From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from he.sipsolutions.net ([78.46.109.217]:43242 "EHLO sipsolutions.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755207Ab1BNOIT (ORCPT ); Mon, 14 Feb 2011 09:08:19 -0500 Subject: Re: [RFC v2 1/2] mac80211: add a function for setting the TIM bit for a specific station From: Johannes Berg To: Felix Fietkau Cc: linux-wireless@vger.kernel.org, j@w1.fi, lrodriguez@atheros.com, m.sujith@gmail.com In-Reply-To: <4D5936D8.3030906@openwrt.org> References: <1297207937-88528-1-git-send-email-nbd@openwrt.org> <1297685367.3785.33.camel@jlt3.sipsolutions.net> <4D5936D8.3030906@openwrt.org> Content-Type: text/plain; charset="UTF-8" Date: Mon, 14 Feb 2011 15:08:14 +0100 Message-ID: <1297692494.3953.0.camel@jlt3.sipsolutions.net> Mime-Version: 1.0 Sender: linux-wireless-owner@vger.kernel.org List-ID: On Mon, 2011-02-14 at 15:06 +0100, Felix Fietkau wrote: > On 2011-02-14 1:09 PM, Johannes Berg wrote: > > On Wed, 2011-02-09 at 00:32 +0100, Felix Fietkau wrote: > >> When a driver wants to buffer some frames internally without feeding them > >> back to mac80211, this allows it to still wake up the station > > > > Why would the driver want to do this though? > If a station enters powersave and the AP still has buffered frames for > aggregation, those frames need to stay in the queue, since the driver > controls the block ack window and keeps some state per frame (e.g. > number of software retransmissions). > If ath9k would send those frames back to mac80211, and mac80211 would > drop some of them, then the client's reorder window would get messed up > when the client comes back. This would also make managing frame sequence > numbers more complicated, since the driver would have to skip assigning > sequence numbers for frames where tx_info->flags has the > IEEE80211_TX_INTFL_RETRANSMISSION bit set, but then also look for gaps > caused by expired frames. Ok, that makes sense. In fact, I think iwlwifi will have the same issue since it buffers in hw queues... will have to check that. johannes