ath9k: report A-MPDU status

The ath9k hardware reports whenever an frame was part of an A-MPDU. MAC80211 already provides the necessary API to pass this additional information along to whomever needs it.

---
Knowing whenever a received frame was part of an A-MPDU allows mac80211 to react to A-MPDUs which have no valid BA agreement in place.

This patch (together with the mac80211 part in:
<http://www.spinics.net/lists/linux-wireless/msg101717.html>)
helps to improve network stability. The new code implements parts of the recommendations from 802.11-2012 10.5.4 "Error recovery upon a peer failure".

While this patch works OK, I think it still needs be improved further:
- ath9k_apply_ampdu_details is a separate subroutine and it is called a bit 'late'. However, I'm not sure if moving it to a different place like ath9k_rx_skb_preprocess
would be any better. it's because we need to have access to ampdu_ref, which is currently stored in ath_softc.rx.

- What about the MPDU delimiter crc?
Is it possible to retrieve it from the rx header, or is it lost?

- (How to handle zero length subframes?
This would be a nice to have feature [i.e.: if someone wants to check if a HT peer really cares about the ampdu density]. However it should be disabled unless we have a running monitor interface.)

BTW: Support for the AMPDU_DETAILS radiotap
extension has already been added to wireshark.
Just make sure you get the latest svn/git
source (1.9.0).

Regards,
Chr

---
 drivers/net/wireless/ath/ath9k/ath9k.h |    2 ++
 drivers/net/wireless/ath/ath9k/recv.c  |   21 +++++++++++++++++++++
 2 files changed, 23 insertions(+)

index 094a932..262fb71 100644
@@ -320,6 +320,8 @@ struct ath_rx {
 	struct ath_rx_edma rx_edma[ATH9K_RX_QUEUE_MAX];
 
 	struct sk_buff *frag;
+
+	u32 ampdu_ref;
 };
 
 int ath_startrecv(struct ath_softc *sc);

index 45f2d47..775cafd 100644
@@ -1128,6 +1128,24 @@ static void ath_process_fft(struct ath_softc *sc, struct ieee80211_hdr *hdr,
 #endif
 }
 
+static void ath9k_apply_ampdu_details(struct ath_softc *sc,
+	struct ath_rx_status *rs, struct ieee80211_rx_status *rxs)
+{
+	if (rs->rs_isaggr) {
+		rxs->flag |= RX_FLAG_AMPDU_DETAILS | RX_FLAG_AMPDU_LAST_KNOWN;
+
+		rxs->ampdu_reference = sc->rx.ampdu_ref;
+
+		if (!rs->rs_moreaggr) {
+			rxs->flag |= RX_FLAG_AMPDU_IS_LAST;
+			sc->rx.ampdu_ref++;
+		}
+
+		if (rs->rs_flags & ATH9K_RX_DELIM_CRC_PRE)
+			rxs->flag |= RX_FLAG_AMPDU_DELIM_CRC_ERROR;
+	}
+}
+
 int ath_rx_tasklet(struct ath_softc *sc, int flush, bool hp)
 {
 	struct ath_buf *bf;

@@ -1343,6 +1362,8 @@ int ath_rx_tasklet(struct ath_softc *sc, int flush, bool hp)
 		if ((ah->caps.hw_caps & ATH9K_HW_CAP_ANT_DIV_COMB) && sc->ant_rx == 3)
 			ath_ant_comb_scan(sc, &rs);
 
+		ath9k_apply_ampdu_details(sc, &rs, rxs);
+
 		ieee80211_rx(hw, skb);
 
 requeue_drop_frag:

1.7.10.4