The IEEE 802.15.4 API and networking subsystem were using several
inconsistent timestamp resolutions and types. This change defines all
timestamps with nanosecond resolution and reduces the number of
available types to represent timestamps to two:
* `struct net_ptp_time` for PTP timestamps
* `net_time_t` for all other high resolution timestamps
All timestamps (including PTP timestamps) are now referred to a
"virtual" local network subsystem clock source based on the well-defined
types above. It is the responsibility of network subsystem L2/driver
implementations (notably Ethernet and IEEE 802.15.4 L2 stacks) to ensure
consistency of all timestamps and radio timer values exposed by the
driver API to such a network subsystem uptime reference clock
independent of internal implementation details.
The "virtual" network clock source may be implemented based on arbitrary
hardware peripherals (e.g. a coarse low power RTC counter during sleep
time plus a high resolution/high precision radio timer while receiving
or sending). Such implementation details must be hidden from API
clients, as if the driver used a single high resolution clock source
instead.
For IEEE 802.15.4, whenever timestamps refer to packet send or receive
times, they are measured when the end of the IEEE 802.15.4 SFD (message
timestamp point) is present at the local antenna (reference plane).
Due to its limited range of ~290 years, net_time_t timestamps (and
therefore net_pkt timestamps and times) must not be used to represent
absolute points in time referred to an external epoch independent of
system uptime (e.g. UTC, TAI, PTP, NTP, ...).
Signed-off-by: Florian Grandel <fgrandel@code-for-humans.de>
a4cd5cee40