Message-ID: <1399466312.10517.34.camel@jlt4.sipsolutions.net> (sfid-20140507_143855_433410_F7C22C53)
Subject: Re: [PATCH v5] mac80211: implement multi-vif in-place reservations
From: Johannes Berg <johannes@sipsolutions.net>
To: Luca Coelho <luca@coelho.fi>
Cc: Michal Kazior <michal.kazior@tieto.com>,
	linux-wireless <linux-wireless@vger.kernel.org>,
	Simon Wunderlich <sw@simonwunderlich.de>
Date: Wed, 07 May 2014 14:38:32 +0200
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On Wed, 2014-05-07 at 15:20 +0300, Luca Coelho wrote:
> On Wed, 2014-05-07 at 14:13 +0200, Johannes Berg wrote:
> > On Wed, 2014-05-07 at 15:08 +0300, Luca Coelho wrote:
> > 
> > > I was thinking about the case where you you need to involve 3 contexts.
> > > Let's say you have 2 vifs in the same context and after the switch you
> > > need to split them into 2 new ones (for instance, if there is some
> > > incompatibility in the new chandefs).
> > > 
> > > With the generic transactions you could do:
> > >  - new chanctx2
> > >  - new chanctx3
> > >  - switch vif1 chanctx1->chanctx2
> > >  - switch vif2 chanctx1->chanctx3
> > >  - del chanctx1
> > 
> > This isn't an interesting case, because it means you have a spare, so
> > you might as well do
> > 
> >  new chanctx3
> >  switch vif2 chanctx1->chanctx3
> >  switch_transaction(chanctx1, chanctx2, vif1)
> 
> Couldn't this potentially break the combinations temporarily again?

I don't see why? You had a spare channel context to start with,
otherwise you'd never have accepted this situation. Therefore, you can
use the spare one before actually doing the proposed
switch_vif_chanctx().


Ultimately, what I'm trying to say is that instead of the proposed
switch_vif_chanctx(), we need to have this:

enum ieee80211_chanctx_switch_mode - as before

        (*switch_vif_chanctx)(struct ieee80211_hw *hw,
                              struct ieee80211_vif **vifs, int n_vifs,
                              struct ieee80211_chanctx_conf *old_ctx,
                              struct ieee80211_chanctx_conf *new_ctx,
                              enum ieee80211_chanctx_switch_mode mode);


johannes