Re: [RFCv1] mac80211: Adds Software / Virtual AMP 80211

[Andrei Emeltchenko <Andrei.Emeltchenko.news@gmail.com>]

Hi Johannes,

On Wed, Apr 18, 2012 at 07:38:08AM -0700, Johannes Berg wrote:
> On 4/18/2012 5:15 AM, Andrei Emeltchenko wrote:
> >>It's never in your best interest to run one supplicant per virtual
> >>interface, you want to run one per piece of hardware so it can
> >>coordinate between virtual interfaces.
> >
> >Do I understand it right that virtual interfaces are like separate devices from
> >user point of view? If I create virtual interface and assign MAC I can
> >transfer data through it without affecting other interfaces? Then
> >wpa_supplicant does not need to know about it at all.
> 
> No, this is incorrect. If one device wants to connect on one
> channel, the other typically has to use the same channel. If one
> device wants to scan, the other will be affected. Some hardware may
> support switching around between two channels, but might also
> support more than 2 virtual interfaces, so again they won't be
> independent.

BTW: which devices can switch channels?

> Therefore, you need something managing all this concurrency. This is
> in a small part the driver which will enforce restrictions (it will
> reject new impossible things), but mostly the supplicant which can
> make policy decisions about which usage should win.

This doesn't sound like a rocket science to me. IMO this might be done in
drivers. Those drivers which can switch channels why do they need
wpa_supplicant involved making this decision?

Best regards 
Andrei Emeltchenko