meshtastic · ndoo · Apr 9, 2026 · Apr 9, 2026 · Apr 9, 2026 · Apr 9, 2026
diff --git a/src/FSCommon.cpp b/src/FSCommon.cpp
@@ -80,10 +80,11 @@ bool renameFile(const char *pathFrom, const char *pathTo)
 {
 #ifdef FSCom
 
-#ifdef ARCH_ESP32
+#if defined(ARCH_ESP32) || defined(ARCH_STM32WL)
     // take SPI Lock
     spiLock->lock();
-    // rename was fixed for ESP32 IDF LittleFS in April
+    // ESP32: rename was fixed for IDF LittleFS in April
+    // STM32WL: STM32_LittleFS::rename() calls lfs_rename() which is atomic
     bool result = FSCom.rename(pathFrom, pathTo);
     spiLock->unlock();
     return result;
@@ -271,8 +272,8 @@ void rmDir(const char *dirname)
 
 #if (defined(ARCH_ESP32) || defined(ARCH_RP2040) || defined(ARCH_PORTDUINO))
     listDir(dirname, 10, true);
-#elif defined(ARCH_NRF52)
-    // nRF52 implementation of LittleFS has a recursive delete function
+#elif defined(ARCH_NRF52) || defined(ARCH_STM32WL)
+    // nRF52 and STM32WL implementations of LittleFS have a recursive delete function
     FSCom.rmdir_r(dirname);
 #endif
 

diff --git a/src/mesh/NodeDB.cpp b/src/mesh/NodeDB.cpp
@@ -1604,7 +1604,8 @@ bool NodeDB::saveToDisk(int saveWhat)
 
     if (!success) {
         LOG_ERROR("Failed to save to disk, retrying");
-#ifdef ARCH_NRF52 // @geeksville is not ready yet to say we should do this on other platforms.  See bug #4184 discussion
+#if defined(ARCH_NRF52) ||                                                                                                       \
+    defined(ARCH_STM32WL) // @geeksville is not ready yet to say we should do this on other platforms.  See bug #4184 discussion
         spiLock->lock();
         FSCom.format();
         spiLock->unlock();
@@ -2189,6 +2190,7 @@ bool NodeDB::checkLowEntropyPublicKey(const meshtastic_Config_SecurityConfig_pub
 }
 #endif
 
+#if !MESHTASTIC_EXCLUDE_BACKUP
 bool NodeDB::backupPreferences(meshtastic_AdminMessage_BackupLocation location)
 {
     bool success = false;
@@ -2276,6 +2278,7 @@ bool NodeDB::restorePreferences(meshtastic_AdminMessage_BackupLocation location,
 #endif
     return success;
 }
+#endif // !MESHTASTIC_EXCLUDE_BACKUP
 
 /// Record an error that should be reported via analytics
 void recordCriticalError(meshtastic_CriticalErrorCode code, uint32_t address, const char *filename)

diff --git a/src/mesh/NodeDB.h b/src/mesh/NodeDB.h
@@ -102,7 +102,9 @@ static constexpr const char *configFileName = "/prefs/config.proto";
 static constexpr const char *uiconfigFileName = "/prefs/uiconfig.proto";
 static constexpr const char *moduleConfigFileName = "/prefs/module.proto";
 static constexpr const char *channelFileName = "/prefs/channels.proto";
+#if !MESHTASTIC_EXCLUDE_BACKUP
 static constexpr const char *backupFileName = "/backups/backup.proto";
+#endif
 
 /// Given a node, return how many seconds in the past (vs now) that we last heard from it
 uint32_t sinceLastSeen(const meshtastic_NodeInfoLite *n);
@@ -316,9 +318,11 @@ class NodeDB
     bool checkLowEntropyPublicKey(const meshtastic_Config_SecurityConfig_public_key_t &keyToTest);
 #endif
 
+#if !MESHTASTIC_EXCLUDE_BACKUP
     bool backupPreferences(meshtastic_AdminMessage_BackupLocation location);
     bool restorePreferences(meshtastic_AdminMessage_BackupLocation location,
                             int restoreWhat = SEGMENT_CONFIG | SEGMENT_MODULECONFIG | SEGMENT_DEVICESTATE | SEGMENT_CHANNELS);
+#endif
 
     /// Notify observers of changes to the DB
     void notifyObservers(bool forceUpdate = false)
@@ -331,9 +335,11 @@ class NodeDB
   private:
     bool duplicateWarned = false;
     bool localPositionUpdatedSinceBoot = false;
-    uint32_t lastNodeDbSave = 0;    // when we last saved our db to flash
+    uint32_t lastNodeDbSave = 0; // when we last saved our db to flash
+#if !MESHTASTIC_EXCLUDE_BACKUP
     uint32_t lastBackupAttempt = 0; // when we last tried a backup automatically or manually
-    uint32_t lastSort = 0;          // When last sorted the nodeDB
+#endif
+    uint32_t lastSort = 0; // When last sorted the nodeDB
     /// Find a node in our DB, create an empty NodeInfoLite if missing
     meshtastic_NodeInfoLite *getOrCreateMeshNode(NodeNum n);
 

diff --git a/src/modules/AdminModule.cpp b/src/modules/AdminModule.cpp
@@ -499,6 +499,7 @@ bool AdminModule::handleReceivedProtobuf(const meshtastic_MeshPacket &mp, meshta
 #endif
         break;
     }
+#if !MESHTASTIC_EXCLUDE_BACKUP
     case meshtastic_AdminMessage_backup_preferences_tag: {
         LOG_INFO("Client requesting to backup preferences");
         if (nodeDB->backupPreferences(r->backup_preferences)) {
@@ -535,6 +536,7 @@ bool AdminModule::handleReceivedProtobuf(const meshtastic_MeshPacket &mp, meshta
 #endif
         break;
     }
+#endif // !MESHTASTIC_EXCLUDE_BACKUP
     case meshtastic_AdminMessage_send_input_event_tag: {
         LOG_INFO("Client requesting to send input event");
         handleSendInputEvent(r->send_input_event);

diff --git a/src/platform/stm32wl/LittleFS.cpp b/src/platform/stm32wl/LittleFS.cpp
@@ -83,31 +83,36 @@ static int _internal_flash_prog(const struct lfs_config *c, lfs_block_t block, l
 
     LFS_UNUSED(c);
 
+    // STM32WL HAL minimum write unit is one 64-bit doubleword (8 bytes)
+    if (size % 8 != 0) {
+        return LFS_ERR_INVAL;
+    }
+
     _LFS_DBG("Programming %d bytes/%d doublewords at address 0x%08x/block %d, offset %d.", size, dw_count, address, block, off);
+
+    // Validate the full write range before touching flash
+    lfs_block_t addr_end = address + (lfs_block_t)(dw_count * 8) - 1;
+    if ((address < LFS_FLASH_ADDR_BASE) || (addr_end > LFS_FLASH_ADDR_END)) {
+        _LFS_DBG("Wanted to program out of bound of FLASH: 0x%08x-0x%08x.\n", address, addr_end);
+        return LFS_ERR_INVAL;
+    }
+
     if (HAL_FLASH_Unlock() != HAL_OK) {
         return LFS_ERR_IO;
     }
+    __HAL_FLASH_CLEAR_FLAG(FLASH_FLAG_ALL_ERRORS);
     for (uint32_t i = 0; i < dw_count; i++) {
-        if ((address < LFS_FLASH_ADDR_BASE) || (address > LFS_FLASH_ADDR_END)) {
-            _LFS_DBG("Wanted to program out of bound of FLASH: 0x%08x.\n", address);
-            HAL_FLASH_Lock();
-            return LFS_ERR_INVAL;
-        }
         hal_rc = HAL_FLASH_Program(FLASH_TYPEPROGRAM_DOUBLEWORD, address, *bufp);
         if (hal_rc != HAL_OK) {
-            /* Error occurred while writing data in Flash memory.
-             * User can add here some code to deal with this error.
-             */
             _LFS_DBG("Program error at (0x%08x), 0x%X, error: 0x%08x\n", address, hal_rc, HAL_FLASH_GetError());
+            break; // Do not continue programming after a failure
         }
         address += 8;
         bufp += 1;
     }
-    if (HAL_FLASH_Lock() != HAL_OK) {
-        return LFS_ERR_IO;
-    }
+    HAL_FLASH_Lock();
 
-    return hal_rc == HAL_OK ? LFS_ERR_OK : LFS_ERR_IO; // If HAL_OK, return LFS_ERR_OK, else return LFS_ERR_IO
+    return hal_rc == HAL_OK ? LFS_ERR_OK : LFS_ERR_IO;
 }
 
 // Erase a block. A block must be erased before being programmed.
@@ -130,7 +135,10 @@ static int _internal_flash_erase(const struct lfs_config *c, lfs_block_t block)
     /* calculate the absolute page, i.e. what the ST wants */
     EraseInitStruct.Page = (address - STM32WL_FLASH_BASE) / STM32WL_PAGE_SIZE;
     _LFS_DBG("Erasing block %d at 0x%08x... ", block, address);
-    HAL_FLASH_Unlock();
+    if (HAL_FLASH_Unlock() != HAL_OK) {
+        return LFS_ERR_IO;
+    }
+    __HAL_FLASH_CLEAR_FLAG(FLASH_FLAG_ALL_ERRORS);
     hal_rc = HAL_FLASHEx_Erase(&EraseInitStruct, &PAGEError);
     HAL_FLASH_Lock();
 

diff --git a/variants/stm32/stm32.ini b/variants/stm32/stm32.ini
@@ -25,6 +25,7 @@ build_flags =
   -DMESHTASTIC_EXCLUDE_BLUETOOTH=1
   -DMESHTASTIC_EXCLUDE_WIFI=1
   -DMESHTASTIC_EXCLUDE_TZ=1 ; Exclude TZ to save some flash space.
+  -DMESHTASTIC_EXCLUDE_BACKUP=1 ; Backup preferences require 2 flash blocks (4 KB); not useful on a flash-constrained node.
   -DSERIAL_RX_BUFFER_SIZE=256 ; For GPS - the default of 64 is too small.
   -DHAS_SCREEN=0 ; Always disable screen for STM32, it is not supported.
   ;-DPIO_FRAMEWORK_ARDUINO_NANOLIB_FLOAT_PRINTF ; Enable this if enabling debugg logging. It is REQUIRED for at least traceroute debug prints - without it the length returned by printf ends up uninitialized.