sierra: use an additional AT+WS46=? to detect LTE capabilities

Some Sierra modems (e.g. MC7710) will report LTE-specific supported modes in the
AT+WS46=? reply, but not +CLTE capability in the AT+GCAP reply:

AT+GCAP
 +GCAP: +CGSM
 OK

AT+WS46=?
 +WS46: (12,22,25,28,29)
 OK

plugins/sierra/mm-broadband-modem-sierra.c

@@ -38,10 +38,139 @@
 static void iface_modem_init (MMIfaceModem *iface);
 static void iface_modem_cdma_init (MMIfaceModemCdma *iface);
 
+static MMIfaceModem *iface_modem_parent;
+
 G_DEFINE_TYPE_EXTENDED (MMBroadbandModemSierra, mm_broadband_modem_sierra, MM_TYPE_BROADBAND_MODEM, 0,
                         G_IMPLEMENT_INTERFACE (MM_TYPE_IFACE_MODEM, iface_modem_init)
                         G_IMPLEMENT_INTERFACE (MM_TYPE_IFACE_MODEM_CDMA, iface_modem_cdma_init))
 
+/*****************************************************************************/
+/* Capabilities loading (Modem interface) */
+
+typedef struct {
+    MMBroadbandModemSierra *self;
+    GSimpleAsyncResult *result;
+    MMModemCapability caps;
+} LoadCapabilitiesContext;
+
+static void
+load_capabilities_context_complete_and_free (LoadCapabilitiesContext *ctx)
+{
+    g_simple_async_result_complete (ctx->result);
+    g_object_unref (ctx->result);
+    g_object_unref (ctx->self);
+    g_slice_free (LoadCapabilitiesContext, ctx);
+}
+
+static MMModemCapability
+load_current_capabilities_finish (MMIfaceModem *self,
+                                  GAsyncResult *res,
+                                  GError **error)
+{
+    MMModemCapability caps;
+    gchar *caps_str;
+
+    if (g_simple_async_result_propagate_error (G_SIMPLE_ASYNC_RESULT (res), error))
+        return MM_MODEM_CAPABILITY_NONE;
+
+    caps = (MMModemCapability) GPOINTER_TO_UINT (g_simple_async_result_get_op_res_gpointer (G_SIMPLE_ASYNC_RESULT (res)));
+    caps_str = mm_modem_capability_build_string_from_mask (caps);
+    mm_dbg ("loaded current (sierra) capabilities: %s", caps_str);
+    g_free (caps_str);
+    return caps;
+}
+
+static void
+supported_modes_ws46_test_ready (MMBaseModem *self,
+                                 GAsyncResult *res,
+                                 LoadCapabilitiesContext *ctx)
+{
+    const gchar *response;
+
+    response = mm_base_modem_at_command_finish (self, res, NULL);
+    if (response &&
+        (strstr (response, "28") != NULL ||   /* 4G only */
+         strstr (response, "30") != NULL ||   /* 2G/4G */
+         strstr (response, "31") != NULL)) {  /* 3G/4G */
+        /* Add LTE caps */
+        ctx->caps &= MM_MODEM_CAPABILITY_LTE;
+    }
+
+    g_simple_async_result_set_op_res_gpointer (
+        ctx->result,
+        GUINT_TO_POINTER (ctx->caps),
+        NULL);
+    load_capabilities_context_complete_and_free (ctx);
+}
+
+static void
+parent_load_current_capabilities_ready (MMIfaceModem *self,
+                                        GAsyncResult *res,
+                                        LoadCapabilitiesContext *ctx)
+{
+    GError *error = NULL;
+
+    ctx->caps = iface_modem_parent->load_current_capabilities_finish (self, res, &error);
+    if (error) {
+        g_simple_async_result_take_error (ctx->result, error);
+        load_capabilities_context_complete_and_free (ctx);
+        return;
+    }
+
+    /* Some sierra modems (e.g. MC7710 won't report +LTE capabilities even
+     * if they have them. So just run AT+WS46=? as well to see if the current
+     * supported modes includes any LTE-specific mode.
+     *
+     * E.g.:
+     *  AT+WS46=?
+     *   +WS46: (12,22,25,28,29)
+     *   OK
+     *
+     */
+    if (ctx->caps & MM_MODEM_CAPABILITY_GSM_UMTS &&
+        !(ctx->caps & MM_MODEM_CAPABILITY_LTE)) {
+        mm_base_modem_at_command (
+            MM_BASE_MODEM (ctx->self),
+            "+WS46=?",
+            3,
+            TRUE, /* allow caching, it's a test command */
+            (GAsyncReadyCallback)supported_modes_ws46_test_ready,
+            ctx);
+        return;
+    }
+
+    /* Otherwise, just set the caps from the parent */
+    g_simple_async_result_set_op_res_gpointer (
+        ctx->result,
+        GUINT_TO_POINTER (ctx->caps),
+        NULL);
+    load_capabilities_context_complete_and_free (ctx);
+}
+
+static void
+load_current_capabilities (MMIfaceModem *self,
+                           GAsyncReadyCallback callback,
+                           gpointer user_data)
+{
+    LoadCapabilitiesContext *ctx;
+
+    mm_dbg ("loading current (sierra) capabilities...");
+
+    ctx = g_slice_new0 (LoadCapabilitiesContext);
+    ctx->self = g_object_ref (self);
+    ctx->result = g_simple_async_result_new (G_OBJECT (self),
+                                             callback,
+                                             user_data,
+                                             load_current_capabilities);
+
+    /* Launch parent loading first */
+    /* Chain up parent's setup */
+    iface_modem_parent->load_current_capabilities (
+        self,
+        (GAsyncReadyCallback)parent_load_current_capabilities_ready,
+        ctx);
+}
+
 /*****************************************************************************/
 /* Load access technologies (Modem interface) */
 
@@ -865,6 +994,10 @@ mm_broadband_modem_sierra_init (MMBroadbandModemSierra *self)
 static void
 iface_modem_init (MMIfaceModem *iface)
 {
+    iface_modem_parent = g_type_interface_peek_parent (iface);
+
+    iface->load_current_capabilities = load_current_capabilities;
+    iface->load_current_capabilities_finish = load_current_capabilities_finish;
     iface->load_allowed_modes = load_allowed_modes;
     iface->load_allowed_modes_finish = load_allowed_modes_finish;
     iface->set_allowed_modes = set_allowed_modes;