linux-kernel - Re: [PATCH 2/2] cfg80211: Use 5MHz bandwidth by default when checking usable channels

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Date:	Sun, 22 Jun 2014 13:41:51 +0200
From:	Felix Fietkau <nbd@...nwrt.org>
To:	Rostislav Lisovy <lisovy@...il.com>,
	Johannes Berg <johannes@...solutions.net>,
	"John W. Linville" <linville@...driver.com>,
	linux-wireless@...r.kernel.org, linux-kernel@...r.kernel.org
CC:	Michal Sojka <sojkam1@....cvut.cz>, s.sander@...dsys.de,
	jan-niklas.meier@...kswagen.de,
	Rostislav Lisovy <rostislav.lisovy@....cvut.cz>
Subject: Re: [PATCH 2/2] cfg80211: Use 5MHz bandwidth by default when checking
 usable channels

On 2014-04-15 14:37, Rostislav Lisovy wrote:
> Current code checks if the 20MHz bandwidth is allowed for
> particular channel -- if it is not, the channel is disabled.
> Since we need to use 5/10 MHz channels, this code is modified in
> the way that the default bandwidth to check is 5MHz. If the
> maximum bandwidth allowed by the channel is smaller than 5MHz,
> the channel is disabled. Otherwise the channel is used and the
> flags are set according to the bandwidth allowed by the channel.
> 
> Signed-off-by: Rostislav Lisovy <rostislav.lisovy@....cvut.cz>
This change causes a regression and needs to be reverted or fixed.
It leaves Channel 12 enabled for US regdomain and does not prevent
bringing up AP mode on it (IEEE80211_CHAN_NO_20MHZ does not get set).

I think the main problem with this change is that max_bandwidth_khz
(which is used to derive the no-10mhz and no-20mhz flags) does not
consider the frequency when calculating the max bandwidth.

- Felix
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