/*

 * This file contains two drivers for Garmin receivers and some code

 * shared by both drivers.

 *

 * One driver "garmin_usb_binary" handles the Garmin binary packet

 * format supported by the USB Garmins tested with the Garmin 18 and

 * other models.  (There is also "garmin_usb_binary_old".)  These are ONLY

 * for USB devices reporting as: 091e:0003.

 *

 * The other driver "garmin_ser_binary" is for Garmin receivers via a

 * serial port, whether or not one uses a USB/serial adaptor or a real

 * serial port.  These receivers provide adequate NMEA support, so it

 * often makes sense to just put them into NMEA mode.

 *

 * On Linux, USB Garmins (091e:0003) need the Linux garmin_gps driver and

 * will not function without it.  On other operating systems, it is clear

 * garmin_usb_binary_old does not work since it requires the Linux

 * garmin_gps module.

 *

 * This code has been tested and at least at one time is known to work on

 * big- and little-endian CPUs and 32 and 64 bit cpu modes.

 *

 *

 * Documentation for the Garmin protocols can be found via

 *   http://www.garmin.com/support/commProtocol.html

 * The file IOSDK.zip contains IntfSpec.pdf, which describes the

 * protocol in terms of Application, Link, and Physical.  This

 * identical file is also available at:

 *   http://www.garmin.com/support/pdf/iop_spec.pdf

 * An older version of iop_spec.pdf that describes only Serial Binary

 * is available at:

 *   http://vancouver-webpages.com/pub/peter/iop_spec.pdf

 * Information about the GPS 18

 *   http://www.garmin.com/manuals/425_TechnicalSpecification.pdf

 *

 * There is one physical link protocol for serial which uses DLE/ETX

 * framing.  There is another physical protocol for USB which relies

 * on the packetization intrinsic to USB bulk pipes.

 *

 * There are several link protocols; all devices implement L000.

 * There are then product-specific protocols; most devices implement

 * L001.  Link protocols are the same and carried over either Physical

 * protocol.

 *

 * Application protocols are named A000 and then with different

 * 3-digit numbers.  They are carried over Link protocols.

 *

 * Thus, much of the higher-level code dealing the data formats is

 * shared between USB Binary and Serial Binary.

 *

 * This code is partly from the Garmin IOSDK and partly from the

 * sample code in the Linux garmin_gps driver.

 *

 * bad code by: Gary E. Miller <gem@rellim.com>

 *

 * -D 3 = packet trace

 * -D 4 = packet details

 * -D 5 = more packet details

 * -D 6 = very excessive details

 *

 * limitations:

 *

 * do not have from garmin:

 *      pdop

 *      hdop

 *      vdop

 *      magnetic variation

 *

 * known bugs:

 *      hangs in the fread loop instead of keeping state and returning.

 *

 * This file is Copyright 2010 by the GPSD project

 * SPDX-License-Identifier: BSD-2-clause

 */

#include "../include/gpsd_config.h"   // must be before all includes

#ifdef GARMIN_ENABLE

#include <errno.h>

#include <math.h>

#include <stdbool.h>

#include <stdio.h>

#include <string.h>

#include <time.h>

#include <unistd.h>

#if defined(HAVE_LIBUSB)

#include <libusb.h>

#endif

#include "../include/gpsd.h"

#include "../include/bits.h"

#include "../include/timespec.h"

#define GPSD_LE16TOH(x) getles16((char *)(&(x)), 0)

#define GPSD_LE32TOH(x) getles32((char *)(&(x)), 0)

#define GPSD_LEF32(x) getlef32((const char *)(&(x)), 0)

#define GPSD_LED64(x) getled64((const char *)(&(x)), 0)

#define USE_RMD 0

// Used in Serial Physical Layer

#define ETX 0x03

#define ACK 0x06

#define DLE 0x10

#define NAK 0x15

#define GARMIN_LAYERID_TRANSPORT (uint8_t)  0

#define GARMIN_LAYERID_APPL      (uint32_t) 20

// Linux Garmin USB driver layer-id to use for some control mechanisms

#define GARMIN_LAYERID_PRIVATE  0x01106E4B

// 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 MODE_NATIVE       0

#define MODE_GARMIN_SERIAL   1

#define GARMIN_PKTID_TRANSPORT_START_SESSION_REQ 5

#define GARMIN_PKTID_TRANSPORT_START_SESSION_RESP 6

#define GARMIN_PKTID_PROTOCOL_ARRAY     253

#define GARMIN_PKTID_PRODUCT_RQST       254

#define GARMIN_PKTID_PRODUCT_DATA       255

// 0x29 ')'

#define GARMIN_PKTID_RMD41_DATA  41

// 0x33 '3'

#define GARMIN_PKTID_PVT_DATA      51

// 0x33 '4'

#define GARMIN_PKTID_RMD_DATA      52

// 0x72 'r'

#define GARMIN_PKTID_SAT_DATA      114

#define GARMIN_PKTID_L001_XFER_CMPLT     12

#define GARMIN_PKTID_L001_COMMAND_DATA   10

#define GARMIN_PKTID_L001_DATE_TIME_DATA 14

#define GARMIN_PKTID_L001_RECORDS       27

#define GARMIN_PKTID_L001_WPT_DATA       35

#define CMND_ABORT                       0

#define CMND_START_PVT_DATA              49

#define CMND_STOP_PVT_DATA               50

#define CMND_START_RM_DATA               110

#define MAX_BUFFER_SIZE 4096

#define GARMIN_CHANNELS 12

// something magic about 64, garmin driver will not return more than

// 64 at a time.  If you read less than 64 bytes the next read will

// just get the last of the 64 byte buffer.

#define ASYNC_DATA_SIZE 64

#pragma pack(1)

// This is the data format of the satellite data from the garmin USB

typedef struct __attribute__((__packed__))

{

    uint8_t svid;

    uint16_t snr;               // 0 - 0xffff

    uint8_t elev;

    uint16_t azmth;

    uint8_t status;             // bit 0, has ephemeris, 1, has diff correction

    // bit 2 used in solution

    // bit 3??

} cpo_sat_data;

/* Garmin D800_Pvt_Datetype_Type

 * packet type:  GARMIN_PKTID_PVT_DATA   51

 * This is the data format of the position data from the garmin USB */

typedef struct __attribute__((__packed__))

{

    float alt;                  // altitude above WGS 84 (meters)

    float epe;                  // estimated position error, 2 sigma (meters)

    float eph;                  // epe, but horizontal only (meters)

    float epv;                  // epe but vertical only (meters )

    int16_t fix;                /* 0 - failed integrity check

                                 * 1 - invalid or unavailable fix

                                 * 2 - 2D

                                 * 3 - 3D

                                 * 4 - 2D Diff

                                 * 5 - 3D Diff

                                 */

    double gps_tow;             // gps time of week (seconds)

    double lat;                 // ->latitude (radians)

    double lon;                 // ->longitude (radians)

    float lon_vel;              // velocity east (meters/second)

    float lat_vel;              // velocity north (meters/second)

    float alt_vel;              // velocity up (meters/sec)

    // Garmin GPS25 uses pkt_id 0x28 and does not output the

    // next 3 items

    float msl_hght;             // height of WGS 84 above MSL (meters)

    int16_t leap_sec;           // diff between GPS and UTC (seconds)

    int32_t grmn_days;          /* days from UTC December 31st, 1989 to the

                                 * beginning of the current week */

} cpo_pvt_data;

typedef struct __attribute__((__packed__))

{

    uint32_t cycles;

    double pr;                  // pseudorange in meters

    uint16_t phase;

    int8_t slp_dtct;

    uint8_t snr_dbhz;

    uint8_t svid;

    int8_t valid;

} cpo_rcv_sv_data;

/* packet type:  GARMIN_PKTID_RMD_DATA   53

 * seems identical to the packet id 0x29 from the Garmin GPS 25 */

typedef struct __attribute__((__packed__))

{

    double rcvr_tow;

    int16_t rcvr_wn;

    cpo_rcv_sv_data sv[GARMIN_CHANNELS];

} cpo_rcv_data;

// This is the packet format to/from the Garmin USB

typedef struct __attribute__((__packed__))

{

    uint8_t mPacketType;

    uint8_t mReserved1;

    uint16_t mReserved2;

    uint16_t mPacketId;

    uint16_t mReserved3;

    uint32_t mDataSize;

    union

    {

        //int8_t chars[MAX_BUFFER_SIZE];

        // cppcheck-suppress unusedStructMember

        uint8_t uchars[MAX_BUFFER_SIZE];

        cpo_pvt_data pvt;

        cpo_sat_data sats;

    } mData;

} Packet_t;

// useful funcs to read/write ints

//  floats and doubles are Intel (little-endian) order only...

// FIXME:  use include/bits.h instead

static inline void set_int16(uint8_t * buf, uint32_t value)

{

    buf[0] = (uint8_t) (0x0FF & value);

    buf[1] = (uint8_t) (0x0FF & (value >> 8));

}

static inline void set_int32(uint8_t * buf, uint32_t value)

{

    buf[0] = (uint8_t)(0x0FF & value);

    buf[1] = (uint8_t)(0x0FF & (value >> 8));

    buf[2] = (uint8_t)(0x0FF & (value >> 16));

    buf[3] = (uint8_t)(0x0FF & (value >> 24));

}

static inline uint16_t get_uint16(const uint8_t * buf)

{

    return (uint16_t)(0xFF & buf[0]) |

           ((uint16_t)(0xFF & buf[1]) << 8);

}

#if defined(HAVE_LIBUSB) && defined(__linux__)

static inline uint32_t get_int32(const uint8_t * buf)

{

    return (uint32_t)(0xFF & buf[0]) |

           ((uint32_t)(0xFF & buf[1]) << 8) |

           ((uint32_t)(0xFF & buf[2]) << 16) |

           ((uint32_t)(0xFF & buf[3]) << 24);

}

#endif  // HAVE_LIBUSB

// convert radians to degrees

static inline double radtodeg(double rad)

{

    return (double)(rad * RAD_2_DEG);

}

static gps_mask_t PrintSERPacket(struct gps_device_t *session,

                                 unsigned char pkt_id, int pkt_len,

                                 unsigned char *buf);

#if defined(HAVE_LIBUSB) && defined(__linux__)

static gps_mask_t PrintUSBPacket(struct gps_device_t *session,

                                 Packet_t * pkt);

#endif  // HAVE_LIBUSB

gps_mask_t PrintSERPacket(struct gps_device_t *session, unsigned char pkt_id,

                          int pkt_len, unsigned char *buf)

{

    gps_mask_t mask = ONLINE_SET;

    int i = 0, j = 0;

    uint16_t prod_id = 0;

    uint16_t ver = 0;

    int maj_ver;

    int min_ver;

    time_t time_l = 0;

    char msg_buf[512] = "";

    char *msg = NULL;

    cpo_sat_data *sats = NULL;

    cpo_pvt_data *pvt = NULL;

    cpo_rcv_data *rmd = NULL;

    double gps_tow = 0;

    GPSD_LOG(LOG_DATA, &session->context->errout,

             "Garmin: PrintSERPacket(, %#02x, %#02x, )\n", pkt_id, pkt_len);

    session->cycle_end_reliable = true;

    switch (pkt_id) {

    case ACK:

        GPSD_LOG(LOG_PROG, &session->context->errout, "Garmin: ACK\n");

        break;

    case NAK:

        GPSD_LOG(LOG_PROG, &session->context->errout, "Garmin: NAK\n");

        break;

    case GARMIN_PKTID_L001_COMMAND_DATA:

        // A010

        if (2 > pkt_len) {

            GPSD_LOG(LOG_WARN, &session->context->errout,

                     "Garmin: %02x-: runt payload %d",

                     pkt_id, pkt_len);

            return 0;

        }

        prod_id = get_uint16((uint8_t *) buf);

        switch (prod_id) {

        case CMND_ABORT:

            msg = "Abort current xfer";

            break;

        case CMND_START_PVT_DATA:

            msg = "Start Xmit PVT data";

            break;

        case CMND_STOP_PVT_DATA:

            msg = "Stop Xmit PVT data";

            break;

        case CMND_START_RM_DATA:

            msg = "Start RMD data";

            break;

        default:

            (void)snprintf(msg_buf, sizeof(msg_buf), "Unknown: %u",

                           (unsigned int)prod_id);

            msg = msg_buf;

            break;

        }

        GPSD_LOG(LOG_PROG, &session->context->errout,

                 "Garmin: Appl, Command Data: %s\n", msg);

        break;

    case GARMIN_PKTID_PRODUCT_RQST:

        GPSD_LOG(LOG_PROG, &session->context->errout,

                 "Garmin: Appl, Product Data req\n");

        break;

    case GARMIN_PKTID_PRODUCT_DATA:

        if (4 > pkt_len) {

            GPSD_LOG(LOG_WARN, &session->context->errout,

                     "Garmin: %02x-: runt payload %d",

                     pkt_id, pkt_len);

            return 0;

        }

        prod_id = get_uint16((uint8_t *) buf);

        ver = get_uint16((uint8_t *) & buf[2]);

        maj_ver = (int)(ver / 100);

        min_ver = (int)(ver - (maj_ver * 100));

        GPSD_LOG(LOG_PROG, &session->context->errout,

                 "Garmin: Appl, Product Data, sz: %d\n",

                 pkt_len);

        (void)snprintf(session->subtype, sizeof(session->subtype),

                       "%d: %d.%02d", (int)prod_id, maj_ver, min_ver);

        GPSD_LOG(LOG_INF, &session->context->errout,

                 "Garmin: Product ID: %d, SoftVer: %d.%02d\n",

                 prod_id, maj_ver, min_ver);

        GPSD_LOG(LOG_INF, &session->context->errout,

                 "Garmin: Product Desc: %s\n", &buf[4]);

        mask |= DEVICEID_SET;

        GPSD_LOG(LOG_DATA, &session->context->errout,

                 "Garmin: PRODUCT_DATA: subtype=%s\n",

                 session->subtype);

        break;

    case GARMIN_PKTID_PVT_DATA:

        // 0x33 (51)

        if (64 > pkt_len) {

            GPSD_LOG(LOG_WARN, &session->context->errout,

                     "Garmin: %02x-: runt payload %d",

                     pkt_id, pkt_len);

            return 0;

        }

        GPSD_LOG(LOG_PROG, &session->context->errout,

                 "Garmin: PVT Data (51) Sz: %d\n", pkt_len);

        pvt = (cpo_pvt_data *) buf;

        session->context->leap_seconds = (int)GPSD_LE16TOH(pvt->leap_sec);

        session->context->valid = LEAP_SECOND_VALID;

        // 631065600, unix seconds for 31 Dec 1989 Zulu

        time_l = (time_t) (631065600 + (GPSD_LE32TOH(pvt->grmn_days) * 86400));

        // TODO, convert grmn_days to context->gps_week

        time_l -= session->context->leap_seconds;

        // gps_tow is always like x.999 or x.998 just round it to nearest sec

        // FIXME! this will break 5Hz garmins...

        gps_tow = GPSD_LED64(pvt->gps_tow);

        time_l += (time_t)round(gps_tow);

        /* sanity check unix time against leap second.

         * Leap second 18 at 1 Jan 2017: 1483228800 */

        if (17 < session->context->leap_seconds &&

            1483228800L > time_l) {

            time_l += 619315200;               // fast forward 1024 weeks

        }

        DTOTS(&session->context->gps_tow, gps_tow);

        session->newdata.time.tv_sec = time_l;

        session->newdata.time.tv_nsec = 0;

        // (long long) for 32-bit systems

        GPSD_LOG(LOG_PROG, &session->context->errout,

                 "Garmin: time_l: %lld\n", (long long)time_l);

        session->newdata.latitude = radtodeg(GPSD_LED64(pvt->lat));

        session->newdata.longitude = radtodeg(GPSD_LED64(pvt->lon));

        // altitude is WGS84

        session->newdata.altHAE = GPSD_LEF32(pvt->alt);

        // geoid separation from WGS 84

        // gpsd sign is opposite of garmin sign

        session->newdata.geoid_sep = -GPSD_LEF32(pvt->msl_hght);

        /* Estimated position error in meters.  Confidence (sigma) not

         * specified by Garmin.

         * We follow the advice at <http://gpsinformation.net/main/errors.htm>.

         * Since GPS data is not gaussian, this is marginal advice...

         * If this assumption changes here, it should also change in

         * nmea_parse.c where we analyze PGRME.

         */

        session->newdata.sep = GPSD_LEF32(pvt->epe) *

                                   (GPSD_CONFIDENCE / CEP50_SIGMA);

        // eph, horizaontal error, 2 sigma

        session->newdata.eph = GPSD_LEF32(pvt->eph) *

                                   (GPSD_CONFIDENCE / CEP50_SIGMA);

        // eph, horizaontal error, 2 sigma

        session->newdata.epv = GPSD_LEF32(pvt->epv) *

                                   (GPSD_CONFIDENCE / CEP50_SIGMA);

        // meters/sec

        session->newdata.NED.velN = GPSD_LEF32(pvt->lat_vel);

        session->newdata.NED.velE = GPSD_LEF32(pvt->lon_vel);

        session->newdata.NED.velD = -GPSD_LEF32(pvt->alt_vel);

        switch (GPSD_LE16TOH(pvt->fix)) {

        case 0:

        case 1:

        default:

            // no fix

            session->newdata.status = STATUS_UNK;

            session->newdata.mode = MODE_NO_FIX;

            break;

        case 2:

            // 2D fix

            session->newdata.status = STATUS_GPS;

            session->newdata.mode = MODE_2D;

            break;

        case 3:

            // 3D fix

            session->newdata.status = STATUS_GPS;

            session->newdata.mode = MODE_3D;

            break;

        case 4:

            // 2D Differential fix

            session->newdata.status = STATUS_DGPS;

            session->newdata.mode = MODE_2D;

            break;

        case 5:

            // 3D differential fix

            session->newdata.status = STATUS_DGPS;

            session->newdata.mode = MODE_3D;

            break;

        }

        GPSD_LOG(LOG_PROG, &session->context->errout,

                 "Garmin: Appl, mode %d, status %d\n",

                 session->newdata.mode, session->newdata.status);

        // save some expensive calculations if not needed

        if (session->context->errout.debug >= LOG_INF) {

            GPSD_LOG(LOG_INF, &session->context->errout,

                     "Garmin: UTC Time: %lld\n",

                     (long long)session->newdata.time.tv_sec);

            GPSD_LOG(LOG_INF, &session->context->errout,

                     "Garmin: Geoid Separation (MSL-WGS84): from garmin %lf, "

                     "calculated %lf\n",

                     session->newdata.geoid_sep,

                     wgs84_separation(session->newdata.latitude,

                                         session->newdata.longitude));

            GPSD_LOG(LOG_INF, &session->context->errout,

                     "Garmin: Alt: %.3f, sep: %.3f, eph: %.3f, Epv: %.3f, "

                     "Fix: %d, Gps_tow: %f, Lat: %.3f, Lon: %.3f, "

                     "velN: %.3f, velE: %.3f, velD: %.3f, geoidsep: %.3f, "

                     "Leap: %d, GarminDays: %ld\n",

                     session->newdata.altHAE,

                     session->newdata.sep,

                     session->newdata.eph,

                     session->newdata.epv,

                     GPSD_LE16TOH(pvt->fix),

                     gps_tow,

                     session->newdata.latitude,

                     session->newdata.longitude,

                     session->newdata.NED.velN,

                     session->newdata.NED.velE,

                     session->newdata.NED.velD,

                     session->newdata.geoid_sep,

                     session->context->leap_seconds,

                     GPSD_LE32TOH(pvt->grmn_days));

        }

        if (session->newdata.mode > MODE_NO_FIX) {

            // data only valid with a fix

            mask |=

                TIME_SET | LATLON_SET | ALTITUDE_SET | STATUS_SET | MODE_SET |

                HERR_SET | PERR_IS | CLEAR_IS | REPORT_IS | VNED_SET;

            /*

             * Garmin documentation says we should wait until four good fixes

             * have been seen before trying to use the device for precision

             * time service.

             */

            if (session->fixcnt > 3)

                mask |= NTPTIME_IS;

        }

        GPSD_LOG(LOG_DATA, &session->context->errout,

                 "Garmin: PVT_DATA: time=%lld, lat=%.2f lon=%.2f "

                 "eph=%.2f sep=%.2f epv=%.2f  mode=%d status=%d\n",

                 (long long)session->newdata.time.tv_sec,

                 session->newdata.latitude,

                 session->newdata.longitude,

                 session->newdata.eph,

                 session->newdata.sep,

                 session->newdata.epv,

                 session->newdata.mode,

                 session->newdata.status);

        break;

    case GARMIN_PKTID_RMD_DATA:

        FALLTHROUGH

    case GARMIN_PKTID_RMD41_DATA:

        rmd = (cpo_rcv_data *) buf;

        GPSD_LOG(LOG_DATA, &session->context->errout,

                 "Garmin: PVT RMD Data Sz: %d\n", pkt_len);

        GPSD_LOG(LOG_PROG, &session->context->errout,

                 "Garmin: PVT RMD rcvr_tow: %f, rcvr_wn: %d\n",

                 GPSD_LED64(rmd->rcvr_tow), GPSD_LE16TOH(rmd->rcvr_wn));

        for (i = 0; i < GARMIN_CHANNELS; i++) {

            GPSD_LOG(LOG_INF, &session->context->errout,

                     "Garmin: PVT RMD Sat: %3u, cycles: %9lu, pr: %16.6f, "

                     "phase: %7.3f, slp_dtct: %3s, snr: %3u, Valid: %3s\n",

                     (int)rmd->sv[i].svid + 1,

                     GPSD_LE32TOH(rmd->sv[i].cycles),

                     GPSD_LED64(rmd->sv[i].pr),

                     (GPSD_LE16TOH(rmd->sv[i].phase) * 360.0) / 2048.0,

                     rmd->sv[i].slp_dtct != 0 ? "Yes" : "No",

                     rmd->sv[i].snr_dbhz,

                     rmd->sv[i].valid != 0 ? "Yes" : "No");

        }

        break;

    case GARMIN_PKTID_SAT_DATA:

        // record ID 0x72 (114)

        GPSD_LOG(LOG_PROG, &session->context->errout,

                 "Garmin: SAT Data Sz: %d\n", pkt_len);

        sats = (cpo_sat_data *) buf;

        session->gpsdata.satellites_used = 0;

        gpsd_zero_satellites(&session->gpsdata);

        for (i = 0, j = 0; i < GARMIN_CHANNELS; i++, sats++) {

            GPSD_LOG(LOG_INF, &session->context->errout,

                     "Garmin: Sat %2d, snr: %5u, elev: %2d, Azmth: %3d, "

                     "Stat: x%x\n",

                     sats->svid, GPSD_LE16TOH(sats->snr), sats->elev,

                     GPSD_LE16TOH(sats->azmth),

                     sats->status);

            if (255 == (int)sats->svid) {

                // Garmin uses 255 for empty

                // gpsd uses 0 for empty

                continue;

            }

            if ((int)sats->svid <= 32) {

                // GPS 1-32

                session->gpsdata.skyview[j].PRN = (short)sats->svid;

                session->gpsdata.skyview[j].svid = (short)sats->svid;

                session->gpsdata.skyview[j].gnssid = GNSSID_GPS;

            } else {

                // SBAS 33-64

                session->gpsdata.skyview[j].PRN = (short)sats->svid;

                session->gpsdata.skyview[j].svid = (short)sats->svid + 87;

                session->gpsdata.skyview[j].gnssid = GNSSID_SBAS;

            }

            session->gpsdata.skyview[j].azimuth =

                (short)GPSD_LE16TOH(sats->azmth);

            session->gpsdata.skyview[j].elevation = (short)sats->elev;

            if (0xffff == sats->snr) {

                session->gpsdata.skyview[j].ss = NAN;

            } else {

                // Garmin does not document this.  snr is in dB*100

                // Known, but not seen satellites have a dB value of -1*100

                session->gpsdata.skyview[j].ss =

                    (float)(GPSD_LE16TOH(sats->snr) / 100.0);

            }

            // FIX-ME: Garmin documents this, but Daniel Dorau

            // <daniel.dorau@gmx.de> says the behavior on his GPSMap60CSX

            // doesn't match it.

            if ((uint8_t) 0 != (sats->status & 4)) {

                // used in solution?

                session->gpsdata.skyview[j].used = true;

                session->gpsdata.satellites_used++;

            }

            session->gpsdata.satellites_visible++;

            j++;

        }

        session->gpsdata.skyview_time.tv_sec = 0;

        session->gpsdata.skyview_time.tv_nsec = 0;

        mask |= USED_IS | SATELLITE_SET;

        GPSD_LOG(LOG_DATA, &session->context->errout,

                 "Garmin: SAT_DATA: visible=%d used=%d\n",

                 session->gpsdata.satellites_visible,

                 session->gpsdata.satellites_used);

        break;

    case GARMIN_PKTID_PROTOCOL_ARRAY:

        // Pid_Protocol_Array, ID 253

        // this packet is never requested, it just comes, in some case

        // after a GARMIN_PKTID_PRODUCT_RQST

        GPSD_LOG(LOG_INF, &session->context->errout,

                 "Garmin: Appl, Product Capability, sz: %d\n",

                 pkt_len);

        for (i = 0; i < pkt_len; i += 3) {

            GPSD_LOG(LOG_INF, &session->context->errout,

                     "Garmin:   %c%03d\n",

                     buf[i],    get_uint16((uint8_t *) & buf[i + 1]));

        }

        break;

    default:

        GPSD_LOG(LOG_WARN, &session->context->errout,

                 "Garmin: Unknown packet id: %#02x, Sz: %#02x\n",

                 pkt_id, pkt_len);

        break;

    }

    GPSD_LOG(LOG_DATA, &session->context->errout,

             "Garmin: PrintSERPacket(, %#02x, %#02x, ) mask=(%s)\n",

             pkt_id, pkt_len, gps_maskdump(mask));

    return mask;

}

#if defined(HAVE_LIBUSB) && defined(__linux__)

// For debugging, decodes and prints some known packets

static gps_mask_t PrintUSBPacket(struct gps_device_t *session, Packet_t * pkt)

{

    gps_mask_t mask = 0;

    int maj_ver;

    int min_ver;

    uint32_t mode = 0;

    uint16_t prod_id = 0;

    uint32_t veri = 0;

    uint32_t serial;

    uint32_t mDataSize = get_int32((uint8_t *) & pkt->mDataSize);

    uint8_t *buffer = (uint8_t *) pkt;

    GPSD_LOG(LOG_PROG, &session->context->errout, "Garmin: PrintUSBPacket()\n");

    if (DLE == pkt->mPacketType) {

        GPSD_LOG(LOG_PROG, &session->context->errout,

                 "Garmin: really a SER packet!\n");

        return PrintSERPacket(session,

                              (unsigned char)buffer[1],

                              (int)buffer[2], (unsigned char *)(buffer + 3));

    }

    if (4096 < mDataSize) {

        GPSD_LOG(LOG_WARN, &session->context->errout,

                 "Garmin: bogus packet, size too large=%d\n",

                 mDataSize);

        return 0;

    }

    switch (pkt->mPacketType) {

    case GARMIN_LAYERID_TRANSPORT:

        // Garmin USB layer specific

        switch (pkt->mPacketId) {

        case GARMIN_PKTID_TRANSPORT_START_SESSION_REQ:

            // Pid_Start_Session, ID 5

            GPSD_LOG(LOG_PROG, &session->context->errout,

                     "Garmin: Transport, Start Session req\n");

            break;

        case GARMIN_PKTID_TRANSPORT_START_SESSION_RESP:

            // Pid_Session_Started, ID 6

            mode = get_int32(&pkt->mData.uchars[0]);

            GPSD_LOG(LOG_PROG, &session->context->errout,

                     "Garmin: Transport, Start Session resp, unit: 0x%x\n",

                     mode);

            break;

        default:

            GPSD_LOG(LOG_PROG, &session->context->errout,

                     "Garmin: Transport, Packet: Type %d %d %d, ID: %d,"

                     "Sz: %d\n",

                     pkt->mPacketType, pkt->mReserved1, pkt->mReserved2,

                     pkt->mPacketId, mDataSize);

            break;

        }

        break;

    case GARMIN_LAYERID_APPL:

        // raw data transport, shared with Garmin Serial Driver

        mask = PrintSERPacket(session,

                              (unsigned char)pkt->mPacketId,

                              (int)mDataSize,

                              (unsigned char *)pkt->mData.uchars);

        break;

    case 75:

        // private, garmin USB kernel driver specific

        switch (pkt->mPacketId) {

        case PRIV_PKTID_SET_MODE:

            prod_id = get_uint16(&pkt->mData.uchars[0]);

            GPSD_LOG(LOG_PROG, &session->context->errout,

                     "Garmin: Private, Set Mode: %d\n", prod_id);

            break;

        case PRIV_PKTID_INFO_REQ:

            GPSD_LOG(LOG_PROG, &session->context->errout,

                     "Garmin: Private, ID: Info Req\n");

            break;

        case PRIV_PKTID_INFO_RESP:

            veri = get_int32(pkt->mData.uchars);

            maj_ver = (int)(veri >> 16);

            min_ver = (int)(veri & 0xffff);

            mode = get_int32(&pkt->mData.uchars[4]);

            serial = get_int32(&pkt->mData.uchars[8]);

            GPSD_LOG(LOG_PROG, &session->context->errout,

                     "Garmin: Private, ID: Info Resp\n");

            GPSD_LOG(LOG_INF, &session->context->errout,

                     "Garmin: USB Driver Version %d.%d Mode %d, Serial# %u\n",

                     maj_ver, min_ver, mode, serial);

            break;

        default:

            GPSD_LOG(LOG_PROG, &session->context->errout,

                     "Garmin: Private, Packet: ID: %d, Sz: %d\n",

                     pkt->mPacketId, mDataSize);

            break;

        }

        break;

    default:

        GPSD_LOG(LOG_PROG, &session->context->errout,

                 "Garmin: Packet: Type %d %d %d, ID: %d, Sz: %d\n",

                 pkt->mPacketType, pkt->mReserved1, pkt->mReserved2,

                 pkt->mPacketId, mDataSize);

        break;

    }

    return mask;

}

#endif  // HAVE_LIBUSB

#if defined(HAVE_LIBUSB) && defined(__linux__)

// build and send a packet w/ USB protocol

static void Build_Send_USB_Packet(struct gps_device_t *session,

                                  uint32_t layer_id, uint32_t pkt_id,

                                  uint32_t length, uint32_t data)

{

    uint8_t *buffer = (uint8_t *) session->driver.garmin.Buffer;

    Packet_t *thePacket = (Packet_t *) buffer;

    ssize_t theBytesReturned = 0;

    ssize_t theBytesToWrite = 12 + (ssize_t) length;

    set_int32(buffer, layer_id);

    set_int32(buffer + 4, pkt_id);

    set_int32(buffer + 8, length);

    if (2 == length) {

        set_int16(buffer + 12, data);

    } else if (4 == length) {

        set_int32(buffer + 12, data);

    }

    (void)PrintUSBPacket(session, thePacket);

    theBytesReturned = gpsd_write(session, (const char *)thePacket,

                                  (size_t) theBytesToWrite);

    GPSD_LOG(LOG_PROG, &session->context->errout,

             "Garmin: SendPacket(), wrote %zd bytes\n",

             theBytesReturned);

    // Garmin says:

    // If the packet size was an exact multiple of the USB packet

    // size, we must make a final write call with no data

    // as a practical matter no known packets are 64 bytes long so

    // this is untested

    // So here goes just in case

    if (0 == (theBytesToWrite % ASYNC_DATA_SIZE)) {

        char *n = "";

        (void)gpsd_write(session, n, 0);

    }

}

#endif  // HAVE_LIBUSB && __linux__

/* build and send a packet in serial protocol

 * layer_id unused */

// FIX-ME: This should go through the common message buffer someday

static void Build_Send_SER_Packet(struct gps_device_t *session,

                                  uint32_t layer_id UNUSED, uint32_t pkt_id,

                                  uint32_t length, uint32_t data)

{

    uint8_t *buffer = (uint8_t *) session->driver.garmin.Buffer;

    uint8_t *buffer0 = buffer;

    Packet_t *thePacket = (Packet_t *) buffer;

    ssize_t theBytesReturned = 0;

    ssize_t theBytesToWrite = 6 + (ssize_t) length;

    uint8_t chksum = 0;

    *buffer++ = (uint8_t) DLE;

    *buffer++ = (uint8_t) pkt_id;

    chksum = pkt_id;

    *buffer++ = (uint8_t) length;

    chksum += length;

    // ??? What is this doing?

    if (2 == length) {

        // careful!  no DLE stuffing here!

        set_int16(buffer, data);

        chksum += buffer[0];

        chksum += buffer[1];

    } else if (4 == length) {

        // careful!  no DLE stuffing here!

        set_int32(buffer, data);

        chksum += buffer[0];

        chksum += buffer[1];

        chksum += buffer[2];

        chksum += buffer[3];

    }

    // ??? How is data copied to the buffer?

    buffer += length;

    // Add checksum

    *buffer++ = -chksum;

    if (DLE == -chksum) {

        // stuff another DLE

        *buffer++ = (uint8_t) DLE;

        theBytesToWrite++;

    }

    // Add DLE, ETX

    *buffer++ = (uint8_t) DLE;

    // we used to say n++ here, but scan-build complains

    *buffer = (uint8_t) ETX;

    (void)PrintSERPacket(session,

                         (unsigned char)buffer0[1],

                         (int)buffer0[2], (unsigned char *)(buffer0 + 3));

    theBytesReturned = gpsd_write(session, (const char *)thePacket,

                                  (size_t) theBytesToWrite);

    GPSD_LOG(LOG_PROG, &session->context->errout,

             "Garmin: SendPacket(), wrote %zd bytes\n",

             theBytesReturned);

}

#if defined(HAVE_LIBUSB) && defined(__linux__)

/*

 * is_usb_device() - is a specified device USB matching given vendor/product?

 *

 * BUG: Doesn't actually match against path yet. Must finish this function

 * by querying /sys/dev/char, either directly or using libudev. Greg KH

 * assures this is possible, though he is vague about how.

 *

 * libudev: http://www.kernel.org/pub/linux/utils/kernel/hotplug/libudev/

 */

static bool is_usb_device(const char *path UNUSED, int vendor, int product,

                          struct gpsd_errout_t *errout)

{

    // discover devices

    libusb_device **list;

    ssize_t cnt;

    ssize_t i = 0;

    bool found = false;

    GPSD_LOG(LOG_INF, errout, "attempting USB device enumeration.\n");

    (void)libusb_init(NULL);

    if (0 > (cnt = libusb_get_device_list(NULL, &list))) {

        GPSD_LOG(LOG_ERROR, errout, "USB device list call failed.\n");

        libusb_exit(NULL);

        return false;

    }

    for (i = 0; i < cnt; i++) {

        struct libusb_device_descriptor desc;

        libusb_device *dev = list[i];

        int r = libusb_get_device_descriptor(dev, &desc);

        if (0 > r) {

            GPSD_LOG(LOG_ERROR, errout,

                     "USB descriptor fetch failed on device %zd.\n", i);

            continue;

        }

        // we can extract device descriptor data

        GPSD_LOG(LOG_INF, errout,

                 "%04x:%04x (bus %d, device %d)\n",

                 desc.idVendor, desc.idProduct,

                 libusb_get_bus_number(dev),

                 libusb_get_device_address(dev));

        // we match if vendor and product ID are right

        if (desc.idVendor == (uint16_t)vendor &&

            desc.idProduct == (uint16_t)product) {

            found = true;

            break;

        }

    }

    GPSD_LOG(LOG_INF, errout,

             "vendor/product match with %04x:%04x %sfound\n",

             vendor, product, found ? "" : "not ");

    libusb_free_device_list(list, 1);

    libusb_exit(NULL);

    return found;

}

#endif  // HAVE_LIBUSB

/*

 * garmin_usb_detect() - detect a Garmin USB device connected to session fd.

 *

 * This is ONLY for USB devices reporting as: 091e:0003.

 *

 * This driver ONLY works in Linux and ONLY when the garmin_gps kernel

 * module is installed.

 *

 * This is only necessary because under Linux Garmin USB devices need a

 * kernel module rather than being normal USB-serial devices.

 *

 * The actual wire protocol from the Garmin device is very strange. There

 * are no delimiters.  End of packet is signaled by a zero-length read

 * on the USB device, and start of packet is the next read.  You can't just

 * ignore the zero reads and pass the data through - you'd never be able

 * to tell where the packet boundaries are.

 *

 * The garmin_usb module's job is to grab the packet and frame it in

 * DLEs (with DLE stuffing).  This makes the USB packets look as

 * though they came from a regular Garmin *serial* device, which is how

 * most of the processing for both types can be unified here.

 *

 * return 1 is device found

 * return 0 if not

 */

static bool garmin_usb_detect(struct gps_device_t *session UNUSED)

{

#if defined(__linux__)

    /*

     * Only perform this check if we're looking at a USB-serial

     * device.  This prevents drivers for attached serial GPSes

     * fronm being rudely elbowed aside by this one if they happen

     * to be trying to coexist with the Garmin.

     */

    if (SOURCE_USB != session->sourcetype) {

        return false;

    }

#ifdef HAVE_LIBUSB

    if (!is_usb_device(session->gpsdata.dev.path, 0x091e, 0x0003,

            &session->context->errout)) {

        return false;

    }

    if (!gpsd_set_raw(session)) {

        GPSD_LOG(LOG_ERROR, &session->context->errout,

                 "Garmin: garmin_usb_detect: error changing port "

                 "attributes: %s\n",

                 strerror(errno));

        return false;

    }

    if (sizeof(session->driver.garmin.Buffer) < sizeof(Packet_t)) {

        // dunno how this happens, but it does on some compilers

        GPSD_LOG(LOG_ERROR, &session->context->errout,

                 "Garmin: garmin_usb_detect: Compile error, "

                 "garmin.Buffer too small.\n");

        return false;

    }

    // FIXME!!! needs to use libusb totally and move garmin_gps aside */

    // set Mode 1, mode 0 is broken somewhere past 2.6.14

    // but how?

    GPSD_LOG(LOG_PROG, &session->context->errout,

             "Garmin: Set garmin_gps driver mode = 0\n");

    Build_Send_USB_Packet(session, GARMIN_LAYERID_PRIVATE,

                          PRIV_PKTID_SET_MODE, 4, MODE_GARMIN_SERIAL);

    // expect no return packet !?

    return true;

#endif  // HAVE_LIBUSB

#endif  // __linux__

    return false;

}

static void garmin_event_hook(struct gps_device_t *session, event_t event)

{

    if (session->context->readonly ||

        session->context->passive) {

        return;

    }

    /*

     * FIX-ME: It might not be necessary to call this on reactivate.

     * Experiment to see if the holds its settings through a close.

     */

    if (event == EVENT_IDENTIFIED ||

        event == EVENT_REACTIVATE) {

        // Tell the device to send product data

        GPSD_LOG(LOG_PROG, &session->context->errout,

                 "Garmin: Get Product Data\n");

        Build_Send_SER_Packet(session, GARMIN_LAYERID_APPL,

                              GARMIN_PKTID_PRODUCT_RQST, 0, 0);

        // turn on PVT data 49

        GPSD_LOG(LOG_PROG, &session->context->errout,

                 "Garmin: Set to send reports every 1 second\n");

        Build_Send_SER_Packet(session, GARMIN_LAYERID_APPL,

                              GARMIN_PKTID_L001_COMMAND_DATA, 2,

                              CMND_START_PVT_DATA);

#if USE_RMD

        // turn on RMD data 110

        GPSD_LOG(LOG_PROG, &session->context->errout,

                 "Garmin: Set to send Raw sat data\n");

        Build_Send_SER_Packet(session, GARMIN_LAYERID_APPL,

                              GARMIN_PKTID_L001_COMMAND_DATA, 2,

                              CMND_START_RM_DATA);

#endif

    }

    if (event == EVENT_DEACTIVATE) {

        // FIX-ME: is any action needed, or is closing the port sufficient?

        GPSD_LOG(LOG_PROG, &session->context->errout,

                 "Garmin: garmin_close()\n");

    }

}

#define Send_ACK()    Build_Send_SER_Packet(session, 0, ACK, 0, 0)

#define Send_NAK()    Build_Send_SER_Packet(session, 0, NAK, 0, 0)

gps_mask_t garmin_ser_parse(struct gps_device_t *session)

{

    unsigned char *buf = session->lexer.outbuffer;

    size_t len = session->lexer.outbuflen;

    unsigned char data_buf[300];  // Max Garmin payload is 255

    unsigned char c;

    int i = 0;

    size_t n = 0;

    int data_index = 0;

    int got_dle = 0;

    unsigned char pkt_id = 0;