin_data_p->write_urbs);

        /* keep reset state so we know that we must start a new session */
        if (garmin_data_p->state != STATE_RESET)
                garmin_data_p->state = STATE_DISCONNECTED;
}


static void garmin_write_bulk_callback(struct urb *urb)
{
        struct usb_serial_port *port = urb->context;

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

                if (getLayerId(urb->transfer_buffer) == GARMIN_LAYERID_APPL) {

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

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

        buffer = kmemdup(buf, count, GFP_ATOMIC);
        if (!buffer)
                return -ENOMEM;

        urb = usb_alloc_urb(0, GFP_ATOMIC);
        if (!urb) {
                kfree(buffer);
                return -ENOMEM;
        }

        usb_serial_debug_data(&port->dev, __func__, 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 (getLayerId(buffer) == GARMIN_LAYERID_APPL) {

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

                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 */
        usb_anchor_urb(urb, &garmin_data_p->write_urbs);
        status = usb_submit_urb(urb, GFP_ATOMIC);
        if (status) {
                dev_err(&port->dev,
                   "%s - usb_submit_urb(write bulk) failed with status = %d\n",
                                __func__, status);
                count = status;
                usb_unanchor_urb(urb);
                kfree(buffer);
        }

        /* 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 tty_struct *tty, struct usb_serial_port *port,
                                         const unsigned char *buf, int count)
{
        struct device *dev = &port->dev;
        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(dev, __func__, count, buf);

        if (garmin_data_p->state == STATE_RESET)
                return -EIO;

        /* 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) &&
                                getLayerId(garmin_data_p->privpkt) ==
                                                GARMIN_LAYERID_PRIVATE) {

                        dev_dbg(dev, "%s - processing private request %d\n",
                                __func__, pktid);

                        /* drop all unfinished transfers */
                        garmin_clear(garmin_data_p);

                        switch (pktid) {
                        case PRIV_PKTID_SET_MODE:
                                if (pktsiz != 4)
                                        return -EINVPKT;
                                garmin_data_p->mode = __le32_to_cpu(privpkt[3]);
                                dev_dbg(dev, "%s - mode set to %d\n",
                                        __func__, garmin_data_p->mode);
                                break;

                        case PRIV_PKTID_INFO_REQ:
                                priv_status_resp(port);
                                break;

                        case PRIV_PKTID_RESET_REQ:
                                process_resetdev_request(port);
                                break;

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

        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 unsigned int garmin_write_room(struct tty_struct *tty)
{
        struct usb_serial_port *port = tty->driver_data;
        /*
         * 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 void garmin_read_process(struct garmin_data *garmin_data_p,
                                 unsigned char *data, unsigned data_length,
                                 int bulk_data)
{
        unsigned long flags;

        if (garmin_data_p->flags & FLAGS_DROP_DATA) {
                /* abort-transfer cmd is active */
                dev_dbg(&garmin_data_p->port->dev, "%s - pkt dropped\n", __func__);
        } else if (garmin_data_p->state != STATE_DISCONNECTED &&
                garmin_data_p->state != STATE_RESET) {

                /* 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 (bulk_data || (data_length >= sizeof(u32) &&
                                getLayerId(data) == GARMIN_LAYERID_APPL)) {

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

                        if (garmin_data_p->mode == MODE_GARMIN_SERIAL) {
                                pkt_add(garmin_data_p, data, data_length);
                        } else {
                                send_to_tty(garmin_data_p->port, data,
                                                data_length);
                        }
                }
                /* ignore system layer packets ... */
        }
}


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

        if (status) {
                dev_dbg(&urb->dev->dev, "%s - nonzero read bulk status received: %d\n",
                        __func__, status);
                return;
        }

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

        garmin_read_process(garmin_data_p, data, urb->actual_length, 1);

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


static void garmin_read_int_callback(struct urb *urb)
{
        unsigned long flags;
        int retval;
        struct usb_serial_port *port = urb->context;
        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 */
                dev_dbg(&urb->dev->dev, "%s - urb shutting down with status: %d\n",
                        __func__, status);
                return;
        default:
                dev_dbg(&urb->dev->dev, "%s - nonzero urb status received: %d\n",
                        __func__, status);
                return;
        }

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

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

                dev_dbg(&port->dev, "%s - bulk data available.\n", __func__);

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

                        /* bulk data available */
                        retval = usb_submit_urb(port->read_urb, GFP_ATOMIC);
                        if (retval) {
                                dev_err(&port->dev,
                                 "%s - failed submitting read urb, error %d\n",
                                                        __func__, retval);
                        } else {
                                spin_lock_irqsave(&garmin_data_p->lock, flags);
                                garmin_data_p->flags |= FLAGS_BULK_IN_ACTIVE;
                                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))
                         && memcmp(data, GARMIN_START_SESSION_REPLY,
                                 sizeof(GARMIN_START_SESSION_REPLY)) == 0) {

                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));

                dev_dbg(&port->dev, "%s - start-of-session reply seen - serial %u.\n",
                        __func__, garmin_data_p->serial_num);
        }

        garmin_read_process(garmin_data_p, data, urb->actual_length, 0);

        retval = usb_submit_urb(urb, GFP_ATOMIC);
        if (retval)
                dev_err(&urb->dev->dev,
                        "%s - Error %d submitting interrupt urb\n",
                        __func__, 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 tty_struct *tty)
{
        struct usb_serial_port *port = tty->driver_data;
        struct garmin_data *garmin_data_p = usb_get_serial_port_data(port);

        /* set flag, data received will be put into a queue
           for later processing */
        spin_lock_irq(&garmin_data_p->lock);
        garmin_data_p->flags |= FLAGS_QUEUING|FLAGS_THROTTLED;
        spin_unlock_irq(&garmin_data_p->lock);
}


static void garmin_unthrottle(struct tty_struct *tty)
{
        struct usb_serial_port *port = tty->driver_data;
        struct garmin_data *garmin_data_p = usb_get_serial_port_data(port);
        int status;

        spin_lock_irq(&garmin_data_p->lock);
        garmin_data_p->flags &= ~FLAGS_THROTTLED;
        spin_unlock_irq(&garmin_data_p->lock);

        /* 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 ((garmin_data_p->flags & FLAGS_BULK_IN_ACTIVE) != 0) {
                status = usb_submit_urb(port->read_urb, GFP_KERNEL);
                if (status)
                        dev_err(&port->dev,
                                "%s - failed resubmitting read urb, error %d\n",
                                __func__, 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(struct timer_list *t)
{
        struct garmin_data *garmin_data_p = timer_container_of(garmin_data_p,
                                                               t, timer);

        /* 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_port_probe(struct usb_serial_port *port)
{
        int status;
        struct garmin_data *garmin_data_p;

        garmin_data_p = kzalloc_obj(struct garmin_data);
        if (!garmin_data_p)
                return -ENOMEM;

        timer_setup(&garmin_data_p->timer, timeout_handler, 0);
        spin_lock_init(&garmin_data_p->lock);
        INIT_LIST_HEAD(&garmin_data_p->pktlist);
        garmin_data_p->port = port;
        garmin_data_p->state = 0;
        garmin_data_p->flags = 0;
        garmin_data_p->count = 0;
        init_usb_anchor(&garmin_data_p->write_urbs);
        usb_set_serial_port_data(port, garmin_data_p);

        status = garmin_init_session(port);
        if (status)
                goto err_free;

        return 0;
err_free:
        kfree(garmin_data_p);

        return status;
}


static void garmin_port_remove(struct usb_serial_port *port)
{
        struct garmin_data *garmin_data_p = usb_get_serial_port_data(port);

        usb_kill_anchored_urbs(&garmin_data_p->write_urbs);
        usb_kill_urb(port->interrupt_in_urb);
        timer_shutdown_sync(&garmin_data_p->timer);
        kfree(garmin_data_p);
}


/* All of the device info needed */
static struct usb_serial_driver garmin_device = {
        .driver = {
                .name        = "garmin_gps",
        },
        .description         = "Garmin GPS usb/tty",
        .id_table            = id_table,
        .num_ports           = 1,
        .open                = garmin_open,
        .close               = garmin_close,
        .throttle            = garmin_throttle,
        .unthrottle          = garmin_unthrottle,
        .port_probe             = garmin_port_probe,
        .port_remove            = garmin_port_remove,
        .write               = garmin_write,
        .write_room          = garmin_write_room,
        .write_bulk_callback = garmin_write_bulk_callback,
        .read_bulk_callback  = garmin_read_bulk_callback,
        .read_int_callback   = garmin_read_int_callback,
};

static struct usb_serial_driver * const serial_drivers[] = {
        &garmin_device, NULL
};

module_usb_serial_driver(serial_drivers, id_table);

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

module_param(initial_mode, int, 0444);
MODULE_PARM_DESC(initial_mode, "Initial mode");