Back out the attempt to use VTIME.

According to Matthias Drochner at
http://lists.lysator.liu.se/pipermail/lsh-bugs/2003q4/000151.html:

   I thought I'd give lsh a try, just to see how it compares to openssh...
   The client didn't work well on NetBSD, got a message like "unexpected
   EWOULDBLOCK" on each keystroke.
   Looked a bit deeper and found that stdin is set to O_NONBLOCK and
   a raw tty mode with c_cc[VMIN] > 1 and c_cc[VTIME] > 0.
   I'll append a little test program which does the same. I've tried
   it on 3 operating systems (Linux, NetBSD, Digital UNIX), and it
   behaves differently on each:

   -on Linux, if a key is pressed, the read returns immediately with
    that one character
   -on NetBSD, the read returns with no data but EWOULDBLOCK
   -on D'UNIX, the poll() doesn't teturn before 4 keypresses are done;
    the read() returns these 4 characters

   Indeed, in SUSv2's termios page is a sentence which says that if
   both O_NONBLOCK and VTIME>0 are set, the behaviour is more or less
   undefined.

   I've solved my immediate problems by setting VMIN to 1 instead of 4
   in unix_interact.c:do_make_raw(), but VTIME is still pointless,
   so I wouldn't call this a clean solution.

All regression tests pass.

18 files changed, 14 insertions, 97 deletions

diff --git a/driver_evermore.c b/driver_evermore.c
index 92a99044..132d1db4 100644
--- a/driver_evermore.c
+++ b/driver_evermore.c
@@ -637,7 +637,6 @@ const struct gps_type_t driver_evermore =
 #ifdef TIMEHINT_ENABLE
     .time_offset     = NULL,		/* no method for NTP fudge factor */
 #endif /* TIMEHINT_ENABLE */
-    .minlength       = 10,		/* min packet length for chunked I/O */
 };
 /* *INDENT-ON* */
 #endif /* defined(EVERMORE_ENABLE) && defined(BINARY_ENABLE) */
diff --git a/driver_garmin.c b/driver_garmin.c
index 7450d5f7..d9d4888d 100644
--- a/driver_garmin.c
+++ b/driver_garmin.c
@@ -1401,7 +1401,6 @@ const struct gps_type_t driver_garmin_usb_binary_old =
 #ifdef TIMEHINT_ENABLE
     .time_offset     = garmin_time_offset,
 #endif /* TIMEHINT_ENABLE */
-    .minlength       = 0;		/* min packet length unknown */
 };
 /* *INDENT-ON* */
 #endif /* __UNUSED__ */
@@ -1432,7 +1431,6 @@ const struct gps_type_t driver_garmin_usb_binary =
 #ifdef TIMEHINT_ENABLE
     .time_offset     = garmin_time_offset,
 #endif /* TIMEHINT_ENABLE */
-    .minlength       = 0,		/* min packet length unknown */
 };
 /* *INDENT-ON* */
 
@@ -1462,7 +1460,6 @@ const struct gps_type_t driver_garmin_ser_binary =
 #ifdef TIMEHINT_ENABLE
     .time_offset     = garmin_time_offset,
 #endif /* TIMEHINT_ENABLE */
-    .minlength       = 0,		/* min packet length unknown */
 };
 /* *INDENT-ON* */
 
diff --git a/driver_geostar.c b/driver_geostar.c
index 06b2d563..11e9ad78 100644
--- a/driver_geostar.c
+++ b/driver_geostar.c
@@ -640,7 +640,6 @@ const struct gps_type_t driver_geostar =
 #ifdef TIMEHINT_ENABLE
     .time_offset     = geostar_time_offset,
 #endif /* TIMEHINT_ENABLE */
-    .minlength       = 24,		/* min packet length for the GeoStar */
 };
 /* *INDENT-ON* */
 
diff --git a/driver_italk.c b/driver_italk.c
index e1cdf483..051376c2 100644
--- a/driver_italk.c
+++ b/driver_italk.c
@@ -432,7 +432,6 @@ const struct gps_type_t driver_italk =
 #ifdef TIMEHINT_ENABLE
     .time_offset     = NULL,		/* no method for NTP fudge factor */
 #endif /* TIMEHINT_ENABLE */
-    .minlength       = 30,		/* min packet length for chunked output */
 };
 /* *INDENT-ON* */
 #endif /* defined(ITRAX_ENABLE) && defined(BINARY_ENABLE) */
diff --git a/driver_navcom.c b/driver_navcom.c
index 067aef0b..925b7b61 100644
--- a/driver_navcom.c
+++ b/driver_navcom.c
@@ -1310,7 +1310,6 @@ const struct gps_type_t driver_navcom =
 #ifdef TIMEHINT_ENABLE
     .time_offset     = NULL,		/* no method for NTP fudge factor */
 #endif /* TIMEHINT_ENABLE */
-    .minlength       = 10,		/* min packet length for chunked I/O */
 };
 /* *INDENT-ON* */
 
diff --git a/driver_nmea2000.c b/driver_nmea2000.c
index 4059dbee..d74233b4 100644
--- a/driver_nmea2000.c
+++ b/driver_nmea2000.c
@@ -1700,7 +1700,6 @@ const struct gps_type_t driver_nmea2000 = {
 #ifdef TIMEHINT_ENABLE
     .time_offset     = NULL,
 #endif /* TIMEHINT_ENABLE */
-    .minlength       = 0,		/* min packet length unknown */
 };
 /* *INDENT-ON* */
 
diff --git a/driver_oncore.c b/driver_oncore.c
index 569e1f4d..8cea6e7c 100644
--- a/driver_oncore.c
+++ b/driver_oncore.c
@@ -520,7 +520,6 @@ const struct gps_type_t driver_oncore = {
 #ifdef TIMEHINT_ENABLE
     .time_offset = oncore_time_offset,		/* NTP offset array */
 #endif /* TIMEHINT_ENABLE */
-    .minlength       = 38,		/* min packet length for chunked I/O */
 };
 /* *INDENT-ON* */
 #endif /* defined(ONCORE_ENABLE) && defined(BINARY_ENABLE) */
diff --git a/driver_proto.c b/driver_proto.c
index e8953cf8..bbbd7c0d 100644
--- a/driver_proto.c
+++ b/driver_proto.c
@@ -533,8 +533,6 @@ const struct gps_type_t driver__proto__binary = {
 #ifdef TIMEHINT_ENABLE
     .time_offset     = _proto_time_offset,
 #endif /* TIMEHINT_ENABLE */
-    /* minimum length of packet, used for I/O optimization */
-    .minlength       = 0;
 /* *INDENT-ON* */
 };
 #endif /* defined(_PROTO__ENABLE) && defined(BINARY_ENABLE) */
diff --git a/driver_sirf.c b/driver_sirf.c
index 87146ce7..20e7b513 100644
--- a/driver_sirf.c
+++ b/driver_sirf.c
@@ -1590,7 +1590,6 @@ const struct gps_type_t driver_sirf =
 #ifdef TIMEHINT_ENABLE
     .time_offset     = sirf_time_offset,
 #endif /* NTP_SHM_ENABLE */
-    .minlength       = 13,		/* minimum SiRF packet length */
 };
 /* *INDENT-ON* */
 #endif /* defined(SIRF_ENABLE) && defined(BINARY_ENABLE) */
diff --git a/driver_superstar2.c b/driver_superstar2.c
index 95d69cd4..94cc3320 100644
--- a/driver_superstar2.c
+++ b/driver_superstar2.c
@@ -585,7 +585,6 @@ const struct gps_type_t driver_superstar2 = {
 #ifdef TIMEHINT_ENABLE
     .time_offset     = NULL,		/* no method for NTP fudge factor */
 #endif /* TIMEHINT_ENABLE */
-    .minlength       = 65,		/* min packet length for chunked I/O */
 };
 /* *INDENT-ON* */
 #endif /* defined(SUPERSTAR2_ENABLE) && defined(BINARY_ENABLE) */
diff --git a/driver_tsip.c b/driver_tsip.c
index 994da718..6134e3d9 100644
--- a/driver_tsip.c
+++ b/driver_tsip.c
@@ -1281,7 +1281,6 @@ const struct gps_type_t driver_tsip =
 #ifdef TIMEHINT_ENABLE
     .time_offset     = tsip_time_offset,
 #endif /* TIMEHINT_ENABLE */
-    .minlength       = 5,		/* min packet length for chunked I/O */
 };
 /* *INDENT-ON* */
 
diff --git a/driver_ubx.c b/driver_ubx.c
index 260c8523..2f2a7358 100644
--- a/driver_ubx.c
+++ b/driver_ubx.c
@@ -992,7 +992,6 @@ const struct gps_type_t driver_ubx = {
 #ifdef TIMEHINT_ENABLE
     .time_offset     = NULL,		/* no method for NTP fudge factor */
 #endif /* TIMEHINT_ENABLE */
-    .minlength       = 17,		/* min packet length for chunked I/O */
 };
 /* *INDENT-ON* */
 #endif /* defined(UBLOX_ENABLE) && defined(BINARY_ENABLE) */
diff --git a/driver_zodiac.c b/driver_zodiac.c
index 1da18bf4..2a0e367e 100644
--- a/driver_zodiac.c
+++ b/driver_zodiac.c
@@ -486,7 +486,6 @@ const struct gps_type_t driver_zodiac =
 #ifdef TIMEHINT_ENABLE
     .time_offset     = zodiac_time_offset,	/* compute NTO fudge factor */
 #endif /* TIMEHINT_ENABLE */
-    .minlength       = 40,		/* min packet length for chunked I/O */
 };
 /* *INDENT-ON* */
 
diff --git a/drivers.c b/drivers.c
index b5c898dc..0003ad11 100644
--- a/drivers.c
+++ b/drivers.c
@@ -16,8 +16,6 @@
 #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);
@@ -104,7 +102,6 @@ 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* */
 
@@ -275,7 +272,6 @@ 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* */
 
@@ -378,7 +374,6 @@ 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 */
@@ -442,7 +437,6 @@ 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 */
@@ -495,7 +489,6 @@ 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 */
@@ -551,7 +544,6 @@ 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 */
@@ -608,7 +600,6 @@ 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 */
@@ -660,7 +651,6 @@ 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 @*/
@@ -788,7 +778,6 @@ 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
@@ -869,7 +858,6 @@ 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
@@ -938,7 +926,6 @@ 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* */
 
@@ -994,7 +981,6 @@ 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 */
@@ -1042,7 +1028,6 @@ 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 */
@@ -1079,7 +1064,6 @@ 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 */
@@ -1176,7 +1160,6 @@ 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 */
@@ -1420,7 +1403,6 @@ 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 */
@@ -1525,7 +1507,6 @@ 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* */
 
diff --git a/gpsd.h-tail b/gpsd.h-tail
index edc8930f..8cdf1761 100644
--- a/gpsd.h-tail
+++ b/gpsd.h-tail
@@ -389,7 +389,6 @@ struct gps_type_t {
 #ifdef TIMEHINT_ENABLE
     /*@null@*/double (*time_offset)(struct gps_device_t *session);
 #endif /* TIMEHINT_ENABLE */
-    int minlength;
 };
 
 /*
@@ -824,7 +823,6 @@ extern void ntrip_report(struct gps_context_t *,
 
 extern void gpsd_tty_init(struct gps_device_t *);
 extern int gpsd_serial_open(struct gps_device_t *);
-extern void gpsd_optimize_io(struct gps_device_t *, const int, const bool);
 extern bool gpsd_set_raw(struct gps_device_t *);
 extern ssize_t gpsd_serial_write(struct gps_device_t *,
 				 const char *, const size_t);
diff --git a/gpsdecode.c b/gpsdecode.c
index ece81d57..f31a59f6 100644
--- a/gpsdecode.c
+++ b/gpsdecode.c
@@ -621,7 +621,7 @@ static void decode(FILE *fpin, FILE*fpout)
 			break;
 		    }
 		}
-		printf("%s (%d): %u\n", np, i-1, (unsigned int)minima[i]);
+		printf("%s (%d): %d\n", np, i-1, (unsigned int)minima[i]);
 	    }
 	}
     }
diff --git a/libgpsd_core.c b/libgpsd_core.c
index 579d32e1..b9868bfa 100644
--- a/libgpsd_core.c
+++ b/libgpsd_core.c
@@ -248,9 +248,6 @@ int gpsd_switch_driver(struct gps_device_t *session, char *type_name)
 			"selecting %s driver...\n",
 			(*dp)->type_name);
 	    gpsd_assert_sync(session);
-	    gpsd_optimize_io(session, 
-			     (*dp)->minlength, 
-			     TEXTUAL_PACKET_TYPE((*dp)->packet_type));
 	    /*@i@*/ session->device_type = *dp;
 	    session->driver_index = i;
 #ifdef RECONFIGURE_ENABLE
diff --git a/serial.c b/serial.c
index 25333678..9bc74e13 100644
--- a/serial.c
+++ b/serial.c
@@ -535,7 +535,19 @@ int gpsd_serial_open(struct gps_device_t *session)
 		     &session->ttyset_old, sizeof(session->ttyset));
 	/*
 	 * Only block until we get at least one character, whatever the
-	 * third arg of read(2) says.
+	 * third arg of read(2) says.  According to 
+	 * http://stackoverflow.com/questions/20154157/termios-vmin-vtime-and-blocking-non-blocking-read-operations
+	 * the VMIN setting may be a no-op because the tty was opened with
+	 * O_NONBLOCK.  Money quote:
+	 *
+	 * "When using select() with a file in non-blocking mode, you
+	 * get an event for every byte that arrives. At high serial
+	 * data rates, this hammers the CPU. It's better to use
+	 * blocking mode with VMIN, so that select() waits for a
+	 * block of data before firing an event, and VTIME to limit
+	 * the delay, for blocks smaller than VMIN."
+	 *
+	 * Would that we could do the latter...
 	 */
 	/*@ ignore @*/
 	memset(session->ttyset.c_cc, 0, sizeof(session->ttyset.c_cc));
@@ -609,61 +621,6 @@ ssize_t gpsd_serial_write(struct gps_device_t * session,
     return status;
 }
 
-void gpsd_optimize_io(struct gps_device_t *session, 
-		      int minlength, const bool textual UNUSED)
-/* optimize I/O mode depending on the minimum packet size */
-{
-    /* bail out if this is not actually a tty */
-    if (isatty(session->gpsdata.gps_fd) == 0)
-	return;
-
-#ifdef __NetBSD__
-    /*
-     * Apparently NetBSD termios (at least on pty on netbsd-[56]) has
-     * trouble with VMIN=n VTIME=1.  Or reads are aftempted when no
-     * bytes are present and none arrive, in which case read is
-     * correct for waiting indefinitely.  Until this is
-     * debugged/fixed, avoid it, because even if it doesn't affect
-     * actual operation (unknown) it's important to preserve
-     * regression tests to allow bisecting for other bugs.
-     * http://pubs.opengroup.org/onlinepubs/007908799/xbd/termios.html
-     */
-    minlength = 1;
-#endif
-
-    /*
-     * This is an optimization hack.  The idea is to get away from
-     * character-at-a-time I/O in order to slow down the rate at
-     * which the main select loop spins (those calls eat power
-     * noticeably in environments like Android phones and the
-     * Raspberry Pi).  We tell the tty layer to wait until it has
-     * either accumulated characters corresponding to the minimum
-     * possible length of a packet or timed out.
-     *
-     * For the moment, we do nothing with the textual flag. We'd like
-     * to use it to set ICANON mode and let the kernel do all the line
-     * buffering itself.  The problem with this is that VTIME stops
-     * working in ICANON mode, so a binary packet coming up the wire
-     * would result in no further input being seen.
-     */
-    if (minlength > 1) {
-	session->ttyset.c_cc[VMIN] = minlength;
-	session->ttyset.c_cc[VTIME] = 1;	/* 0.1 sec */
-    } else {
-	/* raw character-at-at-time I/O, no timeout */
-	session->ttyset.c_cc[VMIN] = 1;
-	session->ttyset.c_cc[VTIME] = 0;
-    }
-
-    if (tcsetattr(session->gpsdata.gps_fd, TCSANOW, &session->ttyset) != 0)
-	return;
-
-    gpsd_report(&session->context->errout, LOG_IO,
-		"tty params optimized for min length %d of %s packets\n",
-		minlength, textual ? "textual" : "binary");
-}
-
-
 /*
  * This constant controls how long the packet sniffer will spend looking
  * for a packet leader before it gives up.  It *must* be larger than