How the KERNEL_PLL switch kills TESTFRAME
Eric S. Raymond
esr at thyrsus.com
Thu Sep 29 15:05:32 UTC 2016
Gary E. Miller <gem at rellim.com>:
> > Which I find strange. Preferred for portability, maybe, but
> > adjtimex() is strictly more powerful.
> really? How do you get that from this text:
> ntp_adjtime ()
> The ntp_adjtime() library function (described in the NTP "Kernel
> Appli‐ cation Program API", KAPI) is a more portable interface
> for performing the same task as adjtimex(). Other than the
> following points, it is identical to adjtime():
> * The constants used in modes are prefixed with "MOD_" rather
> than "ADJ_", and have the same suffixes (thus, MOD_OFFSET,
> MOD_FREQUENCY, and so on), other than the exceptions noted in the
> following points.
> * MOD_CLKA is the synonym for ADJ_OFFSET_SINGLESHOT.
> * MOD_CLKB is the synonym for ADJ_TICK.
> * The is no synonym for ADJ_OFFSET_SS_READ, which is not
> described in the KAPI.
Look at the last paragraph. There's a capability adjtimex has that
isn't in ntp_adjtime().
The documentation is vague, on the details, so I am too. But I think there
are (other) things you can do to the kernel PLL with adjtimex(2) that you can't
do with ntp_adjtime(2). There are certainly more reporting fields.
Perhaps we don't use those capabilities. Feel free to replace calls and
smoke-test the resultl I certainly wouldn't be unhappy if we could sever
our dependency on that call.
<a href="http://www.catb.org/~esr/">Eric S. Raymond</a>
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