Subject: RE: mac80211 20/40 coexist
From: Johannes Berg <johannes@sipsolutions.net>
To: Sujith Manoharan <c_manoha@qca.qualcomm.com>
Cc: "Manoharan, Rajkumar" <rmanohar@qca.qualcomm.com>,
	linux-wireless <linux-wireless@vger.kernel.org>
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Date: Mon, 19 Mar 2012 11:09:03 +0100
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On Mon, 2012-03-19 at 15:34 +0530, Sujith Manoharan wrote:
> Johannes Berg wrote:
> > Actually, no -- that's how we got into this mess to start with :-)
> > Bandwidth here is a per-peer property, BSS_CHANGED_HT is changing the
> > operation mode (things like non-HT protection).
> > 
> > We used to change the channel bandwidth when the AP wanted to only
> > receive 20 MHz, but that seems like a bug because that doesn't even
> > necessarily mean it wants to TX 20 MHz.
> 
> 11.14.4.3 specifies that if the operating bandwidth has been changed by the AP
> to 20 MHz, then transmitting frames in an extension channel is not allowed ?

Ok, good point. Paul's case was regulatory related, where we
(voluntarily) ceased 40 MHz transmissions.

Still though, I think reconfiguring the channel type rather than the
rate control algorithm doesn't make a lot of sense in this case since
it'd make this very special and unlike the other cases (e.g. AP mode).

johannes