Subject: Re: [PATCH v3 1/1] mac80211: tell driver when dtim change detected
From: Johannes Berg <johannes@sipsolutions.net>
To: Jouni Malinen <j@w1.fi>
Cc: wey-yi.w.guy@intel.com, linux-wireless@vger.kernel.org
In-Reply-To: <20100125183543.GB19528@jm.kir.nu>
References: <1264109996-15995-1-git-send-email-wey-yi.w.guy@intel.com>
	 <1264186981.2593.10.camel@johannes.local>
	 <20100125183543.GB19528@jm.kir.nu>
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Date: Mon, 25 Jan 2010 21:11:41 +0100
Message-ID: <1264450301.23766.65.camel@johannes.local>
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On Mon, 2010-01-25 at 10:35 -0800, Jouni Malinen wrote:
> On Fri, Jan 22, 2010 at 08:03:01PM +0100, Johannes Berg wrote:
> > The other solution I see is that we add a new step before or after the
> > direct probe step, which would just be "wait for a beacon". This would
> > ensure we have both probe and beacon information always ready. It would
> > also ensure we have both probe and beacon info for our new userspace
> > reporting of that.
>=20
> I'm somewhat concerned about this as an unconditional change for our
> association process due to the extra latency it adds. At minimum, I
> would like to see a driver flag that can be used to indicate that such
> behavior is really required and skip the extra wait if the driver does
> not need the Beacon frame before association.
>=20
> For most cases, I would also assume it should be possible to update the
> PS settings after having received the first Beacon frame after
> association, but if that is not enough, allowing the driver to request
> mac80211 to wait with association sounds reasonable. I just don't want
> to see additional 50 msec or so (or much worse if the AP is configured
> with insanely long beacon interval) delay popping up with every
> association by default..

Yeah that's a good point, I wondered about that too. I'll look into this
in more detail and see if we can tell the driver about the DTIM period
only with CONF_PS and enable that only after a beacon.

johannes

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