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--- en:developers:p2p:p2p-interface-notes [2015/01/26 09:49]
+++ en:developers:p2p:p2p-interface-notes [2015/01/26 09:49] (current)
@@ Line 1: / Line 1: @@
+**Note: The design on this page is WIP: [[http://thread.gmane.org/gmane.linux.kernel.wireless.general/93044|http://thread.gmane.org/gmane.linux.kernel.wireless.general/93044]]**
+===== Design notes on dedicated P2P interface API =====
+==== Rationale ====
+Some drivers/devices would like to
+  * use a separate MAC address
+  * use a separate control path for P2P usage. This could even help mac80211-based drivers like iwlagn since currently, iwlagn needs to enable P2P in the device when a remain-on-channel is done, and disable it after a timeout or when a P2P interface is used.
+==== API notes ====
+A separate netdev would be the most obvious choice, but can be confusing:
+    * to the user -- new interface is there, what does it do?
+    * to the developer -- no data traffic on this interface
+Better: use dedicated API in nl80211:
+      * start-P2P -> returns cookie
+      * stop-P2P -> uses cookie
+(or maybe don't have "stop-P2P" but simply stop when socket is closed like mgmt frame subscriptions)
+The only issue with this is that things like scan, mgmt-tx etc. need a netdev index now. However, this can be changed, idea:
+        * use cookie to identify the P2P device interface
+        * internally, create a <code>struct wireless_dev</code> but **without** a netdev
+        * modify cfg80211 API (e.g. <code>scan</code>, <code>remain_on_channel</code>) to take <code>struct wireless_dev</code> instead of netdev, driver can check what the type is etc.
+        * this needs separate P2P-device iftype that can't really be used as an iftype, which is fine Questions:
+          * lifetime: does the P2P-device interface become the P2P-group/client interface like in wpa_supplicant, which means that it is removed before/when the real netdev is added? (personally I prefer it would stay around I think since I think discovery/public action things would still be done with it, not the real interface -- Johannes)
+          * pure software implementation of this in mac80211 for drivers that don't care, to unify API? but wpa_s needs old code anyway for backward compatibility
+==== additional thoughts ====
+This could also be a good framework for additional features that we'll need to add:
+            * device-based P2P listen/search timing (soon)
+            * maybe some more P2P offloads (WoP2P anyone? :-) )

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