lkml.org 
[lkml]   [2007]   [Jan]   [8]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: RTC subsystem and fractions of seconds
    On Sun, Jan 07, 2007 at 06:10:30PM -0800, David Brownell wrote:

    > > One usefull addition for my needs and with a m41t81 is the support of
    > > the calibration of the rtc. However this can perhaps be hidden in the
    > > .set_mmss function.
    >
    > Doesn't seem like an set_mmss() mechanism at all. Some drivers give
    > sysfs access to an oscillator "trim" mechanism. What tools do you
    > have which track how far off that crystal is?

    ntp, either from network or from a radio-clock

    and using set_mmss for that purpose seems not so disgusting, because :

    - writing to the clock (the expected work of set_mmss) must be disabled when
    we observe the clock drift
    - set_mmss is always called with a very good precision, so one could
    use the time given to set_mmss to compare it to the time given by the RTC
    over a long enough period of time (more than 11 minutes) to compute the RTC's
    drift and the necessary adjustment.

    Of course, if we want something that is not based on ntp, then we may not
    overload set_mmss.

    Philippe
    -
    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to majordomo@vger.kernel.org
    More majordomo info at http://vger.kernel.org/majordomo-info.html
    Please read the FAQ at http://www.tux.org/lkml/

    \
     
     \ /
      Last update: 2007-01-08 11:27    [W:0.058 / U:0.144 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site