On Wed, 2013-11-06 at 12:31 +0100, Johannes Berg wrote:
> On Wed, 2013-11-06 at 11:28 +0000, Coelho, Luciano wrote:
>
> > In terms of the order of calls, the difference is that in the past we
> > had this:
> >
> > 1. Set CSA beacon;
> > 2. When count reaches 1, the driver calls ieee80211_csa_finish();
> > 3. We call drv_change_chanctx();
> > 4. Set new channel beacon.
> >
> > (This continues to be the case with my patch when count > 1)
> >
> > With my patch, if count <= 1, we do this instead:
> >
> > 1. Call drv_change_chanctx();
> > 2. Set new channel beacon.
> >
> > The main problem without my patch is that the driver shouldn't beacon
> > with the CSA element when the count starts <= 1, so it won't have a
> > chance to check if the count reached 1 to call ieee80211_csa_finish().
>
> I think the other difference is that one calls
> drv_channel_switch_beacon()?
Right, this was part of my "Set CSA beacon" item, I should have been
more explicit.
> The driver might do some channel
> preparations there, though I guess you can audit all the drivers (well,
> one ...) :)
Luckily, all the drivers that use this (well, one... :P) don't do
anything funky with this call. ath9k only uses this call mark that
there is an ongoing CSA, which is not needed in the immediate switch
case.
> But that'd need some more documentation, otherwise I'd guess people
> would start to rely on drv_channel_switch_beacon() and it would mostly
> work - hence my question of whether it makes sense to refuse it at all
> in the case of <=1.
Right. I actually added this to the documentation, but I accidentally
sent it as part of patch 1/2:
> +++ b/include/net/mac80211.h
> @@ -2676,11 +2676,13 @@ enum ieee80211_roc_type {
> * @channel_switch_beacon: Starts a channel switch to a new channel.
[...]
> + * If the CSA count starts as zero or 1, this function will not be called,
> + * since there won't be any time to beacon before the switch anyway.
This change should be in patch 2/2 (actually these two patches should
probably be squashed, I just kept them separate so that reviewing my v2
would be easier).
I can elaborate more in the documentation if you think it's necessary.
--
Cheers,
Luca.
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