Move processing of PHC readings from sys_linux to hwclock, where
statistics can be collected and filtering improved.
In the PHC refclock driver accumulate the samples even if not in the
external timestamping mode to update the context which will be needed
for improved filtering.
If a SHM or PHC refclock has a very large offset compensated by the
offset option, or ignored with the pps or local option, there is a
persistent loss of precision in the calculation of the sample offset
using the double format.
Rework the code to delay the calculation of the accumulated offset to
include the specificed compensation and remaining correction of the
system clock, where the calculation can be split to improve the
precision. In the pps mode ignore integer seconds competely.
The precision of the SOCK refclock is now limited to 1 nanosecond due to
the extra double->timespec->double conversion.
The LOG_FATAL macro expands to (emitting the message and then) exit(1).
So a return after LOG_FATAL isn't reached. Drop all those to simplify
the code a bit.
Add extpps driver option to the PHC refclock to enable external
timestamping of PPS signal and also options to configure the channel and
pin index. In this mode, the driver polling function accumulates samples
for hwclock, which is used to convert received timestamping events to
local time.
It was never used for anything and messages in debug output already
include filenames, which can be easily grepped if there is a need
to see log messages only from a particular file.
Replace struct timeval with struct timespec as the main data type for
timestamps. This will allow the NTP code to work with timestamps in
nanosecond resolution.
Implement a driver which allows using PTP hardware clock (PHC) as a
reference clock. It uses the PTP_SYS_OFFSET ioctl or clock_gettime()
to measure the offset between the PTP clock and the system clock. Ten
readings are made for every driver poll and the fastest one is returned.
As PHCs are typically kept in TAI instead of UTC, it's necessary to set
the TAI/UTC offset manually by the offset option. This could be improved
by obtaining the offset automatically from the right/UTC timezone.
