On Mon, 2011-05-16 at 18:52 +0200, Ingo Molnar wrote:
> * Steven Rostedt <rostedt@xxxxxxxxxxx> wrote:
>
> > I'm a bit nervous about the 'active' role of (trace_)events, because of the
> > way multiple callbacks can be registered. How would:
> >
> > err = event_x();
> > if (err == -EACCESS) {
> >
> > be handled? [...]
>
> The default behavior would be something obvious: to trigger all callbacks and
> use the first non-zero return value.
But how do we know which callback that was from? There's no ordering of
what callbacks are called first.
>
> > [...] Would we need a way to prioritize which call back gets the return
> > value? One way I guess would be to add a check_event option, where you pass
> > in an ENUM of the event you want:
> >
> > event_x();
> > err = check_event_x(MYEVENT);
> >
> > If something registered itself as "MYEVENT" to event_x, then you get the
> > return code of MYEVENT. If the MYEVENT was not registered, a -ENODEV or
> > something could be returned. I'm sure we could even optimize it such a way if
> > no active events have been registered to event_x, that check_event_x() will
> > return -ENODEV without any branches.
>
> I would keep it simple and extensible - that way we can complicate it when the
> need arises! :)
The above is rather trivial to implement. I don't think it complicates
anything.
-- Steve
