cfg80211: don't allow drivers to unset NL80211_FEATURE_SCAN_FLUSH

As the flag is entirely implemented in cfg80211, it should
have been a global feature flag (which I believe didn't
exist at the time). However, there's no reason to allow
drivers to unset the flag, so don't allow it and remove
the validation of NL80211_SCAN_FLAG_FLUSH.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/wireless/core.c

@@ -357,8 +357,6 @@ struct wiphy *wiphy_new(const struct cfg80211_ops *ops, int sizeof_priv)
 	rdev->wiphy.rts_threshold = (u32) -1;
 	rdev->wiphy.coverage_class = 0;
 
-	rdev->wiphy.features = NL80211_FEATURE_SCAN_FLUSH;
-
 	return &rdev->wiphy;
 }
 EXPORT_SYMBOL(wiphy_new);
@@ -566,6 +564,8 @@ int wiphy_register(struct wiphy *wiphy)
 	/* check and set up bitrates */
 	ieee80211_set_bitrate_flags(wiphy);
 
+	rdev->wiphy.features |= NL80211_FEATURE_SCAN_FLUSH;
+
 	rtnl_lock();
 	res = device_add(&rdev->wiphy.dev);
 	if (res) {

net/wireless/nl80211.c

@@ -5342,10 +5342,8 @@ static int nl80211_trigger_scan(struct sk_buff *skb, struct genl_info *info)
 	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)) ||
-		    ((request->flags & NL80211_SCAN_FLAG_FLUSH) &&
-		     !(wiphy->features & NL80211_FEATURE_SCAN_FLUSH))) {
+		if ((request->flags & NL80211_SCAN_FLAG_LOW_PRIORITY) &&
+		    !(wiphy->features & NL80211_FEATURE_LOW_PRIORITY_SCAN)) {
 			err = -EOPNOTSUPP;
 			goto out_free;
 		}
@@ -5585,10 +5583,8 @@ static int nl80211_start_sched_scan(struct sk_buff *skb,
 	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)) ||
-		    ((request->flags & NL80211_SCAN_FLAG_FLUSH) &&
-		     !(wiphy->features & NL80211_FEATURE_SCAN_FLUSH))) {
+		if ((request->flags & NL80211_SCAN_FLAG_LOW_PRIORITY) &&
+		    !(wiphy->features & NL80211_FEATURE_LOW_PRIORITY_SCAN)) {
 			err = -EOPNOTSUPP;
 			goto out_free;
 		}