Re: [PATCH v8] cfg80211: P2P find phase offload

[Vladimir Kondratiev <qca_vkondrat@qca.qualcomm.com>]

On Tuesday, June 04, 2013 09:30:23 PM Jouni Malinen wrote:
> On Tue, Jun 04, 2013 at 07:47:20PM +0300, Vladimir Kondratiev wrote:
> > I am a bit confused. I supposed that if devices A and B (not in a group yet)
> > try to discover each other, it works like the following
> > 
> > A ---- probe-req  ---> B (now B knows A)
> > A <--- probe-resp ---- B (now A knows B)
> 
> This depends on what exactly you mean with "discover". Sure, it is known
> that there is a P2P peer in the environment if a Probe Request frame
> with P2P IE is received from it. However, that does not necessarily mean
> we know enough of that peer to initiate new P2P operations.
> 
> > But if device is discovered by probe-resp only, it mean this should be
> > 
> > A ---- probe-req  ---> B
> > A <--- probe-resp ---- B (now A knows B)
> > A <--- probe-req  ---- B
> > A ---- probe-resp ---> B (now B knows A)
> 
> Probe Response frames include more information about the peer and that
> allows wpa_supplicant to complete the peer entry. This is the point when
> the peer is fully known and indicated to upper layers. The Probe Request
> frame RX case is just used internally within wpa_supplicant. (For
> completeness, number of other frames, i.e., P2P Action frames, can also
> complete the P2P peer entry, so this does not need to be Probe
> Response).

Thanks for clarification. So, I see that wpa_s wants all probe responses and
may want either all or selected probes, depending on the driver's capability
(NL80211_FEATURE_P2P_PROBE_RESP_OFFLOAD) and its own reasons.

Then, I think it would be appropriate to say following in the comment for
start_p2p_find (no code changes, it is only expectations for the friver behavior):

---cut---
While performing P2P discovery, driver should report all received
probe-request and probe-response frames via cfg80211_rx_mgmt,
accordingly to the rx mgmt filter, as set by mgmt_frame_register().
When reporting probes, driver/firmware may do its best to filter out
probes that would not be replied with probe-resp accordingly to the
P2P rules for active device configuration.
---cut---

This makes possible for wpa_s to choose exact configuration, and good
power saving is possible provided firmware answer probes.

Comments?

Thanks, Vladimir