ath9k: clean up block ack window handling

There's no reason to keep pointers to pending tx buffers around, if they're
only used to keep track of which frames are still pending. Use a bitfield
instead.
Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/ath/ath9k/ath9k.h

@@ -254,7 +254,7 @@ struct ath_atx_tid {
 	struct list_head buf_q;
 	struct ath_node *an;
 	struct ath_atx_ac *ac;
-	struct ath_buf *tx_buf[ATH_TID_MAX_BUFS];
+	unsigned long tx_buf[BITS_TO_LONGS(ATH_TID_MAX_BUFS)];
 	u16 seq_start;
 	u16 seq_next;
 	u16 baw_size;

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

@@ -168,9 +168,9 @@ static void ath_tx_update_baw(struct ath_softc *sc, struct ath_atx_tid *tid,
 	index  = ATH_BA_INDEX(tid->seq_start, seqno);
 	cindex = (tid->baw_head + index) & (ATH_TID_MAX_BUFS - 1);
 
-	tid->tx_buf[cindex] = NULL;
+	__clear_bit(cindex, tid->tx_buf);
 
-	while (tid->baw_head != tid->baw_tail && !tid->tx_buf[tid->baw_head]) {
+	while (tid->baw_head != tid->baw_tail && !test_bit(tid->baw_head, tid->tx_buf)) {
 		INCR(tid->seq_start, IEEE80211_SEQ_MAX);
 		INCR(tid->baw_head, ATH_TID_MAX_BUFS);
 	}
@@ -186,9 +186,7 @@ static void ath_tx_addto_baw(struct ath_softc *sc, struct ath_atx_tid *tid,
 
 	index  = ATH_BA_INDEX(tid->seq_start, bf->bf_seqno);
 	cindex = (tid->baw_head + index) & (ATH_TID_MAX_BUFS - 1);
-
-	BUG_ON(tid->tx_buf[cindex] != NULL);
-	tid->tx_buf[cindex] = bf;
+	__set_bit(cindex, tid->tx_buf);
 
 	if (index >= ((tid->baw_tail - tid->baw_head) &
 		(ATH_TID_MAX_BUFS - 1))) {