From 91228c82e659b42c6d5e3540e2af174e4573e3ee Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@koston.org>
Date: Sun, 7 Sep 2025 17:29:45 -0500
Subject: [PATCH] [esp8266][logger] Store LOG_LEVELS strings in PROGMEM to
 reduce RAM usage (#10569)

---
 esphome/components/logger/logger.cpp | 27 ++++++++++++++++++++++++---
 1 file changed, 24 insertions(+), 3 deletions(-)

diff --git a/esphome/components/logger/logger.cpp b/esphome/components/logger/logger.cpp
index 0ade9cedae..5f0e78fc0d 100644
--- a/esphome/components/logger/logger.cpp
+++ b/esphome/components/logger/logger.cpp
@@ -246,14 +246,35 @@ void Logger::add_on_log_callback(std::function<void(uint8_t, const char *, const
   this->log_callback_.add(std::move(callback));
 }
 float Logger::get_setup_priority() const { return setup_priority::BUS + 500.0f; }
+
+#ifdef USE_STORE_LOG_STR_IN_FLASH
+// ESP8266: PSTR() cannot be used in array initializers, so we need to declare
+// each string separately as a global constant first
+static const char LOG_LEVEL_NONE[] PROGMEM = "NONE";
+static const char LOG_LEVEL_ERROR[] PROGMEM = "ERROR";
+static const char LOG_LEVEL_WARN[] PROGMEM = "WARN";
+static const char LOG_LEVEL_INFO[] PROGMEM = "INFO";
+static const char LOG_LEVEL_CONFIG[] PROGMEM = "CONFIG";
+static const char LOG_LEVEL_DEBUG[] PROGMEM = "DEBUG";
+static const char LOG_LEVEL_VERBOSE[] PROGMEM = "VERBOSE";
+static const char LOG_LEVEL_VERY_VERBOSE[] PROGMEM = "VERY_VERBOSE";
+
+static const LogString *const LOG_LEVELS[] = {
+    reinterpret_cast<const LogString *>(LOG_LEVEL_NONE),    reinterpret_cast<const LogString *>(LOG_LEVEL_ERROR),
+    reinterpret_cast<const LogString *>(LOG_LEVEL_WARN),    reinterpret_cast<const LogString *>(LOG_LEVEL_INFO),
+    reinterpret_cast<const LogString *>(LOG_LEVEL_CONFIG),  reinterpret_cast<const LogString *>(LOG_LEVEL_DEBUG),
+    reinterpret_cast<const LogString *>(LOG_LEVEL_VERBOSE), reinterpret_cast<const LogString *>(LOG_LEVEL_VERY_VERBOSE),
+};
+#else
 static const char *const LOG_LEVELS[] = {"NONE", "ERROR", "WARN", "INFO", "CONFIG", "DEBUG", "VERBOSE", "VERY_VERBOSE"};
+#endif
 
 void Logger::dump_config() {
   ESP_LOGCONFIG(TAG,
                 "Logger:\n"
                 "  Max Level: %s\n"
                 "  Initial Level: %s",
-                LOG_LEVELS[ESPHOME_LOG_LEVEL], LOG_LEVELS[this->current_level_]);
+                LOG_STR_ARG(LOG_LEVELS[ESPHOME_LOG_LEVEL]), LOG_STR_ARG(LOG_LEVELS[this->current_level_]));
 #ifndef USE_HOST
   ESP_LOGCONFIG(TAG,
                 "  Log Baud Rate: %" PRIu32 "\n"
@@ -267,14 +288,14 @@ void Logger::dump_config() {
 #endif
 
   for (auto &it : this->log_levels_) {
-    ESP_LOGCONFIG(TAG, "  Level for '%s': %s", it.first.c_str(), LOG_LEVELS[it.second]);
+    ESP_LOGCONFIG(TAG, "  Level for '%s': %s", it.first.c_str(), LOG_STR_ARG(LOG_LEVELS[it.second]));
   }
 }
 
 void Logger::set_log_level(uint8_t level) {
   if (level > ESPHOME_LOG_LEVEL) {
     level = ESPHOME_LOG_LEVEL;
-    ESP_LOGW(TAG, "Cannot set log level higher than pre-compiled %s", LOG_LEVELS[ESPHOME_LOG_LEVEL]);
+    ESP_LOGW(TAG, "Cannot set log level higher than pre-compiled %s", LOG_STR_ARG(LOG_LEVELS[ESPHOME_LOG_LEVEL]));
   }
   this->current_level_ = level;
   this->level_callback_.call(level);