Messages in this thread | | | Date | Fri, 20 Feb 2015 11:52:19 +0100 | From | Ingo Molnar <> | Subject | Re: [PATCH] clockevents: Add (missing) default case for switch blocks |
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* Viresh Kumar <viresh.kumar@linaro.org> wrote:
> > So why is a 'default' mode needed then? It makes the > > addition of new modes to the legacy handler easier, > > which looks backwards. > > The requirement was to add another mode ONESHOT_STOPPED > [1], to be supported only by the new per-mode callbacks..
Why would a callback need any flag, and why would a flag be visible to old legacy callbacks?
> We have got a clear check in core with the patch Peter > mentioned above, which doesn't let us call legacy > ->set_mode() for the newer modes. > > if (dev->set_mode) { > /* Legacy callback doesn't support new modes */ > if (mode > CLOCK_EVT_MODE_RESUME) > return -ENOSYS; > dev->set_mode(mode, dev); > return 0; > }
So here is where one of your problems comes from: why did you add CLOCK_EVT_MODE_RESUME to the interface? Phase it out, it's a legacy interface - new callbacks shouldn't need any mode flags to begin with.
> > So I'm confused: if we are using proper callbacks (like > > my example outlined) , why is a 'mode enum' needed at > > all? > > The enum has two uses today: > > - pass mode to the legacy ->set_mode() callback, which > isn't required for the new callbacks.
But this is misguided, as per above.
> - flag for clockevent core's internal state machine, > which it would still require. For example, it checks > new-mode != old-mode before changing the mode..
Internal state machine state should be decoupled from any interface flags - especially when the interface is legacy.
> I believe the enum is still required for the state > machine, even with new per-mode callbacks.
That needs to be fixed first then, before introducing new API variants.
Thanks,
Ingo
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