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>

drivers/net/wireless/ath/ath9k/rc.c

@@ -1518,23 +1518,11 @@ static void ath_tx_status(void *priv, struct ieee80211_supported_band *sband,
 static void ath_get_rate(void *priv, struct ieee80211_sta *sta, void *priv_sta,
 			 struct ieee80211_tx_rate_control *txrc)
 {
-	struct ieee80211_supported_band *sband = txrc->sband;
-	struct sk_buff *skb = txrc->skb;
-	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
-	struct ieee80211_tx_info *tx_info = IEEE80211_SKB_CB(skb);
 	struct ath_softc *sc = priv;
 	struct ath_rate_priv *ath_rc_priv = priv_sta;
-	__le16 fc = hdr->frame_control;
 
-	/* lowest rate for management and NO_ACK frames */
-	if (!ieee80211_is_data(fc) ||
-	    tx_info->flags & IEEE80211_TX_CTL_NO_ACK || !sta) {
-		tx_info->control.rates[0].idx = rate_lowest_index(sband, sta);
-		tx_info->control.rates[0].count =
-			(tx_info->flags & IEEE80211_TX_CTL_NO_ACK) ?
-				1 : ATH_MGT_TXMAXTRY;
+	if (rate_control_send_low(sta, priv_sta, txrc))
 		return;
-	}
 
 	/* Find tx rate for unicast frames */
 	ath_rc_ratefind(sc, ath_rc_priv, txrc);

drivers/net/wireless/iwlwifi/iwl-3945-rs.c

@@ -673,7 +673,6 @@ static void rs_get_rate(void *priv_r, struct ieee80211_sta *sta,
 	s8 scale_action = 0;
 	unsigned long flags;
 	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
-	__le16 fc;
 	u16 rate_mask = sta ? sta->supp_rates[sband->band] : 0;
 	s8 max_rate_idx = -1;
 	struct iwl_priv *priv = (struct iwl_priv *)priv_r;
@@ -681,16 +680,10 @@ static void rs_get_rate(void *priv_r, struct ieee80211_sta *sta,
 
 	IWL_DEBUG_RATE(priv, "enter\n");
 
-	/* Send management frames and NO_ACK data using lowest rate. */
-	fc = hdr->frame_control;
-	if (!ieee80211_is_data(fc) || info->flags & IEEE80211_TX_CTL_NO_ACK ||
-	    !sta || !priv_sta) {
-		IWL_DEBUG_RATE(priv, "leave: No STA priv data to update!\n");
-		info->control.rates[0].idx = rate_lowest_index(sband, sta);
-		if (info->flags & IEEE80211_TX_CTL_NO_ACK)
-			info->control.rates[0].count = 1;
+	if (rate_control_send_low(sta, priv_sta, txrc))
 		return;
-	}
+
+	rate_mask = sta->supp_rates[sband->band];
 
 	/* get user max rate if set */
 	max_rate_idx = txrc->max_rate_idx;

drivers/net/wireless/iwlwifi/iwl-agn-rs.c

@@ -2481,13 +2481,8 @@ static void rs_get_rate(void *priv_r, struct ieee80211_sta *sta, void *priv_sta,
 	}
 
 	/* Send management frames and NO_ACK data using lowest rate. */
-	if (!ieee80211_is_data(hdr->frame_control) ||
-	    info->flags & IEEE80211_TX_CTL_NO_ACK || !sta || !lq_sta) {
-		info->control.rates[0].idx = rate_lowest_index(sband, sta);
-		if (info->flags & IEEE80211_TX_CTL_NO_ACK)
-			info->control.rates[0].count = 1;
+	if (rate_control_send_low(sta, priv_sta, txrc))
 		return;
-	}
 
 	rate_idx  = lq_sta->last_txrate_idx;
 

include/net/mac80211.h

@@ -2094,6 +2094,29 @@ static inline int rate_supported(struct ieee80211_sta *sta,
 	return (sta == NULL || sta->supp_rates[band] & BIT(index));
 }
 
+/**
+ * rate_control_send_low - helper for drivers for management/no-ack frames
+ *
+ * Rate control algorithms that agree to use the lowest rate to
+ * send management frames and NO_ACK data with the respective hw
+ * retries should use this in the beginning of their mac80211 get_rate
+ * callback. If true is returned the rate control can simply return.
+ * If false is returned we guarantee that sta and sta and priv_sta is
+ * not null.
+ *
+ * Rate control algorithms wishing to do more intelligent selection of
+ * rate for multicast/broadcast frames may choose to not use this.
+ *
+ * @sta: &struct ieee80211_sta pointer to the target destination. Note
+ * 	that this may be null.
+ * @priv_sta: private rate control structure. This may be null.
+ * @txrc: rate control information we sholud populate for mac80211.
+ */
+bool rate_control_send_low(struct ieee80211_sta *sta,
+			   void *priv_sta,
+			   struct ieee80211_tx_rate_control *txrc);
+
+
 static inline s8
 rate_lowest_index(struct ieee80211_supported_band *sband,
 		  struct ieee80211_sta *sta)

net/mac80211/rate.c

@@ -198,6 +198,35 @@ static void rate_control_release(struct kref *kref)
 	kfree(ctrl_ref);
 }
 
+static bool rc_no_data_or_no_ack(struct ieee80211_tx_rate_control *txrc)
+{
+	struct sk_buff *skb = txrc->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));
+}
+
+bool rate_control_send_low(struct ieee80211_sta *sta,
+			   void *priv_sta,
+			   struct ieee80211_tx_rate_control *txrc)
+{
+	struct ieee80211_tx_info *info = IEEE80211_SKB_CB(txrc->skb);
+
+	if (!sta || !priv_sta || rc_no_data_or_no_ack(txrc)) {
+		info->control.rates[0].idx = rate_lowest_index(txrc->sband, sta);
+		info->control.rates[0].count =
+			(info->flags & IEEE80211_TX_CTL_NO_ACK) ?
+			1 : txrc->hw->max_rate_tries;
+		return true;
+	}
+	return false;
+}
+EXPORT_SYMBOL(rate_control_send_low);
+
 void rate_control_get_rate(struct ieee80211_sub_if_data *sdata,
 			   struct sta_info *sta,
 			   struct ieee80211_tx_rate_control *txrc)

net/mac80211/rc80211_minstrel.c

@@ -70,19 +70,6 @@ rix_to_ndx(struct minstrel_sta_info *mi, int rix)
 	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 @@ minstrel_get_rate(void *priv, struct ieee80211_sta *sta,
 		  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 @@ minstrel_get_rate(void *priv, struct ieee80211_sta *sta,
 	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;
 

net/mac80211/rc80211_pid_algo.c

@@ -276,11 +276,9 @@ rate_control_pid_get_rate(void *priv, struct ieee80211_sta *sta,
 {
 	struct sk_buff *skb = txrc->skb;
 	struct ieee80211_supported_band *sband = txrc->sband;
-	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
 	struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
 	struct rc_pid_sta_info *spinfo = priv_sta;
 	int rateidx;
-	__le16 fc;
 
 	if (txrc->rts)
 		info->control.rates[0].count =
@@ -290,15 +288,8 @@ rate_control_pid_get_rate(void *priv, struct ieee80211_sta *sta,
 			txrc->hw->conf.short_frame_max_tx_count;
 
 	/* Send management frames and NO_ACK data using lowest rate. */
-	fc = hdr->frame_control;
-	if (!sta || !spinfo || !ieee80211_is_data(fc) ||
-	    info->flags & IEEE80211_TX_CTL_NO_ACK) {
-		info->control.rates[0].idx = rate_lowest_index(sband, sta);
-		if (info->flags & IEEE80211_TX_CTL_NO_ACK)
-			info->control.rates[0].count = 1;
-
+	if (rate_control_send_low(sta, priv_sta, txrc))
 		return;
-	}
 
 	rateidx = spinfo->txrate_idx;