[openthread] Cache is_connected() for cheap inline access (#14484)

Co-authored-by: J. Nick Koston <nick@home-assistant.io>

esphome/components/openthread/openthread.cpp

@@ -1,9 +1,7 @@
 #include "esphome/core/defines.h"
 #ifdef USE_OPENTHREAD
 #include "openthread.h"
-#if ESP_IDF_VERSION >= ESP_IDF_VERSION_VAL(5, 5, 0)
 #include "esp_openthread.h"
-#endif
 
 #include <freertos/portmacro.h>
 
@@ -48,22 +46,15 @@ void OpenThreadComponent::dump_config() {
   }
 }
 
-bool OpenThreadComponent::is_connected() {
-  auto lock = InstanceLock::try_acquire(100);
-  if (!lock) {
-    ESP_LOGW(TAG, "Failed to acquire OpenThread lock in is_connected");
-    return false;
+void OpenThreadComponent::on_state_changed_(otChangedFlags flags, void *context) {
+  if (flags & OT_CHANGED_THREAD_ROLE) {
+    auto *self = static_cast<OpenThreadComponent *>(context);
+    // This runs on the OpenThread task thread with the OT lock held,
+    // so we can safely call otThreadGetDeviceRole directly.
+    otInstance *instance = esp_openthread_get_instance();
+    otDeviceRole role = otThreadGetDeviceRole(instance);
+    self->connected_ = role >= OT_DEVICE_ROLE_CHILD;
   }
-
-  otInstance *instance = lock->get_instance();
-  if (instance == nullptr) {
-    return false;
-  }
-
-  otDeviceRole role = otThreadGetDeviceRole(instance);
-
-  // TODO: If we're a leader, check that there is at least 1 known peer
-  return role >= OT_DEVICE_ROLE_CHILD;
 }
 
 // Gets the off-mesh routable address

esphome/components/openthread/openthread.h

@@ -8,6 +8,7 @@
 
 #include <openthread/srp_client.h>
 #include <openthread/srp_client_buffers.h>
+#include <openthread/instance.h>
 #include <openthread/thread.h>
 
 #include <optional>
@@ -26,7 +27,7 @@ class OpenThreadComponent : public Component {
   bool teardown() override;
   float get_setup_priority() const override { return setup_priority::WIFI; }
 
-  bool is_connected();
+  bool is_connected() const { return this->connected_; }
   network::IPAddresses get_ip_addresses();
   std::optional<otIp6Address> get_omr_address();
   void ot_main();
@@ -42,6 +43,7 @@ class OpenThreadComponent : public Component {
 
  protected:
   std::optional<otIp6Address> get_omr_address_(InstanceLock &lock);
+  static void on_state_changed_(otChangedFlags flags, void *context);
   std::function<void()> factory_reset_external_callback_;
 #if CONFIG_OPENTHREAD_MTD
   uint32_t poll_period_{0};
@@ -49,6 +51,7 @@ class OpenThreadComponent : public Component {
   std::optional<int8_t> output_power_{};
   bool teardown_started_{false};
   bool teardown_complete_{false};
+  bool connected_{false};
 
  private:
   // Stores a pointer to a string literal (static storage duration).

esphome/components/openthread/openthread_esp.cpp

@@ -175,6 +175,9 @@ void OpenThreadComponent::ot_main() {
   // Pass the existing dataset, or NULL which will use the preprocessor definitions
   ESP_ERROR_CHECK(esp_openthread_auto_start(dataset.mLength > 0 ? &dataset : nullptr));
 
+  // Register state change callback to update connected_ reactively instead of polling
+  otSetStateChangedCallback(instance, OpenThreadComponent::on_state_changed_, this);
+
   esp_openthread_launch_mainloop();
 
   // Clean up