From 76535a3b3318266b691a12bef71db467be47282d Mon Sep 17 00:00:00 2001
From: "Eric S. Raymond" <esr@thyrsus.com>
Date: Thu, 29 Jan 2015 12:49:06 -0500
Subject: Add a minimum packet length to every driver.

Length 0 means the minimum is unknown and the driver should use character I/O.
---
 drivers.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

(limited to 'drivers.c')

diff --git a/drivers.c b/drivers.c
index 0003ad11..b5c898dc 100644
--- a/drivers.c
+++ b/drivers.c
@@ -16,6 +16,8 @@
 #include "bits.h"		/* for getbeu16(), to extract big-endian words */
 #include "strfuncs.h"
 
+#define NMEA_MINLENGTH	16	/* minimum length of NMEA0183 packet */
+
 ssize_t generic_get(struct gps_device_t *session)
 {
     return packet_get(session->gpsdata.gps_fd, &session->lexer);
@@ -102,6 +104,7 @@ const struct gps_type_t driver_unknown = {
 #ifdef TIMEHINT_ENABLE
     .time_offset     = NULL,		/* no method for NTP fudge factor */
 #endif /* TIMEHINT_ENABLE */
+    .minlength	     = 0,		/* minimum packet length is unknown */
 };
 /* *INDENT-ON* */
 
@@ -272,6 +275,7 @@ const struct gps_type_t driver_nmea0183 = {
 #ifdef TIMEHINT_ENABLE
     .time_offset     = NULL,		/* no method for NTP fudge factor */
 #endif /* TIMEHINT_ENABLE */
+    .minlength	    = NMEA_MINLENGTH,	/* min packet length for chunked I/O */
 };
 /* *INDENT-ON* */
 
@@ -374,6 +378,7 @@ const struct gps_type_t driver_garmin = {
 #ifdef TIMEHINT_ENABLE
     .time_offset     = NULL,		/* no method for NTP fudge factor */
 #endif /* TIMEHINT_ENABLE */
+    .minlength	    = NMEA_MINLENGTH,	/* min packet length for chunked I/O */
 };
 /* *INDENT-ON* */
 #endif /* GARMIN_ENABLE && NMEA_ENABLE */
@@ -437,6 +442,7 @@ const struct gps_type_t driver_ashtech = {
 #ifdef TIMEHINT_ENABLE
     .time_offset     = NULL,		/* no method for NTP fudge factor */
 #endif /* TIMEHINT_ENABLE */
+    .minlength	     = 0,		/* minimum packet length is unknown */
 };
 /* *INDENT-ON* */
 #endif /* ASHTECH_ENABLE */
@@ -489,6 +495,7 @@ const struct gps_type_t driver_fv18 = {
 #ifdef TIMEHINT_ENABLE
     .time_offset     = NULL,		/* no method for NTP fudge factor */
 #endif /* TIMEHINT_ENABLE */
+    .minlength	    = NMEA_MINLENGTH,	/* use NMEA minimum length */
 };
 /* *INDENT-ON* */
 #endif /* FV18_ENABLE */
@@ -544,6 +551,7 @@ const struct gps_type_t driver_gpsclock = {
 #ifdef TIMEHINT_ENABLE
     .time_offset     = NULL,		/* no method for NTP fudge factor */
 #endif /* TIMEHINT_ENABLE */
+    .minlength	    = NMEA_MINLENGTH,	/* use NMEA minimum length */
 };
 /* *INDENT-ON* */
 #endif /* GPSCLOCK_ENABLE */
@@ -600,6 +608,7 @@ static const struct gps_type_t driver_tripmate = {
 #ifdef TIMEHINT_ENABLE
     .time_offset     = NULL,		/* no method for NTP fudge factor */
 #endif /* TIMEHINT_ENABLE */
+    .minlength	    = NMEA_MINLENGTH,	/* use NME0183 minimum langth */
 };
 /* *INDENT-ON* */
 #endif /* TRIPMATE_ENABLE */
@@ -651,6 +660,7 @@ static const struct gps_type_t driver_earthmate = {
 #endif /* CONTROLSEND_ENABLE */
 #ifdef TIMEHINT_ENABLE
     .time_offset     = NULL,		/* no method for NTP fudge factor */
+    .minlength	     = 40,		/* use Zodiac minimum langth */
 #endif /* TIMEHINT_ENABLE */
 };
 /*@ -redef @*/
@@ -778,6 +788,7 @@ const struct gps_type_t driver_trueNorth = {
 #ifdef TIMEHINT_ENABLE
     .time_offset     = NULL,
 #endif /* TIMEHINT_ENABLE */
+    .minlength	    = NMEA_MINLENGTH,	/* use NME0183 minimum langth */
 };
 /* *INDENT-ON* */
 #endif
@@ -858,6 +869,7 @@ static const struct gps_type_t driver_oceanServer = {
 #ifdef TIMEHINT_ENABLE
     .time_offset     = NULL,
 #endif /* TIMEHINT_ENABLE */
+    .minlength	    = NMEA_MINLENGTH,	/* use NME0183 minimum langth */
 };
 /* *INDENT-ON* */
 #endif
@@ -926,6 +938,7 @@ static const struct gps_type_t driver_fury = {
 #ifdef TIMEHINT_ENABLE
     .time_offset     = NULL,
 #endif /* TIMEHINT_ENABLE */
+    .minlength	    = NMEA_MINLENGTH,	/* use NME0183 minimum langth */
 };
 /* *INDENT-ON* */
 
@@ -981,6 +994,7 @@ static const struct gps_type_t driver_rtcm104v2 = {
 #ifdef TIMEHINT_ENABLE
     .time_offset     = NULL,
 #endif /* TIMEHINT_ENABLE */
+    .minlength	    = 0,		/* raw I/O - could probably be tuned */
 };
 /* *INDENT-ON* */
 #endif /* RTCM104V2_ENABLE */
@@ -1028,6 +1042,7 @@ static const struct gps_type_t driver_rtcm104v3 = {
 #ifdef TIMEHINT_ENABLE
     .time_offset     = NULL,
 #endif /* TIMEHINT_ENABLE */
+    .minlength	    = 0,		/* raw I/O - could probably be tuned */
 };
 /* *INDENT-ON* */
 #endif /* RTCM104V3_ENABLE */
@@ -1064,6 +1079,7 @@ static const struct gps_type_t driver_garmintxt = {
 #ifdef TIMEHINT_ENABLE
     .time_offset     = NULL,
 #endif /* TIMEHINT_ENABLE */
+    .minlength     = 0,			/* min packet length unknown */
 };
 /* *INDENT-ON* */
 #endif /* GARMINTXT_ENABLE */
@@ -1160,6 +1176,7 @@ const struct gps_type_t driver_mtk3301 = {
 #ifdef TIMEHINT_ENABLE
     .time_offset     = NULL,
 #endif /* TIMEHINT_ENABLE */
+    .minlength	    = NMEA_MINLENGTH,	/* use NME0183 minimum langth */
 };
 /* *INDENT-ON* */
 #endif /* MTK3301_ENABLE */
@@ -1403,6 +1420,7 @@ const struct gps_type_t driver_aivdm = {
 #ifdef TIMEHINT_ENABLE
     .time_offset     = NULL,		/* no NTP communication */
 #endif /* TIMEHINT_ENABLE */
+    .minlength       = 23,		/* minimum AIVDM packet length */
 };
 /* *INDENT-ON* */
 #endif /* AIVDM_ENABLE */
@@ -1507,6 +1525,7 @@ const struct gps_type_t driver_json_passthrough = {
 #ifdef TIMEHINT_ENABLE
     .time_offset     = NULL,		/* no method for NTP fudge factor */
 #endif /* TIMEHINT_ENABLE */
+    .minlength       = 43,		/* minimum JSON packet length */
 };
 /* *INDENT-ON* */
 
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