Merge branch 'wifi-fast-connect-substitution-string' into integration

2026-07-10 08:55:36 +00:00 · 2026-07-05 23:00:39 -05:00
parent b7a2820ffe ac6d2830d9
commit 86779ec841
40 changed files with 693 additions and 48 deletions
@@ -22,7 +22,7 @@ RUN \
    -r /requirements.txt

 # Install the ESPHome Device Builder dashboard.
-RUN uv pip install --no-cache-dir esphome-device-builder==1.0.29
+RUN uv pip install --no-cache-dir esphome-device-builder==1.1.0

 RUN \
    platformio settings set enable_telemetry No \
@@ -6,7 +6,11 @@ from pathlib import Path
 from esphome.components.esp32 import get_esp32_variant, idf_version
 import esphome.config_validation as cv
 from esphome.core import CORE
-from esphome.framework_helpers import get_project_compile_flags, get_project_link_flags
+from esphome.framework_helpers import (
+    get_project_compile_flags,
+    get_project_cxx_compile_flags,
+    get_project_link_flags,
+)
 from esphome.helpers import mkdir_p, write_file_if_changed

 # Replaces the IDF default C++ standard (-std=gnu++2b appended to
@@ -91,6 +95,14 @@ def get_project_cmakelists(minimal: bool = False) -> str:
        for flag in project_compile_opts
    )

+    # Flags registered via cg.add_cxx_build_flag() go on CXX_COMPILE_OPTIONS
+    # (not COMPILE_OPTIONS) because GCC warns when a C++-only flag such as
+    # -Wno-volatile is passed on a C compile.
+    cxx_compile_options = "\n".join(
+        f'idf_build_set_property(CXX_COMPILE_OPTIONS "{flag}" APPEND)'
+        for flag in get_project_cxx_compile_flags()
+    )
+
    cpp_standard_options = (
        CPP_STANDARD_TEMPLATE.format(standard=CORE.cpp_standard)
        if CORE.cpp_standard
@@ -155,6 +167,8 @@ include($ENV{{IDF_PATH}}/tools/cmake/project.cmake)

 {cpp_standard_options}

+{cxx_compile_options}
+
 {extra_compile_options}

 {managed_components_property}
@@ -108,7 +108,6 @@ Import("env")
 def write_cxx_flags_script() -> None:
    path = CORE.relative_build_path(CXX_FLAGS_FILE_NAME)
    contents = CXX_FLAGS_FILE_CONTENTS
-    if not CORE.is_host:
-        contents += 'env.Append(CXXFLAGS=["-Wno-volatile"])'
-        contents += "\n"
+    for flag in sorted(CORE.cxx_build_flags):
+        contents += f'env.Append(CXXFLAGS=["{flag}"])\n'
    write_file_if_changed(path, contents)
@@ -26,6 +26,7 @@ from esphome.cpp_generator import (  # noqa: F401
    add,
    add_build_flag,
    add_build_unflag,
+    add_cxx_build_flag,
    add_define,
    add_global,
    add_library,
@@ -11,8 +11,11 @@ class ESP32PreferenceBackend final {
  bool save(const uint8_t *data, size_t len);
  bool load(uint8_t *data, size_t len);

-  uint32_t key;
-  uint32_t nvs_handle;
+  uint32_t key{0};
+  uint32_t nvs_handle{0};   // NVS (flash) path
+  uint16_t rtc_offset{0};   // RTC path: word offset into the RTC storage region
+  uint8_t length_words{0};  // RTC path: data length in 32-bit words
+  bool in_flash{true};      // true: store in NVS (flash); false: store in RTC memory
 };

 class ESP32Preferences;
@@ -3,7 +3,10 @@
 #include "preferences.h"
 #include "esphome/core/helpers.h"
 #include "esphome/core/log.h"
+#include "esphome/core/preferences_rtc.h"
+#include <esp_attr.h>
 #include <nvs_flash.h>
+#include <soc/soc_caps.h>
 #include <cstring>
 #include <vector>

@@ -18,6 +21,48 @@ struct NVSData {

 static std::vector<NVSData> s_pending_save;  // NOLINT(cppcoreguidelines-avoid-non-const-global-variables)

+// RTC memory backend for preferences requested with in_flash=false. Survives deep sleep and
+// software/CPU resets, but not power loss; integrity is guarded by a per-record checksum so
+// power-on garbage is detected on load. Keep this small: RTC memory is scarce and shared.
+//
+// Only compiled in when USE_ESP32_RTC_PREFERENCES_STORAGE is set (see preferences.h): the storage
+// buffer reserves RTC memory, so it exists only when some config option actually selected RTC
+// storage AND the variant has RTC memory (the ESP32-C2 and -C61 have none, so RTC_NOINIT_ATTR would
+// have no section to land in and fail to link). Otherwise in_flash=false transparently falls back
+// to NVS (see make_preference below).
+//
+// On variants with only RTC fast memory (C3/C6/H2/P4/C5/...) RTC_NOINIT_ATTR lands in RTC fast memory.
+// This is still safe: the linker reserves .rtc_noinit ahead of any RTC-fast-as-heap pool
+// (CONFIG_ESP_SYSTEM_ALLOW_RTC_FAST_MEM_AS_HEAP), and IDF keeps the RTC fast power domain on in deep
+// sleep (forced on whether or not it is used as heap), so the data is retained across both resets and
+// deep sleep -- only power loss clears it.
+#ifdef USE_ESP32_RTC_PREFERENCES_STORAGE
+static constexpr size_t RTC_PREF_SIZE_WORDS = 64;  // 256 bytes
+static constexpr size_t RTC_PREF_MAX_WORDS = 255;  // length_words field is a uint8_t
+
+// NOLINTNEXTLINE(cppcoreguidelines-avoid-non-const-global-variables)
+static RTC_NOINIT_ATTR uint32_t s_rtc_storage[RTC_PREF_SIZE_WORDS];
+
+static bool save_to_rtc(uint16_t offset, uint32_t key, uint8_t length_words, const uint8_t *data, size_t len) {
+  if (rtc_pref_bytes_to_words(len) != length_words)
+    return false;
+  const size_t buffer_size = static_cast<size_t>(length_words) + 1;
+  if (static_cast<size_t>(offset) + buffer_size > RTC_PREF_SIZE_WORDS)
+    return false;
+  rtc_pref_encode(&s_rtc_storage[offset], key, length_words, data, len);
+  return true;
+}
+
+static bool load_from_rtc(uint16_t offset, uint32_t key, uint8_t length_words, uint8_t *data, size_t len) {
+  if (rtc_pref_bytes_to_words(len) != length_words)
+    return false;
+  const size_t buffer_size = static_cast<size_t>(length_words) + 1;
+  if (static_cast<size_t>(offset) + buffer_size > RTC_PREF_SIZE_WORDS)
+    return false;
+  return rtc_pref_decode(&s_rtc_storage[offset], key, length_words, data, len);
+}
+#endif  // USE_ESP32_RTC_PREFERENCES_STORAGE
+
 // open() runs from app_main() before the logger is initialized, so any failure
 // must be deferred until after global_logger is set. This is emitted from the
 // first make_preference() call, which runs from the generated setup() after
@@ -25,6 +70,10 @@ static std::vector<NVSData> s_pending_save;  // NOLINT(cppcoreguidelines-avoid-n
 static esp_err_t s_open_err = ESP_OK;  // NOLINT(cppcoreguidelines-avoid-non-const-global-variables)

 bool ESP32PreferenceBackend::save(const uint8_t *data, size_t len) {
+#ifdef USE_ESP32_RTC_PREFERENCES_STORAGE
+  if (!this->in_flash)
+    return save_to_rtc(this->rtc_offset, this->key, this->length_words, data, len);
+#endif
  // try find in pending saves and update that
  for (auto &obj : s_pending_save) {
    if (obj.key == this->key) {
@@ -41,6 +90,10 @@ bool ESP32PreferenceBackend::save(const uint8_t *data, size_t len) {
 }

 bool ESP32PreferenceBackend::load(uint8_t *data, size_t len) {
+#ifdef USE_ESP32_RTC_PREFERENCES_STORAGE
+  if (!this->in_flash)
+    return load_from_rtc(this->rtc_offset, this->key, this->length_words, data, len);
+#endif
  // try find in pending saves and load from that
  for (auto &obj : s_pending_save) {
    if (obj.key == this->key) {
@@ -94,6 +147,26 @@ void ESP32Preferences::open() {
  }
 }

+ESPPreferenceObject ESP32Preferences::make_preference(size_t length, uint32_t type, bool in_flash) {
+#ifdef USE_ESP32_RTC_PREFERENCES_STORAGE
+  if (!in_flash)
+    return this->make_rtc_preference_(length, type);
+#else
+  if (!in_flash) {
+    // RTC storage is not compiled in (no config option selected it), so this request
+    // falls back to NVS -- the historic ESP32 behavior. Warn once so callers explicitly
+    // asking for RTC storage can discover the fallback.
+    static bool warned = false;
+    if (!warned) {
+      ESP_LOGW(TAG, "RTC preference storage not compiled in; using NVS (enable with 'preferences: rtc_storage: true')");
+      warned = true;
+    }
+  }
+#endif
+  // in_flash, or RTC storage not compiled in: fall back to NVS.
+  return this->make_preference(length, type);
+}
+
 ESPPreferenceObject ESP32Preferences::make_preference(size_t length, uint32_t type) {
  if (s_open_err != ESP_OK) {
    if (this->nvs_handle == 0) {
@@ -106,10 +179,34 @@ ESPPreferenceObject ESP32Preferences::make_preference(size_t length, uint32_t ty
  auto *pref = new ESP32PreferenceBackend();  // NOLINT(cppcoreguidelines-owning-memory)
  pref->nvs_handle = this->nvs_handle;
  pref->key = type;
+  pref->in_flash = true;

  return ESPPreferenceObject(pref);
 }

+#ifdef USE_ESP32_RTC_PREFERENCES_STORAGE
+ESPPreferenceObject ESP32Preferences::make_rtc_preference_(size_t length, uint32_t type) {
+  const uint32_t length_words = rtc_pref_bytes_to_words(length);
+  if (length_words > RTC_PREF_MAX_WORDS) {
+    ESP_LOGE(TAG, "RTC preference too large: %" PRIu32 " words", length_words);
+    return {};
+  }
+  const uint32_t total_words = length_words + 1;  // +1 for checksum
+  if (static_cast<size_t>(this->current_rtc_offset_) + total_words > RTC_PREF_SIZE_WORDS) {
+    ESP_LOGE(TAG, "RTC preference storage full, cannot allocate %" PRIu32 " words", total_words);
+    return {};
+  }
+  auto *pref = new ESP32PreferenceBackend();  // NOLINT(cppcoreguidelines-owning-memory)
+  pref->key = type;
+  pref->in_flash = false;
+  pref->rtc_offset = this->current_rtc_offset_;
+  pref->length_words = static_cast<uint8_t>(length_words);
+  this->current_rtc_offset_ += static_cast<uint16_t>(total_words);
+
+  return ESPPreferenceObject(pref);
+}
+#endif  // USE_ESP32_RTC_PREFERENCES_STORAGE
+
 bool ESP32Preferences::sync() {
  if (s_pending_save.empty())
    return true;
@@ -186,6 +283,12 @@ bool ESP32Preferences::is_changed_(uint32_t nvs_handle, const NVSData &to_save,
 bool ESP32Preferences::reset() {
  ESP_LOGD(TAG, "Erasing storage");
  s_pending_save.clear();
+#ifdef USE_ESP32_RTC_PREFERENCES_STORAGE
+  // Invalidate RTC-backed preferences too (checksum will no longer match). current_rtc_offset_ is
+  // deliberately left alone: existing backends keep pointing at their allocated slots, and reset()
+  // is always followed by a restart (same reason nvs_handle is zeroed below).
+  memset(s_rtc_storage, 0, sizeof(s_rtc_storage));
+#endif

  nvs_flash_deinit();
  nvs_flash_erase();
@@ -2,6 +2,15 @@
 #ifdef USE_ESP32

 #include "esphome/core/preference_backend.h"
+#include <soc/soc_caps.h>
+
+// RTC-backed preference storage is compiled in only when a config option actually selects it
+// (USE_ESP32_RTC_PREFERENCES, emitted during code generation) and the variant has RTC memory
+// (SOC_RTC_MEM_SUPPORTED; the ESP32-C2 and -C61 have none). Otherwise in_flash=false falls
+// back to NVS and no RTC memory is reserved.
+#if defined(USE_ESP32_RTC_PREFERENCES) && SOC_RTC_MEM_SUPPORTED
+#define USE_ESP32_RTC_PREFERENCES_STORAGE
+#endif

 namespace esphome::esp32 {

@@ -11,9 +20,8 @@ class ESP32Preferences final : public PreferencesMixin<ESP32Preferences> {
 public:
  using PreferencesMixin<ESP32Preferences>::make_preference;
  void open();
-  ESPPreferenceObject make_preference(size_t length, uint32_t type, bool in_flash) {
-    return this->make_preference(length, type);
-  }
+  ESPPreferenceObject make_preference(size_t length, uint32_t type, bool in_flash);
+  // Two-argument form defaults to NVS (flash) storage, preserving historic ESP32 behavior.
  ESPPreferenceObject make_preference(size_t length, uint32_t type);
  bool sync();
  bool reset();
@@ -22,6 +30,13 @@ class ESP32Preferences final : public PreferencesMixin<ESP32Preferences> {

 protected:
  bool is_changed_(uint32_t nvs_handle, const NVSData &to_save, const char *key_str);
+
+#ifdef USE_ESP32_RTC_PREFERENCES_STORAGE
+  // RTC-backed storage (in_flash=false).
+  ESPPreferenceObject make_rtc_preference_(size_t length, uint32_t type);
+  // Next free word offset in the RTC storage region (bump allocated in make_preference order).
+  uint16_t current_rtc_offset_{0};
+#endif
 };

 void setup_preferences();
@@ -8,6 +8,7 @@ extern "C" {
 #include "preferences.h"
 #include "esphome/core/helpers.h"
 #include "esphome/core/log.h"
+#include "esphome/core/preferences_rtc.h"

 #include <cstring>

@@ -80,16 +81,6 @@ static uint32_t get_esp8266_flash_sector() {
 }
 static uint32_t get_esp8266_flash_address() { return get_esp8266_flash_sector() * SPI_FLASH_SEC_SIZE; }

-static inline size_t bytes_to_words(size_t bytes) { return (bytes + 3) / 4; }
-
-template<class It> uint32_t calculate_crc(It first, It last, uint32_t type) {
-  uint32_t crc = type;
-  while (first != last) {
-    crc ^= (*first++ * 2654435769UL) >> 1;
-  }
-  return crc;
-}
-
 static bool save_to_flash(size_t offset, const uint32_t *data, size_t len) {
  for (uint32_t i = 0; i < len; i++) {
    uint32_t j = offset + i;
@@ -137,21 +128,19 @@ static constexpr size_t PREF_MAX_BUFFER_WORDS =
    ESP8266_FLASH_STORAGE_SIZE > RTC_NORMAL_REGION_WORDS ? ESP8266_FLASH_STORAGE_SIZE : RTC_NORMAL_REGION_WORDS;

 bool ESP8266PreferenceBackend::save(const uint8_t *data, size_t len) {
-  if (bytes_to_words(len) != this->length_words)
+  if (rtc_pref_bytes_to_words(len) != this->length_words)
    return false;
  const size_t buffer_size = static_cast<size_t>(this->length_words) + 1;
  if (buffer_size > PREF_MAX_BUFFER_WORDS)
    return false;
  uint32_t buffer[PREF_MAX_BUFFER_WORDS];
-  memset(buffer, 0, buffer_size * sizeof(uint32_t));
-  memcpy(buffer, data, len);
-  buffer[this->length_words] = calculate_crc(buffer, buffer + this->length_words, this->type);
+  rtc_pref_encode(buffer, this->type, this->length_words, data, len);
  return this->in_flash ? save_to_flash(this->offset, buffer, buffer_size)
                        : save_to_rtc(this->offset, buffer, buffer_size);
 }

 bool ESP8266PreferenceBackend::load(uint8_t *data, size_t len) {
-  if (bytes_to_words(len) != this->length_words)
+  if (rtc_pref_bytes_to_words(len) != this->length_words)
    return false;
  const size_t buffer_size = static_cast<size_t>(this->length_words) + 1;
  if (buffer_size > PREF_MAX_BUFFER_WORDS)
@@ -161,10 +150,7 @@ bool ESP8266PreferenceBackend::load(uint8_t *data, size_t len) {
                            : load_from_rtc(this->offset, buffer, buffer_size);
  if (!ret)
    return false;
-  if (buffer[this->length_words] != calculate_crc(buffer, buffer + this->length_words, this->type))
-    return false;
-  memcpy(data, buffer, len);
-  return true;
+  return rtc_pref_decode(buffer, this->type, this->length_words, data, len);
 }

 void ESP8266Preferences::setup() {
@@ -177,13 +163,13 @@ void ESP8266Preferences::setup() {
 }

 ESPPreferenceObject ESP8266Preferences::make_preference(size_t length, uint32_t type, bool in_flash) {
-  const uint32_t length_words = bytes_to_words(length);
+  const uint32_t length_words = rtc_pref_bytes_to_words(length);
  if (length_words > MAX_PREFERENCE_WORDS) {
    ESP_LOGE(TAG, "Preference too large: %u words", static_cast<unsigned int>(length_words));
    return {};
  }

-  const uint32_t total_words = length_words + 1;  // +1 for CRC
+  const uint32_t total_words = length_words + 1;  // +1 for checksum
  uint16_t offset;

  if (in_flash) {
@@ -16,6 +16,7 @@ from esphome.components.mipi import (
    delay,
 )
 from esphome.components.spi import TYPE_QUAD
+from esphome.config_validation import UNDEFINED

 DriverChip(
    "T-DISPLAY-S3-AMOLED",
@@ -97,6 +98,9 @@ CO5300 = DriverChip(
    color_order=MODE_RGB,
    bus_mode=TYPE_QUAD,
    no_slpout=True,
+    swap_xy=UNDEFINED,
+    width=480,
+    height=480,
    initsequence=(
        (SLPOUT,),  # Requires early SLPOUT
        (PAGESEL, 0x00),
@@ -282,3 +282,13 @@ ST7789V.extend(
    invert_colors=True,
    data_rate="40MHz",
 )
+
+CO5300.extend(
+    "WAVESHARE-ESP32-S3-TOUCH-AMOLED-1.64",
+    width=280,
+    height=456,
+    offset_width=20,
+    cs_pin=9,
+    reset_pin=21,
+    enable_pin=1,
+)
@@ -200,6 +200,7 @@ DeviceFirmwareUpdate = nrf52_ns.class_("DeviceFirmwareUpdate", cg.Component)

 CONF_DFU = "dfu"
 CONF_DCDC = "dcdc"
+CONF_LIBC_NANO = "libc_nano"
 CONF_REG0 = "reg0"
 CONF_UICR_ERASE = "uicr_erase"

@@ -248,6 +249,7 @@ CONFIG_SCHEMA = cv.All(
            ): cv.Schema(
                {
                    cv.Optional(CONF_VERSION): cv.string_strict,
+                    cv.Optional(CONF_LIBC_NANO, default=True): cv.boolean,
                    cv.Optional(CONF_ADVANCED, default={}): cv.Schema(
                        {
                            cv.Optional(
@@ -273,6 +275,7 @@ def _validate_mcumgr(config):


 def _final_validate(config):
+
    if CONF_DFU in config:
        _validate_mcumgr(config)
    if config[KEY_BOOTLOADER] == BOOTLOADER_ADAFRUIT:
@@ -283,6 +286,13 @@ def _final_validate(config):
    conf = config[CONF_FRAMEWORK]
    advanced = conf[CONF_ADVANCED]

+    if conf[CONF_LIBC_NANO] and "logger" in CORE.loaded_integrations:
+        _LOGGER.warning(
+            "Logger is enabled with newlib-nano (libc_nano: true). Some format specifiers "
+            "such as %%zu are not supported and will print incorrectly. "
+            "Set 'libc_nano: false' under 'framework:' to use the full newlib."
+        )
+
    if advanced[CONF_ENABLE_OTA_ROLLBACK]:
        # "disabled: false" means safe mode *is* enabled.
        safe_mode_config = full_config.get(CONF_SAFE_MODE, {CONF_DISABLED: True})
@@ -379,6 +389,9 @@ async def to_code(config: ConfigType) -> None:
    # Enable OTA rollback support
    if advanced[CONF_ENABLE_OTA_ROLLBACK]:
        cg.add_define("USE_OTA_ROLLBACK")
+    zephyr_add_prj_conf("NEWLIB_LIBC", True)
+    zephyr_add_prj_conf("NEWLIB_LIBC_FLOAT_PRINTF", True)
+    zephyr_add_prj_conf("NEWLIB_LIBC_NANO", conf[CONF_LIBC_NANO])
    # c++ support
    if framework_ver < cv.Version(2, 9, 2):
        zephyr_add_prj_conf("CPLUSPLUS", True)
@@ -1,3 +1,4 @@
+from esphome import preferences
 import esphome.codegen as cg
 import esphome.config_validation as cv
 from esphome.const import CONF_ID
@@ -10,10 +11,17 @@ preferences_ns = cg.esphome_ns.namespace("preferences")
 IntervalSyncer = preferences_ns.class_("IntervalSyncer", cg.Component)

 CONF_FLASH_WRITE_INTERVAL = "flash_write_interval"
+CONF_RTC_STORAGE = "rtc_storage"
 CONFIG_SCHEMA = cv.Schema(
    {
        cv.GenerateID(): cv.declare_id(IntervalSyncer),
        cv.Optional(CONF_FLASH_WRITE_INTERVAL, default="60s"): cv.update_interval,
+        # Compile the RTC-backed storage into the ESP32 preferences backend even
+        # when no other option selects it, so components (including external
+        # ones) requesting in_flash=false are honoured instead of falling back
+        # to NVS. No default: absence means "no request" (see
+        # preferences.validate_rtc_storage for the per-platform rules).
+        cv.Optional(CONF_RTC_STORAGE): preferences.validate_rtc_storage,
    }
 ).extend(cv.COMPONENT_SCHEMA)

@@ -26,4 +34,6 @@ async def to_code(config):
        cg.add_define("USE_PREFERENCES_SYNC_EVERY_LOOP")
    else:
        cg.add(var.set_write_interval(write_interval))
+    if config.get(CONF_RTC_STORAGE):
+        preferences.request_rtc_storage()
    await cg.register_component(var, config)
@@ -1,4 +1,4 @@
-from esphome import automation
+from esphome import automation, preferences
 import esphome.codegen as cg
 import esphome.config_validation as cv
 from esphome.const import (
@@ -7,6 +7,7 @@ from esphome.const import (
    CONF_NUM_ATTEMPTS,
    CONF_REBOOT_TIMEOUT,
    CONF_SAFE_MODE,
+    CONF_STORAGE,
    KEY_PAST_SAFE_MODE,
 )
 from esphome.core import CORE, CoroPriority, coroutine_with_priority
@@ -42,6 +43,7 @@ CONFIG_SCHEMA = cv.All(
                CONF_REBOOT_TIMEOUT, default="5min"
            ): cv.positive_time_period_milliseconds,
            cv.Optional(CONF_ON_SAFE_MODE): automation.validate_automation({}),
+            **preferences.storage_schema(),
        }
    ).extend(cv.COMPONENT_SCHEMA),
    _remove_id_if_disabled,
@@ -87,6 +89,7 @@ async def to_code(config):
            config[CONF_NUM_ATTEMPTS],
            config[CONF_REBOOT_TIMEOUT],
            config[CONF_BOOT_IS_GOOD_AFTER],
+            preferences.is_in_flash(config[CONF_STORAGE]),
        )
        cg.add(RawExpression(f"if ({condition}) return"))

@@ -162,13 +162,13 @@ bool SafeModeComponent::get_safe_mode_pending() {
  return this->read_rtc_() == SafeModeComponent::ENTER_SAFE_MODE_MAGIC;
 }

-bool SafeModeComponent::should_enter_safe_mode(uint8_t num_attempts, uint32_t enable_time,
-                                               uint32_t boot_is_good_after) {
+bool SafeModeComponent::should_enter_safe_mode(uint8_t num_attempts, uint32_t enable_time, uint32_t boot_is_good_after,
+                                               bool in_flash) {
  this->safe_mode_start_time_ = millis();
  this->safe_mode_enable_time_ = enable_time;
  this->safe_mode_boot_is_good_after_ = boot_is_good_after;
  this->safe_mode_num_attempts_ = num_attempts;
-  this->rtc_ = global_preferences->make_preference<uint32_t>(RTC_KEY, false);
+  this->rtc_ = global_preferences->make_preference<uint32_t>(RTC_KEY, in_flash);

 #if defined(USE_ESP32) && defined(USE_OTA_ROLLBACK)
  // Check partition state to detect if bootloader supports rollback
@@ -17,7 +17,7 @@ constexpr uint32_t RTC_KEY = 233825507UL;
 /// SafeModeComponent provides a safe way to recover from repeated boot failures
 class SafeModeComponent final : public Component {
 public:
-  bool should_enter_safe_mode(uint8_t num_attempts, uint32_t enable_time, uint32_t boot_is_good_after);
+  bool should_enter_safe_mode(uint8_t num_attempts, uint32_t enable_time, uint32_t boot_is_good_after, bool in_flash);

  /// Set to true if the next startup will enter safe mode
  void set_safe_mode_pending(const bool &pending);
@@ -1,10 +1,11 @@
 import logging
 import math
+from typing import Any

-from esphome import automation
+from esphome import automation, preferences
 from esphome.automation import Condition
 import esphome.codegen as cg
-from esphome.components.const import CONF_USE_PSRAM
+from esphome.components.const import CONF_ENABLED, CONF_USE_PSRAM
 from esphome.components.esp32 import (
    add_idf_sdkconfig_option,
    const,
@@ -50,6 +51,7 @@ from esphome.const import (
    CONF_REBOOT_TIMEOUT,
    CONF_SSID,
    CONF_STATIC_IP,
+    CONF_STORAGE,
    CONF_SUBNET,
    CONF_TIMEOUT,
    CONF_TTLS_PHASE_2,
@@ -434,6 +436,23 @@ def _validate(config):


 CONF_PASSIVE_SCAN = "passive_scan"
+
+FAST_CONNECT_SCHEMA = cv.Schema(
+    {
+        cv.Optional(CONF_ENABLED, default=True): cv.boolean,
+        **preferences.storage_schema(),
+    }
+)
+
+
+def _fast_connect_schema(value: Any) -> ConfigType:
+    """Accept the historic plain boolean (including boolean-like strings from
+    substitutions) or a dict with enabled/storage keys."""
+    if not isinstance(value, dict):
+        value = {CONF_ENABLED: value}
+    return FAST_CONNECT_SCHEMA(value)
+
+
 CONFIG_SCHEMA = cv.All(
    cv.Schema(
        {
@@ -459,7 +478,7 @@ CONFIG_SCHEMA = cv.All(
                rtl87xx="none",
                ln882x="light",
            ): cv.enum(WIFI_POWER_SAVE_MODES, upper=True),
-            cv.Optional(CONF_FAST_CONNECT, default=False): cv.boolean,
+            cv.Optional(CONF_FAST_CONNECT, default=False): _fast_connect_schema,
            cv.Optional(CONF_USE_ADDRESS): cv.string_strict,
            cv.Optional(CONF_MIN_AUTH_MODE): cv.All(
                VALIDATE_WIFI_MIN_AUTH_MODE,
@@ -619,8 +638,14 @@ async def to_code(config):
    cg.add(var.set_power_save_mode(config[CONF_POWER_SAVE_MODE]))
    if CONF_MIN_AUTH_MODE in config:
        cg.add(var.set_min_auth_mode(config[CONF_MIN_AUTH_MODE]))
-    if config[CONF_FAST_CONNECT]:
+    fast_connect = config[CONF_FAST_CONNECT]
+    if fast_connect[CONF_ENABLED]:
        cg.add_define("USE_WIFI_FAST_CONNECT")
+        # The storage default preserves this preference's historic location:
+        # ESP8266 has always used RTC memory; every other platform effectively
+        # used flash (the in_flash flag was previously ignored outside ESP8266).
+        if preferences.is_in_flash(fast_connect[CONF_STORAGE]):
+            cg.add_define("USE_WIFI_FAST_CONNECT_IN_FLASH")
    # passive_scan defaults to false in C++ - only set if true
    if config[CONF_PASSIVE_SCAN]:
        cg.add(var.set_passive_scan(True))
@@ -649,7 +649,13 @@ void WiFiComponent::start() {

  this->pref_ = global_preferences->make_preference<wifi::SavedWifiSettings>(hash, true);
 #ifdef USE_WIFI_FAST_CONNECT
-  this->fast_connect_pref_ = global_preferences->make_preference<wifi::SavedWifiFastConnectSettings>(hash + 1, false);
+#ifdef USE_WIFI_FAST_CONNECT_IN_FLASH
+  const bool fast_connect_in_flash = true;
+#else
+  const bool fast_connect_in_flash = false;
+#endif
+  this->fast_connect_pref_ =
+      global_preferences->make_preference<wifi::SavedWifiFastConnectSettings>(hash + 1, fast_connect_in_flash);
 #endif

  SavedWifiSettings save{};
@@ -134,9 +134,7 @@ def zephyr_to_code(config: ConfigType) -> None:
    cg.add_define("USE_NATIVE_64BIT_TIME")
    cg.set_cpp_standard("gnu++20")
    # c++ support
-    zephyr_add_prj_conf("NEWLIB_LIBC", True)
    zephyr_add_prj_conf("FPU", True)
-    zephyr_add_prj_conf("NEWLIB_LIBC_FLOAT_PRINTF", True)
    zephyr_add_prj_conf("STD_CPP20", True)
    # random_bytes() uses sys_rand_get() which requires the entropy subsystem
    zephyr_add_prj_conf("ENTROPY_GENERATOR", True)
@@ -976,6 +976,7 @@ CONF_STEP_PIN = "step_pin"
 CONF_STILL_THRESHOLD = "still_threshold"
 CONF_STOP = "stop"
 CONF_STOP_ACTION = "stop_action"
+CONF_STORAGE = "storage"
 CONF_STORE_BASELINE = "store_baseline"
 CONF_SUBNET = "subnet"
 CONF_SUBSCRIBE_QOS = "subscribe_qos"
@@ -627,6 +627,9 @@ class EsphomeCore:
        self.platformio_libraries: dict[str, Library] = {}
        # A set of build flags to set in the platformio project
        self.build_flags: set[str] = set()
+        # A set of build flags that apply to C++ compiles only (CXXFLAGS /
+        # CXX_COMPILE_OPTIONS), for flags GCC rejects or warns about on C
+        self.cxx_build_flags: set[str] = set()
        # A set of build unflags to set in the platformio project
        self.build_unflags: set[str] = set()
        # The C++ language standard for the build (e.g. "gnu++20"), set via cg.set_cpp_standard()
@@ -686,6 +689,7 @@ class EsphomeCore:
        self.global_statements = []
        self.platformio_libraries = {}
        self.build_flags = set()
+        self.cxx_build_flags = set()
        self.build_unflags = set()
        self.cpp_standard = None
        self.defines = set()
@@ -993,6 +997,11 @@ class EsphomeCore:
        _LOGGER.debug("Adding build flag: %s", build_flag)
        return build_flag

+    def add_cxx_build_flag(self, build_flag: str) -> str:
+        self.cxx_build_flags.add(build_flag)
+        _LOGGER.debug("Adding C++ build flag: %s", build_flag)
+        return build_flag
+
    def add_build_unflag(self, build_unflag: str) -> None:
        if self.using_toolchain_esp_idf:
            # The native ESP-IDF build generator does not consume build_unflags
@@ -723,6 +723,15 @@ async def to_code(config: ConfigType) -> None:
    cg.add_build_flag("-Wno-unused-variable")
    cg.add_build_flag("-Wno-unused-but-set-variable")
    cg.add_build_flag("-Wno-sign-compare")
+    # C++20 deprecated ++/--, compound assignment, and chained assignment on
+    # volatile lvalues; GCC warns via -Wvolatile, on by default at gnu++20.
+    # C++23 (P2327R1) removed the deprecation for compound assignment, so the
+    # warning flags patterns that are valid again under newer standards.
+    # C++-only flag: GCC warns when it is passed on a C compile, hence
+    # add_cxx_build_flag. Skipped for host builds, where the compiler may be
+    # clang, which does not know this GCC option.
+    if not CORE.is_host:
+        cg.add_cxx_build_flag("-Wno-volatile")
    if config[CONF_DEBUG_SCHEDULER]:
        cg.add_define("ESPHOME_DEBUG_SCHEDULER")

@@ -240,6 +240,7 @@
 #define USE_OTA_ROLLBACK
 #define USE_OTA_SIGNED_VERIFICATION
 #define USE_ESP32_MIN_CHIP_REVISION_SET
+#define USE_ESP32_RTC_PREFERENCES
 #define USE_ESP32_SRAM1_AS_IRAM

 #define USE_BLUETOOTH_PROXY
@@ -300,6 +301,7 @@
 #define USE_CAPTIVE_PORTAL_GZIP
 #define USE_WIFI_11KV_SUPPORT
 #define USE_WIFI_FAST_CONNECT
+#define USE_WIFI_FAST_CONNECT_IN_FLASH
 #define USE_WIFI_PHY_MODE
 #define USE_WIFI_IP_STATE_LISTENERS
 #define USE_WIFI_SCAN_RESULTS_LISTENERS
@@ -0,0 +1,54 @@
+#pragma once
+
+#include <cstddef>
+#include <cstdint>
+#include <cstring>
+
+namespace esphome {
+
+// Shared storage format for word-addressable preference backends.
+//
+// Several platforms persist preferences as a buffer of 32-bit words followed by a
+// single checksum word, seeded with the preference's `type` (its hashed key). This
+// format is used for RTC user memory (ESP8266, ESP32) and for the ESP8266
+// flash-emulation buffer. The helpers here are platform independent; each backend
+// supplies its own word read/write primitives and offset allocation.
+
+/// Round a byte count up to whole 32-bit words.
+inline size_t rtc_pref_bytes_to_words(size_t bytes) { return (bytes + 3) / 4; }
+
+/// Compute the integrity checksum over [first, last), seeded with `type`.
+/// Iterates over 32-bit words; the result is stored as the trailing word of a record.
+/// (Not a true CRC -- it XORs each word after a Fibonacci-hash multiply -- but the
+/// algorithm is kept as-is for compatibility with records written by old firmware.)
+template<class It> uint32_t rtc_pref_calculate_checksum(It first, It last, uint32_t type) {
+  uint32_t checksum = type;
+  while (first != last) {
+    // UINT32_C keeps the multiply wrapping at 32 bits regardless of the width of
+    // unsigned long, so 64-bit host builds compute the same value as the devices.
+    checksum ^= (*first++ * UINT32_C(2654435769)) >> 1;
+  }
+  return checksum;
+}
+
+/// Encode `len` data bytes into `buffer` (length_words data words + 1 trailing checksum word).
+/// `buffer` must have capacity for at least `length_words + 1` words. Trailing padding in
+/// the final data word is zeroed so the checksum is deterministic.
+inline void rtc_pref_encode(uint32_t *buffer, uint32_t type, uint8_t length_words, const uint8_t *data, size_t len) {
+  memset(buffer, 0, (static_cast<size_t>(length_words) + 1) * sizeof(uint32_t));
+  memcpy(buffer, data, len);
+  buffer[length_words] = rtc_pref_calculate_checksum(buffer, buffer + length_words, type);
+}
+
+/// Verify the checksum of a record held in `buffer` (length_words data words + 1 checksum
+/// word) and, on success, copy `len` bytes out to `data`. Returns false on checksum mismatch
+/// (e.g. the record was never written or RTC memory holds power-on garbage).
+inline bool rtc_pref_decode(const uint32_t *buffer, uint32_t type, uint8_t length_words, uint8_t *data, size_t len) {
+  if (buffer[length_words] != rtc_pref_calculate_checksum(buffer, buffer + length_words, type)) {
+    return false;
+  }
+  memcpy(data, buffer, len);
+  return true;
+}
+
+}  // namespace esphome
@@ -724,6 +724,15 @@ def add_build_flag(build_flag: str):
    CORE.add_build_flag(build_flag)


+def add_cxx_build_flag(build_flag: str) -> None:
+    """Add a global build flag that applies to C++ compiles only.
+
+    Use for flags GCC rejects or warns about when passed on C compiles
+    (e.g. ``-Wno-volatile``).
+    """
+    CORE.add_cxx_build_flag(build_flag)
+
+
 def add_build_unflag(build_unflag: str) -> None:
    """Add a global build unflag to the compiler flags."""
    CORE.add_build_unflag(build_unflag)
@@ -37,6 +37,13 @@ def get_project_compile_flags() -> list[str]:
    ]


+def get_project_cxx_compile_flags() -> list[str]:
+    """Return the sorted flags that apply to C++ compiles only."""
+    from esphome.core import CORE  # local import to avoid circular dependency
+
+    return sorted(CORE.cxx_build_flags)
+
+
 def str_to_lst_of_str(a: str | list[str]) -> list[str]:
    """
    Convert a string to a list of string
@@ -0,0 +1,106 @@
+"""Helpers for letting a component choose where a preference is persisted.
+
+Preferences can be stored either in flash (durable across power loss) or in RTC
+memory (fast, survives deep sleep and soft resets but not power loss). The
+flash-vs-RTC choice is only meaningful on platforms whose preferences backend
+honors the ``in_flash`` flag — currently ESP32 and ESP8266. On other platforms
+the value is accepted only as ``flash`` (the sole supported backend).
+
+Components include :func:`storage_schema` in their config and convert the chosen
+value with :func:`is_in_flash` when calling ``make_preference``.
+"""
+
+import esphome.codegen as cg
+import esphome.config_validation as cv
+from esphome.const import CONF_STORAGE
+from esphome.core import CORE
+
+STORAGE_FLASH = "flash"
+STORAGE_RTC = "rtc"
+
+
+def _rtc_supported() -> bool:
+    """Whether the active platform has an RTC-backed preferences backend.
+
+    Mirrors the C++ ``SOC_RTC_MEM_SUPPORTED`` guard in the ESP32 backend: the ESP32-C2
+    and -C61 have no RTC memory at all, so RTC storage is unavailable there.
+    """
+    if CORE.is_esp8266:
+        return True
+    if CORE.is_esp32:
+        from esphome.components.esp32 import get_esp32_variant
+        from esphome.components.esp32.const import VARIANT_ESP32C2, VARIANT_ESP32C61
+
+        return get_esp32_variant() not in (VARIANT_ESP32C2, VARIANT_ESP32C61)
+    return False
+
+
+def _default_storage() -> str:
+    """Default that preserves each platform's historic behavior.
+
+    ESP8266 has always stored these preferences in RTC memory; every other
+    platform effectively used flash. Evaluated at validation time.
+    """
+    return STORAGE_RTC if CORE.is_esp8266 else STORAGE_FLASH
+
+
+def _validate_storage(value):
+    value = cv.one_of(STORAGE_FLASH, STORAGE_RTC, lower=True)(value)
+    if value == STORAGE_RTC and not _rtc_supported():
+        raise cv.Invalid(
+            f"'{STORAGE_RTC}' storage is not supported on this platform; only "
+            f"'{STORAGE_FLASH}' is available"
+        )
+    return value
+
+
+def storage_schema():
+    """Return an Optional(CONF_STORAGE) entry for merging into a component schema."""
+    return {cv.Optional(CONF_STORAGE, default=_default_storage): _validate_storage}
+
+
+def request_rtc_storage() -> None:
+    """Compile the RTC-backed storage into the ESP32 preferences backend.
+
+    The RTC storage region is left out of ESP32 builds unless something asks for
+    it, so unused builds don't reserve RTC memory. Call this from ``to_code``
+    when a config option selects RTC storage. No-op on other platforms (ESP8266
+    always has its RTC backend).
+    """
+    if CORE.is_esp32:
+        cg.add_define("USE_ESP32_RTC_PREFERENCES")
+
+
+def validate_rtc_storage(value):
+    """Validate a boolean option that requests RTC-backed preference storage.
+
+    ``false`` means "no request", not "disable": it never turns RTC storage off
+    (another option selecting ``storage: rtc`` still compiles it in). On ESP8266
+    the backend is integral and always enabled, so ``false`` is rejected rather
+    than silently ignored; ``true`` is a tolerated no-op there so shared config
+    packages work across mixed fleets.
+    """
+    value = cv.boolean(value)
+    if not value:
+        if CORE.is_esp8266:
+            raise cv.Invalid(
+                "RTC preference storage is always enabled on ESP8266 and cannot "
+                "be disabled"
+            )
+        return value
+    if not _rtc_supported():
+        raise cv.Invalid("RTC preference storage is not supported on this platform")
+    return value
+
+
+def is_in_flash(value: str) -> bool:
+    """Map a CONF_STORAGE value to the ``in_flash`` argument of make_preference.
+
+    Call this from ``to_code``: when RTC storage is selected on ESP32 it also emits
+    the define that compiles the RTC storage buffer into the ESP32 backend (see
+    :func:`request_rtc_storage`).
+    """
+    in_flash = value == STORAGE_FLASH
+    if not in_flash:
+        request_rtc_storage()
+    return in_flash
@@ -20,7 +20,7 @@ resvg-py==0.3.3
 freetype-py==2.5.1
 jinja2==3.1.6
 bleak==2.1.1
-smpclient==6.0.0
+smpclient==7.2.0
 requests==2.34.2
 py7zr==1.1.3
 platformdirs==4.10.0  # native esp-idf toolchain global cache dir
@@ -555,7 +555,7 @@ def lint_constants_usage():
 # Maximum allowed CONF_ constants in esphome/const.py.
 # This file is frozen — new constants go in esphome/components/const/__init__.py.
 # Decrease this number when constants are moved out of const.py.
-CONST_PY_MAX_CONF = 1014
+CONST_PY_MAX_CONF = 1015


@lint_content_check(include=["esphome/const.py"])
@@ -1,5 +1,5 @@
 {
  "target_module": "esphome.__main__",
  "margin_pct": 20,
-  "cumulative_us": 91000
+  "cumulative_us": 95000
 }
@@ -4,5 +4,6 @@ substitutions:
  reset_pin: "21"

 packages:
-  - !include ../../test_build_components/common/i2c/esp32-idf.yaml
-  - !include common.yaml
+  i2c: !include ../../test_build_components/common/i2c/esp32-idf.yaml
+
+<<: !include common.yaml
@@ -2,3 +2,5 @@ nrf52:
  dfu: true
  reg0:
    voltage: 1.8V
+  framework:
+    libc_nano: false
@@ -0,0 +1,4 @@
+# Exercises the opt-in that compiles the RTC-backed preference storage into
+# the ESP32 backend without any other option selecting it.
+preferences:
+  rtc_storage: true
@@ -0,0 +1,4 @@
+# Exercises the ESP32 RTC-backed preferences path (storage: rtc) for safe_mode.
+safe_mode:
+  num_attempts: 3
+  storage: rtc
@@ -0,0 +1,7 @@
+# Exercises the dict form of fast_connect with RTC-backed preference storage.
+wifi:
+  ssid: MySSID
+  password: password1
+  fast_connect:
+    enabled: true
+    storage: rtc
@@ -0,0 +1,7 @@
+# Exercises the dict form of fast_connect overriding the ESP8266 default (rtc)
+# back to flash storage.
+wifi:
+  ssid: MySSID
+  password: password1
+  fast_connect:
+    storage: flash
@@ -0,0 +1,9 @@
+# fast_connect passed through a substitution arrives as a string ("false"),
+# which must be accepted like the historic plain boolean form.
+substitutions:
+  fast_connect_value: "false"
+
+wifi:
+  ssid: MySSID
+  password: password1
+  fast_connect: ${fast_connect_value}
@@ -243,6 +243,7 @@ def test_get_project_cmakelists_no_cpp_standard(tmp_path: Path) -> None:
        patch("esphome.build_gen.espidf.get_esp32_variant", return_value="ESP32"),
        patch.object(CORE, "name", "test"),
        patch.object(CORE, "cpp_standard", None),
+        patch.object(CORE, "cxx_build_flags", set()),
    ):
        from esphome.build_gen.espidf import get_project_cmakelists

@@ -251,6 +252,28 @@ def test_get_project_cmakelists_no_cpp_standard(tmp_path: Path) -> None:
    assert "CXX_COMPILE_OPTIONS" not in content


+def test_get_project_cmakelists_cxx_build_flags(tmp_path: Path) -> None:
+    """Flags registered via cg.add_cxx_build_flag() are appended to
+    CXX_COMPILE_OPTIONS (C++-only, GCC warns if they reach C compiles)
+    between include(project.cmake) and project()."""
+    with (
+        patch("esphome.build_gen.espidf.get_esp32_variant", return_value="ESP32"),
+        patch.object(CORE, "name", "test"),
+        patch.object(CORE, "cpp_standard", None),
+        patch.object(CORE, "cxx_build_flags", {"-Wno-volatile"}),
+    ):
+        from esphome.build_gen.espidf import get_project_cmakelists
+
+        content = get_project_cmakelists(minimal=True)
+
+    flag_line = 'idf_build_set_property(CXX_COMPILE_OPTIONS "-Wno-volatile" APPEND)'
+    assert flag_line in content
+    include_pos = content.index("tools/cmake/project.cmake")
+    flag_pos = content.index(flag_line)
+    project_pos = content.index("project(test)")
+    assert include_pos < flag_pos < project_pos
+
+
 def test_get_component_cmakelists_no_compile_features() -> None:
    """The C++ standard is pinned project-wide via CXX_COMPILE_OPTIONS in the
    top-level CMakeLists; the src component must not set its own."""
@@ -200,3 +200,32 @@ def test_get_ini_content_no_cpp_standard(
    content = platformio.get_ini_content()

    assert "-std=" not in content
+
+
+def test_write_cxx_flags_script_emits_registered_flags(
+    tmp_path: Path, monkeypatch: pytest.MonkeyPatch
+) -> None:
+    """Flags registered via cg.add_cxx_build_flag() are emitted as CXXFLAGS,
+    sorted, so they apply to C++ compiles only."""
+    CORE.build_path = str(tmp_path)
+    monkeypatch.setattr(CORE, "cxx_build_flags", {"-Wno-volatile", "-Wno-deprecated"})
+
+    platformio.write_cxx_flags_script()
+
+    content = (tmp_path / platformio.CXX_FLAGS_FILE_NAME).read_text()
+    assert (
+        'env.Append(CXXFLAGS=["-Wno-deprecated"])\n'
+        'env.Append(CXXFLAGS=["-Wno-volatile"])\n'
+    ) in content
+
+
+def test_write_cxx_flags_script_no_flags(
+    tmp_path: Path, monkeypatch: pytest.MonkeyPatch
+) -> None:
+    CORE.build_path = str(tmp_path)
+    monkeypatch.setattr(CORE, "cxx_build_flags", set())
+
+    platformio.write_cxx_flags_script()
+
+    content = (tmp_path / platformio.CXX_FLAGS_FILE_NAME).read_text()
+    assert "CXXFLAGS" not in content
@@ -26,6 +26,7 @@ from esphome.framework_helpers import (
    create_venv,
    download_from_mirrors,
    get_project_compile_flags,
+    get_project_cxx_compile_flags,
    get_project_link_flags,
    get_python_env_executable_path,
    get_system_python_path,
@@ -1048,3 +1049,25 @@ class TestGetProjectLinkFlags:
        ):
            result = get_project_link_flags()
            assert result == sorted(result)
+
+
+def _make_core_cxx(flags: set[str]) -> MagicMock:
+    core = MagicMock()
+    core.cxx_build_flags = flags
+    return core
+
+
+class TestGetProjectCxxCompileFlags:
+    def test_returns_sorted_flags(self) -> None:
+        with patch(
+            "esphome.core.CORE",
+            _make_core_cxx({"-Wno-volatile", "-Wno-deprecated"}),
+        ):
+            assert get_project_cxx_compile_flags() == [
+                "-Wno-deprecated",
+                "-Wno-volatile",
+            ]
+
+    def test_empty_flags(self) -> None:
+        with patch("esphome.core.CORE", _make_core_cxx(set())):
+            assert get_project_cxx_compile_flags() == []
@@ -0,0 +1,149 @@
+"""Tests for esphome.preferences storage backend selection."""
+
+import pytest
+
+from esphome import preferences
+from esphome.components.esp32 import KEY_ESP32
+from esphome.components.esp32.const import (
+    VARIANT_ESP32,
+    VARIANT_ESP32C2,
+    VARIANT_ESP32C3,
+    VARIANT_ESP32C61,
+)
+import esphome.config_validation as cv
+from esphome.const import (
+    CONF_STORAGE,
+    KEY_CORE,
+    KEY_TARGET_PLATFORM,
+    KEY_VARIANT,
+    PLATFORM_ESP32,
+    PLATFORM_ESP8266,
+    PLATFORM_RP2040,
+)
+from esphome.core import CORE
+
+
+def _set_platform(platform: str) -> None:
+    CORE.data[KEY_CORE] = {KEY_TARGET_PLATFORM: platform}
+
+
+def _set_esp32(variant: str) -> None:
+    _set_platform(PLATFORM_ESP32)
+    CORE.data[KEY_ESP32] = {KEY_VARIANT: variant}
+
+
+def _validate(value: dict):
+    return cv.Schema(preferences.storage_schema())(value)
+
+
+def _define_names() -> set[str]:
+    return {define.name for define in CORE.defines}
+
+
+def test_is_in_flash() -> None:
+    _set_platform(PLATFORM_ESP8266)
+    assert preferences.is_in_flash(preferences.STORAGE_FLASH) is True
+    assert preferences.is_in_flash(preferences.STORAGE_RTC) is False
+    # The RTC storage define is ESP32-specific.
+    assert "USE_ESP32_RTC_PREFERENCES" not in _define_names()
+
+
+def test_is_in_flash_esp32_rtc_emits_define() -> None:
+    _set_esp32(VARIANT_ESP32)
+    assert preferences.is_in_flash(preferences.STORAGE_FLASH) is True
+    assert "USE_ESP32_RTC_PREFERENCES" not in _define_names()
+    assert preferences.is_in_flash(preferences.STORAGE_RTC) is False
+    assert "USE_ESP32_RTC_PREFERENCES" in _define_names()
+
+
+def test_request_rtc_storage_esp32_only() -> None:
+    _set_platform(PLATFORM_ESP8266)
+    preferences.request_rtc_storage()
+    # ESP8266 always has its RTC backend; no define is needed or emitted.
+    assert "USE_ESP32_RTC_PREFERENCES" not in _define_names()
+
+
+def test_request_rtc_storage_esp32_emits_define() -> None:
+    _set_esp32(VARIANT_ESP32)
+    preferences.request_rtc_storage()
+    assert "USE_ESP32_RTC_PREFERENCES" in _define_names()
+
+
+@pytest.mark.parametrize("variant", [VARIANT_ESP32, VARIANT_ESP32C3])
+def test_validate_rtc_storage_accepted(variant: str) -> None:
+    _set_esp32(variant)
+    assert preferences.validate_rtc_storage(True) is True
+    assert preferences.validate_rtc_storage(False) is False
+
+
+def test_validate_rtc_storage_esp8266() -> None:
+    _set_platform(PLATFORM_ESP8266)
+    # Tolerated no-op: the ESP8266 backend always has RTC storage.
+    assert preferences.validate_rtc_storage(True) is True
+    # But it cannot be disabled, so an explicit false is an error.
+    with pytest.raises(cv.Invalid, match="always enabled on ESP8266"):
+        preferences.validate_rtc_storage(False)
+
+
+@pytest.mark.parametrize("variant", [VARIANT_ESP32C2, VARIANT_ESP32C61])
+def test_validate_rtc_storage_rejected_without_rtc_memory(variant: str) -> None:
+    _set_esp32(variant)
+    with pytest.raises(cv.Invalid, match="not supported on this platform"):
+        preferences.validate_rtc_storage(True)
+    # Disabling it is always fine.
+    assert preferences.validate_rtc_storage(False) is False
+
+
+def test_validate_rtc_storage_rejected_on_unsupported_platform() -> None:
+    _set_platform(PLATFORM_RP2040)
+    with pytest.raises(cv.Invalid, match="not supported on this platform"):
+        preferences.validate_rtc_storage(True)
+
+
+@pytest.mark.parametrize(
+    ("platform", "expected"),
+    [
+        # Defaults preserve each platform's historic behavior.
+        (PLATFORM_ESP8266, preferences.STORAGE_RTC),
+        (PLATFORM_RP2040, preferences.STORAGE_FLASH),
+    ],
+)
+def test_default_storage_per_platform(platform: str, expected: str) -> None:
+    _set_platform(platform)
+    assert _validate({})[CONF_STORAGE] == expected
+
+
+@pytest.mark.parametrize("variant", [VARIANT_ESP32, VARIANT_ESP32C2])
+def test_default_storage_esp32_is_flash(variant: str) -> None:
+    # ESP32 defaults to flash on every variant, including those without RTC memory.
+    _set_esp32(variant)
+    assert _validate({})[CONF_STORAGE] == preferences.STORAGE_FLASH
+
+
+def test_rtc_allowed_on_esp8266() -> None:
+    _set_platform(PLATFORM_ESP8266)
+    assert _validate({CONF_STORAGE: "rtc"})[CONF_STORAGE] == preferences.STORAGE_RTC
+
+
+@pytest.mark.parametrize("variant", [VARIANT_ESP32, VARIANT_ESP32C3])
+def test_rtc_allowed_on_esp32_with_rtc_memory(variant: str) -> None:
+    _set_esp32(variant)
+    assert _validate({CONF_STORAGE: "rtc"})[CONF_STORAGE] == preferences.STORAGE_RTC
+
+
+@pytest.mark.parametrize("variant", [VARIANT_ESP32C2, VARIANT_ESP32C61])
+def test_rtc_rejected_on_esp32_without_rtc_memory(variant: str) -> None:
+    _set_esp32(variant)
+    with pytest.raises(cv.Invalid, match="not supported on this platform"):
+        _validate({CONF_STORAGE: "rtc"})
+
+
+def test_rtc_rejected_on_unsupported_platform() -> None:
+    _set_platform(PLATFORM_RP2040)
+    with pytest.raises(cv.Invalid, match="not supported on this platform"):
+        _validate({CONF_STORAGE: "rtc"})
+
+
+def test_flash_allowed_on_unsupported_platform() -> None:
+    _set_platform(PLATFORM_RP2040)
+    assert _validate({CONF_STORAGE: "flash"})[CONF_STORAGE] == preferences.STORAGE_FLASH