Re: [PATCH V7 1/8] ntp: add ADJ_SETOFFSET mode bit

[john stultz <johnstul@us.ibm.com>]

On Sat, 2010-12-18 at 05:16 +0900, Kuwahara,T. wrote:
> On 12/17/10, Richard Cochran <richardcochran@gmail.com> wrote:
> > This patch adds a new mode bit into the timex structure. When set, the bit
> > instructs the kernel to add the given time value to the current time.
> >
> 
> The proposed new control mode, ADJ_SETOFFSET, is logically the same as
> ADJ_OFFSET with timex.constant == -INFINITY. 

I'm not sure if this is correct. Its more like settimeofday, only giving
a relative offset to jump the clock, rather then an absolute time. It
does not slew the clock over time like ADJ_OFFSET does.

>  So it is possible to do
> the same thing without risking forward compatibility.  (I mean by "risking
> forward compatibility" that the mode bit 0x0040 may be defined differently
> by the upstream maintainer anytime in the future.)

adjtimex is a linux specific interface, which is compatible but not
identical to the ntp specified interfaces. The ntp client code already
has Linux specific modifications, so I don't think we have to worry
about 0x40 specifically being reserved by the NTP client.

thanks
-john