[Sugar-devel] announce: alternate power management

David Farning dfarning at sugarlabs.org
Fri Mar 13 17:48:57 EDT 2009

Very cool!

How well will this integrate with the power management systems other
distros are using?  Can it become a 'Value Added' for other netbook


On Fri, Mar 13, 2009 at 4:33 PM,  <pgf at laptop.org> wrote:
> hi --
> i had an itch that needed scratching, and the result is a
> reimplementation of much (but not all) of what ohmd does
> currently.
> i've thought for some time (and i believe cjb agrees) that ohmd
> is needlessly difficult to maintain and modify for our purposes
> on the XO.  small improvements are difficult to implement
> quickly.
> since my heart is with more quasi-embedded systems than the XO's
> current incarnation, part of my goal was to do a rewrite which
> was not dependent on hald, dbus, or X11 -- power management
> should work well from a console screen, and be available even if
> none of those services is running.
> i call the service i wrote "powerd".  it gets user idle/active
> reports from the olpc-kbdshim daemon (which is watching all
> user keypress and touchpad activity in any case), and it gets
> reports regarding the hardware inputs (power button, lid and
> ebook switches, ac adapter status, battery level, etc) either
> from another small daemon that monitors /dev/input/event{0,1,2},
> or from /sys nodes directly.
> it basically recreates ohmd's "dim after a bit, then sleep"
> behavior, with some additions:
>  - a power button splash screen:  a second press of the power
>     button invokes shutdown, simply waiting for a brief timeout
>     invokes suspend, and any user activity cancels.  (i even
>     managed to kinda sorta convey all that with graphics.  i'm
>     sure every UI person that sees it will roll their eyes.)
>  - configurable timeouts for screen dim and sleep.  the dim
>    level is configurable.
>  - different power management behavior when on wall power vs.
>    battery -- many laptop owners don't need to be miserly with
>    power when running from an external source.  powerd makes
>    this behavior selectable.
>  - different power behavior when in ebook mode (though detection
>    may be unreliable -- i think the ebook switch suffers from
>    some issues we previously noticed with the lid switch).  this
>    should let you configure things like a very short timeout until
>    idle-suspend, and/or no screen dimming, when in ebook mode.  (i
>    find the frequent on/off nature of the backlight when reading
>    in ebook mode to be a distraction.)
>  - clean shutdown on critically low battery.  (currently set at
>    a reported 5%, at which point my laptop would only run for
>    another couple of minutes.)
>  - the ability to run arbitrary scripts after a resume.  (perhaps
>    to reinit usb devices that don't suspend/resume properly?  haven't
>    used this much yet.)
>  - ease of customization, given that it's written in everyone's
>    favorite interpreted language.
>  unimplemented:
>  - inhibiting idle suspend based on system or network load.
>    i.e., the system will dim or suspend when watching a video.
>    (there are hooks in place where these features should be
>    implemented -- they're just not coded at all.)  there's
>    no /etc/ohmd directory, so it honors /var/run/inhibit-idle-suspend
>    instead.
>  - no special support for the wireless mesh, whatsoever.  i
>    couldn't remember how it was supposed to work, and i recall
>    cjb saying it's hard to figure out whether the mesh is active
>    or not.
>  - there's some support for wake-on-wlan, but it's not well tested.
>  finally a big one:
>  - proper support for USB keyboards and mice.  i recently
>    realized that since olpc-kbdshim only monitors the built-in
>    keyboard and touchpad, powerd will think the user is idle
>    while they type on a USB keyboard, and cheerfully suspend
>    regardless.  (in my case, most of the time i want to
>    auto-suspend is when i'm running on battery, and not using
>    external devices, so i sort of forgot about this case.)
> anyway, code is available here:
>    http://dev.laptop.org/git/users/pgf/powerd/
> and rpms are here:
>    http://dev.laptop.org/~pgf/rpms/
> you'll need to install both olpc-kbdshim and olpc-powerd (in that
> order).  when installed, olpc-powerd disables ohmd, and reenables
> it when uninstalled.  (so it's relatively safe to try.)
> there's no gui or other convenience for configuration --
> see/etc/powerd/powerd.conf.  the installed defaults should be
> reasonable.  and you'll need to run:
>    echo reconfig >/var/run/powerevents
> after making changes to the config file.
> paul
> =---------------------
>  paul fox, pgf at laptop.org
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