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    SubjectRe: [PATCH 09/23] clocksource: add block notifier

    * 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).

    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.

    thirdly, CLOCKSOURCE_NOTIFY_FREQ is totally unused as well.

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

    Ingo
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