Re: [PATCH] mac80211: Add NoAck per WMM Queue Support

[Simon Wunderlich <simon.wunderlich@s2003.tu-chemnitz.de>]

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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.
> 
> 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 traffic.
This can be applied on devices supporting both traffic classes (e.g. 
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-WMMNoAckPolicyBitValue

> 
> 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.
> 

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.
> 
> 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 kernel
this should be safe. I forgot to explicitly check for rdev->ops->set_txq_noack
and will add this check in v2 ...

I will also remove the debugfs entry.

> 
> 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

> 
> johannes
> 
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