cfg80211: add scan flag to indicate its priority

Add NL80211_SCAN_FLAG_LOW_PRIORITY flag support. It tells drivers
that this is a low priority scan request, so that they can take
necessary action.
Drivers need to advertise low priority scan capability during
registration.

Signed-off-by: Sam Leffler <sleffler@chromium.org>
Tested-by: Amitkumar Karwar <akarwar@marvell.com>
Signed-off-by: Amitkumar Karwar <akarwar@marvell.com>
Signed-off-by: Bing Zhao <bzhao@marvell.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

include/uapi/linux/nl80211.h

@@ -3048,6 +3048,7 @@ enum nl80211_ap_sme_features {
  * @NL80211_FEATURE_SAE: This driver supports simultaneous authentication of
  *	equals (SAE) with user space SME (NL80211_CMD_AUTHENTICATE) in station
  *	mode
+ * @NL80211_FEATURE_LOW_PRIORITY_SCAN: This driver supports low priority scan
  */
 enum nl80211_feature_flags {
 	NL80211_FEATURE_SK_TX_STATUS			= 1 << 0,
@@ -3056,6 +3057,7 @@ enum nl80211_feature_flags {
 	NL80211_FEATURE_CELL_BASE_REG_HINTS		= 1 << 3,
 	NL80211_FEATURE_P2P_DEVICE_NEEDS_CHANNEL	= 1 << 4,
 	NL80211_FEATURE_SAE				= 1 << 5,
+	NL80211_FEATURE_LOW_PRIORITY_SCAN		= 1 << 6,
 };
 
 /**
@@ -3096,9 +3098,11 @@ enum nl80211_connect_failed_reason {
  * Scan request control flags are used to control the handling
  * of NL80211_CMD_TRIGGER_SCAN and NL80211_CMD_START_SCHED_SCAN
  * requests.
- * (will be filled)
+ *
+ * @NL80211_SCAN_FLAG_LOW_PRIORITY: scan request has low priority
+ */
 enum nl80211_scan_flags {
+	NL80211_SCAN_FLAG_LOW_PRIORITY			= 1<<0,
 };
- */
 
 #endif /* __LINUX_NL80211_H */

net/wireless/nl80211.c

@@ -4368,9 +4368,15 @@ static int nl80211_trigger_scan(struct sk_buff *skb, struct genl_info *info)
 		}
 	}
 
-	if (info->attrs[NL80211_ATTR_SCAN_FLAGS])
+	if (info->attrs[NL80211_ATTR_SCAN_FLAGS]) {
 		request->flags = nla_get_u32(
 			info->attrs[NL80211_ATTR_SCAN_FLAGS]);
+		if ((request->flags & NL80211_SCAN_FLAG_LOW_PRIORITY) &&
+		    !(wiphy->features & NL80211_FEATURE_LOW_PRIORITY_SCAN)) {
+			err = -EOPNOTSUPP;
+			goto out_free;
+		}
+	}
 
 	request->no_cck =
 		nla_get_flag(info->attrs[NL80211_ATTR_TX_NO_CCK_RATE]);
@@ -4603,9 +4609,15 @@ static int nl80211_start_sched_scan(struct sk_buff *skb,
 		       request->ie_len);
 	}
 
-	if (info->attrs[NL80211_ATTR_SCAN_FLAGS])
+	if (info->attrs[NL80211_ATTR_SCAN_FLAGS]) {
 		request->flags = nla_get_u32(
 			info->attrs[NL80211_ATTR_SCAN_FLAGS]);
+		if ((request->flags & NL80211_SCAN_FLAG_LOW_PRIORITY) &&
+		    !(wiphy->features & NL80211_FEATURE_LOW_PRIORITY_SCAN)) {
+			err = -EOPNOTSUPP;
+			goto out_free;
+		}
+	}
 
 	request->dev = dev;
 	request->wiphy = &rdev->wiphy;