Re: [PATCH v6 6/6] cfg80211: remove channel_switch combination check

[Johannes Berg <johannes@sipsolutions.net>]

On Fri, 2014-05-23 at 09:04 +0200, Michal Kazior wrote:
> On 22 May 2014 16:57, Johannes Berg <johannes@sipsolutions.net> wrote:
> > On Thu, 2014-05-22 at 16:07 +0200, Michal Kazior wrote:
> >> Make the driver responsible for making sure it is
> >> capable of performing the switch. It might as well
> >> accept a request but then disconnect an interface
> >> if some requirements are not met.
> >
> > Care to elaborate? I'd really like to avoid this case as much as
> > possible, so just mentioning here that it would be valid seems like a
> > bad idea.
> 
> Well, CSA isn't really visible to cfg80211 so you can't enforce anything now.
> 
> Also since CSA requests are submitted one-by-one you already break
> interface combinations and hope:
>  a) userspace sends more CSA requests soon enough to make future
> interface combination valid
>  b) trust drivers deal with it either way
> 
> So why bother?
> 
> The most you can probably do is to prevent CSA requests from switching
> to too many different channels but you can easily guarantee this in a
> driver.

Yeah, absolutely - it's just the fact that you're saying that it might
accept but then disconnect ... that will make people feel OK about that,
when it's really not all that desirable. Better to state that more
explicitly that it should check before :)

johannes