[RFC 0/2] remain-on-channel HW offload

[RFC 0/2] remain-on-channel HW offload

[Johannes Berg]

This adds functionality to enable remain-on-channel
hardware offload to mac80211 drivers. Any frames
transmitted during that time get a new TX flag and
must be transmitted correctly by the driver -- any
other activity isn't stopped, so the device must
have different queues for the different frames.

johannes

[RFC 1/2] mac80211: implement hardware offload for remain-on-channel

[Johannes Berg]

From: Johannes Berg <johannes.berg@intel.com>

This allows drivers to support remain-on-channel
offload if they implement smarter timing or need
to use a device implementation like iwlwifi.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
---
 include/net/mac80211.h      |   19 ++++++++++
 net/mac80211/cfg.c          |   81 ++++++++++++++++++++++++++++++++++++++++++++
 net/mac80211/driver-ops.h   |   30 ++++++++++++++++
 net/mac80211/driver-trace.h |   80 +++++++++++++++++++++++++++++++++++++++++++
 net/mac80211/ieee80211_i.h  |    8 ++++
 net/mac80211/iface.c        |    9 +++-
 net/mac80211/main.c         |    5 ++
 net/mac80211/offchannel.c   |   75 ++++++++++++++++++++++++++++++++++++++++
 8 files changed, 304 insertions(+), 3 deletions(-)

--- wireless-testing.orig/include/net/mac80211.h	2010-12-14 17:06:54.000000000 +0100
+++ wireless-testing/include/net/mac80211.h	2010-12-14 17:07:39.000000000 +0100
@@ -365,6 +365,7 @@ enum mac80211_tx_control_flags {
 	IEEE80211_TX_INTFL_NL80211_FRAME_TX	= BIT(21),
 	IEEE80211_TX_CTL_LDPC			= BIT(22),
 	IEEE80211_TX_CTL_STBC			= BIT(23) | BIT(24),
+	IEEE80211_TX_CTL_TX_OFFCHAN		= BIT(25),
 };
 
 #define IEEE80211_TX_CTL_STBC_SHIFT		23
@@ -1824,6 +1825,12 @@ struct ieee80211_ops {
 	int (*napi_poll)(struct ieee80211_hw *hw, int budget);
 	int (*set_antenna)(struct ieee80211_hw *hw, u32 tx_ant, u32 rx_ant);
 	int (*get_antenna)(struct ieee80211_hw *hw, u32 *tx_ant, u32 *rx_ant);
+
+	int (*remain_on_channel)(struct ieee80211_hw *hw,
+				 struct ieee80211_channel *chan,
+				 enum nl80211_channel_type channel_type,
+				 int duration);
+	int (*cancel_remain_on_channel)(struct ieee80211_hw *hw);
 };
 
 /**
@@ -2727,6 +2734,18 @@ void ieee80211_request_smps(struct ieee8
  */
 void ieee80211_key_removed(struct ieee80211_key_conf *key_conf);
 
+/**
+ * ieee80211_ready_on_channel - notification of remain-on-channel start
+ * @hw: pointer as obtained from ieee80211_alloc_hw()
+ */
+void ieee80211_ready_on_channel(struct ieee80211_hw *hw);
+
+/**
+ * ieee80211_remain_on_channel_expired - remain_on_channel duration expired
+ * @hw: pointer as obtained from ieee80211_alloc_hw()
+ */
+void ieee80211_remain_on_channel_expired(struct ieee80211_hw *hw);
+
 /* Rate control API */
 
 /**
--- wireless-testing.orig/net/mac80211/cfg.c	2010-12-14 17:06:55.000000000 +0100
+++ wireless-testing/net/mac80211/cfg.c	2010-12-14 17:07:39.000000000 +0100
@@ -1562,6 +1562,37 @@ static int ieee80211_set_bitrate_mask(st
 	return 0;
 }
 
+static int ieee80211_remain_on_channel_hw(struct ieee80211_local *local,
+					  struct net_device *dev,
+					  struct ieee80211_channel *chan,
+					  enum nl80211_channel_type chantype,
+					  unsigned int duration, u64 *cookie)
+{
+	int ret;
+	u32 random_cookie;
+
+	lockdep_assert_held(&local->mtx);
+
+	if (local->hw_roc_cookie)
+		return -EBUSY;
+	/* must be nonzero */
+	random_cookie = random32() | 1;
+
+	*cookie = random_cookie;
+	local->hw_roc_dev = dev;
+	local->hw_roc_cookie = random_cookie;
+	local->hw_roc_channel = chan;
+	local->hw_roc_channel_type = chantype;
+	local->hw_roc_duration = duration;
+	ret = drv_remain_on_channel(local, chan, chantype, duration);
+	if (ret) {
+		local->hw_roc_channel = NULL;
+		local->hw_roc_cookie = 0;
+	}
+
+	return ret;
+}
+
 static int ieee80211_remain_on_channel(struct wiphy *wiphy,
 				       struct net_device *dev,
 				       struct ieee80211_channel *chan,
@@ -1570,16 +1601,60 @@ static int ieee80211_remain_on_channel(s
 				       u64 *cookie)
 {
 	struct ieee80211_sub_if_data *sdata = IEEE80211_DEV_TO_SUB_IF(dev);
+	struct ieee80211_local *local = sdata->local;
+
+	if (local->ops->remain_on_channel) {
+		int ret;
+
+		mutex_lock(&local->mtx);
+		ret = ieee80211_remain_on_channel_hw(local, dev,
+						     chan, channel_type,
+						     duration, cookie);
+		mutex_unlock(&local->mtx);
+
+		return ret;
+	}
 
 	return ieee80211_wk_remain_on_channel(sdata, chan, channel_type,
 					      duration, cookie);
 }
 
+static int ieee80211_cancel_remain_on_channel_hw(struct ieee80211_local *local,
+						 u64 cookie)
+{
+	int ret;
+
+	lockdep_assert_held(&local->mtx);
+
+	if (local->hw_roc_cookie != cookie)
+		return -ENOENT;
+
+	ret = drv_cancel_remain_on_channel(local);
+	if (ret)
+		return ret;
+
+	local->hw_roc_cookie = 0;
+	local->hw_roc_channel = NULL;
+
+	return 0;
+}
+
 static int ieee80211_cancel_remain_on_channel(struct wiphy *wiphy,
 					      struct net_device *dev,
 					      u64 cookie)
 {
 	struct ieee80211_sub_if_data *sdata = IEEE80211_DEV_TO_SUB_IF(dev);
+	struct ieee80211_local *local = sdata->local;
+
+	if (local->ops->cancel_remain_on_channel) {
+		int ret;
+
+		mutex_lock(&local->mtx);
+		ret = ieee80211_cancel_remain_on_channel_hw(local, cookie);
+		mutex_unlock(&local->mtx);
+
+		return ret;
+	}
 
 	return ieee80211_wk_cancel_remain_on_channel(sdata, cookie);
 }
@@ -1631,6 +1706,12 @@ static int ieee80211_mgmt_tx(struct wiph
 	     channel_type != local->_oper_channel_type))
 		is_offchan = true;
 
+	if (chan == local->hw_roc_channel) {
+		/* TODO: check channel type? */
+		is_offchan = false;
+		flags |= IEEE80211_TX_CTL_TX_OFFCHAN;
+	}
+
 	if (is_offchan && !offchan)
 		return -EBUSY;
 
--- wireless-testing.orig/net/mac80211/ieee80211_i.h	2010-12-14 17:06:55.000000000 +0100
+++ wireless-testing/net/mac80211/ieee80211_i.h	2010-12-14 17:07:39.000000000 +0100
@@ -938,6 +938,13 @@ struct ieee80211_local {
 	} debugfs;
 #endif
 
+	struct ieee80211_channel *hw_roc_channel;
+	struct net_device *hw_roc_dev;
+	struct work_struct hw_roc_start, hw_roc_done;
+	enum nl80211_channel_type hw_roc_channel_type;
+	unsigned int hw_roc_duration;
+	u32 hw_roc_cookie;
+
 	/* dummy netdev for use w/ NAPI */
 	struct net_device napi_dev;
 
@@ -1129,6 +1136,7 @@ void ieee80211_offchannel_stop_beaconing
 void ieee80211_offchannel_stop_station(struct ieee80211_local *local);
 void ieee80211_offchannel_return(struct ieee80211_local *local,
 				 bool enable_beaconing);
+void ieee80211_hw_roc_setup(struct ieee80211_local *local);
 
 /* interface handling */
 int ieee80211_iface_init(void);
--- wireless-testing.orig/net/mac80211/offchannel.c	2010-12-14 17:06:55.000000000 +0100
+++ wireless-testing/net/mac80211/offchannel.c	2010-12-14 17:07:39.000000000 +0100
@@ -14,6 +14,7 @@
  */
 #include <net/mac80211.h>
 #include "ieee80211_i.h"
+#include "driver-trace.h"
 
 /*
  * inform AP that we will go to sleep so that it will buffer the frames
@@ -190,3 +191,77 @@ void ieee80211_offchannel_return(struct
 	}
 	mutex_unlock(&local->iflist_mtx);
 }
+
+static void ieee80211_hw_roc_start(struct work_struct *work)
+{
+	struct ieee80211_local *local =
+		container_of(work, struct ieee80211_local, hw_roc_start);
+
+	mutex_lock(&local->mtx);
+
+	if (!local->hw_roc_channel) {
+		mutex_unlock(&local->mtx);
+		return;
+	}
+
+	ieee80211_recalc_idle(local);
+
+	cfg80211_ready_on_channel(local->hw_roc_dev, local->hw_roc_cookie,
+				  local->hw_roc_channel,
+				  local->hw_roc_channel_type,
+				  local->hw_roc_duration,
+				  GFP_KERNEL);
+	mutex_unlock(&local->mtx);
+}
+
+void ieee80211_ready_on_channel(struct ieee80211_hw *hw)
+{
+	struct ieee80211_local *local = hw_to_local(hw);
+
+	trace_api_ready_on_channel(local);
+
+	ieee80211_queue_work(hw, &local->hw_roc_start);
+}
+EXPORT_SYMBOL_GPL(ieee80211_ready_on_channel);
+
+static void ieee80211_hw_roc_done(struct work_struct *work)
+{
+	struct ieee80211_local *local =
+		container_of(work, struct ieee80211_local, hw_roc_done);
+
+	mutex_lock(&local->mtx);
+
+	if (!local->hw_roc_channel) {
+		mutex_unlock(&local->mtx);
+		return;
+	}
+
+	cfg80211_remain_on_channel_expired(local->hw_roc_dev,
+					   local->hw_roc_cookie,
+					   local->hw_roc_channel,
+					   local->hw_roc_channel_type,
+					   GFP_KERNEL);
+
+	local->hw_roc_channel = NULL;
+	local->hw_roc_cookie = 0;
+
+	ieee80211_recalc_idle(local);
+
+	mutex_unlock(&local->mtx);
+}
+
+void ieee80211_remain_on_channel_expired(struct ieee80211_hw *hw)
+{
+	struct ieee80211_local *local = hw_to_local(hw);
+
+	trace_api_remain_on_channel_expired(local);
+
+	ieee80211_queue_work(hw, &local->hw_roc_done);
+}
+EXPORT_SYMBOL_GPL(ieee80211_remain_on_channel_expired);
+
+void ieee80211_hw_roc_setup(struct ieee80211_local *local)
+{
+	INIT_WORK(&local->hw_roc_start, ieee80211_hw_roc_start);
+	INIT_WORK(&local->hw_roc_done, ieee80211_hw_roc_done);
+}
--- wireless-testing.orig/net/mac80211/main.c	2010-12-14 17:06:55.000000000 +0100
+++ wireless-testing/net/mac80211/main.c	2010-12-14 17:07:39.000000000 +0100
@@ -603,6 +603,8 @@ struct ieee80211_hw *ieee80211_alloc_hw(
 
 	ieee80211_led_names(local);
 
+	ieee80211_hw_roc_setup(local);
+
 	return local_to_hw(local);
 }
 EXPORT_SYMBOL(ieee80211_alloc_hw);
@@ -747,7 +749,8 @@ int ieee80211_register_hw(struct ieee802
 		}
 	}
 
-	local->hw.wiphy->max_remain_on_channel_duration = 5000;
+	if (!local->ops->remain_on_channel)
+		local->hw.wiphy->max_remain_on_channel_duration = 5000;
 
 	result = wiphy_register(local->hw.wiphy);
 	if (result < 0)
--- wireless-testing.orig/net/mac80211/iface.c	2010-12-14 17:06:55.000000000 +0100
+++ wireless-testing/net/mac80211/iface.c	2010-12-14 17:07:39.000000000 +0100
@@ -1264,7 +1264,7 @@ u32 __ieee80211_recalc_idle(struct ieee8
 {
 	struct ieee80211_sub_if_data *sdata;
 	int count = 0;
-	bool working = false, scanning = false;
+	bool working = false, scanning = false, hw_roc = false;
 	struct ieee80211_work *wk;
 	unsigned int led_trig_start = 0, led_trig_stop = 0;
 
@@ -1308,6 +1308,9 @@ u32 __ieee80211_recalc_idle(struct ieee8
 		local->scan_sdata->vif.bss_conf.idle = false;
 	}
 
+	if (local->hw_roc_channel)
+		hw_roc = true;
+
 	list_for_each_entry(sdata, &local->interfaces, list) {
 		if (sdata->old_idle == sdata->vif.bss_conf.idle)
 			continue;
@@ -1316,7 +1319,7 @@ u32 __ieee80211_recalc_idle(struct ieee8
 		ieee80211_bss_info_change_notify(sdata, BSS_CHANGED_IDLE);
 	}
 
-	if (working || scanning)
+	if (working || scanning || hw_roc)
 		led_trig_start |= IEEE80211_TPT_LEDTRIG_FL_WORK;
 	else
 		led_trig_stop |= IEEE80211_TPT_LEDTRIG_FL_WORK;
@@ -1328,6 +1331,8 @@ u32 __ieee80211_recalc_idle(struct ieee8
 
 	ieee80211_mod_tpt_led_trig(local, led_trig_start, led_trig_stop);
 
+	if (hw_roc)
+		return ieee80211_idle_off(local, "hw remain-on-channel");
 	if (working)
 		return ieee80211_idle_off(local, "working");
 	if (scanning)
--- wireless-testing.orig/net/mac80211/driver-ops.h	2010-12-14 17:06:55.000000000 +0100
+++ wireless-testing/net/mac80211/driver-ops.h	2010-12-14 17:07:39.000000000 +0100
@@ -465,4 +465,34 @@ static inline int drv_get_antenna(struct
 	return ret;
 }
 
+static inline int drv_remain_on_channel(struct ieee80211_local *local,
+					struct ieee80211_channel *chan,
+					enum nl80211_channel_type chantype,
+					unsigned int duration)
+{
+	int ret;
+
+	might_sleep();
+
+	trace_drv_remain_on_channel(local, chan, chantype, duration);
+	ret = local->ops->remain_on_channel(&local->hw, chan, chantype,
+					    duration);
+	trace_drv_return_int(local, ret);
+
+	return ret;
+}
+
+static inline int drv_cancel_remain_on_channel(struct ieee80211_local *local)
+{
+	int ret;
+
+	might_sleep();
+
+	trace_drv_cancel_remain_on_channel(local);
+	ret = local->ops->cancel_remain_on_channel(&local->hw);
+	trace_drv_return_int(local, ret);
+
+	return ret;
+}
+
 #endif /* __MAC80211_DRIVER_OPS */
--- wireless-testing.orig/net/mac80211/driver-trace.h	2010-12-14 17:06:55.000000000 +0100
+++ wireless-testing/net/mac80211/driver-trace.h	2010-12-14 17:07:39.000000000 +0100
@@ -933,6 +933,50 @@ TRACE_EVENT(drv_get_antenna,
 	)
 );
 
+TRACE_EVENT(drv_remain_on_channel,
+	TP_PROTO(struct ieee80211_local *local, struct ieee80211_channel *chan,
+		 enum nl80211_channel_type chantype, unsigned int duration),
+
+	TP_ARGS(local, chan, chantype, duration),
+
+	TP_STRUCT__entry(
+		LOCAL_ENTRY
+		__field(int, center_freq)
+		__field(int, channel_type)
+		__field(unsigned int, duration)
+	),
+
+	TP_fast_assign(
+		LOCAL_ASSIGN;
+		__entry->center_freq = chan->center_freq;
+		__entry->channel_type = chantype;
+		__entry->duration = duration;
+	),
+
+	TP_printk(
+		LOCAL_PR_FMT " freq:%dMHz duration:%dms",
+		LOCAL_PR_ARG, __entry->center_freq, __entry->duration
+	)
+);
+
+TRACE_EVENT(drv_cancel_remain_on_channel,
+	TP_PROTO(struct ieee80211_local *local),
+
+	TP_ARGS(local),
+
+	TP_STRUCT__entry(
+		LOCAL_ENTRY
+	),
+
+	TP_fast_assign(
+		LOCAL_ASSIGN;
+	),
+
+	TP_printk(
+		LOCAL_PR_FMT, LOCAL_PR_ARG
+	)
+);
+
 /*
  * Tracing for API calls that drivers call.
  */
@@ -1170,6 +1214,42 @@ TRACE_EVENT(api_chswitch_done,
 	)
 );
 
+TRACE_EVENT(api_ready_on_channel,
+	TP_PROTO(struct ieee80211_local *local),
+
+	TP_ARGS(local),
+
+	TP_STRUCT__entry(
+		LOCAL_ENTRY
+	),
+
+	TP_fast_assign(
+		LOCAL_ASSIGN;
+	),
+
+	TP_printk(
+		LOCAL_PR_FMT, LOCAL_PR_ARG
+	)
+);
+
+TRACE_EVENT(api_remain_on_channel_expired,
+	TP_PROTO(struct ieee80211_local *local),
+
+	TP_ARGS(local),
+
+	TP_STRUCT__entry(
+		LOCAL_ENTRY
+	),
+
+	TP_fast_assign(
+		LOCAL_ASSIGN;
+	),
+
+	TP_printk(
+		LOCAL_PR_FMT, LOCAL_PR_ARG
+	)
+);
+
 /*
  * Tracing for internal functions
  * (which may also be called in response to driver calls)

[RFC 2/2] mac80211: implement off-channel TX using hw r-o-c offload

[Johannes Berg]

From: Johannes Berg <johannes.berg@intel.com>

When the driver has remain-on-channel offload,
implement off-channel transmission using that
primitive.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
---
 net/mac80211/cfg.c         |   59 +++++++++++++++++++++++++++++++++++++++++++++
 net/mac80211/ieee80211_i.h |    2 +
 net/mac80211/offchannel.c  |   30 +++++++++++++++-------
 3 files changed, 81 insertions(+), 10 deletions(-)

--- wireless-testing.orig/net/mac80211/cfg.c	2010-12-16 08:04:15.000000000 +0100
+++ wireless-testing/net/mac80211/cfg.c	2010-12-16 14:45:18.000000000 +0100
@@ -1610,6 +1610,7 @@ static int ieee80211_remain_on_channel(s
 		ret = ieee80211_remain_on_channel_hw(local, dev,
 						     chan, channel_type,
 						     duration, cookie);
+		local->hw_roc_for_tx = false;
 		mutex_unlock(&local->mtx);
 
 		return ret;
@@ -1749,6 +1750,49 @@ static int ieee80211_mgmt_tx(struct wiph
 
 	*cookie = (unsigned long) skb;
 
+	if (is_offchan && local->ops->remain_on_channel) {
+		unsigned int duration;
+		int ret;
+
+		mutex_lock(&local->mtx);
+		/*
+		 * If the duration is zero, then the driver
+		 * wouldn't actually do anything. Set it to
+		 * 100 for now.
+		 *
+		 * TODO: cancel the off-channel operation
+		 *       when we get the SKB's TX status and
+		 *       the wait time was zero before.
+		 */
+		duration = 100;
+		if (wait)
+			duration = wait;
+		ret = ieee80211_remain_on_channel_hw(local, dev, chan,
+						     channel_type,
+						     duration, cookie);
+		if (ret) {
+			kfree_skb(skb);
+			mutex_unlock(&local->mtx);
+			return ret;
+		}
+
+		local->hw_roc_for_tx = true;
+		local->hw_roc_duration = wait;
+
+		/*
+		 * queue up frame for transmission after
+		 * ieee80211_ready_on_channel call
+		 */
+
+		/* modify cookie to prevent API mismatches */
+		*cookie ^= 2;
+		IEEE80211_SKB_CB(skb)->flags |= IEEE80211_TX_CTL_TX_OFFCHAN;
+		local->hw_roc_skb = skb;
+		mutex_unlock(&local->mtx);
+
+		return 0;
+	}
+
 	/*
 	 * Can transmit right away if the channel was the
 	 * right one and there's no wait involved... If a
@@ -1789,6 +1833,21 @@ static int ieee80211_mgmt_tx_cancel_wait
 	int ret = -ENOENT;
 
 	mutex_lock(&local->mtx);
+
+	if (local->ops->cancel_remain_on_channel) {
+		cookie ^= 2;
+		ret = ieee80211_cancel_remain_on_channel_hw(local, cookie);
+
+		if (ret == 0) {
+			kfree_skb(local->hw_roc_skb);
+			local->hw_roc_skb = NULL;
+		}
+
+		mutex_unlock(&local->mtx);
+
+		return ret;
+	}
+
 	list_for_each_entry(wk, &local->work_list, list) {
 		if (wk->sdata != sdata)
 			continue;
--- wireless-testing.orig/net/mac80211/ieee80211_i.h	2010-12-16 08:04:15.000000000 +0100
+++ wireless-testing/net/mac80211/ieee80211_i.h	2010-12-16 14:39:27.000000000 +0100
@@ -940,10 +940,12 @@ struct ieee80211_local {
 
 	struct ieee80211_channel *hw_roc_channel;
 	struct net_device *hw_roc_dev;
+	struct sk_buff *hw_roc_skb;
 	struct work_struct hw_roc_start, hw_roc_done;
 	enum nl80211_channel_type hw_roc_channel_type;
 	unsigned int hw_roc_duration;
 	u32 hw_roc_cookie;
+	bool hw_roc_for_tx;
 
 	/* dummy netdev for use w/ NAPI */
 	struct net_device napi_dev;
--- wireless-testing.orig/net/mac80211/offchannel.c	2010-12-16 08:04:15.000000000 +0100
+++ wireless-testing/net/mac80211/offchannel.c	2010-12-16 14:41:08.000000000 +0100
@@ -196,6 +196,7 @@ static void ieee80211_hw_roc_start(struc
 {
 	struct ieee80211_local *local =
 		container_of(work, struct ieee80211_local, hw_roc_start);
+	struct ieee80211_sub_if_data *sdata;
 
 	mutex_lock(&local->mtx);
 
@@ -206,11 +207,19 @@ static void ieee80211_hw_roc_start(struc
 
 	ieee80211_recalc_idle(local);
 
-	cfg80211_ready_on_channel(local->hw_roc_dev, local->hw_roc_cookie,
-				  local->hw_roc_channel,
-				  local->hw_roc_channel_type,
-				  local->hw_roc_duration,
-				  GFP_KERNEL);
+	if (local->hw_roc_skb) {
+		sdata = IEEE80211_DEV_TO_SUB_IF(local->hw_roc_dev);
+		ieee80211_tx_skb(sdata, local->hw_roc_skb);
+		local->hw_roc_skb = NULL;
+	} else {
+		cfg80211_ready_on_channel(local->hw_roc_dev,
+					  local->hw_roc_cookie,
+					  local->hw_roc_channel,
+					  local->hw_roc_channel_type,
+					  local->hw_roc_duration,
+					  GFP_KERNEL);
+	}
+
 	mutex_unlock(&local->mtx);
 }
 
@@ -236,11 +245,12 @@ static void ieee80211_hw_roc_done(struct
 		return;
 	}
 
-	cfg80211_remain_on_channel_expired(local->hw_roc_dev,
-					   local->hw_roc_cookie,
-					   local->hw_roc_channel,
-					   local->hw_roc_channel_type,
-					   GFP_KERNEL);
+	if (!local->hw_roc_for_tx)
+		cfg80211_remain_on_channel_expired(local->hw_roc_dev,
+						   local->hw_roc_cookie,
+						   local->hw_roc_channel,
+						   local->hw_roc_channel_type,
+						   GFP_KERNEL);
 
 	local->hw_roc_channel = NULL;
 	local->hw_roc_cookie = 0;

Re: [RFC 0/2] remain-on-channel HW offload

[Johannes Berg]

Chuck,

Allow me to respond on the list, this might be useful for more people.

On Thu, 2010-12-16 at 09:33 -0500, Chuck Crisler wrote:
> Johannes, I missed the discussion about this new capability. Would you 
> either give me a pointer to a doc or send me something that would allow me 
> to better understand what this is intended for? We are currently beginning a 
> re-design of our system and this might be very useful to us. At the least I 
> need to understand what it means.

I haven't really discussed this new functionality with anyone yet. So
you didn't really miss any discussion -- there was none. I just posted
the patchset out of the blue after having tried various approaches to
implementing P2P with Intel hardware.

The problem, it turns out, is that the device will refuse to receive
probe request frames unless put into a "P2P mode". Additionally, the
device implements (periodic) off-channel times for this.

Initially, I tried more involved approaches where we offload the entire
"P2P search" functionality to the device/driver. It turns out, however,
that this requires massive changes in wpa_supplicant, and after poring
over it for a couple of weeks I've come to the conclusion that I can't
make those changes in the short to medium term.

Instead, therefore, I've come up with this approach. When the supplicant
requests an off-channel period for P2P, I will hand it off to the driver
(patch 1). And when it requests an off-channel TX, I'll synthesise that
in mac80211 using the offload (patch 2) -- this I will also need to
extend later.

That's about it. Does that answer your question?

johannes