When the IV Update state enters Normal operation or IV Update in
Progress, we need to keep track of how many hours has passed in the
state, since the specification requires us to remain in the state at
least for 96 hours (Update in Progress has an additional upper limit
of 144 hours).
In order to fulfil the above requirement, even if the node might be
powered off once in a while, we need to store persistently how many
hours the node has been in the state. This doesn't necessarily need to
happen every hour (thanks to the flexible duration range). The exact
cadence will depend a lot on the ways that the node will be used and
what kind of power source it has.
Since there is no single optimal answer, this patch adds a new
configuration option, which allows specifying a divider, i.e. how many
intervals the 96 hour minimum gets split into. After each interval the
duration that the node has been in the current state gets stored to
flash. E.g. the default value of 4 means that the state is saved every
24 hours (96 / 4).
Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
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