2 * Copyright (C) 2010 Felix Fietkau <nbd@openwrt.org>
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License version 2 as
6 * published by the Free Software Foundation.
8 #include <linux/netdevice.h>
9 #include <linux/types.h>
10 #include <linux/skbuff.h>
11 #include <linux/debugfs.h>
12 #include <linux/random.h>
13 #include <linux/ieee80211.h>
14 #include <net/mac80211.h>
16 #include "rc80211_minstrel.h"
17 #include "rc80211_minstrel_ht.h"
19 #define AVG_PKT_SIZE 1200
20 #define SAMPLE_COLUMNS 10
23 /* Number of bits for an average sized packet */
24 #define MCS_NBITS (AVG_PKT_SIZE << 3)
26 /* Number of symbols for a packet with (bps) bits per symbol */
27 #define MCS_NSYMS(bps) ((MCS_NBITS + (bps) - 1) / (bps))
29 /* Transmission time for a packet containing (syms) symbols */
30 #define MCS_SYMBOL_TIME(sgi, syms) \
32 ((syms) * 18 + 4) / 5 : /* syms * 3.6 us */ \
33 (syms) << 2 /* syms * 4 us */ \
36 /* Transmit duration for the raw data part of an average sized packet */
37 #define MCS_DURATION(streams, sgi, bps) MCS_SYMBOL_TIME(sgi, MCS_NSYMS((streams) * (bps)))
39 /* MCS rate information for an MCS group */
40 #define MCS_GROUP(_streams, _sgi, _ht40) { \
41 .streams = _streams, \
43 (_sgi ? IEEE80211_TX_RC_SHORT_GI : 0) | \
44 (_ht40 ? IEEE80211_TX_RC_40_MHZ_WIDTH : 0), \
46 MCS_DURATION(_streams, _sgi, _ht40 ? 54 : 26), \
47 MCS_DURATION(_streams, _sgi, _ht40 ? 108 : 52), \
48 MCS_DURATION(_streams, _sgi, _ht40 ? 162 : 78), \
49 MCS_DURATION(_streams, _sgi, _ht40 ? 216 : 104), \
50 MCS_DURATION(_streams, _sgi, _ht40 ? 324 : 156), \
51 MCS_DURATION(_streams, _sgi, _ht40 ? 432 : 208), \
52 MCS_DURATION(_streams, _sgi, _ht40 ? 486 : 234), \
53 MCS_DURATION(_streams, _sgi, _ht40 ? 540 : 260) \
58 * To enable sufficiently targeted rate sampling, MCS rates are divided into
59 * groups, based on the number of streams and flags (HT40, SGI) that they
62 const struct mcs_group minstrel_mcs_groups[] = {
65 #if MINSTREL_MAX_STREAMS >= 3
71 #if MINSTREL_MAX_STREAMS >= 3
77 #if MINSTREL_MAX_STREAMS >= 3
83 #if MINSTREL_MAX_STREAMS >= 3
88 static u8 sample_table[SAMPLE_COLUMNS][MCS_GROUP_RATES];
91 * Perform EWMA (Exponentially Weighted Moving Average) calculation
94 minstrel_ewma(int old, int new, int weight)
96 return (new * (100 - weight) + old * weight) / 100;
100 * Look up an MCS group index based on mac80211 rate information
103 minstrel_ht_get_group_idx(struct ieee80211_tx_rate *rate)
105 int streams = (rate->idx / MCS_GROUP_RATES) + 1;
106 u32 flags = IEEE80211_TX_RC_SHORT_GI | IEEE80211_TX_RC_40_MHZ_WIDTH;
109 for (i = 0; i < ARRAY_SIZE(minstrel_mcs_groups); i++) {
110 if (minstrel_mcs_groups[i].streams != streams)
112 if (minstrel_mcs_groups[i].flags != (rate->flags & flags))
122 static inline struct minstrel_rate_stats *
123 minstrel_get_ratestats(struct minstrel_ht_sta *mi, int index)
125 return &mi->groups[index / MCS_GROUP_RATES].rates[index % MCS_GROUP_RATES];
130 * Recalculate success probabilities and counters for a rate using EWMA
133 minstrel_calc_rate_ewma(struct minstrel_priv *mp, struct minstrel_rate_stats *mr)
135 if (unlikely(mr->attempts > 0)) {
136 mr->sample_skipped = 0;
137 mr->cur_prob = MINSTREL_FRAC(mr->success, mr->attempts);
139 mr->probability = mr->cur_prob;
141 mr->probability = minstrel_ewma(mr->probability,
142 mr->cur_prob, EWMA_LEVEL);
143 mr->att_hist += mr->attempts;
144 mr->succ_hist += mr->success;
146 mr->sample_skipped++;
148 mr->last_success = mr->success;
149 mr->last_attempts = mr->attempts;
155 * Calculate throughput based on the average A-MPDU length, taking into account
156 * the expected number of retransmissions and their expected length
159 minstrel_ht_calc_tp(struct minstrel_priv *mp, struct minstrel_ht_sta *mi,
162 struct minstrel_rate_stats *mr;
165 mr = &mi->groups[group].rates[rate];
167 if (mr->probability < MINSTREL_FRAC(1, 10)) {
172 usecs = mi->overhead / MINSTREL_TRUNC(mi->avg_ampdu_len);
173 usecs += minstrel_mcs_groups[group].duration[rate];
174 mr->cur_tp = MINSTREL_TRUNC((1000000 / usecs) * mr->probability);
178 * Update rate statistics and select new primary rates
180 * Rules for rate selection:
181 * - max_prob_rate must use only one stream, as a tradeoff between delivery
182 * probability and throughput during strong fluctuations
183 * - as long as the max prob rate has a probability of more than 3/4, pick
184 * higher throughput rates, even if the probablity is a bit lower
187 minstrel_ht_update_stats(struct minstrel_priv *mp, struct minstrel_ht_sta *mi)
189 struct minstrel_mcs_group_data *mg;
190 struct minstrel_rate_stats *mr;
191 int cur_prob, cur_prob_tp, cur_tp, cur_tp2;
194 if (mi->ampdu_packets > 0) {
195 mi->avg_ampdu_len = minstrel_ewma(mi->avg_ampdu_len,
196 MINSTREL_FRAC(mi->ampdu_len, mi->ampdu_packets), EWMA_LEVEL);
198 mi->ampdu_packets = 0;
202 mi->sample_count = 0;
204 mi->max_tp_rate2 = 0;
205 mi->max_prob_rate = 0;
207 for (group = 0; group < ARRAY_SIZE(minstrel_mcs_groups); group++) {
213 mg = &mi->groups[group];
218 mg->max_tp_rate2 = 0;
219 mg->max_prob_rate = 0;
222 for (i = 0; i < MCS_GROUP_RATES; i++) {
223 if (!(mg->supported & BIT(i)))
227 mr->retry_updated = false;
228 index = MCS_GROUP_RATES * group + i;
229 minstrel_calc_rate_ewma(mp, mr);
230 minstrel_ht_calc_tp(mp, mi, group, i);
235 /* ignore the lowest rate of each single-stream group */
236 if (!i && minstrel_mcs_groups[group].streams == 1)
239 if ((mr->cur_tp > cur_prob_tp && mr->probability >
240 MINSTREL_FRAC(3, 4)) || mr->probability > cur_prob) {
241 mg->max_prob_rate = index;
242 cur_prob = mr->probability;
245 if (mr->cur_tp > cur_tp) {
246 swap(index, mg->max_tp_rate);
248 mr = minstrel_get_ratestats(mi, index);
251 if (index >= mg->max_tp_rate)
254 if (mr->cur_tp > cur_tp2) {
255 mg->max_tp_rate2 = index;
256 cur_tp2 = mr->cur_tp;
261 /* try to sample up to half of the availble rates during each interval */
262 mi->sample_count *= 4;
268 for (group = 0; group < ARRAY_SIZE(minstrel_mcs_groups); group++) {
269 mg = &mi->groups[group];
273 mr = minstrel_get_ratestats(mi, mg->max_prob_rate);
274 if (cur_prob_tp < mr->cur_tp &&
275 minstrel_mcs_groups[group].streams == 1) {
276 mi->max_prob_rate = mg->max_prob_rate;
277 cur_prob = mr->cur_prob;
280 mr = minstrel_get_ratestats(mi, mg->max_tp_rate);
281 if (cur_tp < mr->cur_tp) {
282 mi->max_tp_rate = mg->max_tp_rate;
286 mr = minstrel_get_ratestats(mi, mg->max_tp_rate2);
287 if (cur_tp2 < mr->cur_tp) {
288 mi->max_tp_rate2 = mg->max_tp_rate2;
289 cur_tp2 = mr->cur_tp;
293 mi->stats_update = jiffies;
297 minstrel_ht_txstat_valid(struct ieee80211_tx_rate *rate)
305 return !!(rate->flags & IEEE80211_TX_RC_MCS);
309 minstrel_next_sample_idx(struct minstrel_ht_sta *mi)
311 struct minstrel_mcs_group_data *mg;
315 mi->sample_group %= ARRAY_SIZE(minstrel_mcs_groups);
316 mg = &mi->groups[mi->sample_group];
321 if (++mg->index >= MCS_GROUP_RATES) {
323 if (++mg->column >= ARRAY_SIZE(sample_table))
331 minstrel_downgrade_rate(struct minstrel_ht_sta *mi, unsigned int *idx,
334 int group, orig_group;
336 orig_group = group = *idx / MCS_GROUP_RATES;
340 if (!mi->groups[group].supported)
343 if (minstrel_mcs_groups[group].streams >
344 minstrel_mcs_groups[orig_group].streams)
348 *idx = mi->groups[group].max_tp_rate;
350 *idx = mi->groups[group].max_tp_rate2;
356 minstrel_aggr_check(struct minstrel_priv *mp, struct ieee80211_sta *pubsta, struct sk_buff *skb)
358 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
359 struct sta_info *sta = container_of(pubsta, struct sta_info, sta);
362 if (unlikely(!ieee80211_is_data_qos(hdr->frame_control)))
365 if (unlikely(skb->protocol == cpu_to_be16(ETH_P_PAE)))
368 tid = *ieee80211_get_qos_ctl(hdr) & IEEE80211_QOS_CTL_TID_MASK;
369 if (likely(sta->ampdu_mlme.tid_tx[tid]))
372 ieee80211_start_tx_ba_session(pubsta, tid);
376 minstrel_ht_tx_status(void *priv, struct ieee80211_supported_band *sband,
377 struct ieee80211_sta *sta, void *priv_sta,
380 struct minstrel_ht_sta_priv *msp = priv_sta;
381 struct minstrel_ht_sta *mi = &msp->ht;
382 struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
383 struct ieee80211_tx_rate *ar = info->status.rates;
384 struct minstrel_rate_stats *rate, *rate2;
385 struct minstrel_priv *mp = priv;
391 return mac80211_minstrel.tx_status(priv, sband, sta, &msp->legacy, skb);
393 /* This packet was aggregated but doesn't carry status info */
394 if ((info->flags & IEEE80211_TX_CTL_AMPDU) &&
395 !(info->flags & IEEE80211_TX_STAT_AMPDU))
398 if (!info->status.ampdu_len) {
399 info->status.ampdu_ack_len = 1;
400 info->status.ampdu_len = 1;
404 mi->ampdu_len += info->status.ampdu_len;
406 if (!mi->sample_wait && !mi->sample_tries && mi->sample_count > 0) {
407 mi->sample_wait = 4 + 2 * MINSTREL_TRUNC(mi->avg_ampdu_len);
408 mi->sample_tries = 3;
412 if (info->flags & IEEE80211_TX_CTL_RATE_CTRL_PROBE) {
413 mi->sample_packets += info->status.ampdu_len;
414 minstrel_next_sample_idx(mi);
417 for (i = 0; !last; i++) {
418 last = (i == IEEE80211_TX_MAX_RATES - 1) ||
419 !minstrel_ht_txstat_valid(&ar[i + 1]);
421 if (!minstrel_ht_txstat_valid(&ar[i]))
424 group = minstrel_ht_get_group_idx(&ar[i]);
425 rate = &mi->groups[group].rates[ar[i].idx % 8];
427 if (last && (info->flags & IEEE80211_TX_STAT_ACK))
428 rate->success += info->status.ampdu_ack_len;
430 rate->attempts += ar[i].count * info->status.ampdu_len;
434 * check for sudden death of spatial multiplexing,
435 * downgrade to a lower number of streams if necessary.
437 rate = minstrel_get_ratestats(mi, mi->max_tp_rate);
438 if (rate->attempts > 30 &&
439 MINSTREL_FRAC(rate->success, rate->attempts) <
440 MINSTREL_FRAC(20, 100))
441 minstrel_downgrade_rate(mi, &mi->max_tp_rate, true);
443 rate2 = minstrel_get_ratestats(mi, mi->max_tp_rate2);
444 if (rate->attempts > 30 &&
445 MINSTREL_FRAC(rate->success, rate->attempts) <
446 MINSTREL_FRAC(20, 100))
447 minstrel_downgrade_rate(mi, &mi->max_tp_rate2, false);
449 if (time_after(jiffies, mi->stats_update + (mp->update_interval / 2 * HZ) / 1000)) {
450 minstrel_ht_update_stats(mp, mi);
451 minstrel_aggr_check(mp, sta, skb);
456 minstrel_calc_retransmit(struct minstrel_priv *mp, struct minstrel_ht_sta *mi,
459 struct minstrel_rate_stats *mr;
460 const struct mcs_group *group;
461 unsigned int tx_time, tx_time_rtscts, tx_time_data;
462 unsigned int cw = mp->cw_min;
463 unsigned int t_slot = 9; /* FIXME */
464 unsigned int ampdu_len = MINSTREL_TRUNC(mi->avg_ampdu_len);
466 mr = minstrel_get_ratestats(mi, index);
467 if (mr->probability < MINSTREL_FRAC(1, 10)) {
469 mr->retry_count_rtscts = 1;
474 mr->retry_count_rtscts = 2;
475 mr->retry_updated = true;
477 group = &minstrel_mcs_groups[index / MCS_GROUP_RATES];
478 tx_time_data = group->duration[index % MCS_GROUP_RATES] * ampdu_len;
479 tx_time = 2 * (t_slot + mi->overhead + tx_time_data);
480 tx_time_rtscts = 2 * (t_slot + mi->overhead_rtscts + tx_time_data);
483 cw = min(cw, mp->cw_max);
484 tx_time += cw + t_slot + mi->overhead;
485 tx_time_rtscts += cw + t_slot + mi->overhead_rtscts;
486 if (tx_time_rtscts < mp->segment_size)
487 mr->retry_count_rtscts++;
488 } while ((tx_time < mp->segment_size) &&
489 (++mr->retry_count < mp->max_retry));
494 minstrel_ht_set_rate(struct minstrel_priv *mp, struct minstrel_ht_sta *mi,
495 struct ieee80211_tx_rate *rate, int index,
496 struct ieee80211_tx_rate_control *txrc,
497 bool sample, bool rtscts)
499 const struct mcs_group *group = &minstrel_mcs_groups[index / MCS_GROUP_RATES];
500 struct minstrel_rate_stats *mr;
502 mr = minstrel_get_ratestats(mi, index);
503 if (!mr->retry_updated)
504 minstrel_calc_retransmit(mp, mi, index);
506 if (mr->probability < MINSTREL_FRAC(20, 100))
509 rate->count = mr->retry_count_rtscts;
511 rate->count = mr->retry_count;
513 rate->flags = IEEE80211_TX_RC_MCS | group->flags;
514 if (txrc->short_preamble)
515 rate->flags |= IEEE80211_TX_RC_USE_SHORT_PREAMBLE;
516 if (txrc->rts || rtscts)
517 rate->flags |= IEEE80211_TX_RC_USE_RTS_CTS;
518 rate->idx = index % MCS_GROUP_RATES + (group->streams - 1) * MCS_GROUP_RATES;
522 minstrel_get_duration(int index)
524 const struct mcs_group *group = &minstrel_mcs_groups[index / MCS_GROUP_RATES];
525 return group->duration[index % MCS_GROUP_RATES];
529 minstrel_get_sample_rate(struct minstrel_priv *mp, struct minstrel_ht_sta *mi)
531 struct minstrel_rate_stats *mr;
532 struct minstrel_mcs_group_data *mg;
535 if (mi->sample_wait > 0) {
540 if (!mi->sample_tries)
544 mg = &mi->groups[mi->sample_group];
545 sample_idx = sample_table[mg->column][mg->index];
546 mr = &mg->rates[sample_idx];
547 sample_idx += mi->sample_group * MCS_GROUP_RATES;
550 * When not using MRR, do not sample if the probability is already
551 * higher than 95% to avoid wasting airtime
553 if (!mp->has_mrr && (mr->probability > MINSTREL_FRAC(95, 100)))
557 * Make sure that lower rates get sampled only occasionally,
558 * if the link is working perfectly.
560 if (minstrel_get_duration(sample_idx) >
561 minstrel_get_duration(mi->max_tp_rate)) {
562 if (mr->sample_skipped < 10)
565 if (mi->sample_slow++ > 2)
572 minstrel_next_sample_idx(mi);
577 minstrel_ht_get_rate(void *priv, struct ieee80211_sta *sta, void *priv_sta,
578 struct ieee80211_tx_rate_control *txrc)
580 struct ieee80211_tx_info *info = IEEE80211_SKB_CB(txrc->skb);
581 struct ieee80211_tx_rate *ar = info->status.rates;
582 struct minstrel_ht_sta_priv *msp = priv_sta;
583 struct minstrel_ht_sta *mi = &msp->ht;
584 struct minstrel_priv *mp = priv;
587 if (rate_control_send_low(sta, priv_sta, txrc))
591 return mac80211_minstrel.get_rate(priv, sta, &msp->legacy, txrc);
593 info->flags |= mi->tx_flags;
594 sample_idx = minstrel_get_sample_rate(mp, mi);
595 if (sample_idx >= 0) {
596 minstrel_ht_set_rate(mp, mi, &ar[0], sample_idx,
598 minstrel_ht_set_rate(mp, mi, &ar[1], mi->max_tp_rate,
600 info->flags |= IEEE80211_TX_CTL_RATE_CTRL_PROBE;
602 minstrel_ht_set_rate(mp, mi, &ar[0], mi->max_tp_rate,
604 minstrel_ht_set_rate(mp, mi, &ar[1], mi->max_tp_rate2,
607 minstrel_ht_set_rate(mp, mi, &ar[2], mi->max_prob_rate, txrc, false, true);
615 if (mi->total_packets == ~0) {
616 mi->total_packets = 0;
617 mi->sample_packets = 0;
622 minstrel_ht_update_caps(void *priv, struct ieee80211_supported_band *sband,
623 struct ieee80211_sta *sta, void *priv_sta,
624 enum nl80211_channel_type oper_chan_type)
626 struct minstrel_priv *mp = priv;
627 struct minstrel_ht_sta_priv *msp = priv_sta;
628 struct minstrel_ht_sta *mi = &msp->ht;
629 struct ieee80211_mcs_info *mcs = &sta->ht_cap.mcs;
630 struct ieee80211_local *local = hw_to_local(mp->hw);
631 u16 sta_cap = sta->ht_cap.cap;
636 /* fall back to the old minstrel for legacy stations */
637 if (sta && !sta->ht_cap.ht_supported) {
639 memset(&msp->legacy, 0, sizeof(msp->legacy));
640 msp->legacy.r = msp->ratelist;
641 msp->legacy.sample_table = msp->sample_table;
642 return mac80211_minstrel.rate_init(priv, sband, sta, &msp->legacy);
645 BUILD_BUG_ON(ARRAY_SIZE(minstrel_mcs_groups) !=
646 MINSTREL_MAX_STREAMS * MINSTREL_STREAM_GROUPS);
649 memset(mi, 0, sizeof(*mi));
650 mi->stats_update = jiffies;
652 ack_dur = ieee80211_frame_duration(local, 10, 60, 1, 1);
653 mi->overhead = ieee80211_frame_duration(local, 0, 60, 1, 1) + ack_dur;
654 mi->overhead_rtscts = mi->overhead + 2 * ack_dur;
656 mi->avg_ampdu_len = MINSTREL_FRAC(1, 1);
658 /* When using MRR, sample more on the first attempt, without delay */
660 mi->sample_count = 16;
663 mi->sample_count = 8;
666 mi->sample_tries = 4;
668 stbc = (sta_cap & IEEE80211_HT_CAP_RX_STBC) >>
669 IEEE80211_HT_CAP_RX_STBC_SHIFT;
670 mi->tx_flags |= stbc << IEEE80211_TX_CTL_STBC_SHIFT;
672 if (sta_cap & IEEE80211_HT_CAP_LDPC_CODING)
673 mi->tx_flags |= IEEE80211_TX_CTL_LDPC;
675 if (oper_chan_type != NL80211_CHAN_HT40MINUS &&
676 oper_chan_type != NL80211_CHAN_HT40PLUS)
677 sta_cap &= ~IEEE80211_HT_CAP_SUP_WIDTH_20_40;
679 for (i = 0; i < ARRAY_SIZE(mi->groups); i++) {
682 mi->groups[i].supported = 0;
683 if (minstrel_mcs_groups[i].flags & IEEE80211_TX_RC_SHORT_GI) {
684 if (minstrel_mcs_groups[i].flags & IEEE80211_TX_RC_40_MHZ_WIDTH)
685 req |= IEEE80211_HT_CAP_SGI_40;
687 req |= IEEE80211_HT_CAP_SGI_20;
690 if (minstrel_mcs_groups[i].flags & IEEE80211_TX_RC_40_MHZ_WIDTH)
691 req |= IEEE80211_HT_CAP_SUP_WIDTH_20_40;
693 if ((sta_cap & req) != req)
696 mi->groups[i].supported =
697 mcs->rx_mask[minstrel_mcs_groups[i].streams - 1];
702 minstrel_ht_rate_init(void *priv, struct ieee80211_supported_band *sband,
703 struct ieee80211_sta *sta, void *priv_sta)
705 struct minstrel_priv *mp = priv;
707 minstrel_ht_update_caps(priv, sband, sta, priv_sta, mp->hw->conf.channel_type);
711 minstrel_ht_rate_update(void *priv, struct ieee80211_supported_band *sband,
712 struct ieee80211_sta *sta, void *priv_sta,
713 u32 changed, enum nl80211_channel_type oper_chan_type)
715 minstrel_ht_update_caps(priv, sband, sta, priv_sta, oper_chan_type);
719 minstrel_ht_alloc_sta(void *priv, struct ieee80211_sta *sta, gfp_t gfp)
721 struct ieee80211_supported_band *sband;
722 struct minstrel_ht_sta_priv *msp;
723 struct minstrel_priv *mp = priv;
724 struct ieee80211_hw *hw = mp->hw;
728 for (i = 0; i < IEEE80211_NUM_BANDS; i++) {
729 sband = hw->wiphy->bands[i];
730 if (sband && sband->n_bitrates > max_rates)
731 max_rates = sband->n_bitrates;
734 msp = kzalloc(sizeof(struct minstrel_ht_sta), gfp);
738 msp->ratelist = kzalloc(sizeof(struct minstrel_rate) * max_rates, gfp);
742 msp->sample_table = kmalloc(SAMPLE_COLUMNS * max_rates, gfp);
743 if (!msp->sample_table)
749 kfree(msp->sample_table);
756 minstrel_ht_free_sta(void *priv, struct ieee80211_sta *sta, void *priv_sta)
758 struct minstrel_ht_sta_priv *msp = priv_sta;
760 kfree(msp->sample_table);
761 kfree(msp->ratelist);
766 minstrel_ht_alloc(struct ieee80211_hw *hw, struct dentry *debugfsdir)
768 return mac80211_minstrel.alloc(hw, debugfsdir);
772 minstrel_ht_free(void *priv)
774 mac80211_minstrel.free(priv);
777 static struct rate_control_ops mac80211_minstrel_ht = {
778 .name = "minstrel_ht",
779 .tx_status = minstrel_ht_tx_status,
780 .get_rate = minstrel_ht_get_rate,
781 .rate_init = minstrel_ht_rate_init,
782 .rate_update = minstrel_ht_rate_update,
783 .alloc_sta = minstrel_ht_alloc_sta,
784 .free_sta = minstrel_ht_free_sta,
785 .alloc = minstrel_ht_alloc,
786 .free = minstrel_ht_free,
787 #ifdef CONFIG_MAC80211_DEBUGFS
788 .add_sta_debugfs = minstrel_ht_add_sta_debugfs,
789 .remove_sta_debugfs = minstrel_ht_remove_sta_debugfs,
795 init_sample_table(void)
798 u8 rnd[MCS_GROUP_RATES];
800 memset(sample_table, 0xff, sizeof(sample_table));
801 for (col = 0; col < SAMPLE_COLUMNS; col++) {
802 for (i = 0; i < MCS_GROUP_RATES; i++) {
803 get_random_bytes(rnd, sizeof(rnd));
804 new_idx = (i + rnd[i]) % MCS_GROUP_RATES;
806 while (sample_table[col][new_idx] != 0xff)
807 new_idx = (new_idx + 1) % MCS_GROUP_RATES;
809 sample_table[col][new_idx] = i;
815 rc80211_minstrel_ht_init(void)
818 return ieee80211_rate_control_register(&mac80211_minstrel_ht);
822 rc80211_minstrel_ht_exit(void)
824 ieee80211_rate_control_unregister(&mac80211_minstrel_ht);