Re: [PATCH v3 1/1] mac80211: tell driver when dtim change detected

["Guy, Wey-Yi" <wey-yi.w.guy@intel.com>]

On Mon, 2010-01-25 at 12:11 -0800, Johannes Berg wrote:
> 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.
> > 
> > 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.
> > 
> > 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.
> 
I really like the idea of using CONF_PS which will not cause any delay
for association, plus the only STA need to know DTIM is the station in
power save mode.