Date: Wed, 16 Nov 2011 11:51:20 +0100
From: Simon Wunderlich <simon.wunderlich@s2003.tu-chemnitz.de>
To: Johannes Berg <johannes@sipsolutions.net>
Cc: Simon Wunderlich <simon.wunderlich@s2003.tu-chemnitz.de>,
	linux-wireless@vger.kernel.org, linville@tuxdriver.com,
	Simon Wunderlich <siwu@hrz.tu-chemnitz.de>,
	Mathias Kretschmer <mathias.kretschmer@fokus.fraunhofer.de>
Subject: Re: [PATCH] mac80211: Add NoAck per WMM Queue Support
Message-ID: <20111116105120.GA6139@pandem0nium> (sfid-20111116_115131_539496_1D301BE8)
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Hi Johannes,

thanks for the review!

On Wed, Nov 16, 2011 at 08:52:15AM +0100, Johannes Berg wrote:
> On Wed, 2011-11-16 at 00:21 +0100, Simon Wunderlich wrote:
> > This patch adds support for NoAck per WMM Queue. The Unicast QoS
> > Header is adapted accordingly for each outgoing frame.
> > The support is turned on and off through nl80211 by extending
> > the WMM TX Queue Parameters, but can be triggered separately.
>=20
> Can you explain what for? :-)

We want to set NoAck for special traffic classes like video or voice where
"old" packets are not useful, but keep it for background and best effort tr=
affic.
This can be applied on devices supporting both traffic classes (e.g.=20
laptops, smartphones with VoIP software) as well as for backhaul links.

Something similar has been done previously on madwifi, what we used:

http://madwifi-project.org/wiki/UserDocs/UsersGuide#noackpolicy-WMMNoAckPol=
icyBitValue

>=20
> I'm not sure this API is really the best way to handle it either, like I
> just said it might be nicer per connection or so to get reset properly.
>=20

I'm not sure what you mean by "per connection" - do you mean per AP/Sta
connection? We need definitely need it per queue as explained above.

> > I have tested this feature on ath9k as well as ath5k devices. There is
> > an iw patch as well to make use of this feature.
>=20
> Since you're adding 'real API' (unlike the debugfs file which you should
> probably remove now!) you also should think about drivers like mwifiex
> that don't support this and don't use mac80211.

mwifiex neither supports set_txq_params nor the new function, nl80211 should
just return "-EOPNOTSUPP". A short grep revealed that no driver in wireless=
-testing
implements set_txq_params so far, so at least for the drivers within the ke=
rnel
this should be safe. I forgot to explicitly check for rdev->ops->set_txq_no=
ack
and will add this check in v2 ...

I will also remove the debugfs entry.

>=20
> Also, given real API, this impacts the duration calculation etc.

I'm no expert in duration calculation, but will give it a try.

best regards,
	Simon

>=20
> johannes
>=20
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>=20

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