Return to the configured window when the last connection drops; review fixes

esphome/components/ble_device_base/__init__.py

@@ -234,13 +234,13 @@ def validate_scan_parameters(config: ConfigType) -> ConfigType:
     # unit collapses to the same value — silently programming a 100 % duty cycle
     # (radio permanently on) from a config that asked for less.
     interval_units = to_ble_units(interval)
-    window_units = to_ble_units(window)
-    if window_units == interval_units and window < interval:
-        raise cv.Invalid(
-            f"Scan window ({window}) and interval ({interval}) both truncate to "
-            f"{interval_units} x 0.625 ms, which the controller scans at a 100 % duty "
-            f"cycle. Separate them by at least 0.625 ms."
-        )
+    for name, value in windows:
+        if to_ble_units(value) == interval_units and value < interval:
+            raise cv.Invalid(
+                f"Scan {name} ({value}) and interval ({interval}) both truncate to "
+                f"{interval_units} x 0.625 ms, which the controller scans at a 100 % duty "
+                f"cycle. Separate them by at least 0.625 ms."
+            )
 
     if interval.total_microseconds * 3 > duration.total_microseconds:
         raise cv.Invalid(

esphome/components/esp32_ble_tracker/__init__.py

@@ -189,7 +189,9 @@ def _raise_defaulted_scan_window(config: ConfigType) -> ConfigType:
         params[CONF_WINDOW] = copy.copy(params[CONF_INTERVAL])
         # A full-duty scan must not compete with an active GATT connection
         # for airtime, so arm the connection-time fallback window as well
-        # unless the user picked one themselves.
+        # unless the user picked one themselves. Injected after validation;
+        # safe only because it equals the window default, which already
+        # passed the <= interval and controller range checks.
         if CONF_CONNECTION_SCAN_WINDOW not in params:
             params[CONF_CONNECTION_SCAN_WINDOW] = cv.positive_time_period(
                 ble_device_base.DEFAULT_SCAN_WINDOW

esphome/components/esp32_ble_tracker/esp32_ble_tracker.cpp

@@ -144,6 +144,16 @@ void ESP32BLETracker::loop() {
       (this->scan_set_param_failed_ && this->scanner_state_ == ScannerState::RUNNING)) {
     this->handle_scanner_failure_();
   }
+
+  // The window is chosen at scan start, so when the last connection drops
+  // mid-scan the reduced connection-time window would persist for the rest
+  // of the scan period (up to scan_duration_); stop the scan so the restart
+  // below returns to the configured window. Only for continuous scanning:
+  // a user-started scan would not be restarted.
+  if (this->scan_window_reduced_ && !counts.active && this->scan_continuous_ &&
+      this->scanner_state_ == ScannerState::RUNNING) {
+    this->stop_scan_();
+  }
   /*
 
     Avoid starting the scanner if:
@@ -248,11 +258,11 @@ void ESP32BLETracker::start_scan_(bool first) {
   this->scan_params_.scan_filter_policy = BLE_SCAN_FILTER_ALLOW_ALL;
   this->scan_params_.scan_interval = this->scan_interval_;
   uint32_t window = this->scan_window_;
-  if (this->connection_scan_window_ != 0 && this->client_state_counts_.active > 0) {
-    // The defaulted window was raised to full duty for advertisement
-    // throughput; while a GATT connection is active, fall back so the
-    // connection events get guaranteed airtime instead of competing with
-    // a wall-to-wall scan on the shared radio.
+  this->scan_window_reduced_ = this->connection_scan_window_ != 0 && this->client_state_counts_.active > 0;
+  if (this->scan_window_reduced_) {
+    // While a GATT connection is active, fall back to the connection scan
+    // window so the connection events get guaranteed airtime instead of
+    // competing with a wall-to-wall scan on the shared radio.
     ESP_LOGV(TAG, "Connection active, using %" PRIu32 " unit scan window", this->connection_scan_window_);
     window = this->connection_scan_window_;
   }
@@ -417,6 +427,9 @@ void ESP32BLETracker::dump_config() {
                 "  Continuous Scanning: %s",
                 this->scan_duration_, this->scan_interval_ * 0.625f, this->scan_window_ * 0.625f,
                 this->scan_active_ ? "ACTIVE" : "PASSIVE", YESNO(this->scan_continuous_));
+  if (this->connection_scan_window_ != 0) {
+    ESP_LOGCONFIG(TAG, "  Connection Scan Window: %.1f ms", this->connection_scan_window_ * 0.625f);
+  }
   ESP_LOGCONFIG(TAG,
                 "  Scanner State: %s\n"
                 "  Connecting: %d, discovered: %d, disconnecting: %d, active: %d",

esphome/components/esp32_ble_tracker/esp32_ble_tracker.h

@@ -314,8 +314,8 @@ class ESP32BLETracker final : public Component,
   uint32_t scan_duration_;
   uint32_t scan_interval_;
   uint32_t scan_window_;
-  /// Window used while a GATT connection is active; only set when the
-  /// defaulted window was raised to full duty (0 = no fallback).
+  /// Window used while a GATT connection is active; set by the user, or
+  /// defaulted when the window was raised to full duty (0 = no fallback).
   uint32_t connection_scan_window_{0};
   esp_bt_status_t scan_start_failed_{ESP_BT_STATUS_SUCCESS};
   esp_bt_status_t scan_set_param_failed_{ESP_BT_STATUS_SUCCESS};
@@ -341,6 +341,9 @@ class ESP32BLETracker final : public Component,
 #endif
   bool ble_was_disabled_{true};
   bool parse_advertisements_{false};
+  /// The running scan was started with connection_scan_window_; lets loop()
+  /// restart the scan at the configured window when the last connection drops.
+  bool scan_window_reduced_{false};
 #ifdef USE_ESP32_BLE_SOFTWARE_COEXISTENCE
   bool coex_prefer_ble_{false};
 #endif

tests/component_tests/esp32_ble_tracker/test_scan_window_default.py

@@ -163,6 +163,23 @@ def test_connection_scan_window_above_interval_rejected(
         _scan_params({"scan_parameters": {"connection_scan_window": "400ms"}})
 
 
+def test_connection_scan_window_truncation_collapse_rejected(
+    stage_esp32: Callable[..., None],
+) -> None:
+    """A connection window that truncates into the interval's 0.625 ms unit
+    would silently program a full-duty scan during connections."""
+    stage_esp32("5.5.5", wifi=True)
+    with pytest.raises(cv.Invalid, match="connection window .* both truncate"):
+        _scan_params(
+            {
+                "scan_parameters": {
+                    "interval": "320.5ms",
+                    "connection_scan_window": "320.2ms",
+                }
+            }
+        )
+
+
 def test_codegen_connection_window_when_raised(
     generate_main: Callable[[str | Path], str],
     component_config_path: Callable[[str], Path],