Support for "generic" attributes

[josesimoes]

Any chance to add an API to get/set attributes?
A simple byte will suffice to hold the simple (and usual ones) like hidden, read-only, system.
littlefs has this and I've noticed this already being used to store a time stamp.

[BrianPugh]

I haven't had too much of a chance to think about this, but it might be kind of complicated to expose. Lets say we want two functions:

esp_err_t esp_littlefs_getattr(const char *path, uint8_t type, void *buffer, size_t size);
esp_err_t esp_littlefs_setattr(const char *path, uint8_t type, void *buffer, size_t size);

We need to get the esp_littlefs_t context from the path. Normally, this is handled by esp-idf's VFS and passed along to a bunch of hooks that we register. Just skimming the vfs page, I don't see a function that goes from path to context. This is to:

1. Get the main lfs object.
2. Get the correct mutexs so it's all threadsafe.
3. Get the correct path (vfs removes the mounting point prefix for you).

So if we have a way to do that, I can add this functionality.

[josesimoes]

I see... so... what is missing is a "proxy" call in the VFS API to make the bridge, correct?

[BrianPugh]

pretty much. We basically need to translate/lookup the path to the esp_littlefs_context and relative path. E.g. /my_partition/my_folder/my_file.txt to esp_littlefs_t *efs and /my_folder/my_file.txt. If we have that, we can add this feature without much effort.

[BrianPugh]

There are the private get_vfs_for_path and translate_path functions that do exactly what we need, but I'd be a bit hesitant to reach in and use those.

[josesimoes]

@BrianPugh that looks like a good path forward. Understood those are private, still... 😉
Following this I took the liberty to suggest adding API to get/set attributes in VFS. Please follow the issue here espressif/esp-idf#14248.