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SubjectRe: [PATCH 09/23] clocksource: add block notifier
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On Wed, 2007-01-31 at 11:17 +0100, Ingo Molnar wrote:
> * Daniel Walker <dwalker@mvista.com> wrote:
>
> > Adds a call back interface for register/rating change events. This is
> > also used later in this series to signal other interesting events.
>
> This patch adds:
>
> > +#define CLOCKSOURCE_NOTIFY_REGISTER 1
> > +#define CLOCKSOURCE_NOTIFY_RATING 2
> > +#define CLOCKSOURCE_NOTIFY_FREQ 4
>
> and a later patch adds:
>
> > +#define CLOCKSOURCE_NOTIFY_UNSTABLE 8
>
> while i tentatively agree with the introduction of clocksource driver
> notifications in general (given any actual real users of that
> infrastructure), i can see three problems with your notifier changes:
>
> firstly, with the full changes applied, CLOCKSOURCE_NOTIFY_RATING is
> totally unused (and not even driven by the core clocksource code).

True, ratings are constant so the notification never happens (and never
needs to)

> secondly, CLOCKSOURCE_NOTIFY_REGISTER is only used by the core
> clocksource code and no register-notifier interface is exposed: this
> makes the whole thing an expensive NOP.

I don't know what you mean when you say "no register-notifier interface
is exposed" .. The timekeeping code doesn't use this notification , but
it really should. It's not that big of an issue since we don't have many
clocks in modules..

> thirdly, CLOCKSOURCE_NOTIFY_FREQ is totally unused as well.

Indeed . Consider it dropped.

> (there are tons of examples in the kernel of how to do driver
> notification APIs properly.)

Are you referring to the comments above , or something else your seeing
in the code?

Daniel

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