Subject: [PATCH] cfg80211: implement APIs for dedicated radar detection HW
From: Lorenzo Bianconi <[email-masked]>
Date: Sat, 23 Oct 2021 11:10:50 +0200

If a dedicated (off-channel) radar detection hardware (chain)
is available in the hardware/driver, allow this to be used by
calling the NL80211_CMD_RADAR_DETECT command with a new flag
attribute requesting off-channel radar detection is used.

Offchannel CAC (channel availability check) avoids the CAC
downtime when switching to a radar channel or when turning on
the AP.

Drivers advertise support for this using the new feature flag
NL80211_EXT_FEATURE_RADAR_OFFCHAN.

Tested-by: Evelyn Tsai <[email-masked]>
Signed-off-by: Lorenzo Bianconi <[email-masked]>
Link: https://lore.kernel.org/r/[email-masked]
Link: https://lore.kernel.org/r/[email-masked]
Link: https://lore.kernel.org/r/[email-masked]
Link: https://lore.kernel.org/r/[email-masked]
Link: https://lore.kernel.org/r/[email-masked]
[remove offchan_mutex, fix cfg80211_stop_offchan_radar_detection(),
 remove gfp_t argument, fix documentation, fix tracing]
Signed-off-by: Johannes Berg <[email-masked]>
---

--- a/include/net/cfg80211.h
+++ b/include/net/cfg80211.h
@@ -4060,6 +4060,15 @@ struct mgmt_frame_regs {
  * @set_sar_specs: Update the SAR (TX power) settings.
  *
  * @color_change: Initiate a color change.
+ *
+ * @set_radar_offchan: Configure dedicated offchannel chain available for
+ *	radar/CAC detection on some hw. This chain can't be used to transmit
+ *	or receive frames and it is bounded to a running wdev.
+ *	Offchannel radar/CAC detection allows to avoid the CAC downtime
+ *	switching to a different channel during CAC detection on the selected
+ *	radar channel.
+ *	The caller is expected to set chandef pointer to NULL in order to
+ *	disable offchannel CAC/radar detection.
  */
 struct cfg80211_ops {
 	int	(*suspend)(struct wiphy *wiphy, struct cfg80211_wowlan *wow);
@@ -4390,6 +4399,8 @@ struct cfg80211_ops {
 	int	(*color_change)(struct wiphy *wiphy,
 				struct net_device *dev,
 				struct cfg80211_color_change_settings *params);
+	int	(*set_radar_offchan)(struct wiphy *wiphy,
+				     struct cfg80211_chan_def *chandef);
 };
 
 /*
@@ -7611,6 +7622,20 @@ void cfg80211_cac_event(struct net_devic
 			const struct cfg80211_chan_def *chandef,
 			enum nl80211_radar_event event, gfp_t gfp);
 
+/**
+ * cfg80211_offchan_cac_event - Channel Availability Check (CAC) offchan event
+ * @wiphy: the wiphy
+ * @chandef: chandef for the current channel
+ * @event: type of event
+ *
+ * This function is called when a Channel Availability Check (CAC) is finished,
+ * started or aborted by a offchannel dedicated chain.
+ *
+ * Note that this acquires the wiphy lock.
+ */
+void cfg80211_offchan_cac_event(struct wiphy *wiphy,
+				const struct cfg80211_chan_def *chandef,
+				enum nl80211_radar_event event);
 
 /**
  * cfg80211_gtk_rekey_notify - notify userspace about driver rekeying
--- a/include/uapi/linux/nl80211.h
+++ b/include/uapi/linux/nl80211.h
@@ -2608,6 +2608,13 @@ enum nl80211_commands {
  *	Mandatory parameter for the transmitting interface to enable MBSSID.
  *	Optional for the non-transmitting interfaces.
  *
+ * @NL80211_ATTR_RADAR_OFFCHAN: Configure dedicated offchannel chain available for
+ *	radar/CAC detection on some hw. This chain can't be used to transmit
+ *	or receive frames and it is bounded to a running wdev.
+ *	Offchannel radar/CAC detection allows to avoid the CAC downtime
+ *	switching on a different channel during CAC detection on the selected
+ *	radar channel.
+ *
  * @NUM_NL80211_ATTR: total number of nl80211_attrs available
  * @NL80211_ATTR_MAX: highest attribute number currently defined
  * @__NL80211_ATTR_AFTER_LAST: internal use
@@ -3114,6 +3121,8 @@ enum nl80211_attrs {
 	NL80211_ATTR_MBSSID_CONFIG,
 	NL80211_ATTR_MBSSID_ELEMS,
 
+	NL80211_ATTR_RADAR_OFFCHAN,
+
 	/* add attributes here, update the policy in nl80211.c */
 
 	__NL80211_ATTR_AFTER_LAST,
@@ -6013,6 +6022,9 @@ enum nl80211_feature_flags {
  * @NL80211_EXT_FEATURE_BSS_COLOR: The driver supports BSS color collision
  *	detection and change announcemnts.
  *
+ * @NL80211_EXT_FEATURE_RADAR_OFFCHAN: Device supports offchannel radar/CAC
+ *	detection.
+ *
  * @NUM_NL80211_EXT_FEATURES: number of extended features.
  * @MAX_NL80211_EXT_FEATURES: highest extended feature index.
  */
@@ -6078,6 +6090,7 @@ enum nl80211_ext_feature_index {
 	NL80211_EXT_FEATURE_SECURE_RTT,
 	NL80211_EXT_FEATURE_PROT_RANGE_NEGO_AND_MEASURE,
 	NL80211_EXT_FEATURE_BSS_COLOR,
+	NL80211_EXT_FEATURE_RADAR_OFFCHAN,
 
 	/* add new features before the definition below */
 	NUM_NL80211_EXT_FEATURES,
--- a/net/wireless/core.c
+++ b/net/wireless/core.c
@@ -545,6 +545,7 @@ use_default_name:
 	INIT_WORK(&rdev->rfkill_block, cfg80211_rfkill_block_work);
 	INIT_WORK(&rdev->conn_work, cfg80211_conn_work);
 	INIT_WORK(&rdev->event_work, cfg80211_event_work);
+	INIT_DELAYED_WORK(&rdev->offchan_cac_work, cfg80211_offchan_cac_work);
 
 	init_waitqueue_head(&rdev->dev_wait);
 
@@ -1207,6 +1208,8 @@ void __cfg80211_leave(struct cfg80211_re
 
 	cfg80211_pmsr_wdev_down(wdev);
 
+	cfg80211_stop_offchan_radar_detection(wdev);
+
 	switch (wdev->iftype) {
 	case NL80211_IFTYPE_ADHOC:
 		__cfg80211_leave_ibss(rdev, dev, true);
--- a/net/wireless/core.h
+++ b/net/wireless/core.h
@@ -84,6 +84,10 @@ struct cfg80211_registered_device {
 
 	struct delayed_work dfs_update_channels_wk;
 
+	struct wireless_dev *offchan_radar_wdev;
+	struct cfg80211_chan_def offchan_radar_chandef;
+	struct delayed_work offchan_cac_work;
+
 	/* netlink port which started critical protocol (0 means not started) */
 	u32 crit_proto_nlportid;
 
@@ -491,6 +495,15 @@ cfg80211_chandef_dfs_cac_time(struct wip
 
 void cfg80211_sched_dfs_chan_update(struct cfg80211_registered_device *rdev);
 
+int
+cfg80211_start_offchan_radar_detection(struct cfg80211_registered_device *rdev,
+				       struct wireless_dev *wdev,
+				       struct cfg80211_chan_def *chandef);
+
+void cfg80211_stop_offchan_radar_detection(struct wireless_dev *wdev);
+
+void cfg80211_offchan_cac_work(struct work_struct *work);
+
 bool cfg80211_any_wiphy_oper_chan(struct wiphy *wiphy,
 				  struct ieee80211_channel *chan);
 
--- a/net/wireless/mlme.c
+++ b/net/wireless/mlme.c
@@ -970,3 +970,116 @@ void cfg80211_cac_event(struct net_devic
 	nl80211_radar_notify(rdev, chandef, event, netdev, gfp);
 }
 EXPORT_SYMBOL(cfg80211_cac_event);
+
+void cfg80211_offchan_cac_work(struct work_struct *work)
+{
+	struct delayed_work *delayed_work = to_delayed_work(work);
+	struct cfg80211_registered_device *rdev;
+
+	rdev = container_of(delayed_work, struct cfg80211_registered_device,
+			    offchan_cac_work);
+	cfg80211_offchan_cac_event(&rdev->wiphy, &rdev->offchan_radar_chandef,
+				   NL80211_RADAR_CAC_FINISHED);
+}
+
+static void
+__cfg80211_offchan_cac_event(struct cfg80211_registered_device *rdev,
+			     struct wireless_dev *wdev,
+			     const struct cfg80211_chan_def *chandef,
+			     enum nl80211_radar_event event)
+{
+	struct wiphy *wiphy = &rdev->wiphy;
+	struct net_device *netdev;
+
+	lockdep_assert_wiphy(&rdev->wiphy);
+
+	if (event != NL80211_RADAR_CAC_STARTED && !rdev->offchan_radar_wdev)
+		return;
+
+	switch (event) {
+	case NL80211_RADAR_CAC_FINISHED:
+		cfg80211_set_dfs_state(wiphy, chandef, NL80211_DFS_AVAILABLE);
+		memcpy(&rdev->cac_done_chandef, chandef, sizeof(*chandef));
+		queue_work(cfg80211_wq, &rdev->propagate_cac_done_wk);
+		cfg80211_sched_dfs_chan_update(rdev);
+		wdev = rdev->offchan_radar_wdev;
+		rdev->offchan_radar_wdev = NULL;
+		break;
+	case NL80211_RADAR_CAC_ABORTED:
+		cancel_delayed_work(&rdev->offchan_cac_work);
+		wdev = rdev->offchan_radar_wdev;
+		rdev->offchan_radar_wdev = NULL;
+		break;
+	case NL80211_RADAR_CAC_STARTED:
+		WARN_ON(!wdev);
+		rdev->offchan_radar_wdev = wdev;
+		break;
+	default:
+		return;
+	}
+
+	netdev = wdev ? wdev->netdev : NULL;
+	nl80211_radar_notify(rdev, chandef, event, netdev, GFP_KERNEL);
+}
+
+void cfg80211_offchan_cac_event(struct wiphy *wiphy,
+				const struct cfg80211_chan_def *chandef,
+				enum nl80211_radar_event event)
+{
+	struct cfg80211_registered_device *rdev = wiphy_to_rdev(wiphy);
+
+	wiphy_lock(wiphy);
+	__cfg80211_offchan_cac_event(rdev, NULL, chandef, event);
+	wiphy_unlock(wiphy);
+}
+EXPORT_SYMBOL(cfg80211_offchan_cac_event);
+
+int
+cfg80211_start_offchan_radar_detection(struct cfg80211_registered_device *rdev,
+				       struct wireless_dev *wdev,
+				       struct cfg80211_chan_def *chandef)
+{
+	unsigned int cac_time_ms;
+	int err;
+
+	lockdep_assert_wiphy(&rdev->wiphy);
+
+	if (!wiphy_ext_feature_isset(&rdev->wiphy,
+				     NL80211_EXT_FEATURE_RADAR_OFFCHAN))
+		return -EOPNOTSUPP;
+
+	if (rdev->offchan_radar_wdev)
+		return -EBUSY;
+
+	err = rdev_set_radar_offchan(rdev, chandef);
+	if (err)
+		return err;
+
+	cac_time_ms = cfg80211_chandef_dfs_cac_time(&rdev->wiphy, chandef);
+	if (!cac_time_ms)
+		cac_time_ms = IEEE80211_DFS_MIN_CAC_TIME_MS;
+
+	rdev->offchan_radar_chandef = *chandef;
+	__cfg80211_offchan_cac_event(rdev, wdev, chandef,
+				     NL80211_RADAR_CAC_STARTED);
+	queue_delayed_work(cfg80211_wq, &rdev->offchan_cac_work,
+			   msecs_to_jiffies(cac_time_ms));
+
+	return 0;
+}
+
+void cfg80211_stop_offchan_radar_detection(struct wireless_dev *wdev)
+{
+	struct wiphy *wiphy = wdev->wiphy;
+	struct cfg80211_registered_device *rdev = wiphy_to_rdev(wiphy);
+
+	lockdep_assert_wiphy(wiphy);
+
+	if (wdev != rdev->offchan_radar_wdev)
+		return;
+
+	rdev_set_radar_offchan(rdev, NULL);
+
+	__cfg80211_offchan_cac_event(rdev, NULL, NULL,
+				     NL80211_RADAR_CAC_ABORTED);
+}
--- a/net/wireless/nl80211.c
+++ b/net/wireless/nl80211.c
@@ -802,6 +802,7 @@ static const struct nla_policy nl80211_p
 	[NL80211_ATTR_MBSSID_CONFIG] =
 			NLA_POLICY_NESTED(nl80211_mbssid_config_policy),
 	[NL80211_ATTR_MBSSID_ELEMS] = { .type = NLA_NESTED },
+	[NL80211_ATTR_RADAR_OFFCHAN] = { .type = NLA_FLAG },
 };
 
 /* policy for the key attributes */
@@ -9291,12 +9292,6 @@ static int nl80211_start_radar_detection
 	if (err)
 		return err;
 
-	if (netif_carrier_ok(dev))
-		return -EBUSY;
-
-	if (wdev->cac_started)
-		return -EBUSY;
-
 	err = cfg80211_chandef_dfs_required(wiphy, &chandef, wdev->iftype);
 	if (err < 0)
 		return err;
@@ -9307,6 +9302,16 @@ static int nl80211_start_radar_detection
 	if (!cfg80211_chandef_dfs_usable(wiphy, &chandef))
 		return -EINVAL;
 
+	if (nla_get_flag(info->attrs[NL80211_ATTR_RADAR_OFFCHAN]))
+		return cfg80211_start_offchan_radar_detection(rdev, wdev,
+							      &chandef);
+
+	if (netif_carrier_ok(dev))
+		return -EBUSY;
+
+	if (wdev->cac_started)
+		return -EBUSY;
+
 	/* CAC start is offloaded to HW and can't be started manually */
 	if (wiphy_ext_feature_isset(wiphy, NL80211_EXT_FEATURE_DFS_OFFLOAD))
 		return -EOPNOTSUPP;
--- a/net/wireless/rdev-ops.h
+++ b/net/wireless/rdev-ops.h
@@ -1381,4 +1381,21 @@ static inline int rdev_color_change(stru
 	return ret;
 }
 
+static inline int
+rdev_set_radar_offchan(struct cfg80211_registered_device *rdev,
+		       struct cfg80211_chan_def *chandef)
+{
+	struct wiphy *wiphy = &rdev->wiphy;
+	int ret;
+
+	if (!rdev->ops->set_radar_offchan)
+		return -EOPNOTSUPP;
+
+	trace_rdev_set_radar_offchan(wiphy, chandef);
+	ret = rdev->ops->set_radar_offchan(wiphy, chandef);
+	trace_rdev_return_int(wiphy, ret);
+
+	return ret;
+}
+
 #endif /* __CFG80211_RDEV_OPS */
--- a/net/wireless/trace.h
+++ b/net/wireless/trace.h
@@ -3643,6 +3643,25 @@ TRACE_EVENT(cfg80211_bss_color_notify,
 		  __entry->color_bitmap)
 );
 
+TRACE_EVENT(rdev_set_radar_offchan,
+	TP_PROTO(struct wiphy *wiphy, struct cfg80211_chan_def *chandef),
+
+	TP_ARGS(wiphy, chandef),
+
+	TP_STRUCT__entry(
+		WIPHY_ENTRY
+		CHAN_DEF_ENTRY
+	),
+
+	TP_fast_assign(
+		WIPHY_ASSIGN;
+		CHAN_DEF_ASSIGN(chandef)
+	),
+
+	TP_printk(WIPHY_PR_FMT ", " CHAN_DEF_PR_FMT,
+		  WIPHY_PR_ARG, CHAN_DEF_PR_ARG)
+);
+
 #endif /* !__RDEV_OPS_TRACE || TRACE_HEADER_MULTI_READ */
 
 #undef TRACE_INCLUDE_PATH