linux-kernel - Re: [PATCH v2] cfg80211: Try multiple bandwidths when checking usable channels.

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Date:	Mon, 11 Aug 2014 17:12:05 +0200
From:	Johannes Berg <johannes@...solutions.net>
To:	Rostislav Lisovy <lisovy@...il.com>,
	"Luis R. Rodriguez" <mcgrof@...not-panic.com>
Cc:	"John W. Linville" <linville@...driver.com>,
	linux-wireless@...r.kernel.org, linux-kernel@...r.kernel.org,
	Michal Sojka <sojkam1@....cvut.cz>, s.sander@...dsys.de,
	jan-niklas.meier@...kswagen.de,
	Rostislav Lisovy <rostislav.lisovy@....cvut.cz>
Subject: Re: [PATCH v2] cfg80211: Try multiple bandwidths when checking
 usable channels.

On Thu, 2014-07-24 at 14:43 +0200, Rostislav Lisovy wrote:
> Current code checks if at least 20MHz bandwidth is allowed for
> particular channel -- if it is not, the channel is disabled.
> This disables usage of 5/10 MHz channels.
> Another issue with the current code is that it may allow a channel
> with bandwidth which is although less or the same as the "maximum
> bandwidth allowed" but overlaps the border of the band.
> 
> The new approach is that there are multiple checks for one channel --
> one for each bandwidth: 5, 10, 20, 40, 80, 160 MHz (when we hit a
> bandwidth that is not allowed, greater bandwidths are automatically
> disabled as well).  This prevents the following scenario to happen:
> The 5 MHz bandwidth channel at the very end of the band is
> successfully checked to fit which is followed by setting flags
> IEEE80211_CHAN_NO_* according to the maximum bandwidth allowed by the
> particular regulatory rule (which may be greater than the 5 MHz).
> When someone will try to use that particular channel with the maximum
> bandwidth allowed (e.g. 20 MHz), the resulting channel will not be in
> the range of the band anymore (will overlap the border).

I really don't know what to do with this. I don't quite understand
what's going on, to be honest.

Luis?

johannes

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