linux-kernel - Re: Update on Android PM enhancements - CONFIG_HAS

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Message-ID: <87vcz1rvp1.fsf@purkki.adurom.net>
Date:	Wed, 30 Mar 2011 09:03:54 +0300
From:	Kalle Valo <kvalo@...rom.com>
To:	Johannes Berg <johannes@...solutions.net>
Cc:	Arve Hjønnevåg <arve@...roid.com>,
	"Luis R. Rodriguez" <mcgrof@...il.com>,
	linux-kernel@...r.kernel.org, "Rafael J. Wysocki" <rjw@...k.pl>,
	devel@...uxdriverproject.org, Naveen Singh <nsingh@...eros.com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Jouni Malinen <Jouni.Malinen@...eros.com>,
	Vipin Mehta <vmehta@...eros.com>,
	linux-wireless <linux-wireless@...r.kernel.org>
Subject: Re: Update on Android PM enhancements - CONFIG_HAS_EARLYSUSPEND and friends

Kalle Valo <kvalo@...rom.com> writes:

> In maemo, to save power, we decreased the dynamic power save timeout
> whenever display was turned off. This was all done from user space and
> wifi driver in the kernel was completely unaware of the display state.

[...]

> And before someone suggests adding dynamic timeout variable to
> nl80211: I think it's very much implementation specific parameter. Not
> all drivers support it and it might be that even in future mac80211
> uses something else. So having the timeout variable in nl80211 is not
> a long term solution.

I totally forgot that Juuso added QoS requirements support to
mac80211. And that's the proper wayq to do this, user space sets QoS
requirements based on display state, and whatever else it thinks is
important, and mac80211 adapts the power save parameters accordingly.
In this method we are not revealing any implemention details to user
space, and that's always a good thing.

-- 
Kalle Valo
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