Re: Prevent auto scan in wireless devices

[Dan Williams <dcbw redhat com>]

On Mon, 2009-02-02 at 00:25 +0000, Marc Herbert wrote:
> >>>> > But at the end of the day, if you want to save power, you'll want to
> >>>> > turn off the wifi chipset when the user isn't going to use it.
> >>
> >> Well, not necessarily. With my hardware, turning off background scanning
> >> seems enough to save power.
> 
> Translating myself: when using ifdown, I do not even need to turn off
> the wifi chipset to save power. ifdown is enough to save power, since
> it does no background scan.

Note that when using NetworkManager, you have another process on the
system, so that could translate into more wakeups, which could be
causing the additional power usage.  There were patches committed to
NetworkManager that will be in 0.7.1 that will reduce power usage.

However, when you uncheck "Enable Wireless", NetworkManager will *not*
do any scanning, because wireless is disabled.  So I would expect that
when wireless is disabled in NetworkManager, any difference in power
consumption between that and ifupdown would reflect someting *other*
than scanning.

Any chance you can run 'powertop' on your system and see what it says
(if anything) about NetworkManager?  I would not expect many wakeups
with the g_timeout_add_seconds() patch, since that patch moves wakeups
onto second boundaries to save power.

> > Right click the NM applet, uncheck "Enable wireless". When you want to
> > connect to something again check it again. Isn't that good enough for
> > you?
> 
> Like probably every user I did this in the first place. The background
> scan power problem it caused is precisely what led me to this thread.

But NetworkManager won't be scanning or doing *anything* with the
wireless device when you uncheck "Disable Wireless".  If it does,
there's a bug.

Dan