Hello Felix,
I've stumbled into this conundrum a while ago...
then as usual: forgot that it existed, until yesterday:
As you know minstrel (our non ht fallback) enables mrr-mode
only if the driver sets hw->max_rates to 4 or more.
minstrel_ht - on the other hand - just prepares a set
of 3 rates, so at least one additional retry with
different tx-vectors remains unused...
How the last tries should be used is up for debate,
I've opted out for lowest possible MCS.
(although, some devices may also use a legacy
rate for the final tries...)
And the reason why I think it's worth to do an additional
round: The reordering penalty for lost MPDUs on the receiver-
side can be as high as 100ms, which is quite expensive compared
to some extra airtime...
---
diff --git a/net/mac80211/rc80211_minstrel_ht.c b/net/mac80211/rc80211_minstrel_ht.c
index c5b4659..5f44c0b 100644
--- a/net/mac80211/rc80211_minstrel_ht.c
+++ b/net/mac80211/rc80211_minstrel_ht.c
@@ -584,7 +584,7 @@ minstrel_ht_get_rate(void *priv, struct ieee80211_sta *sta, void *priv_sta,
struct minstrel_ht_sta_priv *msp = priv_sta;
struct minstrel_ht_sta *mi = &msp->ht;
struct minstrel_priv *mp = priv;
- int sample_idx;
+ int sample_idx, i = 0;
if (rate_control_send_low(sta, priv_sta, txrc))
return;
@@ -595,21 +595,29 @@ minstrel_ht_get_rate(void *priv, struct ieee80211_sta *sta, void *priv_sta,
info->flags |= mi->tx_flags;
sample_idx = minstrel_get_sample_rate(mp, mi);
if (sample_idx >= 0) {
- minstrel_ht_set_rate(mp, mi, &ar[0], sample_idx,
+ minstrel_ht_set_rate(mp, mi, &ar[i++], sample_idx,
txrc, true, false);
- minstrel_ht_set_rate(mp, mi, &ar[1], mi->max_tp_rate,
+ minstrel_ht_set_rate(mp, mi, &ar[i++], mi->max_tp_rate,
txrc, false, true);
info->flags |= IEEE80211_TX_CTL_RATE_CTRL_PROBE;
} else {
- minstrel_ht_set_rate(mp, mi, &ar[0], mi->max_tp_rate,
+ minstrel_ht_set_rate(mp, mi, &ar[i++], mi->max_tp_rate,
txrc, false, false);
- minstrel_ht_set_rate(mp, mi, &ar[1], mi->max_tp_rate2,
+ minstrel_ht_set_rate(mp, mi, &ar[i++], mi->max_tp_rate2,
txrc, false, true);
}
- minstrel_ht_set_rate(mp, mi, &ar[2], mi->max_prob_rate, txrc, false, true);
+ minstrel_ht_set_rate(mp, mi, &ar[i++], mi->max_prob_rate,
+ txrc, false, true);
- ar[3].count = 0;
- ar[3].idx = -1;
+ for (;i < mp->hw->max_rates; i++) {
+ minstrel_ht_set_rate(mp, mi, &ar[i++], 0,
+ txrc, false, true);
+ }
+
+ for (; i < IEEE80211_TX_MAX_RATES; i++) {
+ ar[i].count = 0;
+ ar[i].idx = -1;
+ }
mi->total_packets++;
--
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