mt76: add mt76_default_basic_rate more devices can rely on

add mt76_default_basic_rate to mt76 core more devices can rely on
to send frames which require the rate in the basic rates.
Suggested-by: Ryder Lee <ryder.lee@mediatek.com>
Signed-off-by: Sean Wang <sean.wang@mediatek.com>
Signed-off-by: Felix Fietkau <nbd@nbd.name>

drivers/net/wireless/mediatek/mt76/mac80211.c

@@ -1351,3 +1351,17 @@ mt76_init_queue(struct mt76_dev *dev, int qid, int idx, int n_desc,
 	return hwq;
 }
 EXPORT_SYMBOL_GPL(mt76_init_queue);
+
+u16 mt76_default_basic_rate(struct mt76_phy *phy, struct ieee80211_vif *vif)
+{
+	int i = ffs(vif->bss_conf.basic_rates) - 1, offset = 0;
+	struct ieee80211_rate *rate;
+
+	if (phy->chandef.chan->band == NL80211_BAND_5GHZ)
+		offset = 4;
+
+	rate = &mt76_rates[offset + i];
+
+	return rate->hw_value;
+}
+EXPORT_SYMBOL_GPL(mt76_default_basic_rate);

drivers/net/wireless/mediatek/mt76/mt76.h

@@ -891,6 +891,7 @@ int mt76_get_of_eeprom(struct mt76_dev *dev, void *data, int offset, int len);
 struct mt76_queue *
 mt76_init_queue(struct mt76_dev *dev, int qid, int idx, int n_desc,
 		int ring_base);
+u16 mt76_default_basic_rate(struct mt76_phy *phy, struct ieee80211_vif *vif);
 static inline int mt76_init_tx_queue(struct mt76_phy *phy, int qid, int idx,
 				     int n_desc, int ring_base)
 {