How about LittleFS.begin()

1

I’m experimenting with LittleFS.
What does the function ‘LittleFS.begin()’ realy do?
PlatformIO gives me this:

  bool fs::LittleFSFS::begin(
  	bool formatOnFail = false, 
  	const char* basePath = "/littlefs",     <== default values?
  	uint8_t maxOpenFiles = (uint8_t)10U, 
  	const char* partitionLabel = "spiffs"
  )

From this bit of information I understand that:
1.
bool formatOnFail = false, => LittleFS will format the complete ‘disk’ and all data will belost.
2.
basePath = “/littlefs” => this is a default value that’s used when this parameter is omitted.
3.
maxOpenFiles = (uint8_t)10U, => ibid
4.
partitionLabel = “spiffs” => ibid.
=> Also, that when there is no NAME = ‘spiffs’ key*value combination
=> in the partiontable the whole thing will not work.
Stated otherwise:
The partitiontable.csv must have a corresponding value, like so:

# Name,   Type, SubType, Offset,  Size, Flags
nvs,      data, nvs,     0x9000,  20480,
otadata,  data, ota,     ,  	  8192,
app0,     app,  ota_0,   , 		  1966080,
spiffs,   data, spiffs,  ,		  2097152,
coredump, data, coredump,,		  65536,

Can you please confirm or deny this?

2

When .begin() is called, it first looks to mount an existing LittleFS filesystem (from the address derived in the partition table for the littelfs/“spiffs” section). When mounting fails, because e.g. the filesystem is corrupted or has never been formatted, it will format it in the LitteFS format, if formatOnFail = true. After that, mounting the freshly formatted filesystem should work and .begin() will most likely return true. If formatOnFail = false, and mounting fails, then false is returned and no data is erased.

In a way, .begin() is just a fancy wrapper around the underlying functions lfs_mount(), lfs_format() (source) and integrating the filepaths into Espressif’s “Virtual File System” (VFS).

Everything else seems to be correct.

1 Like
3

Thank you Max,
That clears the air with respect to the ‘formatOnFail’ part.
Now, as I understand it: ‘basePath’ can have a value that I - the programmer - can set. And that goes as well for ‘partitionLabel’.
Only: the value for ‘partitionLable’ MUST be the same as the value in the partition tabel; where Name ‘xyz’ corresponds with partitionLabel = ‘xyz’
Am I right?

4

Yes. If you’re using default partition tables, you should not need any of these extra parameters, except the formatOnFail.

So, if you want to always have an initialized (formatted if needed) filesystem, LittleFS.begin(true); is the right choice.

5

Max,
Again thank you. You make me happy.