cfg80211/nl80211: add DFS offload flag

Add wiphy EXT_FEATURE flag to indicate that HW or driver does
all DFS actions by itself.
User-space functionality already implemented in hostapd using
vendor-specific (QCA) OUI to advertise DFS offload support.
Need to introduce generic flag to inform about DFS offload support.
For devices with DFS_OFFLOAD flag set user-space will no longer
need to issue CAC or do any actions in response to
"radar detected" events. HW will do everything by itself and send
events to user-space to indicate that CAC was started/finished, etc.

Signed-off-by: Dmitrii Lebed <dlebed@quantenna.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

include/uapi/linux/nl80211.h

@@ -4999,6 +4999,12 @@ enum nl80211_feature_flags {
  * @NL80211_EXT_FEATURE_LOW_SPAN_SCAN: Driver supports low span scan.
  * @NL80211_EXT_FEATURE_LOW_POWER_SCAN: Driver supports low power scan.
  * @NL80211_EXT_FEATURE_HIGH_ACCURACY_SCAN: Driver supports high accuracy scan.
+ * @NL80211_EXT_FEATURE_DFS_OFFLOAD: HW/driver will offload DFS actions.
+ *	Device or driver will do all DFS-related actions by itself,
+ *	informing user-space about CAC progress, radar detection event,
+ *	channel change triggered by radar detection event.
+ *	No need to start CAC from user-space, no need to react to
+ *	"radar detected" event.
  *
  * @NUM_NL80211_EXT_FEATURES: number of extended features.
  * @MAX_NL80211_EXT_FEATURES: highest extended feature index.
@@ -5029,6 +5035,7 @@ enum nl80211_ext_feature_index {
 	NL80211_EXT_FEATURE_LOW_SPAN_SCAN,
 	NL80211_EXT_FEATURE_LOW_POWER_SCAN,
 	NL80211_EXT_FEATURE_HIGH_ACCURACY_SCAN,
+	NL80211_EXT_FEATURE_DFS_OFFLOAD,
 
 	/* add new features before the definition below */
 	NUM_NL80211_EXT_FEATURES,

net/wireless/nl80211.c

@@ -7551,12 +7551,13 @@ static int nl80211_start_radar_detection(struct sk_buff *skb,
 	struct cfg80211_registered_device *rdev = info->user_ptr[0];
 	struct net_device *dev = info->user_ptr[1];
 	struct wireless_dev *wdev = dev->ieee80211_ptr;
+	struct wiphy *wiphy = wdev->wiphy;
 	struct cfg80211_chan_def chandef;
 	enum nl80211_dfs_regions dfs_region;
 	unsigned int cac_time_ms;
 	int err;
 
-	dfs_region = reg_get_dfs_region(wdev->wiphy);
+	dfs_region = reg_get_dfs_region(wiphy);
 	if (dfs_region == NL80211_DFS_UNSET)
 		return -EINVAL;
 
@@ -7570,17 +7571,20 @@ static int nl80211_start_radar_detection(struct sk_buff *skb,
 	if (wdev->cac_started)
 		return -EBUSY;
 
-	err = cfg80211_chandef_dfs_required(wdev->wiphy, &chandef,
-					    wdev->iftype);
+	err = cfg80211_chandef_dfs_required(wiphy, &chandef, wdev->iftype);
 	if (err < 0)
 		return err;
 
 	if (err == 0)
 		return -EINVAL;
 
-	if (!cfg80211_chandef_dfs_usable(wdev->wiphy, &chandef))
+	if (!cfg80211_chandef_dfs_usable(wiphy, &chandef))
 		return -EINVAL;
 
+	/* 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;
+
 	if (!rdev->ops->start_radar_detection)
 		return -EOPNOTSUPP;