Split firmwqre version query out of the init method.

This enables us to force readonly off while it's being called.
The practical effect is that gpsmon can get a firmware version (if this
is possible) without reconfiguring the device.

18 files changed, 110 insertions, 32 deletions

diff --git a/TODO b/TODO
index aee80655..4184320c 100644
--- a/TODO
+++ b/TODO
@@ -39,11 +39,6 @@ uncertainty in output JSON.
 
 *** Client bugs
 
-*** gpsmon on a SiRF doesn't get firmware version ***
-
-For this to work, the firmware probe needs to be split out of the
-configure method so gpsmon can call it separately.
-
 **** In gpsmon's PPS Offset field
 
 Presently PPS Offset is displayed in direct mode for NMEA, SiRF, and
diff --git a/driver_evermore.c b/driver_evermore.c
index d8ec713c..ea315643 100644
--- a/driver_evermore.c
+++ b/driver_evermore.c
@@ -623,6 +623,7 @@ const struct gps_type_t driver_evermore =
     .get_packet     = generic_get,		/* use generic one */
     .parse_packet   = generic_parse_input,	/* parse message packets */
     .rtcm_writer    = gpsd_write,		/* send RTCM data straight */
+    .init_query     = NULL,			/* non-perturbing query */
     .event_hook     = evermore_event_hook,	/* lifetime event handler */
 #ifdef RECONFIGURE_ENABLE
     .speed_switcher = evermore_speed,		/* we can change baud rates */
diff --git a/driver_garmin.c b/driver_garmin.c
index 4ecdad49..acdbc90b 100644
--- a/driver_garmin.c
+++ b/driver_garmin.c
@@ -1384,6 +1384,7 @@ const struct gps_type_t driver_garmin_usb_binary_old =
     .get_packet     = garmin_get_packet,/* how to grab a packet */
     .parse_packet   = garmin_usb_parse,	/* parse message packets */
     .rtcm_writer    = NULL,		/* don't send DGPS corrections */
+    .init_query     = NULL,		/* non-perturbing initial query */
     .event_hook     = garmin_event_hook,/* lifetime event handler */
 #ifdef RECONFIGURE_ENABLE
     .speed_switcher = NULL,		/* no speed switcher */
@@ -1413,6 +1414,7 @@ const struct gps_type_t driver_garmin_usb_binary =
     .get_packet     = generic_get,      /* how to grab a packet */
     .parse_packet   = garmin_ser_parse,	/* parse message packets */
     .rtcm_writer    = NULL,		/* don't send DGPS corrections */
+    .init_query     = NULL,		/* non-perturbing initial query */
     .event_hook     = garmin_event_hook,/* lifetime ebent handler */
 #ifdef RECONFIGURE_ENABLE
     .speed_switcher = NULL,		/* no speed switcher */
@@ -1441,6 +1443,7 @@ const struct gps_type_t driver_garmin_ser_binary =
     .get_packet     = generic_get,       /* how to grab a packet */
     .parse_packet   = garmin_ser_parse,	/* parse message packets */
     .rtcm_writer    = NULL,		/* don't send DGPS corrections */
+    .init_query     = NULL,		/* non-perturbing initial query */
     .event_hook     = NULL,	        /* lifetime event handler */
 #ifdef RECONFIGURE_ENABLE
     .speed_switcher = NULL,		/* no speed switcher */
diff --git a/driver_geostar.c b/driver_geostar.c
index e2f5899e..a7c37689 100644
--- a/driver_geostar.c
+++ b/driver_geostar.c
@@ -502,6 +502,14 @@ static ssize_t geostar_control_send(struct gps_device_t *session,
 }
 #endif /* CONTROLSEND_ENABLE */
 
+
+static void geostar_init_query(struct gps_device_t *session)
+{
+    unsigned char buf[2 * 4];
+    /* Poll Software Version */
+    (void)geostar_write(session, 0xc1, buf, 1);
+}
+
 static void geostar_event_hook(struct gps_device_t *session, event_t event)
 {
     unsigned char buf[2 * 4];
@@ -537,8 +545,6 @@ static void geostar_event_hook(struct gps_device_t *session, event_t event)
 	(void)geostar_write(session, 0x8e, buf, 1);
 	/* Poll binary packets selected */
 	(void)geostar_write(session, 0x8f, buf, 1);
-	/* Poll Software Version */
-	(void)geostar_write(session, 0xc1, buf, 1);
     }
 
     if (event == event_deactivate) {
@@ -620,6 +626,7 @@ const struct gps_type_t driver_geostar =
     .get_packet     = generic_get,	/* use the generic packet getter */
     .parse_packet   = geostar_parse_input,	/* parse message packets */
     .rtcm_writer    = NULL,		/* doesn't accept DGPS corrections */
+    .init_query     = geostar_init_query,	/* non-perturbing initial query */
     .event_hook     = geostar_event_hook,	/* fire on various lifetime events */
 #ifdef RECONFIGURE_ENABLE
     .speed_switcher = geostar_speed_switch,/* change baud rate */
diff --git a/driver_italk.c b/driver_italk.c
index 75f8e738..94f78118 100644
--- a/driver_italk.c
+++ b/driver_italk.c
@@ -416,6 +416,7 @@ const struct gps_type_t driver_italk =
     .get_packet     = generic_get,	/* use generic packet grabber */
     .parse_packet   = italk_parse_input,/* parse message packets */
     .rtcm_writer    = gpsd_write,	/* send RTCM data straight */
+    .init_query     = NULL,		/* non-perturbing initial query */
     .event_hook     = NULL,		/* lifetime event handler */
 #ifdef RECONFIGURE_ENABLE
     .speed_switcher = NULL,		/* no speed switcher */
diff --git a/driver_navcom.c b/driver_navcom.c
index fdecf661..213b6d25 100644
--- a/driver_navcom.c
+++ b/driver_navcom.c
@@ -1285,6 +1285,7 @@ const struct gps_type_t driver_navcom =
     .get_packet     = generic_get,		/* use generic one */
     .parse_packet   = navcom_parse_input,	/* parse message packets */
     .rtcm_writer    = gpsd_write,		/* send RTCM data straight */
+    .init_query     = NULL,			/* non-perturbing query */
     .event_hook     = navcom_event_hook,	/* lifetime event handler */
 #ifdef RECONFIGURE_ENABLE
     .speed_switcher = navcom_speed,		/* we do change baud rates */
diff --git a/driver_nmea2000.c b/driver_nmea2000.c
index 147eba57..dc6eb474 100644
--- a/driver_nmea2000.c
+++ b/driver_nmea2000.c
@@ -1675,6 +1675,7 @@ const struct gps_type_t driver_nmea2000 = {
     .get_packet     = nmea2000_get,	/* how to get a packet */
     .parse_packet   = nmea2000_parse_input,	/* how to interpret a packet */
     .rtcm_writer    = NULL,		/* Don't send RTCM to this */
+    .init_query     = NULL,		/* non-perturbing query */
     .event_hook     = NULL,
 #ifdef RECONFIGURE_ENABLE
     .speed_switcher = NULL,		/* no speed switcher */
diff --git a/driver_oncore.c b/driver_oncore.c
index d745b476..e9dbecfd 100644
--- a/driver_oncore.c
+++ b/driver_oncore.c
@@ -498,7 +498,8 @@ const struct gps_type_t driver_oncore = {
     .get_packet       = generic_get,		/* packet getter */
     .parse_packet     = oncore_parse_input,	/* packet parser */
     .rtcm_writer      = gpsd_write,		/* device accepts RTCM */
-    .event_hook     = oncore_event_hook,	/* lifetime event hook */
+    .init_query       = NULL,			/* non-perturbing query */
+    .event_hook       = oncore_event_hook,	/* lifetime event hook */
 #ifdef RECONFIGURE_ENABLE
     .speed_switcher   = NULL,			/* no speed setter */
     .mode_switcher    = NULL,			/* no mode setter */
diff --git a/driver_proto.c b/driver_proto.c
index d0de2410..10fb05ac 100644
--- a/driver_proto.c
+++ b/driver_proto.c
@@ -512,6 +512,8 @@ const struct gps_type_t driver__proto__binary = {
     .parse_packet     = _proto__parse_input,
     /* RTCM handler (using default routine) */
     .rtcm_writer      = pass_rtcm,
+    /* non-perturbing initial query (e.g. for version) */
+    .init_query        = NULL,
     /* fire on various lifetime events */
     .event_hook       = _proto__event_hook,
 #ifdef RECONFIGURE_ENABLE
diff --git a/driver_sirf.c b/driver_sirf.c
index d0506e7f..0a81781c 100644
--- a/driver_sirf.c
+++ b/driver_sirf.c
@@ -1373,6 +1373,13 @@ static gps_mask_t sirfbin_parse_input(struct gps_device_t *session)
 	return 0;
 }
 
+static void sirfbin_init_query(struct gps_device_t *session)
+{
+    gpsd_report(session->context->debug, LOG_PROG,
+		"SiRF: Probing for firmware version.\n");
+    (void)sirf_write(session, versionprobe);
+}
+
 static void sirfbin_event_hook(struct gps_device_t *session, event_t event)
 {
     if (session->context->readonly)
@@ -1401,9 +1408,11 @@ static void sirfbin_event_hook(struct gps_device_t *session, event_t event)
 	    return;
 
 	case 1:
+	    /* disable navigation debug messages (the value 5 is magic) */
 	    gpsd_report(session->context->debug, LOG_PROG,
-			"SiRF: Probing for firmware version.\n");
-	    (void)sirf_write(session, versionprobe);
+			"SiRF: disable MID 7, 28, 29, 30, 31.\n");
+	    putbyte(unsetmidXX, 5, 0x05);
+	    (void)sirf_write(session, unsetmidXX);
 	    break;
 
 	case 2:
@@ -1484,14 +1493,6 @@ static void sirfbin_event_hook(struct gps_device_t *session, event_t event)
 	    }
 	    break;
 
-	case 12:
-	    /* disable navigation debug messages (the value 5 is magic) */
-	    gpsd_report(session->context->debug, LOG_PROG,
-			"SiRF: disable MID 7, 28, 29, 30, 31.\n");
-	    putbyte(unsetmidXX, 5, 0x05);
-	    (void)sirf_write(session, unsetmidXX);
-	    break;
-
 #endif /* RECONFIGURE_ENABLE */
 	default:
 	    /* initialization is done */
@@ -1546,6 +1547,7 @@ const struct gps_type_t driver_sirf =
     .get_packet     = generic_get,	/* be prepared for SiRF or NMEA */
     .parse_packet   = sirfbin_parse_input,/* parse message packets */
     .rtcm_writer    = gpsd_write,	/* send RTCM data straight */
+    .init_query     = sirfbin_init_query,/* non-perturbing initial qury */
     .event_hook     = sirfbin_event_hook,/* lifetime event handler */
 #ifdef RECONFIGURE_ENABLE
     .speed_switcher = sirfbin_speed,	/* we can change baud rate */
diff --git a/driver_superstar2.c b/driver_superstar2.c
index ff151f6d..9db21e02 100644
--- a/driver_superstar2.c
+++ b/driver_superstar2.c
@@ -430,6 +430,8 @@ superstar2_dispatch(struct gps_device_t * session, unsigned char *buf,
  *
  **********************************************************/
 
+/* FIXME: factor out Superstar init_query for version */
+
 static void superstar2_event_hook(struct gps_device_t *session, event_t event)
 {
     if (session->context->readonly)
@@ -556,6 +558,8 @@ const struct gps_type_t driver_superstar2 = {
     .parse_packet	= superstar2_parse_input,
     /* RTCM handler (using default routine) */
     .rtcm_writer	= gpsd_write,
+    /* non-perturbing initial query */
+    .init_query         = NULL,
     /* Fire on various lifetime events */
     .event_hook		= superstar2_event_hook,
 #ifdef RECONFIGURE_ENABLE
diff --git a/driver_tsip.c b/driver_tsip.c
index ea29145e..d8736736 100644
--- a/driver_tsip.c
+++ b/driver_tsip.c
@@ -1012,6 +1012,19 @@ static ssize_t tsip_control_send(struct gps_device_t *session,
 }
 #endif /* CONTROLSEND_ENABLE */
 
+static void tsip_init_query(struct gps_device_t *session)
+{
+    unsigned char buf[100];
+
+    /* Request Hardware Version Information */
+    putbyte(buf, 0, 0x03); /* Subcode */
+    (void)tsip_write(session, 0x1c, buf, 1);
+    /* 
+     * After HW information packet is received, a 
+     * decision is made how to configure the device.
+     */
+}
+
 static void tsip_event_hook(struct gps_device_t *session, event_t event)
 {
     if (session->context->readonly)
@@ -1020,7 +1033,7 @@ static void tsip_event_hook(struct gps_device_t *session, event_t event)
 	unsigned char buf[100];
 	
 	/*
-	 * Set basic configuration, in case no hardware config resonse
+	 * Set basic configuration, in case no hardware config response
 	 * comes back.
 	 */
 	putbyte(buf, 0, 0x1e);	/* Position: DP, MSL, LLA */
@@ -1028,14 +1041,6 @@ static void tsip_event_hook(struct gps_device_t *session, event_t event)
 	putbyte(buf, 2, 0x00);	/* Time: GPS */
 	putbyte(buf, 3, 0x08);	/* Aux: dBHz */
 	(void)tsip_write(session, 0x35, buf, 4);
-
-	/* Request Hardware Version Information */
-	putbyte(buf, 0, 0x03); /* Subcode */
-	(void)tsip_write(session, 0x1c, buf, 1);
-	/* 
-	 * After HW information packet is received, a 
-	 * decision is made how to configure the device.
-	 */
     }
     if (event == event_configure && session->packet.counter == 0) {
 	/*
@@ -1256,6 +1261,7 @@ const struct gps_type_t driver_tsip =
     .get_packet     = generic_get,	/* use the generic packet getter */
     .parse_packet   = tsip_parse_input,	/* parse message packets */
     .rtcm_writer    = NULL,		/* doesn't accept DGPS corrections */
+    .init_query     = tsip_init_query,	/* non-perturbing initial query */
     .event_hook     = tsip_event_hook,	/* fire on various lifetime events */
 #ifdef RECONFIGURE_ENABLE
     .speed_switcher = tsip_speed_switch,/* change baud rate */
diff --git a/driver_ubx.c b/driver_ubx.c
index 88633919..cf51afd0 100644
--- a/driver_ubx.c
+++ b/driver_ubx.c
@@ -619,6 +619,16 @@ static ssize_t ubx_control_send(struct gps_device_t *session, char *msg,
 }
 #endif /* CONTROLSEND_ENABLE */
 
+static void ubx_init_query(struct gps_device_t *session)
+{
+    unsigned char msg[32];
+
+    /*@ -type @*/
+    /* MON_VER: query for version information */
+    (void)ubx_write(session, UBX_CLASS_MON, 0x04, msg, 0);
+    /*@ +type @*/
+}
+
 static void ubx_event_hook(struct gps_device_t *session, event_t event)
 {
     if (session->context->readonly)
@@ -638,9 +648,6 @@ static void ubx_event_hook(struct gps_device_t *session, event_t event)
 	msg[6] = 0x00;
 	msg[7] = 0x00;
 	(void)ubx_write(session, 0x06u, 0x16, msg, 8);
-
-	/* MON_VER: query for version information */
-	(void)ubx_write(session, UBX_CLASS_MON, 0x04, msg, 0);
 	/*@ +type @*/
 
 #ifdef RECONFIGURE_ENABLE
@@ -969,6 +976,7 @@ const struct gps_type_t driver_ubx = {
     .get_packet       = generic_get,    /* Packet getter (using default routine) */
     .parse_packet     = parse_input,    /* Parse message packets */
     .rtcm_writer      = gpsd_write,      /* RTCM handler (using default routine) */
+    .init_query       = ubx_init_query,	/* non-perturbing initial query */
     .event_hook       = ubx_event_hook,	/* Fire on various lifetime events */
 #ifdef RECONFIGURE_ENABLE
     .speed_switcher   = ubx_speed,      /* Speed (baudrate) switch */
diff --git a/driver_zodiac.c b/driver_zodiac.c
index 240c7909..be7d8b54 100644
--- a/driver_zodiac.c
+++ b/driver_zodiac.c
@@ -474,6 +474,7 @@ const struct gps_type_t driver_zodiac =
     .get_packet     = generic_get,	/* use the generic packet getter */
     .parse_packet   = zodiac_analyze,	/* parse message packets */
     .rtcm_writer    = zodiac_send_rtcm,	/* send DGPS correction */
+    .init_query     = NULL,		/* non-perturbing initial query */
     .event_hook     = NULL,		/* no configuration */
 #ifdef RECONFIGURE_ENABLE
     .speed_switcher = zodiac_speed_switch,/* we can change baud rate */
diff --git a/drivers.c b/drivers.c
index 13cf4ef8..725fb709 100644
--- a/drivers.c
+++ b/drivers.c
@@ -87,6 +87,7 @@ const struct gps_type_t driver_unknown = {
     .get_packet     = generic_get,	/* use generic packet getter */
     .parse_packet   = generic_parse_input,	/* how to interpret a packet */
     .rtcm_writer    = NULL,		/* write RTCM data straight */
+    .init_query     = NULL,		/* non-perturbing initial query */
     .event_hook     = NULL,		/* lifetime event handler */
 #ifdef RECONFIGURE_ENABLE
     .speed_switcher = NULL,		/* no speed switcher */
@@ -252,6 +253,7 @@ const struct gps_type_t driver_nmea0183 = {
     .get_packet     = generic_get,	/* use generic packet getter */
     .parse_packet   = generic_parse_input,	/* how to interpret a packet */
     .rtcm_writer    = gpsd_write,	/* write RTCM data straight */
+    .init_query     = NULL,		/* non-perturbing initial query */
     .event_hook     = nmea_event_hook,	/* lifetime event handler */
 #ifdef RECONFIGURE_ENABLE
     .speed_switcher = NULL,		/* no speed switcher */
@@ -357,6 +359,7 @@ const struct gps_type_t driver_garmin = {
     .get_packet     = generic_get,	/* use generic packet getter */
     .parse_packet   = generic_parse_input,	/* how to interpret a packet */
     .rtcm_writer    = NULL,		/* some do, some don't, skip for now */
+    .init_query     = NULL,		/* non-perturbing initial query */
     .event_hook     = garmin_nmea_event_hook,	/* lifetime event handler */
 #ifdef RECONFIGURE_ENABLE
     .speed_switcher = NULL,			/* no speed switcher */
@@ -419,6 +422,7 @@ const struct gps_type_t driver_ashtech = {
     .get_packet     = generic_get,	/* how to get a packet */
     .parse_packet   = generic_parse_input,	/* how to interpret a packet */
     .rtcm_writer    = gpsd_write,	/* write RTCM data straight */
+    .init_query     = NULL,		/* non-perturbing initial query */
     .event_hook     = ashtech_event_hook, /* lifetime event handler */
 #ifdef RECONFIGURE_ENABLE
     .speed_switcher = NULL,		/* no speed switcher */
@@ -470,6 +474,7 @@ const struct gps_type_t driver_fv18 = {
     .get_packet     = generic_get,	/* how to get a packet */
     .parse_packet   = generic_parse_input,	/* how to interpret a packet */
     .rtcm_writer    = gpsd_write,	/* write RTCM data straight */
+    .init_query     = NULL,		/* non-perturbing initial query */
     .event_hook     = fv18_event_hook,	/* lifetime event handler */
 #ifdef RECONFIGURE_ENABLE
     .speed_switcher = NULL,		/* no speed switcher */
@@ -524,6 +529,7 @@ const struct gps_type_t driver_gpsclock = {
     .get_packet     = generic_get,	/* how to get a packet */
     .parse_packet   = generic_parse_input,	/* how to interpret a packet */
     .rtcm_writer    = gpsd_write,	/* write RTCM data straight */
+    .init_query     = NULL,		/* non-perturbing initial query */
     .event_hook     = gpsclock_event_hook,	/* lifetime event handler */
 #ifdef RECONFIGURE_ENABLE
     .speed_switcher = NULL,		/* no speed switcher */
@@ -577,8 +583,9 @@ static const struct gps_type_t driver_tripmate = {
     .channels      = 12,			/* consumer-grade GPS */
     .probe_detect  = NULL,			/* no probe */
     .get_packet    = generic_get,		/* how to get a packet */
-    .parse_packet  = generic_parse_input,		/* how to interpret a packet */
-    .rtcm_writer   = gpsd_write,			/* send RTCM data straight */
+    .parse_packet  = generic_parse_input,	/* how to interpret a packet */
+    .rtcm_writer   = gpsd_write,		/* send RTCM data straight */
+    .init_query    = NULL,			/* non-perturbing query */
     .event_hook    = tripmate_event_hook,	/* lifetime event handler */
 #ifdef RECONFIGURE_ENABLE
     .speed_switcher= NULL,			/* no speed switcher */
@@ -630,6 +637,7 @@ static const struct gps_type_t driver_earthmate = {
     .get_packet    = generic_get,		/* how to get a packet */
     .parse_packet  = generic_parse_input,	/* how to interpret a packet */
     .rtcm_writer   = NULL,			/* don't send RTCM data */
+    .init_query     = NULL,			/* non-perturbing query */
     .event_hook    = earthmate_event_hook,	/* lifetime event handler */
 #ifdef RECONFIGURE_ENABLE
     .speed_switcher= NULL,			/* no speed switcher */
@@ -755,6 +763,7 @@ const struct gps_type_t driver_trueNorth = {
     .get_packet     = generic_get,	/* how to get a packet */
     .parse_packet   = generic_parse_input,	/* how to interpret a packet */
     .rtcm_writer    = NULL,		/* Don't send */
+    .init_query     = NULL,		/* non-perturbing initial query */
     .event_hook     = tnt_event_hook,	/* lifetime event handler */
 #ifdef RECONFIGURE_ENABLE
     .speed_switcher = tnt_speed,	/* no speed switcher */
@@ -833,6 +842,7 @@ static const struct gps_type_t driver_oceanServer = {
     .get_packet     = generic_get,	/* how to get a packet */
     .parse_packet   = generic_parse_input,	/* how to interpret a packet */
     .rtcm_writer    = NULL,		/* Don't send */
+    .init_query     = NULL,		/* non-perturbing initial query */
     .event_hook     = oceanserver_event_hook,
 #ifdef RECONFIGURE_ENABLE
     .speed_switcher = NULL,		/* no speed switcher */
@@ -900,6 +910,7 @@ static const struct gps_type_t driver_fury = {
     .get_packet     = generic_get,	/* how to get a packet */
     .parse_packet   = generic_parse_input,	/* how to interpret a packet */
     .rtcm_writer    = NULL,		/* Don't send */
+    .init_query     = NULL,		/* non-perturbing initial query */
     .event_hook     = fury_event_hook,
 #ifdef RECONFIGURE_ENABLE
     .speed_switcher = NULL,		/* no speed switcher */
@@ -954,6 +965,7 @@ static const struct gps_type_t driver_rtcm104v2 = {
     .get_packet    = generic_get,	/* how to get a packet */
     .parse_packet  = rtcm104v2_analyze,	/*  */
     .rtcm_writer   = NULL,		/* don't send RTCM data,  */
+    .init_query     = NULL,		/* non-perturbing initial query */
     .event_hook    = NULL,		/* no event_hook */
 #ifdef RECONFIGURE_ENABLE
     .speed_switcher= NULL,		/* no speed switcher */
@@ -1000,6 +1012,7 @@ static const struct gps_type_t driver_rtcm104v3 = {
     .get_packet    = generic_get,	/* how to get a packet */
     .parse_packet  = rtcm104v3_analyze,	/*  */
     .rtcm_writer   = NULL,		/* don't send RTCM data,  */
+    .init_query    = NULL,		/* non-perturbing initial query */
     .event_hook    = NULL,		/* no event hook */
 #ifdef RECONFIGURE_ENABLE
     .speed_switcher= NULL,		/* no speed switcher */
@@ -1035,6 +1048,7 @@ static const struct gps_type_t driver_garmintxt = {
     .get_packet    = generic_get,	/* how to get a packet */
     .parse_packet  = garmintxt_parse,	/* how to parse one */
     .rtcm_writer   = NULL,		/* don't send RTCM data,  */
+    .init_query     = NULL,		/* non-perturbing initial query */
     .event_hook    = NULL,		/* no event hook */
 #ifdef RECONFIGURE_ENABLE
     .speed_switcher= NULL,		/* no speed switcher */
@@ -1130,6 +1144,7 @@ const struct gps_type_t driver_mtk3301 = {
     .get_packet     = generic_get,	/* how to get a packet */
     .parse_packet   = generic_parse_input,	/* how to interpret a packet */
     .rtcm_writer    = gpsd_write,	/* write RTCM data straight */
+    .init_query     = NULL,		/* non-perturbing initial query */
     .event_hook     = mtk3301_event_hook,	/* lifetime event handler */
 #ifdef RECONFIGURE_ENABLE
     .speed_switcher = NULL,		/* no speed switcher */
@@ -1372,6 +1387,7 @@ const struct gps_type_t driver_aivdm = {
     .get_packet       = generic_get,	/* how to get a packet */
     .parse_packet     = aivdm_analyze,	/* how to analyze a packet */
     .rtcm_writer      = NULL,		/* don't send RTCM data,  */
+    .init_query       = NULL,		/* non-perturbing initial query */
     .event_hook       = NULL,		/* lifetime event handler */
 #ifdef RECONFIGURE_ENABLE
     .speed_switcher   = NULL,		/* no speed switcher */
@@ -1475,6 +1491,7 @@ const struct gps_type_t driver_json_passthrough = {
     .get_packet     = generic_get,	/* use generic packet getter */
     .parse_packet   = json_pass_packet,	/* how to interpret a packet */
     .rtcm_writer    = NULL,		/* write RTCM data straight */
+    .init_query     = NULL,		/* non-perturbing initial query */
     .event_hook     = NULL,		/* lifetime event handler */
 #ifdef RECONFIGURE_ENABLE
     .speed_switcher = NULL,		/* no speed switcher */
diff --git a/gpsd.h-tail b/gpsd.h-tail
index 34bfe71e..f28152b8 100644
--- a/gpsd.h-tail
+++ b/gpsd.h-tail
@@ -345,6 +345,7 @@ struct gps_type_t {
     /*@null@*/ssize_t (*get_packet)(struct gps_device_t *session);
     /*@null@*/gps_mask_t (*parse_packet)(struct gps_device_t *session);
     /*@null@*/ssize_t (*rtcm_writer)(struct gps_device_t *session, const char *rtcmbuf, size_t rtcmbytes);
+    /*@null@*/void (*init_query)(struct gps_device_t *session);
     /*@null@*/void (*event_hook)(struct gps_device_t *session, event_t event);
 #ifdef RECONFIGURE_ENABLE
     /*@null@*/bool (*speed_switcher)(struct gps_device_t *session,
diff --git a/libgpsd_core.c b/libgpsd_core.c
index f7e8075c..f11e4831 100644
--- a/libgpsd_core.c
+++ b/libgpsd_core.c
@@ -1325,6 +1325,20 @@ gps_mask_t gpsd_poll(struct gps_device_t *session)
 			timestamp() - session->opentime,
 			(unsigned int)speed);
 	    /*@+nullderef@*/
+
+	    /* fire the init_query method */
+	    if (session->device_type != NULL
+		&& session->device_type->init_query != NULL) {
+		/*
+		 * We can force readonly off knowing this method does
+		 * not alter device state.
+		 */
+		bool saved = session->context->readonly;
+		session->context->readonly = false;
+		session->device_type->init_query(session);
+		session->context->readonly = saved;
+	    }
+
 	    /* fire the identified hook */
 	    if (session->device_type != NULL
 		&& session->device_type->event_hook != NULL)
diff --git a/www/writing-a-driver.xml b/www/writing-a-driver.xml
index 91e751b4..9cac39b3 100644
--- a/www/writing-a-driver.xml
+++ b/www/writing-a-driver.xml
@@ -15,6 +15,14 @@
 
 <revhistory>
    <revision>
+      <revnumber>1.13</revnumber>
+      <date>25 Aug 2014</date>
+      <authorinitials>er</authorinitials>
+      <revremark>
+	 Updated by esr; added init_query method.
+      </revremark>
+   </revision>
+   <revision>
       <revnumber>1.12</revnumber>
       <date>31 Oct 2013</date>
       <authorinitials>er</authorinitials>
@@ -639,6 +647,11 @@ original settings for later restoration, probably by
 <structfield>.wrapup</structfield> mentioned below. Later in this
 document I discuss my work to implement this function.</para>
 
+<!-- added by ESR, 2014 -->
+<para><structfield>.init_query</structfield> points to a block of code
+that will be called to query the firmware version of the device.  This
+code <emphasis>must not</emphasis> alter device state or settings.</para>
+
 <para><structfield>.event_hook</structfield> points to a block of code
 that will be executed on and after various events, distinguished by a
 second argument that specifies the event type.  The event_hook hook is