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>
diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h
index a27921e..3e4ac3f 100644
--- a/net/mac80211/ieee80211_i.h
+++ b/net/mac80211/ieee80211_i.h
@@ -494,8 +494,8 @@
 	 */
 	struct ieee80211_if_ap *bss;
 
-	int force_unicast_rateidx; /* forced TX rateidx for unicast frames */
-	int max_ratectrl_rateidx; /* max TX rateidx for rate control */
+	/* bitmap of allowed (non-MCS) rate indexes for rate control */
+	u32 rc_rateidx_mask[IEEE80211_NUM_BANDS];
 
 	union {
 		struct ieee80211_if_ap ap;