Currently WDT_WARNING_PERIOD is only supported on the sam0 platform.
If there is already a Kconfig symbol for that, we should make the option depend on that so it's not available when it would do nothing.

The problem here is, why this is in the documentation of a common peripheral interface when only one platform supports it? We can add a check to see if MODULE_PERIPH_WDT_CB is there (although nrf5x has it and does not use this option yet), as the documentation indicates.

Also the range of this value will depend on the individual hardware implementation.
Maybe the option should rather live in cpu/$arch/periph

I wouldn't move it to a CPU folder as this configuration, as it is documented, is part of the WDT API.

The problem here is, why this is in the documentation of a common peripheral interface when only one platform supports it?

Only one platform currently supports it, but when drafting out the API we saw that many platforms could support this, although not all, that is why it was in the public api.

The issue was that how each platform handles the wakeup varies a lot, in some cases is it configurable through some range, in others it only has a some discrete values, and in some cases these are just % of the timeout time, e.g. 50% of the timeout. For others its a fixed amount of time independent or dependent of the timeout.

I wouldn't move it to a CPU folder as this configuration, as it is documented, is part of the WDT API.

I think we should change the definition in the public to:

#if defined(DOXYGEN)
#define WDT_WARNING_PERIOD
#endif

And then as @benpicco suggested have the symbol definition in cpu/$arch/periph. That way each implementation can specify specific ranges or state that it is not configurable, or whatever the case.

What do you think @leandrolanzieri ?

And then as @benpicco suggested have the symbol definition in cpu/$arch/periph. That way each implementation can specify specific ranges or state that it is not configurable, or whatever the case.

What do you think @leandrolanzieri ?

Is the plan to have this option in most of the platforms? We could leave the definition on this common file and add a dependency to indicate that it's available. Then, every platform can extend the symbol to its needs. It could look like:

# drivers/periph_common/Kconfig

config HAS_WDT_WARNING_PERIOD
    bool
    help
        Indicates that a WDT peripheral driver implementation suppports the
        configuration of a warning period.

config WDT_WARNING_PERIOD
    int "Warning period (in ms)"
    depends on HAS_WDT_WARNING_PERIOD
    help
        Period in ms before reboot where wdt_cb() is executed.

# cpu/sam0_common/Kconfig

config HAS_WDT_WARNING_PERIOD
    default y

config WDT_WARNING_PERIOD
    default 1
    range 1 10

@fjmolinas thoughts?

@leandrolanzieri seems good!

@fjmolinas done. I had to replicate the dependencies in the CPU-specific Kconfig so they do not weaken.

@leandrolanzieri this one needs rebase!

@fjmolinas rebased

This works for samd boards just fine, but other boards I get no configuration option, shouldn't I see a disabled feature? Otherwise I agree with the aproach.

I get no configuration option, shouldn't I see a disabled feature?

By default disabled options do not show up, you can toggle the show-all mode with a, you should see it.

@fjmolinas all green

Thanks all for reviewing and testing!