Embedded Transaction filesystem (ETFS)

The limits for ETFS are:

Filename length
91 bytes.
Pathname length
256 bytes, not including the mountpoint or the terminating NUL.
File size
2 GB − 1; 32-bit filesystem limit.
Absolute maximum number of files
32768 (15 bits).
Default maximum number of files
4096 (controlled by the driver's -f option; see the entry for fs-etfs-ram in the Utilities Reference).
Note: Filenames that are more than 32 bytes long use two directory entries, reducing the number of files that you can actually have.
Max cluster size
Maximum filesystem size
64 GB.

For NAND flash, some additional limitations apply:


For ETFS on NAND, you can perform 1-bit software error correction coding (ECC) for the data in the spare area. Support configurations are available for:

Once calculated, the spare area receives the ECC value from devio_postcluster(), and then writes it to NAND flash. To determine the appropriately sized ECC value, use the following:

To take advantage of the spare area, you'll need to make the following changes for BSPs: