modules: storage: Add littleFS backend

Add littleFS based flash storage backend for the storage module.
Uses a file per storage data type to store a circular buffer of records.

Signed-off-by: Trond F. Christiansen <[email protected]>

Author: Trond-F-Christiansen

app/src/main.c

@@ -1927,8 +1927,20 @@ static void fota_rebooting_entry(void *o)
 {
 	ARG_UNUSED(o);
 
+        struct storage_msg msg = { .type = STORAGE_CLEAR };
+        int err;
+
 	LOG_DBG("%s", __func__);
 
+        /* Tell storage module to clear any stored data */
+        err = zbus_chan_pub(&STORAGE_CHAN, &msg, K_MSEC(ZBUS_PUBLISH_TIMEOUT_MS));
+	if (err) {
+		LOG_ERR("Failed to publish storage clear message, error: %d", err);
+		SEND_FATAL_ERROR();
+
+		return;
+	}
+
 	/* Reboot the device */
 	LOG_WRN("Rebooting the device to apply the FOTA update");
 

app/src/modules/storage/CMakeLists.txt

@@ -16,6 +16,9 @@ zephyr_linker_sources(SECTIONS storage_sections.ld)
 target_sources_ifdef(CONFIG_APP_STORAGE_BACKEND_RAM app PRIVATE
     backends/ram_ring_buffer_backend.c
 )
+target_sources_ifdef(CONFIG_APP_STORAGE_BACKEND_LITTLEFS app PRIVATE
+    backends/littlefs_backend.c
+)
 
 target_sources_ifdef(CONFIG_APP_STORAGE_SHELL app PRIVATE
     storage_shell.c

app/src/modules/storage/Kconfig.storage

@@ -12,14 +12,38 @@ if APP_STORAGE
 
 config APP_STORAGE_THREAD_STACK_SIZE
 	int "Storage module thread stack size"
-	default 1536
+	default 1536 if APP_STORAGE_BACKEND_RAM
+	default 4096 if APP_STORAGE_BACKEND_LITTLEFS
+
+choice APP_STORAGE_BACKEND
+	prompt "Storage backend"
+	default APP_STORAGE_BACKEND_RAM
+	help
+	  Select the storage backend to use for storing data samples.
 
 config APP_STORAGE_BACKEND_RAM
 	bool "RAM storage backend"
-	default y
 	help
 	  Store data in RAM. Data will be lost on power loss or reset.
 
+config APP_STORAGE_BACKEND_LITTLEFS
+	bool "LittleFS storage backend"
+	select FILE_SYSTEM_LITTLEFS
+	select PM_PARTITION_REGION_LITTLEFS_EXTERNAL
+	help
+	  Store data in LittleFS filesystem. Data will persist across power
+	  loss and resets, as long as the underlying flash storage is intact.
+
+endchoice
+
+if APP_STORAGE_BACKEND_LITTLEFS
+
+# Setup PM partition size for LittleFS to 64KB by default
+config PM_PARTITION_SIZE_LITTLEFS
+	default 0x10000
+
+endif # APP_STORAGE_BACKEND_LITTLEFS
+
 config APP_STORAGE_MAX_TYPES
 	int "Maximum number of data types"
 	default 4
@@ -97,6 +121,7 @@ endchoice
 config APP_STORAGE_SHELL
 	bool "Enable storage shell commands"
 	default y if SHELL
+	select FILE_SYSTEM_SHELL if APP_STORAGE_BACKEND_LITTLEFS
 	help
 	  Enable shell commands for interacting with the storage module.
 	  This allows you to manage stored data from the command line.