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Date: Fri, 20 Feb 2015 14:22:20 +0100
From: Ingo Molnar <mingo@kernel.org>
To: Viresh Kumar <viresh.kumar@linaro.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
        Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>,
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Subject: Re: [PATCH] clockevents: Add (missing) default case for switch blocks
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* Viresh Kumar <viresh.kumar@linaro.org> wrote:

> On 20 February 2015 at 17:11, Ingo Molnar <mingo@kernel.org> wrote:
> >
> > * Peter Zijlstra <peterz@infradead.org> wrote:
> 
> >> Maybe we should break that enum into two; one for devices
> >> and one for the core interface and avoid the problem that
> >> way.
> >
> > Yeah, that would do the trick.
> 
> Thanks for your suggestions. Just to confirm (before I spam lists with
> patches), is
> this somewhat similar to what you are looking for ?
> 
> diff --git a/include/linux/clockchips.h b/include/linux/clockchips.h
> index 59af26b54d15..80b669cb836d 100644
> --- a/include/linux/clockchips.h
> +++ b/include/linux/clockchips.h
> @@ -32,17 +32,24 @@ enum clock_event_nofitiers {
>  struct clock_event_device;
>  struct module;
> 
> -/* Clock event mode commands */
> +/* Clock event mode commands for legacy ->set_mode(): OBSOLETE */
>  enum clock_event_mode {
>         CLOCK_EVT_MODE_UNUSED = 0,
>         CLOCK_EVT_MODE_SHUTDOWN,
>         CLOCK_EVT_MODE_PERIODIC,
>         CLOCK_EVT_MODE_ONESHOT,
>         CLOCK_EVT_MODE_RESUME,
> -
> -       /* Legacy ->set_mode() callback doesn't support below modes */
>  };
> 
> +/* Clock event modes, only for core's internal use */
> +enum clock_event_dev_mode {
> +       CLOCK_EVT_DEV_MODE_UNUSED = 0,

What is 'unused' - not initialized yet?

> +       CLOCK_EVT_DEV_MODE_SHUTDOWN,
> +       CLOCK_EVT_DEV_MODE_PERIODIC,
> +       CLOCK_EVT_DEV_MODE_ONESHOT,
> +       CLOCK_EVT_DEV_MODE_RESUME,

What is 'resume' mode?

> +       CLOCK_EVT_DEV_MODE_ONESHOT_STOPPED,  /* This would be the new
> mode which I will add later */

What does this mode express?

So for state machines it's important to document the states 
and the transitions between them very clearly - please 
start with that.

> +};

Also, this should not be in a generic header, it should be 
somewhere internal in kernel/time/.

> Ofcourse, we also need to replace 'clock_event_mode' with 
> 'clock_event_dev_mode' and 'CLOCK_EVT_MODE_*' with 
> 'CLOCK_EVT_DEV_MODE_*' in all core code..

Yes.

Thanks,

	Ingo