[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
manufacturers?
david
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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