powersaving when interface is up but not associated

powersaving when interface is up but not associated

[Johannes Berg]

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Hi!

Just had this idea -- when our networking interfaces are UP, but not
actually doing anything, the RF chains consume power. This is, often,
the default state, since you'll have your wifi on due to NM wanting to
find APs, but not associated, for example when on the road. Sure, you
can manually turn it off, but...

However, it doesn't seem necessary. When we are not associated to an AP,
and there are no extra interfaces in mac80211 active like monitor
interfaces, it seems that we could very well turn off the radio while
not scanning. It would be entirely trivial for mac80211 to do this,
probably a 20 line patch or so (need some bookkeeping about why radio is
disabled so it's not just four lines).

Thoughts?

johannes

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Re: powersaving when interface is up but not associated

[John W. Linville]

On Wed, Apr 22, 2009 at 10:15:56PM +0200, Johannes Berg wrote:
> Hi!
> 
> Just had this idea -- when our networking interfaces are UP, but not
> actually doing anything, the RF chains consume power. This is, often,
> the default state, since you'll have your wifi on due to NM wanting to
> find APs, but not associated, for example when on the road. Sure, you
> can manually turn it off, but...
> 
> However, it doesn't seem necessary. When we are not associated to an AP,
> and there are no extra interfaces in mac80211 active like monitor
> interfaces, it seems that we could very well turn off the radio while
> not scanning. It would be entirely trivial for mac80211 to do this,
> probably a 20 line patch or so (need some bookkeeping about why radio is
> disabled so it's not just four lines).

Makes sense to me...

-- 
John W. Linville		Someday the world will need a hero, and you
linville@tuxdriver.com			might be all we have.  Be ready.

Re: powersaving when interface is up but not associated

[Kalle Valo]

Johannes Berg <johannes@sipsolutions.net> writes:

> Hi!

Hello,

> Just had this idea -- when our networking interfaces are UP, but not
> actually doing anything, the RF chains consume power. 

Yes, and also firmware consumes power. For example stlc4550 has a
hibernate feature to put the firmware sleep and wake it up quickly.

> This is, often, the default state, since you'll have your wifi on due
> to NM wanting to find APs, but not associated, for example when on the
> road. Sure, you can manually turn it off, but...

That's what we do in Nokia Internet tablets. wlancond it putting
interface up and down all the time and it's a hack.

> However, it doesn't seem necessary. When we are not associated to an AP,
> and there are no extra interfaces in mac80211 active like monitor
> interfaces, it seems that we could very well turn off the radio while
> not scanning. It would be entirely trivial for mac80211 to do this,
> probably a 20 line patch or so (need some bookkeeping about why radio is
> disabled so it's not just four lines).
>
> Thoughts?

I think it's a good idea. Sometimes I have thought myself that we would
need something like this.

-- 
Kalle Valo