Fix: correct return type and PSRAM handling in nvs_config_get_string()

Author: 0x-fran

main/nvs_config.cpp

@@ -38,6 +38,15 @@ typedef struct {
 static ConfigCacheEntry* config_cache = nullptr;
 static SemaphoreHandle_t config_mutex = nullptr;
 
+// Duplicates a string into specified memory (PSRAM) using heap_caps_malloc().
+static char* heap_caps_strdup(const char* src, uint32_t caps) {
+    if (!src) return nullptr;
+    size_t len = strlen(src) + 1;
+    char* dst = (char*) heap_caps_malloc(len, caps);
+    if (dst) memcpy(dst, src, len);
+    return dst;
+}
+
 // --- Initialize cache and mutex ---
 void init_cache() {
     if (!config_mutex) {
@@ -76,17 +85,18 @@ static ConfigCacheEntry* get_cache_entry(const char* key, config_type_t type) {
 }
 
 // --- API Functions ---
-const char *nvs_config_get_string(const char *key, const char *default_value) {
+char *nvs_config_get_string(const char *key, const char *default_value) {
     CONFIG_LOCK();
     ConfigCacheEntry* entry = get_cache_entry(key, CONFIG_TYPE_STRING);
     if (!entry) {
         CONFIG_UNLOCK();
-        return default_value ? default_value : ""; // Return default or empty string, but never NULL
+        const char* fallback = default_value ? default_value : ""; // Return default or empty string, but never NULL
+        return heap_caps_strdup(fallback, MALLOC_CAP_SPIRAM);
     }
 
     if (entry->valid) {
         ESP_LOGD(TAG, "Cache hit for string key: %s", key);
-        const char* result = entry->data.str_value;
+        char* result = heap_caps_strdup(entry->data.str_value, MALLOC_CAP_SPIRAM);
         CONFIG_UNLOCK();
         return result;
     }
@@ -123,7 +133,7 @@ const char *nvs_config_get_string(const char *key, const char *default_value) {
     entry->data.str_value = loaded_value;
     entry->valid = true;
 
-    const char* result = entry->data.str_value;
+    char* result = heap_caps_strdup(loaded_value, MALLOC_CAP_SPIRAM);
     CONFIG_UNLOCK();
     return result;
 }

main/nvs_config.h

@@ -172,5 +172,5 @@ namespace Config {
     void init_cache();         // Allocate PSRAM-backed cache and mutex
     void flush_nvs_changes();  // Flush cached config values to NVS
     bool has_dirty();          // Check if any cached values are dirty
-    void dump_cache_status()   // in case we want to monitor the nvs-cache - not used currently
+    void dump_cache_status();  // in case we want to monitor the nvs-cache - not used currently
 }