cfg80211: regulatory: handle S1G channels

S1G channels have a minimum bandwidth of 1Mhz, and there
is a 1:1 mapping of allowed bandwidth to channel number.
Signed-off-by: Thomas Pedersen <thomas@adapt-ip.com>
Link: https://lore.kernel.org/r/20200908190323.15814-4-thomas@adapt-ip.comSigned-off-by: Johannes Berg <johannes.berg@intel.com>

net/wireless/reg.c

@@ -1617,9 +1617,11 @@ __freq_reg_info(struct wiphy *wiphy, u32 center_freq, u32 min_bw)
 {
 	const struct ieee80211_regdomain *regd = reg_get_regdomain(wiphy);
 	const struct ieee80211_reg_rule *reg_rule = NULL;
+	const u32 bws[] = {0, 1, 2, 4, 5, 8, 10, 16, 20};
+	int i = ARRAY_SIZE(bws) - 1;
 	u32 bw;
 
-	for (bw = MHZ_TO_KHZ(20); bw >= min_bw; bw = bw / 2) {
+	for (bw = MHZ_TO_KHZ(bws[i]); bw >= min_bw; bw = MHZ_TO_KHZ(bws[i--])) {
 		reg_rule = freq_reg_info_regd(center_freq, regd, bw);
 		if (!IS_ERR(reg_rule))
 			return reg_rule;
@@ -1631,7 +1633,9 @@ __freq_reg_info(struct wiphy *wiphy, u32 center_freq, u32 min_bw)
 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));
+	u32 min_bw = center_freq < MHZ_TO_KHZ(1000) ? 1 : 20;
+
+	return __freq_reg_info(wiphy, center_freq, MHZ_TO_KHZ(min_bw));
 }
 EXPORT_SYMBOL(freq_reg_info);
 
@@ -1659,6 +1663,7 @@ static uint32_t reg_rule_to_chan_bw_flags(const struct ieee80211_regdomain *regd
 {
 	const struct ieee80211_freq_range *freq_range = NULL;
 	u32 max_bandwidth_khz, center_freq_khz, bw_flags = 0;
+	bool is_s1g = chan->band == NL80211_BAND_S1GHZ;
 
 	freq_range = &reg_rule->freq_range;
 
@@ -1678,16 +1683,57 @@ static uint32_t reg_rule_to_chan_bw_flags(const struct ieee80211_regdomain *regd
 					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;
-	if (max_bandwidth_khz < MHZ_TO_KHZ(80))
-		bw_flags |= IEEE80211_CHAN_NO_80MHZ;
-	if (max_bandwidth_khz < MHZ_TO_KHZ(160))
-		bw_flags |= IEEE80211_CHAN_NO_160MHZ;
+	if (is_s1g) {
+		/* S1G is strict about non overlapping channels. We can
+		 * calculate which bandwidth is allowed per channel by finding
+		 * the largest bandwidth which cleanly divides the freq_range.
+		 */
+		int edge_offset;
+		int ch_bw = max_bandwidth_khz;
+
+		while (ch_bw) {
+			edge_offset = (center_freq_khz - ch_bw / 2) -
+				      freq_range->start_freq_khz;
+			if (edge_offset % ch_bw == 0) {
+				switch (KHZ_TO_MHZ(ch_bw)) {
+				case 1:
+					bw_flags |= IEEE80211_CHAN_1MHZ;
+					break;
+				case 2:
+					bw_flags |= IEEE80211_CHAN_2MHZ;
+					break;
+				case 4:
+					bw_flags |= IEEE80211_CHAN_4MHZ;
+					break;
+				case 8:
+					bw_flags |= IEEE80211_CHAN_8MHZ;
+					break;
+				case 16:
+					bw_flags |= IEEE80211_CHAN_16MHZ;
+					break;
+				default:
+					/* If we got here, no bandwidths fit on
+					 * this frequency, ie. band edge.
+					 */
+					bw_flags |= IEEE80211_CHAN_DISABLED;
+					break;
+				}
+				break;
+			}
+			ch_bw /= 2;
+		}
+	} else {
+		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;
+		if (max_bandwidth_khz < MHZ_TO_KHZ(80))
+			bw_flags |= IEEE80211_CHAN_NO_80MHZ;
+		if (max_bandwidth_khz < MHZ_TO_KHZ(160))
+			bw_flags |= IEEE80211_CHAN_NO_160MHZ;
+	}
 	return bw_flags;
 }