From: Johannes Berg <johannes.berg@xxxxxxxxx>
The description for buf_size was misleading and
just said you couldn't TX larger aggregates, but
of course you can't TX aggregates in a way that
would exceed the window either, which is possible
even if the aggregates are shorter than that.
Expand the description, thanks to Emmanuel for
explaining this to me.
Cc: Emmanuel Grumbach <egrumbach@xxxxxxxxx>
Signed-off-by: Johannes Berg <johannes.berg@xxxxxxxxx>
---
v2: fix explanation bug :)
include/net/mac80211.h | 15 +++++++++++++--
1 file changed, 13 insertions(+), 2 deletions(-)
--- a/include/net/mac80211.h 2011-03-31 12:26:15.000000000 +0200
+++ b/include/net/mac80211.h 2011-04-01 13:49:33.000000000 +0200
@@ -1753,8 +1753,19 @@ enum ieee80211_ampdu_mlme_action {
* that TX/RX_STOP can pass NULL for this parameter.
* The @buf_size parameter is only valid when the action is set to
* %IEEE80211_AMPDU_TX_OPERATIONAL and indicates the peer's reorder
- * buffer size (number of subframes) for this session -- aggregates
- * containing more subframes than this may not be transmitted to the peer.
+ * buffer size (number of subframes) for this session -- the driver
+ * may neither send aggregates containing more subframes than this
+ * nor send aggregates in a way that lost frames would exceed the
+ * buffer size. If just limiting the aggregate size, this would be
+ * possible with a buf_size of 8:
+ * - TX: 1.....7
+ * - RX: 2....7 (lost frame #1)
+ * - TX: 8..1...
+ * which is invalid since #1 was now re-transmitted well past the
+ * buffer size of 8. Correct ways to retransmit #1 would be:
+ * - TX: 1 or 18 or 81
+ * Even "189" would be wrong since 1 could be lost again.
+ *
* Returns a negative error code on failure.
* The callback can sleep.
*
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