storage/stream: Add persistent write progress to stream_flash

Add additional API to stream_flash that can be used to make
stream write progress persistent using the settings subsystem.
This functionality makes it possible to resume a write operation
after it was interrupted, e.g. by power loss.

Signed-off-by: Jonathan Nilsen <Jonathan.Nilsen@nordicsemi.no>

subsys/storage/stream/Kconfig

@@ -17,6 +17,15 @@ config STREAM_FLASH_ERASE
 	  If disabled an external actor must erase the flash area being written
 	  to.
 
+config STREAM_FLASH_PROGRESS
+	bool "Persistent stream write progress"
+	depends on SETTINGS
+	depends on !SETTINGS_NONE
+	help
+	  Enable API for loading and storing the current write progress to flash
+	  using the settings subsystem. In case of power failure or device
+	  reset, the API can be used to resume writing from the latest state.
+
 module = STREAM_FLASH
 module-str = stream flash
 source "subsys/logging/Kconfig.template.log_config"

subsys/storage/stream/stream_flash.c

@@ -16,6 +16,62 @@ LOG_MODULE_REGISTER(LOG_MODULE_NAME, CONFIG_STREAM_FLASH_LOG_LEVEL);
 
 #include <storage/stream_flash.h>
 
+#ifdef CONFIG_STREAM_FLASH_PROGRESS
+#include <settings/settings.h>
+
+static int settings_direct_loader(const char *key, size_t len,
+				  settings_read_cb read_cb, void *cb_arg,
+				  void *param)
+{
+	struct stream_flash_ctx *ctx = (struct stream_flash_ctx *) param;
+
+	/* Handle the subtree if it is an exact key match. */
+	if (settings_name_next(key, NULL) == 0) {
+		size_t bytes_written = 0;
+		ssize_t len = read_cb(cb_arg, &bytes_written,
+				      sizeof(bytes_written));
+
+		if (len != sizeof(ctx->bytes_written)) {
+			LOG_ERR("Unable to read bytes_written from storage");
+			return len;
+		}
+
+		/* Check that loaded progress is not outdated. */
+		if (bytes_written >= ctx->bytes_written) {
+			ctx->bytes_written = bytes_written;
+		} else {
+			LOG_WRN("Loaded outdated bytes_written %zu < %zu",
+				bytes_written, ctx->bytes_written);
+			return 0;
+		}
+
+#ifdef CONFIG_STREAM_FLASH_ERASE
+		int rc;
+		struct flash_pages_info page;
+		off_t offset = (off_t) (ctx->offset + ctx->bytes_written) - 1;
+
+		/* Update the last erased page to avoid deleting already
+		 * written data.
+		 */
+		if (ctx->bytes_written > 0) {
+			rc = flash_get_page_info_by_offs(ctx->fdev, offset,
+							 &page);
+			if (rc != 0) {
+				LOG_ERR("Error %d while getting page info", rc);
+				return rc;
+			}
+			ctx->last_erased_page_start_offset = page.start_offset;
+		} else {
+			ctx->last_erased_page_start_offset = -1;
+		}
+#endif /* CONFIG_STREAM_FLASH_ERASE */
+	}
+
+	return 0;
+}
+
+#endif /* CONFIG_STREAM_FLASH_PROGRESS */
+
 #ifdef CONFIG_STREAM_FLASH_ERASE
 
 int stream_flash_erase_page(struct stream_flash_ctx *ctx, off_t off)
@@ -201,6 +257,15 @@ int stream_flash_init(struct stream_flash_ctx *ctx, const struct device *fdev,
 		return -EFAULT;
 	}
 
+#ifdef CONFIG_STREAM_FLASH_PROGRESS
+	int rc = settings_subsys_init();
+
+	if (rc != 0) {
+		LOG_ERR("Error %d initializing settings subsystem", rc);
+		return rc;
+	}
+#endif
+
 	struct _inspect_flash inspect_flash_ctx = {
 		.buf_len = buf_len,
 		.total_size = 0
@@ -241,3 +306,62 @@ int stream_flash_init(struct stream_flash_ctx *ctx, const struct device *fdev,
 
 	return 0;
 }
+
+#ifdef CONFIG_STREAM_FLASH_PROGRESS
+
+int stream_flash_progress_load(struct stream_flash_ctx *ctx,
+			       const char *settings_key)
+{
+	if (!ctx || !settings_key) {
+		return -EFAULT;
+	}
+
+	int rc = settings_load_subtree_direct(settings_key,
+					      settings_direct_loader,
+					      (void *) ctx);
+
+	if (rc != 0) {
+		LOG_ERR("Error %d while loading progress for \"%s\"",
+			rc, settings_key);
+	}
+
+	return rc;
+}
+
+int stream_flash_progress_save(struct stream_flash_ctx *ctx,
+			       const char *settings_key)
+{
+	if (!ctx || !settings_key) {
+		return -EFAULT;
+	}
+
+	int rc = settings_save_one(settings_key,
+				   &ctx->bytes_written,
+				   sizeof(ctx->bytes_written));
+
+	if (rc != 0) {
+		LOG_ERR("Error %d while storing progress for \"%s\"",
+			rc, settings_key);
+	}
+
+	return rc;
+}
+
+int stream_flash_progress_clear(struct stream_flash_ctx *ctx,
+				const char *settings_key)
+{
+	if (!ctx || !settings_key) {
+		return -EFAULT;
+	}
+
+	int rc = settings_delete(settings_key);
+
+	if (rc != 0) {
+		LOG_ERR("Error %d while deleting progress for \"%s\"",
+			rc, settings_key);
+	}
+
+	return rc;
+}
+
+#endif  /* CONFIG_STREAM_FLASH_PROGRESS */