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    SubjectRe: [PATCH 1/2] posix clocks: introduce a syscall for clock tuning.
    On Thu, 9 Sep 2010, john stultz wrote:
    > On Thu, 2010-09-09 at 12:49 +0200, Thomas Gleixner wrote:
    > > But what I see is an approach which tries to implement disconnected
    > > special purpose clocks which have the ability to be adjusted
    > > independently. What's the purpose of this ? Why can't we just use the
    > > existing clocks and make PTP work on them ?
    >
    > So this too was my initial gut response. It seems ridiculous to expose
    > two clock_ids (CLOCK_REALTIME and CLOCK_PTP)that conceptually represent
    > the same thing (ie: number of seconds,nanoseconds since 1970).
    >
    > It doesn't help that one of the use cases that Richard suggests is "for
    > example in an embedded control application. The userland software can
    > simply ignore the wrong system time."
    >
    > As someone who's spent a *lot* of time trying to fix the "wrong system
    > time" these use cases reek of work-around solutions instead of properly
    > fixing whatever keeps the system time from being accurately sycned.
    >
    > However, as I've worked on understanding the issue, I realize that there
    > is some validity to needing to expose more then one hardware clock the
    > conceptually is the same as CLOCK_REALTIME. And that most of my gut
    > reaction to this was me being a bit oversensitive. :)

    Yup. It still scares me that we might end up with a dozen different
    notions of ONE second elapsed on the same machine :)

    > However, since there may be multiple PTP clocks or audio clocks or
    > whatever, allocating static clockids for each type isn't quite useful,

    Yeah, I corrected myself on that one, but I really want to see some
    confinement into well defined clock classes rather than the "hooray
    here is my clock of the day" approach.

    Thanks,

    tglx


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