From: Johannes Stezenbach <js@sig21.net>
To: Ivo Van Doorn <ivdoorn@gmail.com>
Cc: Johannes Berg <johannes@sipsolutions.net>,
linux-wireless@vger.kernel.org, users@rt2x00.serialmonkey.com
Subject: Re: [rt2x00-users] [RFC] rt2x00: Add autowakeup timer for receiving beacons while in powersave mode
Date: Mon, 31 Jan 2011 16:54:20 +0100 [thread overview]
Message-ID: <20110131155420.GA7552@sig21.net> (raw)
In-Reply-To: <AANLkTikzz0b+2N1ktVLz_CFZUBKzwrPF5y6xYLvmknbS@mail.gmail.com>
On Mon, Jan 31, 2011 at 04:38:16PM +0100, Ivo Van Doorn wrote:
> >>
> >> TODO: Split out mac80211 changes into a separate patch. We also need
> >> to know if we need this check in mac80211 or in the driver. Personally I think the
> >> check belongs in mac80211, but at this time that work has been deferred to the drivers.
> >> However this means that a lot of logic is needed in the driver to check if the correct IE
> >> is available, and then check the value, while mac80211 will obtains that exact IE anyway
> >> during RX processing anyway...
> >
> > Hmm. I've always said that there's no efficient way to do this in
> > mac80211. If you do it close to the beacon, unexpected latency means
> > that we miss -- this can be severe if something else is happening in the
> > system, especially with USB devices. If you do it early before the
> > beacon, then you don't save much power. As a consequence, I don't really
> > like this in mac80211.
> >
> > However, it seems you only added "stay awake after beacon" code to
> > mac80211 that checks the TIM. Assuming the device actually stays awake
> > for multicast traffic by itself that seems like an option, though I
> > wouldn't wait for the next beacon before going to sleep again --
> > wouldn't that happen with the timer anyway?
>
> The timer is needed to automatically wake the device up in time to receive
> the beacon. When the beacon is received all the driver needs to know if the
> device should go back to sleep again for the next beacon period.
>
> This is a similar behavior as carl9170 driver, which currently checks for
> pending Mcast/Bcast frames in the RX path just before the frame is send
> to mac80211.
FWIW, this bc/mc check is also on the mac80211 TODO list:
http://wireless.kernel.org/en/developers/todo-list#power_saving
Johannes
next prev parent reply other threads:[~2011-01-31 15:54 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-01-31 15:00 [RFC] rt2x00: Add autowakeup timer for receiving beacons while in powersave mode Ivo van Doorn
2011-01-31 15:22 ` Johannes Berg
2011-01-31 15:38 ` Ivo Van Doorn
2011-01-31 15:54 ` Johannes Stezenbach [this message]
2011-01-31 18:17 ` Johannes Stezenbach
2011-01-31 19:00 ` Ivo Van Doorn
2011-01-31 21:05 ` Johannes Stezenbach
2011-02-02 17:42 ` Kalle Valo
2011-02-02 19:09 ` Ivo Van Doorn
2011-02-10 5:24 ` RA-Jay Hung
2011-02-14 10:14 ` Ivo Van Doorn
2011-02-14 10:25 ` Johannes Berg
2011-02-02 21:29 ` Johannes Stezenbach
2011-02-07 23:33 ` [rt2x00-users] " Aleksandar Milivojevic
2011-02-08 8:48 ` Kalle Valo
2011-02-08 19:11 ` Aleksandar Milivojevic
2011-02-09 12:17 ` Kalle Valo
2011-02-09 14:31 ` Johannes Stezenbach
2011-02-08 8:27 ` Kalle Valo
2011-02-08 20:09 ` Johannes Stezenbach
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