On Tue, 31 Aug 2021 14:07:32 +0000 Machnikowski, Maciej wrote: > > > I agree that this also is useful for Time card, yet it's also useful here. > > > PTP subsystem should implement a similar logic to this one for > > > DPLL-driven timers which can lock its frequency to external sources. > > > > Why would we have two APIs for doing the same thing? IIUC Richard does > > not want this in the PTP ioctls which is fair, but we need to cater to devices > > which do not have netdevs. > > From technical point of view - it can be explained by the fact that the DPLL > driving the SyncE logic can be separate from the one driving PTP. Also > SyncE is frequency-only oriented and doesn't care about phase and > Time of Day that PTP also needs. The GNSS lock on the PTP side will be > multi-layered, as the full lock would mean that our PTP clock is not only > syntonized, but also has its time and phase set correctly. Just because GNSS lock addresses more parameters (potentially) doesn't mean the syntonization part shouldn't be addressed by the same API. > A PTP can reuse the "physical" part of this interface later on, but it also needs > to solve more SW-specific challenges, like reporting the PTP lock on a SW level. > > I agree that having such API for PTP subsystem will be very useful, > but let's address SyncE in netdev first and build the PTP netlink on top of what > we learn here. We can always move the structures defined here to the layer > above without affecting any APIs. It's a reasonable SW design strategy to start simple. Unfortunately, it doesn't apply to stable uAPI design. You're adding a RTNL op, which will have to be supported for ever. If we add anything "later" it will be a strict addition, and will have to be backward compatible. Which I'm not sure how to do when the object we'd operate on would be completely different (clock vs netdev). As I said I can write the boilerplate code for you if you prefer, the code implementing the command and the driver interface will be almost identical. Is there a reason why RTNL is better?
