[PATCH 2/2] mac80211: Don't use a buf_size=0 in ADDBA requests

[Helmut Schaa <helmut.schaa@googlemail.com>]

According to 802.11-2007, 7.3.1.14 it is compliant to use a buf_size of
0 in ADDBA requests. But some devices (AVM Fritz Stick N) arn't able to
handle that correctly and will reply with an ADDBA reponse with a
buf_size of 0 which in turn will disallow BA sessions for these
devices.

To work around this problem, if the hardware doesn't specify an upper
limit for the number of subframes in an AMPDU send the maximum 0x40 by
default in ADDBA requests.

Signed-off-by: Helmut Schaa <helmut.schaa@googlemail.com>
---
 net/mac80211/agg-tx.c |    4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)

diff --git a/net/mac80211/agg-tx.c b/net/mac80211/agg-tx.c
index b7075f3..13dbd00 100644
--- a/net/mac80211/agg-tx.c
+++ b/net/mac80211/agg-tx.c
@@ -345,7 +345,9 @@ void ieee80211_tx_ba_session_handle_start(struct sta_info *sta, int tid)
 	/* send AddBA request */
 	ieee80211_send_addba_request(sdata, sta->sta.addr, tid,
 				     tid_tx->dialog_token, start_seq_num,
-				     local->hw.max_tx_aggregation_subframes,
+				     local->hw.max_tx_aggregation_subframes ?
+				     local->hw.max_tx_aggregation_subframes :
+				     0x40,
 				     tid_tx->timeout);
 }
 
-- 
1.7.3.4