// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2010-2013 Felix Fietkau <nbd@openwrt.org>
 * Copyright (C) 2019-2022 Intel Corporation
 */
#include <linux/netdevice.h>
#include <linux/types.h>
#include <linux/skbuff.h>
#include <linux/debugfs.h>
#include <linux/random.h>
#include <linux/moduleparam.h>
#include <linux/ieee80211.h>
#include <linux/minmax.h>
#include <net/mac80211.h>
#include "rate.h"
#include "sta_info.h"
#include "rc80211_minstrel_ht.h"

#define AVG_AMPDU_SIZE  16
#define AVG_PKT_SIZE    1200

/* Number of bits for an average sized packet */
#define MCS_NBITS ((AVG_PKT_SIZE * AVG_AMPDU_SIZE) << 3)

/* Number of symbols for a packet with (bps) bits per symbol */
#define MCS_NSYMS(bps) DIV_ROUND_UP(MCS_NBITS, (bps))

/* Transmission time (nanoseconds) for a packet containing (syms) symbols */
#define MCS_SYMBOL_TIME(sgi, syms)                                      \
        (sgi ?                                                          \
          ((syms) * 18000 + 4000) / 5 : /* syms * 3.6 us */             \
          ((syms) * 1000) << 2          /* syms * 4 us */               \
        )

/* Transmit duration for the raw data part of an average sized packet */
#define MCS_DURATION(streams, sgi, bps) \
        (MCS_SYMBOL_TIME(sgi, MCS_NSYMS((streams) * (bps))) / AVG_AMPDU_SIZE)

#define BW_20                   0
#define BW_40                   1
#define BW_80                   2

/*
 * Define group sort order: HT40 -> SGI -> #streams
 */
#define GROUP_IDX(_streams, _sgi, _ht40)        \
        MINSTREL_HT_GROUP_0 +                   \
        MINSTREL_MAX_STREAMS * 2 * _ht40 +      \
        MINSTREL_MAX_STREAMS * _sgi +   \
        _streams - 1

#define _MAX(a, b) (((a)>(b))?(a):(b))

#define GROUP_SHIFT(duration)                                           \
        _MAX(0, 16 - __builtin_clz(duration))

/* MCS rate information for an MCS group */
#define __MCS_GROUP(_streams, _sgi, _ht40, _s)                          \
        [GROUP_IDX(_streams, _sgi, _ht40)] = {                          \
        .streams = _streams,                                            \
        .shift = _s,                                                    \
        .bw = _ht40,                                                    \
        .flags =                                                        \
                IEEE80211_TX_RC_MCS |                                   \
                (_sgi ? IEEE80211_TX_RC_SHORT_GI : 0) |                 \
                (_ht40 ? IEEE80211_TX_RC_40_MHZ_WIDTH : 0),             \
        .duration = {                                                   \
                MCS_DURATION(_streams, _sgi, _ht40 ? 54 : 26) >> _s,    \
                MCS_DURATION(_streams, _sgi, _ht40 ? 108 : 52) >> _s,   \
                MCS_DURATION(_streams, _sgi, _ht40 ? 162 : 78) >> _s,   \
                MCS_DURATION(_streams, _sgi, _ht40 ? 216 : 104) >> _s,  \
                MCS_DURATION(_streams, _sgi, _ht40 ? 324 : 156) >> _s,  \
                MCS_DURATION(_streams, _sgi, _ht40 ? 432 : 208) >> _s,  \
                MCS_DURATION(_streams, _sgi, _ht40 ? 486 : 234) >> _s,  \
                MCS_DURATION(_streams, _sgi, _ht40 ? 540 : 260) >> _s   \
        }                                                               \
}

#define MCS_GROUP_SHIFT(_streams, _sgi, _ht40)                          \
        GROUP_SHIFT(MCS_DURATION(_streams, _sgi, _ht40 ? 54 : 26))

#define MCS_GROUP(_streams, _sgi, _ht40)                                \
        __MCS_GROUP(_streams, _sgi, _ht40,                              \
                    MCS_GROUP_SHIFT(_streams, _sgi, _ht40))

#define VHT_GROUP_IDX(_streams, _sgi, _bw)                              \
        (MINSTREL_VHT_GROUP_0 +                                         \
         MINSTREL_MAX_STREAMS * 2 * (_bw) +                             \
         MINSTREL_MAX_STREAMS * (_sgi) +                                \
         (_streams) - 1)

#define BW2VBPS(_bw, r3, r2, r1)                                        \
        (_bw == BW_80 ? r3 : _bw == BW_40 ? r2 : r1)

#define __VHT_GROUP(_streams, _sgi, _bw, _s)                            \
        [VHT_GROUP_IDX(_streams, _sgi, _bw)] = {                        \
        .streams = _streams,                                            \
        .shift = _s,                                                    \
        .bw = _bw,                                                      \
        .flags =                                                        \
                IEEE80211_TX_RC_VHT_MCS |                               \
                (_sgi ? IEEE80211_TX_RC_SHORT_GI : 0) |                 \
                (_bw == BW_80 ? IEEE80211_TX_RC_80_MHZ_WIDTH :          \
                 _bw == BW_40 ? IEEE80211_TX_RC_40_MHZ_WIDTH : 0),      \
        .duration = {                                                   \
                MCS_DURATION(_streams, _sgi,                            \
                             BW2VBPS(_bw,  117,  54,  26)) >> _s,       \
                MCS_DURATION(_streams, _sgi,                            \
                             BW2VBPS(_bw,  234, 108,  52)) >> _s,       \
                MCS_DURATION(_streams, _sgi,                            \
                             BW2VBPS(_bw,  351, 162,  78)) >> _s,       \
                MCS_DURATION(_streams, _sgi,                            \
                             BW2VBPS(_bw,  468, 216, 104)) >> _s,       \
                MCS_DURATION(_streams, _sgi,                            \
                             BW2VBPS(_bw,  702, 324, 156)) >> _s,       \
                MCS_DURATION(_streams, _sgi,                            \
                             BW2VBPS(_bw,  936, 432, 208)) >> _s,       \
                MCS_DURATION(_streams, _sgi,                            \
                             BW2VBPS(_bw, 1053, 486, 234)) >> _s,       \
                MCS_DURATION(_streams, _sgi,                            \
                             BW2VBPS(_bw, 1170, 540, 260)) >> _s,       \
                MCS_DURATION(_streams, _sgi,                            \
                             BW2VBPS(_bw, 1404, 648, 312)) >> _s,       \
                MCS_DURATION(_streams, _sgi,                            \
                             BW2VBPS(_bw, 1560, 720, 346)) >> _s        \
        }                                                               \
}

#define VHT_GROUP_SHIFT(_streams, _sgi, _bw)                            \
        GROUP_SHIFT(MCS_DURATION(_streams, _sgi,                        \
                                 BW2VBPS(_bw,  117,  54,  26)))

#define VHT_GROUP(_streams, _sgi, _bw)                                  \
        __VHT_GROUP(_streams, _sgi, _bw,                                \
                    VHT_GROUP_SHIFT(_streams, _sgi, _bw))

#define CCK_DURATION(_bitrate, _short)                  \
        (1000 * (10 /* SIFS */ +                        \
         (_short ? 72 + 24 : 144 + 48) +                \
         (8 * (AVG_PKT_SIZE + 4) * 10) / (_bitrate)))

#define CCK_DURATION_LIST(_short, _s)                   \
        CCK_DURATION(10, _short) >> _s,                 \
        CCK_DURATION(20, _short) >> _s,                 \
        CCK_DURATION(55, _short) >> _s,                 \
        CCK_DURATION(110, _short) >> _s

#define __CCK_GROUP(_s)                                 \
        [MINSTREL_CCK_GROUP] = {                        \
                .streams = 1,                           \
                .flags = 0,                             \
                .shift = _s,                            \
                .duration = {                           \
                        CCK_DURATION_LIST(false, _s),   \
                        CCK_DURATION_LIST(true, _s)     \
                }                                       \
        }

#define CCK_GROUP_SHIFT                                 \
        GROUP_SHIFT(CCK_DURATION(10, false))

#define CCK_GROUP __CCK_GROUP(CCK_GROUP_SHIFT)

#define OFDM_DURATION(_bitrate)                         \
        (1000 * (16 /* SIFS + signal ext */ +           \
         16 /* T_PREAMBLE */ +                          \
         4 /* T_SIGNAL */ +                             \
         4 * (((16 + 80 * (AVG_PKT_SIZE + 4) + 6) /     \
              ((_bitrate) * 4)))))

#define OFDM_DURATION_LIST(_s)                          \
        OFDM_DURATION(60) >> _s,                        \
        OFDM_DURATION(90) >> _s,                        \
        OFDM_DURATION(120) >> _s,                       \
        OFDM_DURATION(180) >> _s,                       \
        OFDM_DURATION(240) >> _s,                       \
        OFDM_DURATION(360) >> _s,                       \
        OFDM_DURATION(480) >> _s,                       \
        OFDM_DURATION(540) >> _s

#define __OFDM_GROUP(_s)                                \
        [MINSTREL_OFDM_GROUP] = {                       \
                .streams = 1,                           \
                .flags = 0,                             \
                .shift = _s,                            \
                .duration = {                           \
                        OFDM_DURATION_LIST(_s),         \
                }                                       \
        }

#define OFDM_GROUP_SHIFT                                \
        GROUP_SHIFT(OFDM_DURATION(60))

#define OFDM_GROUP __OFDM_GROUP(OFDM_GROUP_SHIFT)


static bool minstrel_vht_only = true;
module_param(minstrel_vht_only, bool, 0644);
MODULE_PARM_DESC(minstrel_vht_only,
                 "Use only VHT rates when VHT is supported by sta.");

/*
 * To enable sufficiently targeted rate sampling, MCS rates are divided into
 * groups, based on the number of streams and flags (HT40, SGI) that they
 * use.
 *
 * Sortorder has to be fixed for GROUP_IDX macro to be applicable:
 * BW -> SGI -> #streams
 */
const struct mcs_group minstrel_mcs_groups[] = {
        MCS_GROUP(1, 0, BW_20),
        MCS_GROUP(2, 0, BW_20),
        MCS_GROUP(3, 0, BW_20),
        MCS_GROUP(4, 0, BW_20),

        MCS_GROUP(1, 1, BW_20),
        MCS_GROUP(2, 1, BW_20),
        MCS_GROUP(3, 1, BW_20),
        MCS_GROUP(4, 1, BW_20),

        MCS_GROUP(1, 0, BW_40),
        MCS_GROUP(2, 0, BW_40),
        MCS_GROUP(3, 0, BW_40),
        MCS_GROUP(4, 0, BW_40),

        MCS_GROUP(1, 1, BW_40),
        MCS_GROUP(2, 1, BW_40),
        MCS_GROUP(3, 1, BW_40),
        MCS_GROUP(4, 1, BW_40),

        CCK_GROUP,
        OFDM_GROUP,

        VHT_GROUP(1, 0, BW_20),
        VHT_GROUP(2, 0, BW_20),
        VHT_GROUP(3, 0, BW_20),
        VHT_GROUP(4, 0, BW_20),

        VHT_GROUP(1, 1, BW_20),
        VHT_GROUP(2, 1, BW_20),
        VHT_GROUP(3, 1, BW_20),
        VHT_GROUP(4, 1, BW_20),

        VHT_GROUP(1, 0, BW_40),
        VHT_GROUP(2, 0, BW_40),
        VHT_GROUP(3, 0, BW_40),
        VHT_GROUP(4, 0, BW_40),

        VHT_GROUP(1, 1, BW_40),
        VHT_GROUP(2, 1, BW_40),
        VHT_GROUP(3, 1, BW_40),
        VHT_GROUP(4, 1, BW_40),

        VHT_GROUP(1, 0, BW_80),
        VHT_GROUP(2, 0, BW_80),
        VHT_GROUP(3, 0, BW_80),
        VHT_GROUP(4, 0, BW_80),

        VHT_GROUP(1, 1, BW_80),
        VHT_GROUP(2, 1, BW_80),
        VHT_GROUP(3, 1, BW_80),
        VHT_GROUP(4, 1, BW_80),
};

const s16 minstrel_cck_bitrates[4] = { 10, 20, 55, 110 };
const s16 minstrel_ofdm_bitrates[8] = { 60, 90, 120, 180, 240, 360, 480, 540 };
static u8 sample_table[SAMPLE_COLUMNS][MCS_GROUP_RATES] __read_mostly;
static const u8 minstrel_sample_seq[] = {
        MINSTREL_SAMPLE_TYPE_INC,
        MINSTREL_SAMPLE_TYPE_JUMP,
        MINSTREL_SAMPLE_TYPE_INC,
        MINSTREL_SAMPLE_TYPE_JUMP,
        MINSTREL_SAMPLE_TYPE_INC,
        MINSTREL_SAMPLE_TYPE_SLOW,
};

static void
minstrel_ht_update_rates(struct minstrel_priv *mp, struct minstrel_ht_sta *mi);

/*
 * Some VHT MCSes are invalid (when Ndbps / Nes is not an integer)
 * e.g for MCS9@20MHzx1Nss: Ndbps=8x52*(5/6) Nes=1
 *
 * Returns the valid mcs map for struct minstrel_mcs_group_data.supported
 */
static u16
minstrel_get_valid_vht_rates(int bw, int nss, __le16 mcs_map)
{
        u16 mask = 0;

        if (bw == BW_20) {
                if (nss != 3 && nss != 6)
                        mask = BIT(9);
        } else if (bw == BW_80) {
                if (nss == 3 || nss == 7)
                        mask = BIT(6);
                else if (nss == 6)
                        mask = BIT(9);
        } else {
                WARN_ON(bw != BW_40);
        }

        switch ((le16_to_cpu(mcs_map) >> (2 * (nss - 1))) & 3) {
        case IEEE80211_VHT_MCS_SUPPORT_0_7:
                mask |= 0x300;
                break;
        case IEEE80211_VHT_MCS_SUPPORT_0_8:
                mask |= 0x200;
                break;
        case IEEE80211_VHT_MCS_SUPPORT_0_9:
                break;
        default:
                mask = 0x3ff;
        }

        return 0x3ff & ~mask;
}

static bool
minstrel_ht_is_legacy_group(int group)
{
        return group == MINSTREL_CCK_GROUP ||
               group == MINSTREL_OFDM_GROUP;
}

/*
 * Look up an MCS group index based on mac80211 rate information
 */
static int
minstrel_ht_get_group_idx(struct ieee80211_tx_rate *rate)
{
        return GROUP_IDX((rate->idx / 8) + 1,
                         !!(rate->flags & IEEE80211_TX_RC_SHORT_GI),
                         !!(rate->flags & IEEE80211_TX_RC_40_MHZ_WIDTH));
}

/*
 * Look up an MCS group index based on new cfg80211 rate_info.
 */
static int
minstrel_ht_ri_get_group_idx(struct rate_info *rate)
{
        return GROUP_IDX((rate->mcs / 8) + 1,
                         !!(rate->flags & RATE_INFO_FLAGS_SHORT_GI),
                         !!(rate->bw & RATE_INFO_BW_40));
}

static int
minstrel_vht_get_group_idx(struct ieee80211_tx_rate *rate)
{
        return VHT_GROUP_IDX(ieee80211_rate_get_vht_nss(rate),
                             !!(rate->flags & IEEE80211_TX_RC_SHORT_GI),
                             !!(rate->flags & IEEE80211_TX_RC_40_MHZ_WIDTH) +
                             2*!!(rate->flags & IEEE80211_TX_RC_80_MHZ_WIDTH));
}

/*
 * Look up an MCS group index based on new cfg80211 rate_info.
 */
static int
minstrel_vht_ri_get_group_idx(struct rate_info *rate)
{
        return VHT_GROUP_IDX(rate->nss,
                             !!(rate->flags & RATE_INFO_FLAGS_SHORT_GI),
                             !!(rate->bw & RATE_INFO_BW_40) +
                             2*!!(rate->bw & RATE_INFO_BW_80));
}

static struct minstrel_rate_stats *
minstrel_ht_get_stats(struct minstrel_priv *mp, struct minstrel_ht_sta *mi,
                      struct ieee80211_tx_rate *rate)
{
        int group, idx;

        if (rate->flags & IEEE80211_TX_RC_MCS) {
                group = minstrel_ht_get_group_idx(rate);
                idx = rate->idx % 8;
                goto out;
        }

        if (rate->flags & IEEE80211_TX_RC_VHT_MCS) {
                group = minstrel_vht_get_group_idx(rate);
                idx = ieee80211_rate_get_vht_mcs(rate);
                goto out;
        }

        group = MINSTREL_CCK_GROUP;
        for (idx = 0; idx < ARRAY_SIZE(mp->cck_rates); idx++) {
                if (!(mi->supported[group] & BIT(idx)))
                        continue;

                if (rate->idx != mp->cck_rates[idx])
                        continue;

                /* short preamble */
                if ((mi->supported[group] & BIT(idx + 4)) &&
                    (rate->flags & IEEE80211_TX_RC_USE_SHORT_PREAMBLE))
                        idx += 4;
                goto out;
        }

        group = MINSTREL_OFDM_GROUP;
        for (idx = 0; idx < ARRAY_SIZE(mp->ofdm_rates[0]); idx++)
                if (rate->idx == mp->ofdm_rates[mi->band][idx])
                        goto out;

        idx = 0;
out:
        return &mi->groups[group].rates[idx];
}

/*
 * Get the minstrel rate statistics for specified STA and rate info.
 */
static struct minstrel_rate_stats *
minstrel_ht_ri_get_stats(struct minstrel_priv *mp, struct minstrel_ht_sta *mi,
                          struct ieee80211_rate_status *rate_status)
{
        int group, idx;
        struct rate_info *rate = &rate_status->rate_idx;

        if (rate->flags & RATE_INFO_FLAGS_MCS) {
                group = minstrel_ht_ri_get_group_idx(rate);
                idx = rate->mcs % 8;
                goto out;
        }

        if (rate->flags & RATE_INFO_FLAGS_VHT_MCS) {
                group = minstrel_vht_ri_get_group_idx(rate);
                idx = rate->mcs;
                goto out;
        }

        group = MINSTREL_CCK_GROUP;
        for (idx = 0; idx < ARRAY_SIZE(mp->cck_rates); idx++) {
                if (rate->legacy != minstrel_cck_bitrates[ mp->cck_rates[idx] ])
                        continue;

                /* short preamble */
                if ((mi->supported[group] & BIT(idx + 4)) &&
                                                        mi->use_short_preamble)
                        idx += 4;
                goto out;
        }

        group = MINSTREL_OFDM_GROUP;
        for (idx = 0; idx < ARRAY_SIZE(mp->ofdm_rates[0]); idx++)
                if (rate->legacy == minstrel_ofdm_bitrates[ mp->ofdm_rates[mi->band][idx] ])
                        goto out;

        idx = 0;
out:
        return &mi->groups[group].rates[idx];
}

static inline struct minstrel_rate_stats *
minstrel_get_ratestats(struct minstrel_ht_sta *mi, int index)
{
        return &mi->groups[MI_RATE_GROUP(index)].rates[MI_RATE_IDX(index)];
}

static inline int minstrel_get_duration(int index)
{
        const struct mcs_group *group = &minstrel_mcs_groups[MI_RATE_GROUP(index)];
        unsigned int duration = group->duration[MI_RATE_IDX(index)];

        return duration << group->shift;
}

static unsigned int
minstrel_ht_avg_ampdu_len(struct minstrel_ht_sta *mi)
{
        int duration;

        if (mi->avg_ampdu_len)
                return MINSTREL_TRUNC(mi->avg_ampdu_len);

        if (minstrel_ht_is_legacy_group(MI_RATE_GROUP(mi->max_tp_rate[0])))
                return 1;

        duration = minstrel_get_duration(mi->max_tp_rate[0]);

        if (duration > 400 * 1000)
                return 2;

        if (duration > 250 * 1000)
                return 4;

        if (duration > 150 * 1000)
                return 8;

        return 16;
}

/*
 * Return current throughput based on the average A-MPDU length, taking into
 * account the expected number of retransmissions and their expected length
 */
int
minstrel_ht_get_tp_avg(struct minstrel_ht_sta *mi, int group, int rate,
                       int prob_avg)
{
        unsigned int nsecs = 0, overhead = mi->overhead;
        unsigned int ampdu_len = 1;

        /* do not account throughput if success prob is below 10% */
        if (prob_avg < MINSTREL_FRAC(10, 100))
                return 0;

        if (minstrel_ht_is_legacy_group(group))
                overhead = mi->overhead_legacy;
        else
                ampdu_len = minstrel_ht_avg_ampdu_len(mi);

        nsecs = 1000 * overhead / ampdu_len;
        nsecs += minstrel_mcs_groups[group].duration[rate] <<
                 minstrel_mcs_groups[group].shift;

        /*
         * For the throughput calculation, limit the probability value to 90% to
         * account for collision related packet error rate fluctuation
         * (prob is scaled - see MINSTREL_FRAC above)
         */
        if (prob_avg > MINSTREL_FRAC(90, 100))
                prob_avg = MINSTREL_FRAC(90, 100);

        return MINSTREL_TRUNC(100 * ((prob_avg * 1000000) / nsecs));
}

/*
 * Find & sort topmost throughput rates
 *
 * If multiple rates provide equal throughput the sorting is based on their
 * current success probability. Higher success probability is preferred among
 * MCS groups, CCK rates do not provide aggregation and are therefore at last.
 */
static void
minstrel_ht_sort_best_tp_rates(struct minstrel_ht_sta *mi, u16 index,
                               u16 *tp_list)
{
        int cur_group, cur_idx, cur_tp_avg, cur_prob;
        int tmp_group, tmp_idx, tmp_tp_avg, tmp_prob;
        int j = MAX_THR_RATES;

        cur_group = MI_RATE_GROUP(index);
        cur_idx = MI_RATE_IDX(index);
        cur_prob = mi->groups[cur_group].rates[cur_idx].prob_avg;
        cur_tp_avg = minstrel_ht_get_tp_avg(mi, cur_group, cur_idx, cur_prob);

        do {
                tmp_group = MI_RATE_GROUP(tp_list[j - 1]);
                tmp_idx = MI_RATE_IDX(tp_list[j - 1]);
                tmp_prob = mi->groups[tmp_group].rates[tmp_idx].prob_avg;
                tmp_tp_avg = minstrel_ht_get_tp_avg(mi, tmp_group, tmp_idx,
                                                    tmp_prob);
                if (cur_tp_avg < tmp_tp_avg ||
                    (cur_tp_avg == tmp_tp_avg && cur_prob <= tmp_prob))
                        break;
                j--;
        } while (j > 0);

        if (j < MAX_THR_RATES - 1) {
                memmove(&tp_list[j + 1], &tp_list[j], (sizeof(*tp_list) *
                       (MAX_THR_RATES - (j + 1))));
        }
        if (j < MAX_THR_RATES)
                tp_list[j] = index;
}

/*
 * Find and set the topmost probability rate per sta and per group
 */
static void
minstrel_ht_set_best_prob_rate(struct minstrel_ht_sta *mi, u16 *dest, u16 index)
{
        struct minstrel_mcs_group_data *mg;
        struct minstrel_rate_stats *mrs;
        int tmp_group, tmp_idx, tmp_tp_avg, tmp_prob;
        int max_tp_group, max_tp_idx, max_tp_prob;
        int cur_tp_avg, cur_group, cur_idx;
        int max_gpr_group, max_gpr_idx;
        int max_gpr_tp_avg, max_gpr_prob;

        cur_group = MI_RATE_GROUP(index);
        cur_idx = MI_RATE_IDX(index);
        mg = &mi->groups[cur_group];
        mrs = &mg->rates[cur_idx];

        tmp_group = MI_RATE_GROUP(*dest);
        tmp_idx = MI_RATE_IDX(*dest);
        tmp_prob = mi->groups[tmp_group].rates[tmp_idx].prob_avg;
        tmp_tp_avg = minstrel_ht_get_tp_avg(mi, tmp_group, tmp_idx, tmp_prob);

        /* if max_tp_rate[0] is from MCS_GROUP max_prob_rate get selected from
         * MCS_GROUP as well as CCK_GROUP rates do not allow aggregation */
        max_tp_group = MI_RATE_GROUP(mi->max_tp_rate[0]);
        max_tp_idx = MI_RATE_IDX(mi->max_tp_rate[0]);
        max_tp_prob = mi->groups[max_tp_group].rates[max_tp_idx].prob_avg;

        if (minstrel_ht_is_legacy_group(MI_RATE_GROUP(index)) &&
            !minstrel_ht_is_legacy_group(max_tp_group))
                return;

        /* skip rates faster than max tp rate with lower prob */
        if (minstrel_get_duration(mi->max_tp_rate[0]) > minstrel_get_duration(index) &&
            mrs->prob_avg < max_tp_prob)
                return;

        max_gpr_group = MI_RATE_GROUP(mg->max_group_prob_rate);
        max_gpr_idx = MI_RATE_IDX(mg->max_group_prob_rate);
        max_gpr_prob = mi->groups[max_gpr_group].rates[max_gpr_idx].prob_avg;

        if (mrs->prob_avg > MINSTREL_FRAC(75, 100)) {
                cur_tp_avg = minstrel_ht_get_tp_avg(mi, cur_group, cur_idx,
                                                    mrs->prob_avg);
                if (cur_tp_avg > tmp_tp_avg)
                        *dest = index;

                max_gpr_tp_avg = minstrel_ht_get_tp_avg(mi, max_gpr_group,
                                                        max_gpr_idx,
                                                        max_gpr_prob);
                if (cur_tp_avg > max_gpr_tp_avg)
                        mg->max_group_prob_rate = index;
        } else {
                if (mrs->prob_avg > tmp_prob)
                        *dest = index;
                if (mrs->prob_avg > max_gpr_prob)
                        mg->max_group_prob_rate = index;
        }
}


/*
 * Assign new rate set per sta and use CCK rates only if the fastest
 * rate (max_tp_rate[0]) is from CCK group. This prohibits such sorted
 * rate sets where MCS and CCK rates are mixed, because CCK rates can
 * not use aggregation.
 */
static void
minstrel_ht_assign_best_tp_rates(struct minstrel_ht_sta *mi,
                                 u16 tmp_mcs_tp_rate[MAX_THR_RATES],
                                 u16 tmp_legacy_tp_rate[MAX_THR_RATES])
{
        unsigned int tmp_group, tmp_idx, tmp_cck_tp, tmp_mcs_tp, tmp_prob;
        int i;

        tmp_group = MI_RATE_GROUP(tmp_legacy_tp_rate[0]);
        tmp_idx = MI_RATE_IDX(tmp_legacy_tp_rate[0]);
        tmp_prob = mi->groups[tmp_group].rates[tmp_idx].prob_avg;
        tmp_cck_tp = minstrel_ht_get_tp_avg(mi, tmp_group, tmp_idx, tmp_prob);

        tmp_group = MI_RATE_GROUP(tmp_mcs_tp_rate[0]);
        tmp_idx = MI_RATE_IDX(tmp_mcs_tp_rate[0]);
        tmp_prob = mi->groups[tmp_group].rates[tmp_idx].prob_avg;
        tmp_mcs_tp = minstrel_ht_get_tp_avg(mi, tmp_group, tmp_idx, tmp_prob);

        if (tmp_cck_tp > tmp_mcs_tp) {
                for(i = 0; i < MAX_THR_RATES; i++) {
                        minstrel_ht_sort_best_tp_rates(mi, tmp_legacy_tp_rate[i],
                                                       tmp_mcs_tp_rate);
                }
        }

}

/*
 * Try to increase robustness of max_prob rate by decrease number of
 * streams if possible.
 */
static inline void
minstrel_ht_prob_rate_reduce_streams(struct minstrel_ht_sta *mi)
{
        struct minstrel_mcs_group_data *mg;
        int tmp_max_streams, group, tmp_idx, tmp_prob;
        int tmp_tp = 0;

        if (!mi->sta->deflink.ht_cap.ht_supported)
                return;

        group = MI_RATE_GROUP(mi->max_tp_rate[0]);
        tmp_max_streams = minstrel_mcs_groups[group].streams;
        for (group = 0; group < ARRAY_SIZE(minstrel_mcs_groups); group++) {
                mg = &mi->groups[group];
                if (!mi->supported[group] || group == MINSTREL_CCK_GROUP)
                        continue;

                tmp_idx = MI_RATE_IDX(mg->max_group_prob_rate);
                tmp_prob = mi->groups[group].rates[tmp_idx].prob_avg;

                if (tmp_tp < minstrel_ht_get_tp_avg(mi, group, tmp_idx, tmp_prob) &&
                   (minstrel_mcs_groups[group].streams < tmp_max_streams)) {
                                mi->max_prob_rate = mg->max_group_prob_rate;
                                tmp_tp = minstrel_ht_get_tp_avg(mi, group,
                                                                tmp_idx,
                                                                tmp_prob);
                }
        }
}

static u16
__minstrel_ht_get_sample_rate(struct minstrel_ht_sta *mi,
                              enum minstrel_sample_type type)
{
        u16 *rates = mi->sample[type].sample_rates;
        u16 cur;
        int i;

        for (i = 0; i < MINSTREL_SAMPLE_RATES; i++) {
                if (!rates[i])
                        continue;

                cur = rates[i];
                rates[i] = 0;
                return cur;
        }

        return 0;
}

static inline int
minstrel_ewma(int old, int new, int weight)
{
        int diff, incr;

        diff = new - old;
        incr = (EWMA_DIV - weight) * diff / EWMA_DIV;

        return old + incr;
}

static inline int minstrel_filter_avg_add(u16 *prev_1, u16 *prev_2, s32 in)
{
        s32 out_1 = *prev_1;
        s32 out_2 = *prev_2;
        s32 val;

        if (!in)
                in += 1;

        if (!out_1) {
                val = out_1 = in;
                goto out;
        }

        val = MINSTREL_AVG_COEFF1 * in;
        val += MINSTREL_AVG_COEFF2 * out_1;
        val += MINSTREL_AVG_COEFF3 * out_2;
        val >>= MINSTREL_SCALE;

        if (val > 1 << MINSTREL_SCALE)
                val = 1 << MINSTREL_SCALE;
        if (val < 0)
                val = 1;

out:
        *prev_2 = out_1;
        *prev_1 = val;

        return val;
}

/*
* Recalculate statistics and counters of a given rate
*/
static void
minstrel_ht_calc_rate_stats(struct minstrel_priv *mp,
                            struct minstrel_rate_stats *mrs)
{
        unsigned int cur_prob;

        if (unlikely(mrs->attempts > 0)) {
                cur_prob = MINSTREL_FRAC(mrs->success, mrs->attempts);
                minstrel_filter_avg_add(&mrs->prob_avg,
                                        &mrs->prob_avg_1, cur_prob);
                mrs->att_hist += mrs->attempts;
                mrs->succ_hist += mrs->success;
        }

        mrs->last_success = mrs->success;
        mrs->last_attempts = mrs->attempts;
        mrs->success = 0;
        mrs->attempts = 0;
}

static bool
minstrel_ht_find_sample_rate(struct minstrel_ht_sta *mi, int type, int idx)
{
        int i;

        for (i = 0; i < MINSTREL_SAMPLE_RATES; i++) {
                u16 cur = mi->sample[type].sample_rates[i];

                if (cur == idx)
                        return true;

                if (!cur)
                        break;
        }

        return false;
}

static int
minstrel_ht_move_sample_rates(struct minstrel_ht_sta *mi, int type,
                              u32 fast_rate_dur, u32 slow_rate_dur)
{
        u16 *rates = mi->sample[type].sample_rates;
        int i, j;

        for (i = 0, j = 0; i < MINSTREL_SAMPLE_RATES; i++) {
                u32 duration;
                bool valid = false;
                u16 cur;

                cur = rates[i];
                if (!cur)
                        continue;

                duration = minstrel_get_duration(cur);
                switch (type) {
                case MINSTREL_SAMPLE_TYPE_SLOW:
                        valid = duration > fast_rate_dur &&
                                duration < slow_rate_dur;
                        break;
                case MINSTREL_SAMPLE_TYPE_INC:
                case MINSTREL_SAMPLE_TYPE_JUMP:
                        valid = duration < fast_rate_dur;
                        break;
                default:
                        valid = false;
                        break;
                }

                if (!valid) {
                        rates[i] = 0;
                        continue;
                }

                if (i == j)
                        continue;

                rates[j++] = cur;
                rates[i] = 0;
        }

        return j;
}

static int
minstrel_ht_group_min_rate_offset(struct minstrel_ht_sta *mi, int group,
                                  u32 max_duration)
{
        u16 supported = mi->supported[group];
        int i;

        for (i = 0; i < MCS_GROUP_RATES && supported; i++, supported >>= 1) {
                if (!(supported & BIT(0)))
                        continue;

                if (minstrel_get_duration(MI_RATE(group, i)) >= max_duration)
                        continue;

                return i;
        }

        return -1;
}

/*
 * Incremental update rates:
 * Flip through groups and pick the first group rate that is faster than the
 * highest currently selected rate
 */
static u16
minstrel_ht_next_inc_rate(struct minstrel_ht_sta *mi, u32 fast_rate_dur)
{
        u8 type = MINSTREL_SAMPLE_TYPE_INC;
        int i, index = 0;
        u8 group;

        group = mi->sample[type].sample_group;
        for (i = 0; i < ARRAY_SIZE(minstrel_mcs_groups); i++) {
                group = (group + 1) % ARRAY_SIZE(minstrel_mcs_groups);

                index = minstrel_ht_group_min_rate_offset(mi, group,
                                                          fast_rate_dur);
                if (index < 0)
                        continue;

                index = MI_RATE(group, index & 0xf);
                if (!minstrel_ht_find_sample_rate(mi, type, index))
                        goto out;
        }
        index = 0;

out:
        mi->sample[type].sample_group = group;

        return index;
}

static int
minstrel_ht_next_group_sample_rate(struct minstrel_ht_sta *mi, int group,
                                   u16 supported, int offset)
{
        struct minstrel_mcs_group_data *mg = &mi->groups[group];
        u16 idx;
        int i;

        for (i = 0; i < MCS_GROUP_RATES; i++) {
                idx = sample_table[mg->column][mg->index];
                if (++mg->index >= MCS_GROUP_RATES) {
                        mg->index = 0;
                        if (++mg->column >= ARRAY_SIZE(sample_table))
                                mg->column = 0;
                }

                if (idx < offset)
                        continue;

                if (!(supported & BIT(idx)))
                        continue;

                return MI_RATE(group, idx);
        }

        return -1;
}

/*
 * Jump rates:
 * Sample random rates, use those that are faster than the highest
 * currently selected rate. Rates between the fastest and the slowest
 * get sorted into the slow sample bucket, but only if it has room
 */
static u16
minstrel_ht_next_jump_rate(struct minstrel_ht_sta *mi, u32 fast_rate_dur,
                           u32 slow_rate_dur, int *slow_rate_ofs)
{
        struct minstrel_rate_stats *mrs;
        u32 max_duration = slow_rate_dur;
        int i, index, offset;
        u16 *slow_rates;
        u16 supported;
        u32 duration;
        u8 group;

        if (*slow_rate_ofs >= MINSTREL_SAMPLE_RATES)
                max_duration = fast_rate_dur;

        slow_rates = mi->sample[MINSTREL_SAMPLE_TYPE_SLOW].sample_rates;
        group = mi->sample[MINSTREL_SAMPLE_TYPE_JUMP].sample_group;
        for (i = 0; i < ARRAY_SIZE(minstrel_mcs_groups); i++) {
                u8 type;

                group = (group + 1) % ARRAY_SIZE(minstrel_mcs_groups);

                supported = mi->supported[group];
                if (!supported)
                        continue;

                offset = minstrel_ht_group_min_rate_offset(mi, group,
                                                           max_duration);
                if (offset < 0)
                        continue;

                index = minstrel_ht_next_group_sample_rate(mi, group, supported,
                                                           offset);
                if (index < 0)
                        continue;

                duration = minstrel_get_duration(index);
                if (duration < fast_rate_dur)
                        type = MINSTREL_SAMPLE_TYPE_JUMP;
                else
                        type = MINSTREL_SAMPLE_TYPE_SLOW;

                if (minstrel_ht_find_sample_rate(mi, type, index))
                        continue;

                if (type == MINSTREL_SAMPLE_TYPE_JUMP)
                        goto found;

                if (*slow_rate_ofs >= MINSTREL_SAMPLE_RATES)
                        continue;

                if (duration >= slow_rate_dur)
                        continue;

                /* skip slow rates with high success probability */
                mrs = minstrel_get_ratestats(mi, index);
                if (mrs->prob_avg > MINSTREL_FRAC(95, 100))
                        continue;

                slow_rates[(*slow_rate_ofs)++] = index;
                if (*slow_rate_ofs >= MINSTREL_SAMPLE_RATES)
                        max_duration = fast_rate_dur;
        }
        index = 0;

found:
        mi->sample[MINSTREL_SAMPLE_TYPE_JUMP].sample_group = group;

        return index;
}

static void
minstrel_ht_refill_sample_rates(struct minstrel_ht_sta *mi)
{
        u32 prob_dur = minstrel_get_duration(mi->max_prob_rate);
        u32 tp_dur = minstrel_get_duration(mi->max_tp_rate[0]);
        u32 tp2_dur = minstrel_get_duration(mi->max_tp_rate[1]);
        u32 fast_rate_dur = min(min(tp_dur, tp2_dur), prob_dur);
        u32 slow_rate_dur = max(max(tp_dur, tp2_dur), prob_dur);
        u16 *rates;
        int i, j;

        rates = mi->sample[MINSTREL_SAMPLE_TYPE_INC].sample_rates;
        i = minstrel_ht_move_sample_rates(mi, MINSTREL_SAMPLE_TYPE_INC,
                                          fast_rate_dur, slow_rate_dur);
        while (i < MINSTREL_SAMPLE_RATES) {
                rates[i] = minstrel_ht_next_inc_rate(mi, tp_dur);
                if (!rates[i])
                        break;

                i++;
        }

        rates = mi->sample[MINSTREL_SAMPLE_TYPE_JUMP].sample_rates;
        i = minstrel_ht_move_sample_rates(mi, MINSTREL_SAMPLE_TYPE_JUMP,
                                          fast_rate_dur, slow_rate_dur);
        j = minstrel_ht_move_sample_rates(mi, MINSTREL_SAMPLE_TYPE_SLOW,
                                          fast_rate_dur, slow_rate_dur);
        while (i < MINSTREL_SAMPLE_RATES) {
                rates[i] = minstrel_ht_next_jump_rate(mi, fast_rate_dur,
                                                      slow_rate_dur, &j);
                if (!rates[i])
                        break;

                i++;
        }

        for (i = 0; i < ARRAY_SIZE(mi->sample); i++)
                memcpy(mi->sample[i].cur_sample_rates, mi->sample[i].sample_rates,
                       sizeof(mi->sample[i].cur_sample_rates));
}


/*
 * Update rate statistics and select new primary rates
 *
 * Rules for rate selection:
 *  - max_prob_rate must use only one stream, as a tradeoff between delivery
 *    probability and throughput during strong fluctuations
 *  - as long as the max prob rate has a probability of more than 75%, pick
 *    higher throughput rates, even if the probability is a bit lower
 */
static void
minstrel_ht_update_stats(struct minstrel_priv *mp, struct minstrel_ht_sta *mi)
{
        struct minstrel_mcs_group_data *mg;
        struct minstrel_rate_stats *mrs;
        int group, i, j, cur_prob;
        u16 tmp_mcs_tp_rate[MAX_THR_RATES], tmp_group_tp_rate[MAX_THR_RATES];
        u16 tmp_legacy_tp_rate[MAX_THR_RATES], tmp_max_prob_rate;
        u16 index;
        bool ht_supported = mi->sta->deflink.ht_cap.ht_supported;

        if (mi->ampdu_packets > 0) {
                if (!ieee80211_hw_check(mp->hw, TX_STATUS_NO_AMPDU_LEN))
                        mi->avg_ampdu_len = minstrel_ewma(mi->avg_ampdu_len,
                                MINSTREL_FRAC(mi->ampdu_len, mi->ampdu_packets),
                                              EWMA_LEVEL);
                else
                        mi->avg_ampdu_len = 0;
                mi->ampdu_len = 0;
                mi->ampdu_packets = 0;
        }

        if (mi->supported[MINSTREL_CCK_GROUP])
                group = MINSTREL_CCK_GROUP;
        else if (mi->supported[MINSTREL_OFDM_GROUP])
                group = MINSTREL_OFDM_GROUP;
        else
                group = 0;

        index = MI_RATE(group, 0);
        for (j = 0; j < ARRAY_SIZE(tmp_legacy_tp_rate); j++)
                tmp_legacy_tp_rate[j] = index;

        if (mi->supported[MINSTREL_VHT_GROUP_0])
                group = MINSTREL_VHT_GROUP_0;
        else if (ht_supported)
                group = MINSTREL_HT_GROUP_0;
        else if (mi->supported[MINSTREL_CCK_GROUP])
                group = MINSTREL_CCK_GROUP;
        else
                group = MINSTREL_OFDM_GROUP;

        index = MI_RATE(group, 0);
        tmp_max_prob_rate = index;
        for (j = 0; j < ARRAY_SIZE(tmp_mcs_tp_rate); j++)
                tmp_mcs_tp_rate[j] = index;

        /* Find best rate sets within all MCS groups*/
        for (group = 0; group < ARRAY_SIZE(minstrel_mcs_groups); group++) {
                u16 *tp_rate = tmp_mcs_tp_rate;
                u16 last_prob = 0;

                mg = &mi->groups[group];
                if (!mi->supported[group])
                        continue;

                /* (re)Initialize group rate indexes */
                for(j = 0; j < MAX_THR_RATES; j++)
                        tmp_group_tp_rate[j] = MI_RATE(group, 0);

                if (group == MINSTREL_CCK_GROUP && ht_supported)
                        tp_rate = tmp_legacy_tp_rate;

                for (i = MCS_GROUP_RATES - 1; i >= 0; i--) {
                        if (!(mi->supported[group] & BIT(i)))
                                continue;

                        index = MI_RATE(group, i);

                        mrs = &mg->rates[i];
                        mrs->retry_updated = false;
                        minstrel_ht_calc_rate_stats(mp, mrs);

                        if (mrs->att_hist)
                                last_prob = max(last_prob, mrs->prob_avg);
                        else
                                mrs->prob_avg = max(last_prob, mrs->prob_avg);
                        cur_prob = mrs->prob_avg;

                        if (minstrel_ht_get_tp_avg(mi, group, i, cur_prob) == 0)
                                continue;

                        /* Find max throughput rate set */
                        minstrel_ht_sort_best_tp_rates(mi, index, tp_rate);

                        /* Find max throughput rate set within a group */
                        minstrel_ht_sort_best_tp_rates(mi, index,
                                                       tmp_group_tp_rate);
                }

                memcpy(mg->max_group_tp_rate, tmp_group_tp_rate,
                       sizeof(mg->max_group_tp_rate));
        }

        /* Assign new rate set per sta */
        minstrel_ht_assign_best_tp_rates(mi, tmp_mcs_tp_rate,
                                         tmp_legacy_tp_rate);
        memcpy(mi->max_tp_rate, tmp_mcs_tp_rate, sizeof(mi->max_tp_rate));

        for (group = 0; group < ARRAY_SIZE(minstrel_mcs_groups); group++) {
                if (!mi->supported[group])
                        continue;

                mg = &mi->groups[group];
                mg->max_group_prob_rate = MI_RATE(group, 0);

                for (i = 0; i < MCS_GROUP_RATES; i++) {
                        if (!(mi->supported[group] & BIT(i)))
                                continue;

                        index = MI_RATE(group, i);

                        /* Find max probability rate per group and global */
                        minstrel_ht_set_best_prob_rate(mi, &tmp_max_prob_rate,
                                                       index);
                }
        }

        mi->max_prob_rate = tmp_max_prob_rate;

        /* Try to increase robustness of max_prob_rate*/
        minstrel_ht_prob_rate_reduce_streams(mi);
        minstrel_ht_refill_sample_rates(mi);

#ifdef CONFIG_MAC80211_DEBUGFS
        /* use fixed index if set */
        if (mp->fixed_rate_idx != -1) {
                for (i = 0; i < 4; i++)
                        mi->max_tp_rate[i] = mp->fixed_rate_idx;
                mi->max_prob_rate = mp->fixed_rate_idx;
        }
#endif

        /* Reset update timer */
        mi->last_stats_update = jiffies;
        mi->sample_time = jiffies;
}

static bool
minstrel_ht_txstat_valid(struct minstrel_priv *mp, struct minstrel_ht_sta *mi,
                         struct ieee80211_tx_rate *rate)
{
        int i;

        if (rate->idx < 0)
                return false;

        if (!rate->count)
                return false;

        if (rate->flags & IEEE80211_TX_RC_MCS ||
            rate->flags & IEEE80211_TX_RC_VHT_MCS)
                return true;

        for (i = 0; i < ARRAY_SIZE(mp->cck_rates); i++)
                if (rate->idx == mp->cck_rates[i])
                        return true;

        for (i = 0; i < ARRAY_SIZE(mp->ofdm_rates[0]); i++)
                if (rate->idx == mp->ofdm_rates[mi->band][i])
                        return true;

        return false;
}

/*
 * Check whether rate_status contains valid information.
 */
static bool
minstrel_ht_ri_txstat_valid(struct minstrel_priv *mp,
                            struct minstrel_ht_sta *mi,
                            struct ieee80211_rate_status *rate_status)
{
        int i;

        if (!rate_status)
                return false;
        if (!rate_status->try_count)
                return false;

        if (rate_status->rate_idx.flags & RATE_INFO_FLAGS_MCS ||
            rate_status->rate_idx.flags & RATE_INFO_FLAGS_VHT_MCS)
                return true;

        for (i = 0; i < ARRAY_SIZE(mp->cck_rates); i++) {
                if (rate_status->rate_idx.legacy ==
                    minstrel_cck_bitrates[ mp->cck_rates[i] ])
                        return true;
        }

        for (i = 0; i < ARRAY_SIZE(mp->ofdm_rates); i++) {
                if (rate_status->rate_idx.legacy ==
                    minstrel_ofdm_bitrates[ mp->ofdm_rates[mi->band][i] ])
                        return true;
        }

        return false;
}

static void
minstrel_downgrade_rate(struct minstrel_ht_sta *mi, u16 *idx, bool primary)
{
        int group, orig_group;

        orig_group = group = MI_RATE_GROUP(*idx);
        while (group > 0) {
                group--;

                if (!mi->supported[group])
                        continue;

                if (minstrel_mcs_groups[group].streams >
                    minstrel_mcs_groups[orig_group].streams)
                        continue;

                if (primary)
                        *idx = mi->groups[group].max_group_tp_rate[0];
                else
                        *idx = mi->groups[group].max_group_tp_rate[1];
                break;
        }
}

static void
minstrel_ht_tx_status(void *priv, struct ieee80211_supported_band *sband,
                      void *priv_sta, struct ieee80211_tx_status *st)
{
        struct ieee80211_tx_info *info = st->info;
        struct minstrel_ht_sta *mi = priv_sta;
        struct ieee80211_tx_rate *ar = info->status.rates;
        struct minstrel_rate_stats *rate, *rate2;
        struct minstrel_priv *mp = priv;
        u32 update_interval = mp->update_interval;
        bool last, update = false;
        int i;

        /* Ignore packet that was sent with noAck flag */
        if (info->flags & IEEE80211_TX_CTL_NO_ACK)
                return;

        /* This packet was aggregated but doesn't carry status info */
        if ((info->flags & IEEE80211_TX_CTL_AMPDU) &&
            !(info->flags & IEEE80211_TX_STAT_AMPDU))
                return;

        if (!(info->flags & IEEE80211_TX_STAT_AMPDU)) {
                info->status.ampdu_ack_len =
                        (info->flags & IEEE80211_TX_STAT_ACK ? 1 : 0);
                info->status.ampdu_len = 1;
        }

        /* wraparound */
        if (mi->total_packets >= ~0 - info->status.ampdu_len) {
                mi->total_packets = 0;
                mi->sample_packets = 0;
        }

        mi->total_packets += info->status.ampdu_len;
        if (info->flags & IEEE80211_TX_CTL_RATE_CTRL_PROBE)
                mi->sample_packets += info->status.ampdu_len;

        mi->ampdu_packets++;
        mi->ampdu_len += info->status.ampdu_len;

        if (st->rates && st->n_rates) {
                last = !minstrel_ht_ri_txstat_valid(mp, mi, &(st->rates[0]));
                for (i = 0; !last; i++) {
                        last = (i == st->n_rates - 1) ||
                                !minstrel_ht_ri_txstat_valid(mp, mi,
                                                        &(st->rates[i + 1]));

                        rate = minstrel_ht_ri_get_stats(mp, mi,
                                                        &(st->rates[i]));

                        if (last)
                                rate->success += info->status.ampdu_ack_len;

                        rate->attempts += st->rates[i].try_count *
                                          info->status.ampdu_len;
                }
        } else {
                last = !minstrel_ht_txstat_valid(mp, mi, &ar[0]);
                for (i = 0; !last; i++) {
                        last = (i == IEEE80211_TX_MAX_RATES - 1) ||
                                !minstrel_ht_txstat_valid(mp, mi, &ar[i + 1]);

                        rate = minstrel_ht_get_stats(mp, mi, &ar[i]);
                        if (last)
                                rate->success += info->status.ampdu_ack_len;

                        rate->attempts += ar[i].count * info->status.ampdu_len;
                }
        }

        if (mp->hw->max_rates > 1) {
                /*
                 * check for sudden death of spatial multiplexing,
                 * downgrade to a lower number of streams if necessary.
                 */
                rate = minstrel_get_ratestats(mi, mi->max_tp_rate[0]);
                if (rate->attempts > 30 &&
                    rate->success < rate->attempts / 4) {
                        minstrel_downgrade_rate(mi, &mi->max_tp_rate[0], true);
                        update = true;
                }

                rate2 = minstrel_get_ratestats(mi, mi->max_tp_rate[1]);
                if (rate2->attempts > 30 &&
                    rate2->success < rate2->attempts / 4) {
                        minstrel_downgrade_rate(mi, &mi->max_tp_rate[1], false);
                        update = true;
                }
        }

        if (time_after(jiffies, mi->last_stats_update + update_interval)) {
                update = true;
                minstrel_ht_update_stats(mp, mi);
        }

        if (update)
                minstrel_ht_update_rates(mp, mi);
}

static void
minstrel_calc_retransmit(struct minstrel_priv *mp, struct minstrel_ht_sta *mi,
                         int index)
{
        struct minstrel_rate_stats *mrs;
        unsigned int tx_time, tx_time_rtscts, tx_time_data;
        unsigned int cw = mp->cw_min;
        unsigned int ctime = 0;
        unsigned int t_slot = 9; /* FIXME */
        unsigned int ampdu_len = minstrel_ht_avg_ampdu_len(mi);
        unsigned int overhead = 0, overhead_rtscts = 0;

        mrs = minstrel_get_ratestats(mi, index);
        if (mrs->prob_avg < MINSTREL_FRAC(1, 10)) {
                mrs->retry_count = 1;
                mrs->retry_count_rtscts = 1;
                return;
        }

        mrs->retry_count = 2;
        mrs->retry_count_rtscts = 2;
        mrs->retry_updated = true;

        tx_time_data = minstrel_get_duration(index) * ampdu_len / 1000;

        /* Contention time for first 2 tries */
        ctime = (t_slot * cw) >> 1;
        cw = min((cw << 1) | 1, mp->cw_max);
        ctime += (t_slot * cw) >> 1;
        cw = min((cw << 1) | 1, mp->cw_max);

        if (minstrel_ht_is_legacy_group(MI_RATE_GROUP(index))) {
                overhead = mi->overhead_legacy;
                overhead_rtscts = mi->overhead_legacy_rtscts;
        } else {
                overhead = mi->overhead;
                overhead_rtscts = mi->overhead_rtscts;
        }

        /* Total TX time for data and Contention after first 2 tries */
        tx_time = ctime + 2 * (overhead + tx_time_data);
        tx_time_rtscts = ctime + 2 * (overhead_rtscts + tx_time_data);

        /* See how many more tries we can fit inside segment size */
        do {
                /* Contention time for this try */
                ctime = (t_slot * cw) >> 1;
                cw = min((cw << 1) | 1, mp->cw_max);

                /* Total TX time after this try */
                tx_time += ctime + overhead + tx_time_data;
                tx_time_rtscts += ctime + overhead_rtscts + tx_time_data;

                if (tx_time_rtscts < mp->segment_size)
                        mrs->retry_count_rtscts++;
        } while ((tx_time < mp->segment_size) &&
                 (++mrs->retry_count < mp->max_retry));
}


static void
minstrel_ht_set_rate(struct minstrel_priv *mp, struct minstrel_ht_sta *mi,
                     struct ieee80211_sta_rates *ratetbl, int offset, int index)
{
        int group_idx = MI_RATE_GROUP(index);
        const struct mcs_group *group = &minstrel_mcs_groups[group_idx];
        struct minstrel_rate_stats *mrs;
        u8 idx;
        u16 flags = group->flags;

        mrs = minstrel_get_ratestats(mi, index);
        if (!mrs->retry_updated)
                minstrel_calc_retransmit(mp, mi, index);

        if (mrs->prob_avg < MINSTREL_FRAC(20, 100) || !mrs->retry_count) {
                ratetbl->rate[offset].count = 2;
                ratetbl->rate[offset].count_rts = 2;
                ratetbl->rate[offset].count_cts = 2;
        } else {
                ratetbl->rate[offset].count = mrs->retry_count;
                ratetbl->rate[offset].count_cts = mrs->retry_count;
                ratetbl->rate[offset].count_rts = mrs->retry_count_rtscts;
        }

        index = MI_RATE_IDX(index);
        if (group_idx == MINSTREL_CCK_GROUP)
                idx = mp->cck_rates[index % ARRAY_SIZE(mp->cck_rates)];
        else if (group_idx == MINSTREL_OFDM_GROUP)
                idx = mp->ofdm_rates[mi->band][index %
                                               ARRAY_SIZE(mp->ofdm_rates[0])];
        else if (flags & IEEE80211_TX_RC_VHT_MCS)
                idx = ((group->streams - 1) << 4) |
                      (index & 0xF);
        else
                idx = index + (group->streams - 1) * 8;

        /* enable RTS/CTS if needed:
         *  - if station is in dynamic SMPS (and streams > 1)
         *  - for fallback rates, to increase chances of getting through
         */
        if (offset > 0 ||
            (mi->sta->deflink.smps_mode == IEEE80211_SMPS_DYNAMIC &&
             group->streams > 1)) {
                ratetbl->rate[offset].count = ratetbl->rate[offset].count_rts;
                flags |= IEEE80211_TX_RC_USE_RTS_CTS;
        }

        ratetbl->rate[offset].idx = idx;
        ratetbl->rate[offset].flags = flags;
}

static inline int
minstrel_ht_get_prob_avg(struct minstrel_ht_sta *mi, int rate)
{
        int group = MI_RATE_GROUP(rate);
        rate = MI_RATE_IDX(rate);
        return mi->groups[group].rates[rate].prob_avg;
}

static int
minstrel_ht_get_max_amsdu_len(struct minstrel_ht_sta *mi)
{
        int group = MI_RATE_GROUP(mi->max_prob_rate);
        const struct mcs_group *g = &minstrel_mcs_groups[group];
        int rate = MI_RATE_IDX(mi->max_prob_rate);
        unsigned int duration;

        /* Disable A-MSDU if max_prob_rate is bad */
        if (mi->groups[group].rates[rate].prob_avg < MINSTREL_FRAC(50, 100))
                return 1;

        duration = g->duration[rate];
        duration <<= g->shift;

        /* If the rate is slower than single-stream MCS1, make A-MSDU limit small */
        if (duration > MCS_DURATION(1, 0, 52))
                return 500;

        /*
         * If the rate is slower than single-stream MCS4, limit A-MSDU to usual
         * data packet size
         */
        if (duration > MCS_DURATION(1, 0, 104))
                return 1600;

        /*
         * If the rate is slower than single-stream MCS7, or if the max throughput
         * rate success probability is less than 75%, limit A-MSDU to twice the usual
         * data packet size
         */
        if (duration > MCS_DURATION(1, 0, 260) ||
            (minstrel_ht_get_prob_avg(mi, mi->max_tp_rate[0]) <
             MINSTREL_FRAC(75, 100)))
                return 3200;

        /*
         * HT A-MPDU limits maximum MPDU size under BA agreement to 4095 bytes.
         * Since aggregation sessions are started/stopped without txq flush, use
         * the limit here to avoid the complexity of having to de-aggregate
         * packets in the queue.
         */
        if (!mi->sta->deflink.vht_cap.vht_supported)
                return IEEE80211_MAX_MPDU_LEN_HT_BA;

        /* unlimited */
        return 0;
}

static void
minstrel_ht_update_rates(struct minstrel_priv *mp, struct minstrel_ht_sta *mi)
{
        struct ieee80211_sta_rates *rates;
        int i = 0;
        int max_rates = min_t(int, mp->hw->max_rates, IEEE80211_TX_RATE_TABLE_SIZE);

        rates = kzalloc_obj(*rates, GFP_ATOMIC);
        if (!rates)
                return;

        /* Start with max_tp_rate[0] */
        minstrel_ht_set_rate(mp, mi, rates, i++, mi->max_tp_rate[0]);

        /* Fill up remaining, keep one entry for max_probe_rate */
        for (; i < (max_rates - 1); i++)
                minstrel_ht_set_rate(mp, mi, rates, i, mi->max_tp_rate[i]);

        if (i < max_rates)
                minstrel_ht_set_rate(mp, mi, rates, i++, mi->max_prob_rate);

        if (i < IEEE80211_TX_RATE_TABLE_SIZE)
                rates->rate[i].idx = -1;

        mi->sta->deflink.agg.max_rc_amsdu_len = minstrel_ht_get_max_amsdu_len(mi);
        ieee80211_sta_recalc_aggregates(mi->sta);
        rate_control_set_rates(mp->hw, mi->sta, rates);
}

static u16
minstrel_ht_get_sample_rate(struct minstrel_priv *mp, struct minstrel_ht_sta *mi)
{
        u8 seq;

        if (mp->hw->max_rates > 1) {
                seq = mi->sample_seq;
                mi->sample_seq = (seq + 1) % ARRAY_SIZE(minstrel_sample_seq);
                seq = minstrel_sample_seq[seq];
        } else {
                seq = MINSTREL_SAMPLE_TYPE_INC;
        }

        return __minstrel_ht_get_sample_rate(mi, seq);
}

static void
minstrel_ht_get_rate(void *priv, struct ieee80211_sta *sta, void *priv_sta,
                     struct ieee80211_tx_rate_control *txrc)
{
        const struct mcs_group *sample_group;
        struct ieee80211_tx_info *info = IEEE80211_SKB_CB(txrc->skb);
        struct ieee80211_tx_rate *rate = &info->status.rates[0];
        struct minstrel_ht_sta *mi = priv_sta;
        struct minstrel_priv *mp = priv;
        u16 sample_idx;

        info->flags |= mi->tx_flags;

#ifdef CONFIG_MAC80211_DEBUGFS
        if (mp->fixed_rate_idx != -1)
                return;
#endif

        /* Don't use EAPOL frames for sampling on non-mrr hw */
        if (mp->hw->max_rates == 1 &&
            (info->control.flags & IEEE80211_TX_CTRL_PORT_CTRL_PROTO))
                return;

        if (time_is_after_jiffies(mi->sample_time))
                return;

        mi->sample_time = jiffies + MINSTREL_SAMPLE_INTERVAL;
        sample_idx = minstrel_ht_get_sample_rate(mp, mi);
        if (!sample_idx)
                return;

        sample_group = &minstrel_mcs_groups[MI_RATE_GROUP(sample_idx)];
        sample_idx = MI_RATE_IDX(sample_idx);

        if (sample_group == &minstrel_mcs_groups[MINSTREL_CCK_GROUP] &&
            (sample_idx >= 4) != txrc->short_preamble)
                return;

        info->flags |= IEEE80211_TX_CTL_RATE_CTRL_PROBE;
        rate->count = 1;

        if (sample_group == &minstrel_mcs_groups[MINSTREL_CCK_GROUP]) {
                int idx = sample_idx % ARRAY_SIZE(mp->cck_rates);
                rate->idx = mp->cck_rates[idx];
        } else if (sample_group == &minstrel_mcs_groups[MINSTREL_OFDM_GROUP]) {
                int idx = sample_idx % ARRAY_SIZE(mp->ofdm_rates[0]);
                rate->idx = mp->ofdm_rates[mi->band][idx];
        } else if (sample_group->flags & IEEE80211_TX_RC_VHT_MCS) {
                ieee80211_rate_set_vht(rate, MI_RATE_IDX(sample_idx),
                                       sample_group->streams);
        } else {
                rate->idx = sample_idx + (sample_group->streams - 1) * 8;
        }

        rate->flags = sample_group->flags;
}

static void
minstrel_ht_update_cck(struct minstrel_priv *mp, struct minstrel_ht_sta *mi,
                       struct ieee80211_supported_band *sband,
                       struct ieee80211_sta *sta)
{
        int i;

        if (sband->band != NL80211_BAND_2GHZ)
                return;

        if (sta->deflink.ht_cap.ht_supported &&
            !ieee80211_hw_check(mp->hw, SUPPORTS_HT_CCK_RATES))
                return;

        for (i = 0; i < 4; i++) {
                if (mp->cck_rates[i] == 0xff ||
                    !rate_supported(sta, sband->band, mp->cck_rates[i]))
                        continue;

                mi->supported[MINSTREL_CCK_GROUP] |= BIT(i);
                if (sband->bitrates[i].flags & IEEE80211_RATE_SHORT_PREAMBLE)
                        mi->supported[MINSTREL_CCK_GROUP] |= BIT(i + 4);
        }
}

static void
minstrel_ht_update_ofdm(struct minstrel_priv *mp, struct minstrel_ht_sta *mi,
                        struct ieee80211_supported_band *sband,
                        struct ieee80211_sta *sta)
{
        const u8 *rates;
        int i;

        if (sta->deflink.ht_cap.ht_supported)
                return;

        rates = mp->ofdm_rates[sband->band];
        for (i = 0; i < ARRAY_SIZE(mp->ofdm_rates[0]); i++) {
                if (rates[i] == 0xff ||
                    !rate_supported(sta, sband->band, rates[i]))
                        continue;

                mi->supported[MINSTREL_OFDM_GROUP] |= BIT(i);
        }
}

static void
minstrel_ht_update_caps(void *priv, struct ieee80211_supported_band *sband,
                        struct cfg80211_chan_def *chandef,
                        struct ieee80211_sta *sta, void *priv_sta)
{
        struct minstrel_priv *mp = priv;
        struct minstrel_ht_sta *mi = priv_sta;
        struct ieee80211_mcs_info *mcs = &sta->deflink.ht_cap.mcs;
        u16 ht_cap = sta->deflink.ht_cap.cap;
        struct ieee80211_sta_vht_cap *vht_cap = &sta->deflink.vht_cap;
        const struct ieee80211_rate *ctl_rate;
        struct sta_info *sta_info;
        bool ldpc, erp;
        int use_vht;
        int ack_dur;
        int stbc;
        int i;

        BUILD_BUG_ON(ARRAY_SIZE(minstrel_mcs_groups) != MINSTREL_GROUPS_NB);

        if (vht_cap->vht_supported)
                use_vht = vht_cap->vht_mcs.tx_mcs_map != cpu_to_le16(~0);
        else
                use_vht = 0;

        memset(mi, 0, sizeof(*mi));

        mi->sta = sta;
        mi->band = sband->band;
        mi->last_stats_update = jiffies;

        ack_dur = ieee80211_frame_duration(sband->band, 10, 60, 1, 1);
        mi->overhead = ieee80211_frame_duration(sband->band, 0, 60, 1, 1);
        mi->overhead += ack_dur;
        mi->overhead_rtscts = mi->overhead + 2 * ack_dur;

        ctl_rate = &sband->bitrates[rate_lowest_index(sband, sta)];
        erp = ctl_rate->flags & IEEE80211_RATE_ERP_G;
        ack_dur = ieee80211_frame_duration(sband->band, 10,
                                           ctl_rate->bitrate, erp, 1);
        mi->overhead_legacy = ack_dur;
        mi->overhead_legacy_rtscts = mi->overhead_legacy + 2 * ack_dur;

        mi->avg_ampdu_len = MINSTREL_FRAC(1, 1);

        if (!use_vht) {
                stbc = (ht_cap & IEEE80211_HT_CAP_RX_STBC) >>
                        IEEE80211_HT_CAP_RX_STBC_SHIFT;

                ldpc = ht_cap & IEEE80211_HT_CAP_LDPC_CODING;
        } else {
                stbc = (vht_cap->cap & IEEE80211_VHT_CAP_RXSTBC_MASK) >>
                        IEEE80211_VHT_CAP_RXSTBC_SHIFT;

                ldpc = vht_cap->cap & IEEE80211_VHT_CAP_RXLDPC;
        }

        mi->tx_flags |= stbc << IEEE80211_TX_CTL_STBC_SHIFT;
        if (ldpc)
                mi->tx_flags |= IEEE80211_TX_CTL_LDPC;

        for (i = 0; i < ARRAY_SIZE(mi->groups); i++) {
                u32 gflags = minstrel_mcs_groups[i].flags;
                int bw, nss;

                mi->supported[i] = 0;
                if (minstrel_ht_is_legacy_group(i))
                        continue;

                if (gflags & IEEE80211_TX_RC_SHORT_GI) {
                        if (gflags & IEEE80211_TX_RC_40_MHZ_WIDTH) {
                                if (!(ht_cap & IEEE80211_HT_CAP_SGI_40))
                                        continue;
                        } else {
                                if (!(ht_cap & IEEE80211_HT_CAP_SGI_20))
                                        continue;
                        }
                }

                if (gflags & IEEE80211_TX_RC_40_MHZ_WIDTH &&
                    sta->deflink.bandwidth < IEEE80211_STA_RX_BW_40)
                        continue;

                nss = minstrel_mcs_groups[i].streams;

                /* Mark MCS > 7 as unsupported if STA is in static SMPS mode */
                if (sta->deflink.smps_mode == IEEE80211_SMPS_STATIC && nss > 1)
                        continue;

                /* HT rate */
                if (gflags & IEEE80211_TX_RC_MCS) {
                        if (use_vht && minstrel_vht_only)
                                continue;

                        mi->supported[i] = mcs->rx_mask[nss - 1];
                        continue;
                }

                /* VHT rate */
                if (!vht_cap->vht_supported ||
                    WARN_ON(!(gflags & IEEE80211_TX_RC_VHT_MCS)) ||
                    WARN_ON(gflags & IEEE80211_TX_RC_160_MHZ_WIDTH))
                        continue;

                if (gflags & IEEE80211_TX_RC_80_MHZ_WIDTH) {
                        if (sta->deflink.bandwidth < IEEE80211_STA_RX_BW_80 ||
                            ((gflags & IEEE80211_TX_RC_SHORT_GI) &&
                             !(vht_cap->cap & IEEE80211_VHT_CAP_SHORT_GI_80))) {
                                continue;
                        }
                }

                if (gflags & IEEE80211_TX_RC_40_MHZ_WIDTH)
                        bw = BW_40;
                else if (gflags & IEEE80211_TX_RC_80_MHZ_WIDTH)
                        bw = BW_80;
                else
                        bw = BW_20;

                mi->supported[i] = minstrel_get_valid_vht_rates(bw, nss,
                                vht_cap->vht_mcs.tx_mcs_map);
        }

        sta_info = container_of(sta, struct sta_info, sta);
        mi->use_short_preamble = test_sta_flag(sta_info, WLAN_STA_SHORT_PREAMBLE) &&
                                 sta_info->sdata->vif.bss_conf.use_short_preamble;

        minstrel_ht_update_cck(mp, mi, sband, sta);
        minstrel_ht_update_ofdm(mp, mi, sband, sta);

        /* create an initial rate table with the lowest supported rates */
        minstrel_ht_update_stats(mp, mi);
        minstrel_ht_update_rates(mp, mi);
}

static void
minstrel_ht_rate_init(void *priv, struct ieee80211_supported_band *sband,
                      struct cfg80211_chan_def *chandef,
                      struct ieee80211_sta *sta, void *priv_sta)
{
        minstrel_ht_update_caps(priv, sband, chandef, sta, priv_sta);
}

static void
minstrel_ht_rate_update(void *priv, struct ieee80211_supported_band *sband,
                        struct cfg80211_chan_def *chandef,
                        struct ieee80211_sta *sta, void *priv_sta,
                        u32 changed)
{
        minstrel_ht_update_caps(priv, sband, chandef, sta, priv_sta);
}

static void *
minstrel_ht_alloc_sta(void *priv, struct ieee80211_sta *sta, gfp_t gfp)
{
        struct ieee80211_supported_band *sband;
        struct minstrel_ht_sta *mi;
        struct minstrel_priv *mp = priv;
        struct ieee80211_hw *hw = mp->hw;
        int max_rates = 0;
        int i;

        for (i = 0; i < NUM_NL80211_BANDS; i++) {
                sband = hw->wiphy->bands[i];
                if (sband && sband->n_bitrates > max_rates)
                        max_rates = sband->n_bitrates;
        }

        return kzalloc_obj(*mi, gfp);
}

static void
minstrel_ht_free_sta(void *priv, struct ieee80211_sta *sta, void *priv_sta)
{
        kfree(priv_sta);
}

static void
minstrel_ht_fill_rate_array(u8 *dest, struct ieee80211_supported_band *sband,
                            const s16 *bitrates, int n_rates)
{
        int i, j;

        for (i = 0; i < sband->n_bitrates; i++) {
                struct ieee80211_rate *rate = &sband->bitrates[i];

                for (j = 0; j < n_rates; j++) {
                        if (rate->bitrate != bitrates[j])
                                continue;

                        dest[j] = i;
                        break;
                }
        }
}

static void
minstrel_ht_init_cck_rates(struct minstrel_priv *mp)
{
        static const s16 bitrates[4] = { 10, 20, 55, 110 };
        struct ieee80211_supported_band *sband;

        memset(mp->cck_rates, 0xff, sizeof(mp->cck_rates));
        sband = mp->hw->wiphy->bands[NL80211_BAND_2GHZ];
        if (!sband)
                return;

        BUILD_BUG_ON(ARRAY_SIZE(mp->cck_rates) != ARRAY_SIZE(bitrates));
        minstrel_ht_fill_rate_array(mp->cck_rates, sband,
                                    minstrel_cck_bitrates,
                                    ARRAY_SIZE(minstrel_cck_bitrates));
}

static void
minstrel_ht_init_ofdm_rates(struct minstrel_priv *mp, enum nl80211_band band)
{
        static const s16 bitrates[8] = { 60, 90, 120, 180, 240, 360, 480, 540 };
        struct ieee80211_supported_band *sband;

        memset(mp->ofdm_rates[band], 0xff, sizeof(mp->ofdm_rates[band]));
        sband = mp->hw->wiphy->bands[band];
        if (!sband)
                return;

        BUILD_BUG_ON(ARRAY_SIZE(mp->ofdm_rates[band]) != ARRAY_SIZE(bitrates));
        minstrel_ht_fill_rate_array(mp->ofdm_rates[band], sband,
                                    minstrel_ofdm_bitrates,
                                    ARRAY_SIZE(minstrel_ofdm_bitrates));
}

static void *
minstrel_ht_alloc(struct ieee80211_hw *hw)
{
        struct minstrel_priv *mp;
        int i;

        mp = kzalloc_obj(struct minstrel_priv, GFP_ATOMIC);
        if (!mp)
                return NULL;

        /* contention window settings
         * Just an approximation. Using the per-queue values would complicate
         * the calculations and is probably unnecessary */
        mp->cw_min = 15;
        mp->cw_max = 1023;

        /* maximum time that the hw is allowed to stay in one MRR segment */
        mp->segment_size = 6000;

        if (hw->max_rate_tries > 0)
                mp->max_retry = hw->max_rate_tries;
        else
                /* safe default, does not necessarily have to match hw properties */
                mp->max_retry = 7;

        mp->hw = hw;
        mp->update_interval = HZ / 20;

        minstrel_ht_init_cck_rates(mp);
        for (i = 0; i < ARRAY_SIZE(mp->hw->wiphy->bands); i++)
            minstrel_ht_init_ofdm_rates(mp, i);

        return mp;
}

#ifdef CONFIG_MAC80211_DEBUGFS
static void minstrel_ht_add_debugfs(struct ieee80211_hw *hw, void *priv,
                                    struct dentry *debugfsdir)
{
        struct minstrel_priv *mp = priv;

        mp->fixed_rate_idx = (u32) -1;
        debugfs_create_u32("fixed_rate_idx", S_IRUGO | S_IWUGO, debugfsdir,
                           &mp->fixed_rate_idx);
}
#endif

static void
minstrel_ht_free(void *priv)
{
        kfree(priv);
}

static u32 minstrel_ht_get_expected_throughput(void *priv_sta)
{
        struct minstrel_ht_sta *mi = priv_sta;
        int i, j, prob, tp_avg;

        i = MI_RATE_GROUP(mi->max_tp_rate[0]);
        j = MI_RATE_IDX(mi->max_tp_rate[0]);
        prob = mi->groups[i].rates[j].prob_avg;

        /* convert tp_avg from pkt per second in kbps */
        tp_avg = minstrel_ht_get_tp_avg(mi, i, j, prob) * 10;
        tp_avg = tp_avg * AVG_PKT_SIZE * 8 / 1024;

        return tp_avg;
}

static const struct rate_control_ops mac80211_minstrel_ht = {
        .name = "minstrel_ht",
        .capa = RATE_CTRL_CAPA_AMPDU_TRIGGER,
        .tx_status_ext = minstrel_ht_tx_status,
        .get_rate = minstrel_ht_get_rate,
        .rate_init = minstrel_ht_rate_init,
        .rate_update = minstrel_ht_rate_update,
        .alloc_sta = minstrel_ht_alloc_sta,
        .free_sta = minstrel_ht_free_sta,
        .alloc = minstrel_ht_alloc,
        .free = minstrel_ht_free,
#ifdef CONFIG_MAC80211_DEBUGFS
        .add_debugfs = minstrel_ht_add_debugfs,
        .add_sta_debugfs = minstrel_ht_add_sta_debugfs,
#endif
        .get_expected_throughput = minstrel_ht_get_expected_throughput,
};


static void __init init_sample_table(void)
{
        int col, i, new_idx;
        u8 rnd[MCS_GROUP_RATES];

        memset(sample_table, 0xff, sizeof(sample_table));
        for (col = 0; col < SAMPLE_COLUMNS; col++) {
                get_random_bytes(rnd, sizeof(rnd));
                for (i = 0; i < MCS_GROUP_RATES; i++) {
                        new_idx = (i + rnd[i]) % MCS_GROUP_RATES;
                        while (sample_table[col][new_idx] != 0xff)
                                new_idx = (new_idx + 1) % MCS_GROUP_RATES;

                        sample_table[col][new_idx] = i;
                }
        }
}

int __init
rc80211_minstrel_init(void)
{
        init_sample_table();
        return ieee80211_rate_control_register(&mac80211_minstrel_ht);
}

void
rc80211_minstrel_exit(void)
{
        ieee80211_rate_control_unregister(&mac80211_minstrel_ht);
}