[lug] adjtimex doc?

[Ed Hill]

On Thu, 2003-03-20 at 12:24, Steve Sullivan wrote:
> Hi,
> I've looked all over for some good doc on the syscall adjtimex.
> It's all pretty cryptic ... basically a man page with
> the parm names - offset, freq, status, precision, etc -
> but no real doc on how the parms are used.


Hi Steve,

Honestly, your claim that you've "looked all over" is quite suspect.  A
quick stab at Google turns up *MANY* links describing adjtimex
including:

  http://www.tldp.org/HOWTO/mini/Clock-3.html
  http://wwwacs.gantep.edu.tr/cgi-bin/man-cgi?adjtimex


> My question is:  when I issue a gettimeofday() call, exactly
> how are all those adjtimex parms used in calculating the result?

From my reading of the docs, they aren't used directly.  According to
the adjtimex(8) man page:

  "adjtimex adjusts only the system clock -- the one that
   runs while the computer is powered up.  To set or regulate
   the CMOS clock, see hwclock(8)."

So its an interface to Linux kernel-level functionality and can be 
used to calibrate the system clock.  It can correct for *systematic* 
drift and is, in general, less useful than NTP daemons which can 
correct for all sorts of drifts including non-constant deviations.


> Or are they?  If not, how are they used in the kernel?

The theory, source code, and documentation are all available on the
Net.  A lot of it is located on David Mills' site:

  http://www.eecis.udel.edu/~mills/

and I suggest you put a little more effort into your research.

Ed


-- 
Edward H. Hill III, PhD 
Post-Doctoral Researcher   |  Email:  ed at eh3.com,  ehill at mines.edu
Division of ESE            |  URLs:   http://www.eh3.com
Colorado School of Mines   |    http://cesep.mines.edu/people/hill.htm
Golden, CO  80401          |  Phones:  303-384-2094, 303-273-3483
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