On Sun, 14 Mar 2010, Rafael J. Wysocki wrote: > On Sunday 14 March 2010, Alan Stern wrote: > > On Sun, 14 Mar 2010, Rafael J. Wysocki wrote: > > > > > > You know, maybe we should allow bus types to use both the old and new > > > > interfaces. It would make life easier for other subsystems in addition > > > > to i2c. > > > > > > > > This doesn't mean that the core would end up calling two sets of > > > > suspend routines. If the bus type uses legacy routines then all the > > > > non-runtime entries in the pm_ops structure would be empty. > > > > > > > > The changes to the PM core necessary to do this are quite small. > > > > > > Not really. The detection that the particular callback is not present happens > > > in pm_op(), while the decision which framework to use is made at the > > > device_[suspend|resume]() level. > > > > All you have to do is change the "else if" lines in > > device_[suspend|resume]() to "if". > > Then, if a bus type implements both "new" and "old" callbacks, we'll end up > calling both. Not nice. Why would a bus type implement both? Or looked at another way, if it did implement both then wouldn't it want both sets of callbacks to be invoked? If a bus type does define both types of callback by mistake and only wants one of them to be used, that's a bug -- pure and simple. It's not the PM core's fault if something goes wrong under those circumstances. > > Sure. But suppose you _don't_ want to spend the time implementing new > > callbacks to replace the existing legacy suspend and resume methods, > > whereas you _do_ want to implement runtime PM. Runtime PM forces the > > bus type to have a pm_ops member, > > Which is very much on purpose, because the legacy suspend and resume have no > idea about the runtime stuff. > > > which as you point out, will prevent the legacy methods from being called. > > Yes, that's intentional. > > That said, I think we might modify the generic callbacks in generic_ops.c to > call the drivers' legacy callbacks if the "new" ones are not defined. That's no good -- the routines in generic_ops.c invoke the _driver's_ callbacks, not the _bus type's_ callbacks. I suppose you could write a new set of generic "legacy" callbacks that would work just as though the new ops weren't defined. Removing those "else"s would be a lot simpler, though. Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
