> > I'm probably missing something then, but let's assume you have a driver > that wants its clock prepared and enabled in an hypothetical enable() > callback, and disabled / unprepared in a disable() callback. > > From a PM management perspective, this usecase makes total sense, is a > valid usecase, is widely used in the kernel, and is currently supported > by both the C and Rust clk APIs. > > The only solution to this you suggested so far (I think?) to implement > this on top of the new clk API you propose is to have a driver specific > enum that would store each of the possible state transition.
Yes, you need an enum _if_ you want to model transitions at runtime. IIUC you only need two variants to implement the pattern you described. I do not consider this “boilerplate”, but rather a small cost to pay. I would understand if this was some elaborate pattern that had to be implemented by all drivers, but a two-variant enum is as straightforward as it gets. > > That's the boilerplate I'm talking about. If every driver wanting to > implement that pattern has to make such an enum, with all the relevant > traits implementation that might come with it, we go from an API where > everything works at no-cost from a code-size perspective to a situation > where every driver has to develop and maintain that enum. > > Maxime There are no "traits that come with it". It's just an enum, with two variants. > API where everything works at no-cost The previous API was far from “everything works”. It was fundamentally broken by design in multiple ways, i.e.: > a) It only keeps track of a count to clk_get(), which means that users have > to manually call disable() and unprepare(), or a variation of those, like > disable_unprepare(). > > b) It allows repeated calls to prepare() or enable(), but it keeps no track > of how often these were called, i.e., it's currently legal to write the > following: > > clk.prepare(); > clk.prepare(); > clk.enable(); > clk.enable(); > > And nothing gets undone on drop(). IMHO, what we have here is an improvement that has been long overdue. — Daniel
