Re: [PATCH] clockevents: Add (missing) default case for switch blocks

* 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