This propagates the use of "struct ts2phc_private" all the way into the
master API, in preparation of a new use case that will be supported
soon: some PPS masters (to be precise, the "PHC" kind) instantiate a
struct clock which could be disciplined by ts2phc.
When a PHC A emits a pulse and another PHC B timestamps it, the offset
between their precise timestamps can be used to synchronize either one
of them. So far in ts2phc, only the slave PHC (the one using extts) has
been synchronized to the master (the one using perout).
This is partly because there is no proper kernel API to report the
precise timestamp of a perout pulse. We only have the periodic API, and
that doesn't report precise timestamps either; we just use vague
approximations of what the PPS master PHC's time was, based on reading
that PHC immediately after a slave extts event was received by the
application. While this is far from ideal, it does work, and does allow
PHC A to be synchronized to B.
This is particularly useful with the yet-to-be-introduced "automatic"
mode of ts2phc (similar to '-a' of phc2sys), and the PPS distribution
tree is fixed in hardware (as opposed to port states, which in
"automatic" mode are dynamic, as the name suggests).
Signed-off-by: Vladimir Oltean <olteanv@gmail.com>
Many GPS radios provide both a 1-PPS and time of day information via
NMEA sentences. This patch introduces a ts2phc master that decodes
the "recommended minimum data" sentence, RMC, which provides UTC time
and a validity flag. Together with the file based leap second table,
this sentence provides adequate time of day for determining the time
of the PPS edge.
Signed-off-by: Richard Cochran <richardcochran@gmail.com>
Vladimir Oltean
Richard Cochran