esp-idf/components/wear_levelling/README.rst

Wear Levelling APIs
===================

Overview
--------
Most of the flash devices and specially SPI flash devices that are used in ESP32
have sector based organization and have limited amount of erase/modification cycles 
per memory sector. To avoid situation when one sector reach the limit of erases when 
other sectors was used not often, we have made a component that avoid this situation.
The wear levelling component share the amount of erases between all sectors in the 
memory without user interaction.
The wear_levelling component contains APIs related to reading, writing, erasing,
memory mapping data in the external SPI flash through the partition component. It 
also has higher-level APIs which work with FAT filesystem defined in 
the :doc:`FAT filesystem </api-reference/storage/fatfs>`.

The wear levelling component does not cache data in RAM. Write and erase functions 
modify flash directly, and flash contents is consistent when the function returns.


Wear Levelling access APIs
--------------------------

This is the set of APIs for working with data in flash:

- ``wl_mount`` mount wear levelling module for defined partition
- ``wl_unmount`` used to unmount levelling module
- ``wl_erase_range`` used to erase range of addresses in flash
- ``wl_write`` used to write data to the partition
- ``wl_read`` used to read data from the partition
- ``wl_size`` return size of avalible memory in bytes
- ``wl_sector_size`` returns size of one sector

Generally, try to avoid using the raw wear levelling functions in favor of
filesystem-specific functions.

Memory Size
-----------

The memory size calculated in the wear Levelling module based on parameters of 
partition. The module use few sectors of flash for internal data.