cfg80211: regulatory: handle 5 and 10 MHz channels properly

The original assumption of 20MHz wide channels hasn't been true since
the addition of support for 5 and 10 MHz channels.
Change the code to no longer disable all channels that don't fit into
the 20MHz grid, but instead set the appropriate flags to disable
operation on specific bandwidths.
Signed-off-by: Matthias May <matthias.may@neratec.com>
[reword commit message]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/wireless/reg.c

@@ -1004,7 +1004,7 @@ static u32 map_regdom_flags(u32 rd_flags)
 
 static const struct ieee80211_reg_rule *
 freq_reg_info_regd(struct wiphy *wiphy, u32 center_freq,
-		   const struct ieee80211_regdomain *regd)
+		   const struct ieee80211_regdomain *regd, u32 bw)
 {
 	int i;
 	bool band_rule_found = false;
@@ -1028,7 +1028,7 @@ freq_reg_info_regd(struct wiphy *wiphy, u32 center_freq,
 		if (!band_rule_found)
 			band_rule_found = freq_in_rule_band(fr, center_freq);
 
-		bw_fits = reg_does_bw_fit(fr, center_freq, MHZ_TO_KHZ(20));
+		bw_fits = reg_does_bw_fit(fr, center_freq, bw);
 
 		if (band_rule_found && bw_fits)
 			return rr;
@@ -1040,14 +1040,26 @@ freq_reg_info_regd(struct wiphy *wiphy, u32 center_freq,
 	return ERR_PTR(-EINVAL);
 }
 
-const struct ieee80211_reg_rule *freq_reg_info(struct wiphy *wiphy,
-					       u32 center_freq)
+const struct ieee80211_reg_rule *__freq_reg_info(struct wiphy *wiphy,
+						 u32 center_freq, u32 min_bw)
 {
-	const struct ieee80211_regdomain *regd;
+	const struct ieee80211_regdomain *regd = reg_get_regdomain(wiphy);
+	const struct ieee80211_reg_rule *reg_rule = NULL;
+	u32 bw;
 
-	regd = reg_get_regdomain(wiphy);
+	for (bw = MHZ_TO_KHZ(20); bw >= min_bw; bw = bw / 2) {
+		reg_rule = freq_reg_info_regd(wiphy, center_freq, regd, bw);
+		if (!IS_ERR(reg_rule))
+			return reg_rule;
+	}
 
-	return freq_reg_info_regd(wiphy, center_freq, regd);
+	return reg_rule;
+}
+
+const struct ieee80211_reg_rule *freq_reg_info(struct wiphy *wiphy,
+					       u32 center_freq)
+{
+	return __freq_reg_info(wiphy, center_freq, MHZ_TO_KHZ(20));
 }
 EXPORT_SYMBOL(freq_reg_info);
 
@@ -1176,8 +1188,20 @@ static void handle_channel(struct wiphy *wiphy,
 	if (reg_rule->flags & NL80211_RRF_AUTO_BW)
 		max_bandwidth_khz = reg_get_max_bandwidth(regd, reg_rule);
 
+	/* If we get a reg_rule we can assume that at least 5Mhz fit */
+	if (!reg_does_bw_fit(freq_range, MHZ_TO_KHZ(chan->center_freq),
+			     MHZ_TO_KHZ(10)))
+		bw_flags |= IEEE80211_CHAN_NO_10MHZ;
+	if (!reg_does_bw_fit(freq_range, MHZ_TO_KHZ(chan->center_freq),
+			     MHZ_TO_KHZ(20)))
+		bw_flags |= IEEE80211_CHAN_NO_20MHZ;
+
+	if (max_bandwidth_khz < MHZ_TO_KHZ(10))
+		bw_flags |= IEEE80211_CHAN_NO_10MHZ;
+	if (max_bandwidth_khz < MHZ_TO_KHZ(20))
+		bw_flags |= IEEE80211_CHAN_NO_20MHZ;
 	if (max_bandwidth_khz < MHZ_TO_KHZ(40))
-		bw_flags = IEEE80211_CHAN_NO_HT40;
+		bw_flags |= IEEE80211_CHAN_NO_HT40;
 	if (max_bandwidth_khz < MHZ_TO_KHZ(80))
 		bw_flags |= IEEE80211_CHAN_NO_80MHZ;
 	if (max_bandwidth_khz < MHZ_TO_KHZ(160))
@@ -1695,9 +1719,15 @@ static void handle_channel_custom(struct wiphy *wiphy,
 	const struct ieee80211_power_rule *power_rule = NULL;
 	const struct ieee80211_freq_range *freq_range = NULL;
 	u32 max_bandwidth_khz;
+	u32 bw;
 
-	reg_rule = freq_reg_info_regd(wiphy, MHZ_TO_KHZ(chan->center_freq),
-				      regd);
+	for (bw = MHZ_TO_KHZ(20); bw >= MHZ_TO_KHZ(5); bw = bw / 2) {
+		reg_rule = freq_reg_info_regd(wiphy,
+					      MHZ_TO_KHZ(chan->center_freq),
+					      regd, bw);
+		if (!IS_ERR(reg_rule))
+			break;
+	}
 
 	if (IS_ERR(reg_rule)) {
 		REG_DBG_PRINT("Disabling freq %d MHz as custom regd has no rule that fits it\n",
@@ -1721,8 +1751,20 @@ static void handle_channel_custom(struct wiphy *wiphy,
 	if (reg_rule->flags & NL80211_RRF_AUTO_BW)
 		max_bandwidth_khz = reg_get_max_bandwidth(regd, reg_rule);
 
+	/* If we get a reg_rule we can assume that at least 5Mhz fit */
+	if (!reg_does_bw_fit(freq_range, MHZ_TO_KHZ(chan->center_freq),
+			     MHZ_TO_KHZ(10)))
+		bw_flags |= IEEE80211_CHAN_NO_10MHZ;
+	if (!reg_does_bw_fit(freq_range, MHZ_TO_KHZ(chan->center_freq),
+			     MHZ_TO_KHZ(20)))
+		bw_flags |= IEEE80211_CHAN_NO_20MHZ;
+
+	if (max_bandwidth_khz < MHZ_TO_KHZ(10))
+		bw_flags |= IEEE80211_CHAN_NO_10MHZ;
+	if (max_bandwidth_khz < MHZ_TO_KHZ(20))
+		bw_flags |= IEEE80211_CHAN_NO_20MHZ;
 	if (max_bandwidth_khz < MHZ_TO_KHZ(40))
-		bw_flags = IEEE80211_CHAN_NO_HT40;
+		bw_flags |= IEEE80211_CHAN_NO_HT40;
 	if (max_bandwidth_khz < MHZ_TO_KHZ(80))
 		bw_flags |= IEEE80211_CHAN_NO_80MHZ;
 	if (max_bandwidth_khz < MHZ_TO_KHZ(160))