On Wed, 2009-12-02 at 11:27 -0500, Mathieu Desnoyers wrote: > A few questions about the semantic: > > Is "declare" here always only used as a declaration ? (e.g. only in > headers, never impacted by CREATE_TRACE_POINT ?) Well yes it is impacted by CREATE_TRACE_POINT, but so is DECLARE_TRACE for that matter ;-) The difference is that DECLARE_EVENT_CLASS will at most (with CREATE_TRACE_POINT) only create the functions that can be used by other events. It does not create an event itself. That is, it's not much different than making a "static inline function" except that function will not be static nor will it be inline ;-) > > Is "define" here always mapping to a definition ? (e.g. to be used in a > C file to define the class or event handling stub) The DEFINE_* will create something that can be hooked to the trace points in other C files. > > I feel that your DEFINE_EVENT_CLASS might actually be doing a bit more > than just "defining", it would actually also perform the declaration. > Same goes for "DEFINE_EVENT". So can you tell us a bit more about that > is the context of templates ? Well, the macros used by these are totally off the wall anyway :-) So any name we come up with will not match what the rest of the kernel does regardless. But we need to give something that is close. I'm liking more the: DECLARE_EVENT_CLASS, DEFINE_EVENT, DEFINE_EVENT_CLASS, because I think that comes the closest to other semantics in the kernel. That is (once again) DECLARE_EVENT_CLASS - makes only the class. It does create helper functions, but if there's no DEFINE_EVENT that uses them, then they are just wasting space. The DEFINE_EVENT will create the trace points in the C file that has CREATE_TRACE_POINTS defined. But it requires the helper functions created by a previous DECLARE_EVENT_CLASS. DEFINE_EVENT_CLASS will do both create a EVENT_CLASS template, as well as a EVENT that uses the class. The name of the class is a separate namespace as the event. Here both the class and the event have the same name, but other events can use this class by referencing the name. DEFINE_EVENT_CLASS(x, ...); DEFINE_EVENT(x, y, ...); The DEFINE_EVENT_CLASS will create a class x and an event x, then the DEFINE_EVENT will create another event y that uses the same class x. Actually, with the above, we may not need to have DECLARE_EVENT_CLASS() at all, because why declare a class if you don't have an event to use it? But then again, you may not want the name of the class also a name of an event. -- Steve -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html