devd predates service in the system. Modernize usage to use service to
start/stop things in reaction to events rather than calling the rc
file directly.
This was pointed out in my talk at BSDcan as well as indirectly
referrred to as a barrier to entry for OpenRC in that working group.
Summary:
Add a polling loop (1Hz) to monitor the battery and AC status, to notify devd
like ACPI does for power monitoring. This allows /etc/rc.d/power_profile to
work on PowerPC laptops
Test Plan:
Tested on a Titanium PowerBook, configuring economy_cpu_freq and
performance_cpu_freq, disabling powerd.
Reviewers: #powerpc, nwhitehorn
Reviewed By: nwhitehorn
Subscribers: rpaulo
Differential Revision: https://reviews.freebsd.org/D937
