Stream Flash
The Stream Flash module takes contiguous fragments of a stream of data (e.g. from radio packets), aggregates them into a user-provided buffer, then when the buffer fills (or stream ends) writes it to a raw flash partition. It supports providing the read-back buffer to the client to use in validating the persisted stream content.
One typical use of a stream write operation is when receiving a new firmware image to be used in a DFU operation.
There are several reasons why one might want to use buffered writes instead of writing the data directly as it is made available. Some devices have hardware limitations which does not allow flash writes to be performed in parallel with other operations, such as radio RX and TX. Also, fewer write operations result in faster response times seen from the application.
Persistent stream write progress
Some stream write operations, such as DFU operations, may run for a long time. When performing such long running operations it can be useful to be able to save the stream write progress to persistent storage so that the operation can resume at the same point after an unexpected interruption.
The Stream Flash module offers an API for loading, saving and clearing stream
write progress to persistent storage using the Settings
module. The API can be enabled using CONFIG_STREAM_FLASH_PROGRESS.