netdev - Re: [PATCH] mac80211: fix channel switch for chanctx-based drivers

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Message-ID: <1408370365.20137.11.camel@dubbel>
Date:	Mon, 18 Aug 2014 16:59:25 +0300
From:	Luca Coelho <luca@...lho.fi>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Michal Kazior <michal.kazior@...to.com>,
	Johannes Berg <johannes.berg@...el.com>,
	Emmanuel Grumbach <emmanuel.grumbach@...el.com>,
	Intel Linux Wireless <ilw@...ux.intel.com>,
	"John W. Linville" <linville@...driver.com>,
	Linux Wireless List <linux-wireless@...r.kernel.org>,
	Network Development <netdev@...r.kernel.org>
Subject: Re: [PATCH] mac80211: fix channel switch for chanctx-based drivers

Hi Linus,

On Mon, 2014-08-18 at 08:53 -0500, Linus Torvalds wrote:
> On Mon, Aug 18, 2014 at 6:19 AM, Michal Kazior <michal.kazior@...to.com> wrote:
> >
> > I've verified this fix with iwlmvm & 7260.
> 
> So I'm running a kernel with this manually applied, and so far so
> good. But I don't know what actually triggered the problem, and it
> definitely didn't happen all the time, so my testing of this is
> dubious. But the patch certainly seems to match the symptoms. Thanks,

What triggers this is a "Channel Switch Announcement" on which the
access point tells the clients to move to another channel at a specified
time.  This is not very common, but some enterprise APs use it to
improve the operating radio conditions, for instance.

Previously, as a client, we would simply disconnect from the current
channel and reconnect on the new channel after the time specified by the
AP.  Now we implemented a more advanced switch where we don't lose
connectivity, but "simply" switch channels.

Hope this clarifies a bit.

--
Cheers,
Luca.

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