doc: NVS and FCB: Clarify integrity checks #68699
Description
Is your enhancement proposal related to a problem? Please describe.
It is not clear from NVS Documentation if NVS does integrity checks, or what it uses its CRC for. NVS Does not protect its data (ref #49937).
the data is written one after the other from the start of the sector. The metadata consists of: id, data offset in sector, data length, part (unused) and a crc.
NVS checks the id-data pair before writing data to flash. If the id-data pair is unchanged no write to flash is performed.
The same is true for FCB docs:
Entries in the flash are checksummed. That is how FCB detects whether writing entry to flash completed ok. It will skip over entries which don’t have a valid checksum.
From this, it looks like FCB data is protected, but from the FCB source, I can not find how it is protected, so I suspect it is not.
Describe the solution you'd like
I suggest that documentation is updated to reflect that the data is itself not protected by the checksums/crcs.