Vehicles: Unmark FORMAT_VERSION as read-only

[tpwrules]

Match behavior of all vehicles. Allows GCSes to use documented behavior of a zero write to FORMAT_VERSION to reset EEPROM contents.

Verified that this does not change the built firmware contents. Presumably GCSes will need to update their parameter metadata.

[peterbarker]

Match behavior of all vehicles. Allows GCSes to use documented behavior of a zero write to FORMAT_VERSION to reset EEPROM contents.

Verified that this does not change the built firmware contents. Presumably GCSes will need to update their parameter metadata.

You know the "correct" way to do this is not via setting a parameter, but rather to send in a mavlink command explicitly designed to clear parameter storage? The Sub guys implemented that feature, they might be a little miffed if we un-READONLY the parameter.

i.e. the correct fix is to fix the documentation (and the GCSs).

Consistency is good. We should hide this parameter eventually. But we should mark all of these read-only or merge this PR.

[tpwrules]

The wiki notes that writing 0 to FORMAT_VERSION resets more than parameters: https://ardupilot.org/copter/docs/common-parameter-reset.html

I talked with Andrew Tridgell on discord and he said that not being read only is a bug.

[peterbarker]

I talked with Andrew Tridgell on discord and he said that not being read only is a bug.

DYM the fact it is marked read-only is a bug? I agree with that bit :-) Just saying that others may not.

@Williangalvani do you see any problems marking FORMAT_VERSION as not read-only in sub? For consistency, basically.

[tpwrules]

Sorry, yes, he agreed all of the instances should not be read only.

Does Sub support erasing the parameters and auxiliary data by writing that parameter the same way the other vehicles do? If not then it doesn't make sense to have it be read-write.

[peterbarker]

Sorry, yes, he agreed all of the instances should not be read only.

Does Sub support erasing the parameters and auxiliary data by writing that parameter the same way the other vehicles do? If not then it doesn't make sense to have it be read-write.

It does - it's just that the Sub guys tend to use QGC which I think has an erase-parameters button which sends in a standard mavlink-ish way of erasing the state.

Labelling for DevCallEu where we'll probably merge...