embassy-usb-dfu: Add a trait for the update logic

[paroga]

I'd like to introduce a trait use embassy-usb-dfu without embassy-boot and implement my own update logic.

Before finishing that / cleaning it up, I'd like to get some feedback on the API and how to upstream that, since it's a very intrusive change and will break all downstream implementations.

[ExplodingWaffle]

Have you seen #2407? It seems to me that the preferred way would be to make DFU just another class in embassy-usb (unless dirbaio changed his mind)

[paroga]

Have you seen #2407? It seems to me that the preferred way would be to make DFU just another class in embassy-usb (unless dirbaio changed his mind)

no, I didn't. thanks for the information. any idea how i can help in getting that merged?

@Dirbaio is there something like a list of required things in #2407? can i help somehow to finish it?

[Dirbaio]

Yes I'd prefer to add the "unopinionated" class implementation to embassy-usb, then the embassy-usb-dfu crate could just use that and wrap it into an "opinionated" api that uses embassy-boot.

The missing thing in #2407 was to change embassy-usb-dfu to use the class so we don't have two implementations. Anyway, it's now quite old, it's probably easier to start from scratch.

[paroga]

Yes I'd prefer to add the "unopinionated" class implementation to embassy-usb, then the embassy-usb-dfu crate could just use that and wrap it into an "opinionated" api that uses embassy-boot.

The missing thing in #2407 was to change embassy-usb-dfu to use the class so we don't have two implementations. Anyway, it's now quite old, it's probably easier to start from scratch.

@Dirbaio if you're ok, i'll try to rebase it to latest main and adopt embassy-usb-dfu to use it in the next days/weeks and update this PR with it.

[paroga]

@Dirbaio Since the remaining logic is minimal I'd move the embassy-boot adaptation directly into that create and deprecate embassy-usb-dfu. Does that sound reasonable?

If the basic structure looks good, I'll add the missing documentation and adopt the examples too.

[Dirbaio]

sounds good yes.