mac80211: add helper for management / no-ack frame rate decision

All current rate control algorithms agree to send management and no-ack
frames at the lowest rate. They also agree to do this when sta
and the private rate control data is NULL. We add a hlper to mac80211
for this and simplify the rate control algorithm code.

Developers wishing to make enhancements to rate control algorithms
are for broadcast/multicast can opt to not use this in their
gate_rate() mac80211 callback.

Cc: Zhu Yi <yi.zhu@intel.com>
Acked-by: Reinette Chatre <reinette.chatre@intel.com>
Cc: ipw3945-devel@lists.sourceforge.net
Cc: Gabor Juhos <juhosg@openwrt.org>
Acked-by: Felix Fietkau <nbd@openwrt.org>
Cc: Derek Smithies <derek@indranet.co.nz>
Cc: Chittajit Mitra <Chittajit.Mitra@Atheros.com>
Signed-off-by: Luis R. Rodriguez <lrodriguez@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/net/mac80211/rc80211_minstrel.c b/net/mac80211/rc80211_minstrel.c
index 5bdce0c..7c51429 100644
--- a/net/mac80211/rc80211_minstrel.c
+++ b/net/mac80211/rc80211_minstrel.c
@@ -70,19 +70,6 @@
 	return i;
 }
 
-static inline bool
-use_low_rate(struct sk_buff *skb)
-{
-	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
-	struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
-	__le16 fc;
-
-	fc = hdr->frame_control;
-
-	return ((info->flags & IEEE80211_TX_CTL_NO_ACK) || !ieee80211_is_data(fc));
-}
-
-
 static void
 minstrel_update_stats(struct minstrel_priv *mp, struct minstrel_sta_info *mi)
 {
@@ -231,7 +218,6 @@
 		  void *priv_sta, struct ieee80211_tx_rate_control *txrc)
 {
 	struct sk_buff *skb = txrc->skb;
-	struct ieee80211_supported_band *sband = txrc->sband;
 	struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
 	struct minstrel_sta_info *mi = priv_sta;
 	struct minstrel_priv *mp = priv;
@@ -244,14 +230,8 @@
 	int mrr_ndx[3];
 	int sample_rate;
 
-	if (!sta || !mi || use_low_rate(skb)) {
-		ar[0].idx = rate_lowest_index(sband, sta);
-		if (info->flags & IEEE80211_TX_CTL_NO_ACK)
-			ar[0].count = 1;
-		else
-			ar[0].count = mp->max_retry;
+	if (rate_control_send_low(sta, priv_sta, txrc))
 		return;
-	}
 
 	mrr = mp->has_mrr && !txrc->rts && !txrc->bss_conf->use_cts_prot;