fp6-img/aports/temp/modemmanager/0003-shared-qmi-derive-location-from-Position-Report-indi.patch

From 7566587e77d299ab0f67613ae03cab9973e351db Mon Sep 17 00:00:00 2001
From: Jorijn van der Graaf <jorijnvdgraaf@catcrafts.net>
Date: Thu, 2 Jul 2026 15:44:16 +0200
Subject: [PATCH 3/3] shared-qmi: derive location from Position Report
 indications

Some GNSS engines (e.g. gnss8 in the SM7635/Fairphone 6) report fixes
only via QMI_LOC Position Report indications and never emit NMEA (Set
NMEA Types returns NotSupported), while location is derived exclusively
from NMEA traces. As a result no location was surfaced even with the
engine running and tracking satellites.

Register for the POSITION_REPORT event and synthesize minimal $GPGGA
and $GPRMC sentences from Position Report indications carrying a
successful fix (intermediate reports are disabled at engine start),
feeding the existing NMEA-based pipeline so that gps-raw and gps-nmea
both work on these engines too. Synthesizing NMEA rather than extending
the location interface keeps the change local to the QMI backend.

To avoid polluting the location output of engines that do emit NMEA
with duplicate synthesized sentences, position reports are ignored as
soon as a real NMEA indication has been seen for the current engine
run. In the worst case an NMEA-emitting engine could have a few
synthesized sentences slip in before its first real NMEA arrives, but
NMEA engines emit sentences immediately (fix or not) while a position
report needs a valid fix, so real NMEA wins that race in practice.
Values the position report does not carry are left as empty NMEA
fields rather than invented, and $GPRMC is only synthesized when the
report carries a UTC timestamp, as an RMC sentence without one is
meaningless.

Tested on the Fairphone 6 (SM7635): with both patches applied,
enabling gps-nmea/gps-raw via mmcli surfaces a correct live fix
(lat/lon/altitude/UTC) from the synthesized sentences; position
reports without a valid fix (session status 'timeout' while indoors)
are correctly ignored. The effect on other LOC engines (now also
receiving the POSITION_REPORT registration) has not been verified on
real hardware.

Signed-off-by: Jorijn van der Graaf <jorijnvdgraaf@catcrafts.net>
---
 src/mm-shared-qmi.c | 147 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 147 insertions(+)

diff --git a/src/mm-shared-qmi.c b/src/mm-shared-qmi.c
index 09aa987a..cad75080 100644
--- a/src/mm-shared-qmi.c
+++ b/src/mm-shared-qmi.c
@@ -88,6 +88,8 @@ typedef struct {
     gulong                          pds_location_event_report_indication_id;
     QmiClient                      *loc_client;
     gulong                          loc_location_nmea_indication_id;
+    gulong                          loc_location_position_report_indication_id;
+    gboolean                        loc_location_nmea_received;
     gchar                         **loc_assistance_data_servers;
     guint32                         loc_assistance_data_max_file_size;
     guint32                         loc_assistance_data_max_part_size;
@@ -126,6 +128,8 @@ private_free (Private *priv)
         g_object_unref (priv->pds_client);
     if (priv->loc_location_nmea_indication_id)
         g_signal_handler_disconnect (priv->loc_client, priv->loc_location_nmea_indication_id);
+    if (priv->loc_location_position_report_indication_id)
+        g_signal_handler_disconnect (priv->loc_client, priv->loc_location_position_report_indication_id);
     if (priv->loc_assistance_inject_time_req_indication_id)
         g_signal_handler_disconnect (priv->loc_client, priv->loc_assistance_inject_time_req_indication_id);
     if (priv->loc_assistance_inject_position_req_indication_id)
@@ -5161,6 +5165,10 @@ loc_stop_ready (QmiClientLoc *client,
             g_signal_handler_disconnect (priv->loc_client, priv->loc_location_nmea_indication_id);
             priv->loc_location_nmea_indication_id = 0;
         }
+        if (priv->loc_location_position_report_indication_id != 0) {
+            g_signal_handler_disconnect (priv->loc_client, priv->loc_location_position_report_indication_id);
+            priv->loc_location_position_report_indication_id = 0;
+        }
         g_clear_object (&priv->loc_client);
     }
 
@@ -5264,11 +5272,142 @@ loc_location_nmea_indication_cb (QmiClientLoc               *client,
     if (!nmea)
         return;
 
+    priv->loc_location_nmea_received = TRUE;
+
     mm_obj_dbg (self, "[NMEA] %s", nmea);
     mm_iface_modem_location_gps_update (MM_IFACE_MODEM_LOCATION (self), nmea);
     mm_location_cache_update_from_nmea (priv->location_cache, nmea);
 }
 
+/* Build a NMEA sentence ("$" + body + "*" + XOR checksum) from its body */
+static gchar *
+nmea_sentence_new (const gchar *body)
+{
+    guint8       checksum = 0;
+    const gchar *p;
+
+    for (p = body; *p; p++)
+        checksum ^= (guint8) *p;
+    return g_strdup_printf ("$%s*%02X", body, checksum);
+}
+
+/* Some GNSS engines (e.g. gnss8 in the SM7635) report fixes only via
+ * Position Report indications and never emit NMEA. Synthesize minimal
+ * $GPGGA/$GPRMC sentences from the position report so that the existing
+ * NMEA-based location pipeline (gps-raw and gps-nmea) also works on those
+ * engines. Not used on engines seen emitting NMEA themselves. */
+static void
+loc_location_position_report_indication_cb (QmiClientLoc                         *client,
+                                            QmiIndicationLocPositionReportOutput *output,
+                                            MMSharedQmi                          *self)
+{
+    Private             *priv;
+    QmiLocSessionStatus  session_status = QMI_LOC_SESSION_STATUS_GENERAL_FAILURE;
+    gdouble              latitude = 0.0;
+    gdouble              longitude = 0.0;
+    gfloat               altitude = 0.0;
+    gfloat               speed = 0.0;
+    gfloat               heading = 0.0;
+    guint64              timestamp = 0;
+    gdouble              absolute;
+    gdouble              minutes;
+    guint                degrees;
+    gchar                ns;
+    gchar                ew;
+    gchar                latbuf[32];
+    gchar                lonbuf[32];
+    gchar                timebuf[16] = "";
+    gchar                datebuf[8] = "";
+    gchar                altbuf[16] = "";
+    gchar                speedbuf[16] = "";
+    gchar                headingbuf[16] = "";
+    g_autofree gchar    *gga_body = NULL;
+    g_autofree gchar    *gga = NULL;
+
+    priv = get_private (self);
+
+    /* Engines that emit NMEA themselves don't need synthesized sentences */
+    if (priv->loc_location_nmea_received)
+        return;
+
+    /* Only surface reports carrying a valid fix; intermediate reports are
+     * disabled at engine start */
+    if (!qmi_indication_loc_position_report_output_get_session_status (output, &session_status, NULL) ||
+        (session_status != QMI_LOC_SESSION_STATUS_SUCCESS))
+        return;
+
+    if (!qmi_indication_loc_position_report_output_get_latitude (output, &latitude, NULL) ||
+        !qmi_indication_loc_position_report_output_get_longitude (output, &longitude, NULL))
+        return;
+
+    /* Unavailable optional values are left as empty NMEA fields */
+    if (qmi_indication_loc_position_report_output_get_utc_timestamp (output, &timestamp, NULL)) {
+        g_autoptr(GDateTime) utc = NULL;
+
+        utc = g_date_time_new_from_unix_utc ((gint64) (timestamp / 1000));
+        if (utc) {
+            g_snprintf (timebuf, sizeof (timebuf), "%02d%02d%02d.%02u",
+                        g_date_time_get_hour (utc),
+                        g_date_time_get_minute (utc),
+                        g_date_time_get_second (utc),
+                        (guint) ((timestamp % 1000) / 10));
+            g_snprintf (datebuf, sizeof (datebuf), "%02d%02d%02d",
+                        g_date_time_get_day_of_month (utc),
+                        g_date_time_get_month (utc),
+                        g_date_time_get_year (utc) % 100);
+        }
+    }
+    if (qmi_indication_loc_position_report_output_get_altitude_from_sealevel (output, &altitude, NULL))
+        g_snprintf (altbuf, sizeof (altbuf), "%.1f", (gdouble) altitude);
+    if (qmi_indication_loc_position_report_output_get_horizontal_speed (output, &speed, NULL))
+        g_snprintf (speedbuf, sizeof (speedbuf), "%.1f", (gdouble) speed * 1.943844); /* m/s -> knots */
+    if (qmi_indication_loc_position_report_output_get_heading (output, &heading, NULL))
+        g_snprintf (headingbuf, sizeof (headingbuf), "%.1f", (gdouble) heading);
+
+    ns = (latitude >= 0.0) ? 'N' : 'S';
+    absolute = (latitude >= 0.0) ? latitude : -latitude;
+    degrees = (guint) absolute;
+    minutes = (absolute - degrees) * 60.0;
+    /* %.6f rounding must not print out-of-spec 60.000000 minutes */
+    if (minutes >= 60.0 - 0.0000005) {
+        minutes = 0.0;
+        degrees++;
+    }
+    g_snprintf (latbuf, sizeof (latbuf), "%02u%09.6f", degrees, minutes);
+
+    ew = (longitude >= 0.0) ? 'E' : 'W';
+    absolute = (longitude >= 0.0) ? longitude : -longitude;
+    degrees = (guint) absolute;
+    minutes = (absolute - degrees) * 60.0;
+    if (minutes >= 60.0 - 0.0000005) {
+        minutes = 0.0;
+        degrees++;
+    }
+    g_snprintf (lonbuf, sizeof (lonbuf), "%03u%09.6f", degrees, minutes);
+
+    gga_body = g_strdup_printf ("GPGGA,%s,%s,%c,%s,%c,1,,,%s,M,,M,,",
+                                timebuf, latbuf, ns, lonbuf, ew, altbuf);
+    gga = nmea_sentence_new (gga_body);
+
+    mm_obj_dbg (self, "[position-report] %s", gga);
+    mm_iface_modem_location_gps_update (MM_IFACE_MODEM_LOCATION (self), gga);
+    mm_location_cache_update_from_nmea (priv->location_cache, gga);
+
+    /* An RMC sentence without a UTC timestamp would be meaningless */
+    if (timebuf[0]) {
+        g_autofree gchar *rmc_body = NULL;
+        g_autofree gchar *rmc = NULL;
+
+        rmc_body = g_strdup_printf ("GPRMC,%s,A,%s,%c,%s,%c,%s,%s,%s,,",
+                                    timebuf, latbuf, ns, lonbuf, ew, speedbuf, headingbuf, datebuf);
+        rmc = nmea_sentence_new (rmc_body);
+
+        mm_obj_dbg (self, "[position-report] %s", rmc);
+        mm_iface_modem_location_gps_update (MM_IFACE_MODEM_LOCATION (self), rmc);
+        mm_location_cache_update_from_nmea (priv->location_cache, rmc);
+    }
+}
+
 /*****************************************************************************/
 /* Location: internal helper: setup minimum required NMEA traces */
 
@@ -5662,6 +5801,7 @@ gps_engine_loc_register_events (QmiClientLoc *client,
     guint64                           event_mask;
 
     event_mask = QMI_LOC_EVENT_REGISTRATION_FLAG_NMEA |
+                 QMI_LOC_EVENT_REGISTRATION_FLAG_POSITION_REPORT |
                  QMI_LOC_EVENT_REGISTRATION_FLAG_INJECT_TIME_REQUEST |
                  QMI_LOC_EVENT_REGISTRATION_FLAG_INJECT_POSITION_REQUEST;
     input = qmi_message_loc_register_events_input_new ();
@@ -5713,12 +5853,19 @@ loc_start_ready (QmiClientLoc *client,
 
     g_assert (!priv->loc_client);
     g_assert (!priv->loc_location_nmea_indication_id);
+    g_assert (!priv->loc_location_position_report_indication_id);
     priv->loc_client = QMI_CLIENT (g_object_ref (client));
+    priv->loc_location_nmea_received = FALSE;
     priv->loc_location_nmea_indication_id =
         g_signal_connect (client,
                           "nmea",
                           G_CALLBACK (loc_location_nmea_indication_cb),
                           self);
+    priv->loc_location_position_report_indication_id =
+        g_signal_connect (client,
+                          "position-report",
+                          G_CALLBACK (loc_location_position_report_indication_cb),
+                          self);
 
     g_task_return_boolean (task, TRUE);
     g_object_unref (task);
-- 
2.55.0