Some powerd(8) defaults

[Jukka Ruohonen <jruohonen%iki.fi@localhost>]

Hello.

Here are some proposed changes to the powerd(8) scripts which I find good
enough to be enabled by default. Also other suggestions are welcomed.

  1. Provide a generic "sleep" script and link the current "sleep_button"
     and "lid_switch" to it appropriately. This means that the default action
     upon closing the laptop lid changes to "suspend". By default, we already
     resume (in-kernel) automatically when the lid is opened.

  2. By default, stop/start the cron(8) deamon upon changes in the AC adapter.
     This behavior is already in the script, but it was commented out.

  3. New laptops are notoriously bad at thermal management. Currently NetBSD
     lacks a well-defined thermal management interface, but the least we could
     do is to gracefully shutdown the system when "sensor_temperature" is
     called with "critical" or "critical-over" events. This has saved my
     ThinkPad many times from the CPU's forceful shutdown detector.

  4. Before the "low-power" event is called in "sensor_battery", use wall(1)
     to display a warning during the earlier event. This was requested by
     jakllsch@ and jmcneill@.

  5. Even though NetBSD also lacks an uniform interface to control the
     display brightness levels, use the acpivga(4)'s sysctls (and possibly
     other MD sysctls) to set the brightness to, say, 75 % when the AC
     adapter is disconnected, and set it back to 100 % when the power cord
     is again plugged.

- Jukka.