cfg80211/mac80211: Use more generic bitrate mask for rate control

Extend struct cfg80211_bitrate_mask to actually use a bitfield mask
instead of just a single fixed or maximum rate index. This change
itself does not modify the behavior (except for debugfs files), but it
prepares cfg80211 and mac80211 for a new nl80211 command for setting
which rates can be used in TX rate control.

Since frames are now going through the rate control algorithm
unconditionally, the internal IEEE80211_TX_INTFL_RCALGO flag can now
be removed. The RC implementations can use the rate_idx_mask value to
optimize their behavior if only a single rate is enabled.

The old max_rate_idx in struct ieee80211_tx_rate_control is maintained
(but commented as deprecated) for backwards compatibility with existing
RC implementations. Once these implementations have been updated to
use the more generic rate_idx_mask, the max_rate_idx value can be
removed.

Signed-off-by: Jouni Malinen <jouni.malinen@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 52 insertions, 11 deletions

diff --git a/net/mac80211/rate.c b/net/mac80211/rate.c
index 6349e7f..c74b7c8 100644
--- a/net/mac80211/rate.c
+++ b/net/mac80211/rate.c
@@ -249,6 +249,38 @@ bool rate_control_send_low(struct ieee80211_sta *sta,
 }
 EXPORT_SYMBOL(rate_control_send_low);
 
+static void rate_idx_match_mask(struct ieee80211_tx_rate *rate,
+				int n_bitrates, u32 mask)
+{
+	int j;
+
+	/* See whether the selected rate or anything below it is allowed. */
+	for (j = rate->idx; j >= 0; j--) {
+		if (mask & (1 << j)) {
+			/* Okay, found a suitable rate. Use it. */
+			rate->idx = j;
+			return;
+		}
+	}
+
+	/* Try to find a higher rate that would be allowed */
+	for (j = rate->idx + 1; j < n_bitrates; j++) {
+		if (mask & (1 << j)) {
+			/* Okay, found a suitable rate. Use it. */
+			rate->idx = j;
+			return;
+		}
+	}
+
+	/*
+	 * Uh.. No suitable rate exists. This should not really happen with
+	 * sane TX rate mask configurations. However, should someone manage to
+	 * configure supported rates and TX rate mask in incompatible way,
+	 * allow the frame to be transmitted with whatever the rate control
+	 * selected.
+	 */
+}
+
 void rate_control_get_rate(struct ieee80211_sub_if_data *sdata,
 			   struct sta_info *sta,
 			   struct ieee80211_tx_rate_control *txrc)
@@ -258,6 +290,7 @@ void rate_control_get_rate(struct ieee80211_sub_if_data *sdata,
 	struct ieee80211_sta *ista = NULL;
 	struct ieee80211_tx_info *info = IEEE80211_SKB_CB(txrc->skb);
 	int i;
+	u32 mask;
 
 	if (sta) {
 		ista = &sta->sta;
@@ -270,23 +303,31 @@ void rate_control_get_rate(struct ieee80211_sub_if_data *sdata,
 		info->control.rates[i].count = 1;
 	}
 
-	if (sta && sdata->force_unicast_rateidx > -1) {
-		info->control.rates[0].idx = sdata->force_unicast_rateidx;
-	} else {
-		ref->ops->get_rate(ref->priv, ista, priv_sta, txrc);
-		info->flags |= IEEE80211_TX_INTFL_RCALGO;
-	}
+	ref->ops->get_rate(ref->priv, ista, priv_sta, txrc);
 
 	/*
-	 * try to enforce the maximum rate the user wanted
+	 * Try to enforce the rateidx mask the user wanted. skip this if the
+	 * default mask (allow all rates) is used to save some processing for
+	 * the common case.
 	 */
-	if (sdata->max_ratectrl_rateidx > -1)
+	mask = sdata->rc_rateidx_mask[info->band];
+	if (mask != (1 << txrc->sband->n_bitrates) - 1) {
+		if (sta) {
+			/* Filter out rates that the STA does not support */
+			mask &= sta->sta.supp_rates[info->band];
+		}
+		/*
+		 * Make sure the rate index selected for each TX rate is
+		 * included in the configured mask and change the rate indexes
+		 * if needed.
+		 */
 		for (i = 0; i < IEEE80211_TX_MAX_RATES; i++) {
+			/* Rate masking supports only legacy rates for now */
 			if (info->control.rates[i].flags & IEEE80211_TX_RC_MCS)
 				continue;
-			info->control.rates[i].idx =
-				min_t(s8, info->control.rates[i].idx,
-				      sdata->max_ratectrl_rateidx);
+			rate_idx_match_mask(&info->control.rates[i],
+					    txrc->sband->n_bitrates, mask);
+		}
 	}
 
 	BUG_ON(info->control.rates[0].idx < 0);