Use zephyr Settings API with AT24C256 EEPROM as backend

[MaazSk]

Hello Everyone,
I want to use zephyr settings API with AT24C256 EEPROM as a backend. I am not sure how to do the same. Is there any example to do it specifically a eeprom as a backend. I went through the example in samples/subsys/settings but was unable to find out how to add EEPROM as a backend any example would be great. I am using STM32H750B_DK as the dev board

[Laczen]

There is no in tree support for using settings on eeprom.

[Laczen]

What do you mean? Can you contribute a eeprom settings backend? Of course.

[MaazSk]

Can you contribute a eeprom settings backend? Of course.

This is something I can try.

But this is what I am trying and what I wanted to do is, use EEPROM as a custom backend to store the settings. I came across custom backend where we can use a custom backend to store settings. I am curious to know if I can use EEPROM as a backend using these custom backend api's?

[Laczen]

The CUSTOM_BACKEND kconfig option is to signal the settings config that a alternative backend will be provided. There is no custom backend API. When a settings backend for eeprom is contributed it could be selected by EEPROM_BACKEND. It needs to provide a settings store solution and a settings_backend_init.

[MaazSk]

So can we have the eeprom calls inside settings_custom_load and settings_custom_save just want to know is it possible or not?

Like follows

static int settings_custom_load(struct settings_store *cs,
                                const struct settings_load_arg *arg)
{
    eeprom_read(eeprom_dev, address, &value);
}

static int settings_custom_save(struct settings_store *cs, const char *name,
                                const char *value, size_t val_len)
{
    eeprom_read(eeprom_dev, address, value);
}

[Laczen]

Yes, you can use eeprom_read and eeprom_write inside these routines. But you need to create some kind of storage solution on eeprom that can read/write key(name)-value data. The settings_custom_load() will need to walk over the data in the eeprom and call the settings_call_set_handler() for each of the key(name)-value pairs that are on the eeprom. The settings_custom_save() will need to save the key(name)-value combination to eeprom in such a way that it can be retrieved by custom_settings_load().