Block count defined twice about littlefs HOT 1 OPEN

Hi @tredlich00 thanks for opening an issue. littlefs predates GitHub's discussions feature and I've been procrastinating on figuring out how that works, so that's on me (enabling discussions is irreversible).

As I built my code to do this I came to realize that there is a block_count variable in lfs_t and a block_count variable in struct lfs_config.

Ah, this is a bit of a limitation of C's "header-is-documentation". The documented struct lfs_config struct should be filled out when calling lfs_mount, but the undocumented lfs_t struct is an implementation detail that does not need to (shouldn't?) be filled out.

But lfs_t needs to be fully defined in the header file so C knows its size/alignment.

The technical reason block_count occurs twice:

You don't need to know the block count before mounting the disk. If struct lfs_config's block_count is 0, the actual block_count is read from metadata stored on disk.

We can't store this in struct lfs_config's block_count, because struct lfs_config is const, and may be stored in ROM. So the only option is a duplicated field.

Because of these duplicated fields, a ROM backed struct lfs_config is less appealing than it initially was, so in the future we may move to not requiring struct lfs_config to live as long as lfs_t. Though this may require a major version change.

As I dug deeper I found some solutions that suggested I needed to erase my NOR flash device myself and that would correct the issue.

I'm curious, what led you down this path? littlefs's lfs_format function should be stateless, unless the block device layers below littlefs has some weird external requirement.

Then, suddenly after the sixth or seventh test I could no longer mount the media.

This is all suggesting that the erase callback is not implemented correctly. Out of the factory, your device may be pre-erased, which would allow a small number of commits to be written. But then littlefs will need to erase a block for new commits, which could lead to this error. This would also explain why reformatting didn't work.

from littlefs.