I just released laptop-mode-tools version 1.56.

This release adds many goodies. We now have a better calling application to rely upon, udev. The linux kernel generates many events based on conditions. udev is a framework that acts on those events and can call-in applications based on conditions. This is something I wanted to do for laptop- mode-tools.

Power State

First was power state. The power_supply subsystem can sense changes and generate events. We simply act on the change action here and call in laptop-mode-tools because we want laptop-mode-tools run on both ON_AC and ON_BAT


Suspend/Resume was my bigger concern. pm-utils no more likes us. In fact it now has direct Conflict: defined in the Package Managers. For laptop-mode- tools, on suspend, there was not much to care about. But I did want to ensure that we act on resume because:

  • User could suspend when ON_AC
  • Go back home
  • Resume when ON_BAT

The machinecheck subsystem helped here. I hope my assumption that this event in only seen during suspend/resume stands true.

Multi Events and Locking

Acting on events is good but can be challenging because the kernel can generate a large number of events and we have a danger of ending up spawning just too many instances. flock came to the rescue there.

So overall, by depending on events, we are better now. We can cut down on many dependencies. Especially the Power Management Daemon dependency because different arches had diffrerent managers.

pm-utils conflict is disappointing especially for the fact that that conflict is inherited in Debian too. I hope the pm-utils maintainer reconsiders. Uninstalling pm-utils has the challenge that the DEs lose the suspend functionality. Does anyone know how the DEs call them? Can a minor hacky workaround be provided?

See also