mac80211: add documentation and verbose variable names in

Add documentation and more verbose variable names to minstrel's
multi-rate-retry setup within function minstrel_get_rate() to
increase the readability of the algorithm.

Acked-by: Felix Fietkau <nbd@openwrt.org>
Signed-off-by: Thomas Huehn <thomas@net.t-labs.tu-berlin.de>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

diff --git a/net/mac80211/rc80211_minstrel.c b/net/mac80211/rc80211_minstrel.c
index c9b9902379913ffb668e71ea482efb796bb283e8..152bb0e3786576b99731e81b6f6a2d6e14750649 100644 (file)
--- a/net/mac80211/rc80211_minstrel.c
+++ b/net/mac80211/rc80211_minstrel.c
@@ -78,7 +78,6 @@ minstrel_update_stats(struct minstrel_priv *mp, struct minstrel_sta_info *mi)
        u32 usecs;
        int i;
 
-       mi->stats_update = jiffies;
        for (i = 0; i < mi->n_rates; i++) {
                struct minstrel_rate *mr = &mi->r[i];
 
@@ -144,6 +143,9 @@ minstrel_update_stats(struct minstrel_priv *mp, struct minstrel_sta_info *mi)
        mi->max_tp_rate = index_max_tp;
        mi->max_tp_rate2 = index_max_tp2;
        mi->max_prob_rate = index_max_prob;
+
+       /* Reset update timer */
+       mi->stats_update = jiffies;
 }
 
 static void
@@ -204,10 +206,10 @@ static int
 minstrel_get_next_sample(struct minstrel_sta_info *mi)
 {
        unsigned int sample_ndx;
-       sample_ndx = SAMPLE_TBL(mi, mi->sample_idx, mi->sample_column);
-       mi->sample_idx++;
-       if ((int) mi->sample_idx > (mi->n_rates - 2)) {
-               mi->sample_idx = 0;
+       sample_ndx = SAMPLE_TBL(mi, mi->sample_row, mi->sample_column);
+       mi->sample_row++;
+       if ((int) mi->sample_row > (mi->n_rates - 2)) {
+               mi->sample_row = 0;
                mi->sample_column++;
                if (mi->sample_column >= SAMPLE_COLUMNS)
                        mi->sample_column = 0;
@@ -225,31 +227,37 @@ minstrel_get_rate(void *priv, struct ieee80211_sta *sta,
        struct minstrel_priv *mp = priv;
        struct ieee80211_tx_rate *ar = info->control.rates;
        unsigned int ndx, sample_ndx = 0;
-       bool mrr;
-       bool sample_slower = false;
-       bool sample = false;
+       bool mrr_capable;
+       bool indirect_rate_sampling = false;
+       bool rate_sampling = false;
        int i, delta;
        int mrr_ndx[3];
-       int sample_rate;
+       int sampling_ratio;
 
+       /* management/no-ack frames do not use rate control */
        if (rate_control_send_low(sta, priv_sta, txrc))
                return;
 
-       mrr = mp->has_mrr && !txrc->rts && !txrc->bss_conf->use_cts_prot;
+       /* check multi-rate-retry capabilities & adjust lookaround_rate */
+       mrr_capable = mp->has_mrr &&
+                     !txrc->rts &&
+                     !txrc->bss_conf->use_cts_prot;
+       if (mrr_capable)
+               sampling_ratio = mp->lookaround_rate_mrr;
+       else
+               sampling_ratio = mp->lookaround_rate;
 
+       /* init rateindex [ndx] with max throughput rate */
        ndx = mi->max_tp_rate;
 
-       if (mrr)
-               sample_rate = mp->lookaround_rate_mrr;
-       else
-               sample_rate = mp->lookaround_rate;
-
+       /* increase sum packet counter */
        mi->packet_count++;
-       delta = (mi->packet_count * sample_rate / 100) -
+
+       delta = (mi->packet_count * sampling_ratio / 100) -
                        (mi->sample_count + mi->sample_deferred / 2);
 
        /* delta > 0: sampling required */
-       if ((delta > 0) && (mrr || !mi->prev_sample)) {
+       if ((delta > 0) && (mrr_capable || !mi->prev_sample)) {
                struct minstrel_rate *msr;
                if (mi->packet_count >= 10000) {
                        mi->sample_deferred = 0;
@@ -268,21 +276,25 @@ minstrel_get_rate(void *priv, struct ieee80211_sta *sta,
                        mi->sample_count += (delta - mi->n_rates * 2);
                }
 
+               /* get next random rate sample */
                sample_ndx = minstrel_get_next_sample(mi);
                msr = &mi->r[sample_ndx];
-               sample = true;
-               sample_slower = mrr && (msr->perfect_tx_time >
-                       mi->r[ndx].perfect_tx_time);
+               rate_sampling = true;
 
-               if (!sample_slower) {
+               /* Decide if direct ( 1st mrr stage) or indirect (2nd mrr stage)
+                * rate sampling method should be used */
+               if (mrr_capable &&
+                   msr->perfect_tx_time > mi->r[ndx].perfect_tx_time)
+                               indirect_rate_sampling = true;
+
+               if (!indirect_rate_sampling) {
                        if (msr->sample_limit != 0) {
                                ndx = sample_ndx;
                                mi->sample_count++;
                                if (msr->sample_limit > 0)
                                        msr->sample_limit--;
-                       } else {
-                               sample = false;
-                       }
+                       } else
+                               rate_sampling = false;
                } else {
                        /* Only use IEEE80211_TX_CTL_RATE_CTRL_PROBE to mark
                         * packets that have the sampling rate deferred to the
@@ -294,34 +306,39 @@ minstrel_get_rate(void *priv, struct ieee80211_sta *sta,
                        mi->sample_deferred++;
                }
        }
-       mi->prev_sample = sample;
+       mi->prev_sample = rate_sampling;
 
        /* If we're not using MRR and the sampling rate already
         * has a probability of >95%, we shouldn't be attempting
         * to use it, as this only wastes precious airtime */
-       if (!mrr && sample && (mi->r[ndx].probability > MINSTREL_FRAC(95, 100)))
+       if (!mrr_capable && rate_sampling &&
+          (mi->r[ndx].probability > MINSTREL_FRAC(95, 100)))
                ndx = mi->max_tp_rate;
 
+       /* mrr setup for 1st stage */
        ar[0].idx = mi->r[ndx].rix;
        ar[0].count = minstrel_get_retry_count(&mi->r[ndx], info);
 
-       if (!mrr) {
-               if (!sample)
+       /* non mrr setup for 2nd stage */
+       if (!mrr_capable) {
+               if (!rate_sampling)
                        ar[0].count = mp->max_retry;
                ar[1].idx = mi->lowest_rix;
                ar[1].count = mp->max_retry;
                return;
        }
 
-       /* MRR setup */
-       if (sample) {
-               if (sample_slower)
+       /* mrr setup for 2nd stage */
+       if (rate_sampling) {
+               if (indirect_rate_sampling)
                        mrr_ndx[0] = sample_ndx;
                else
                        mrr_ndx[0] = mi->max_tp_rate;
        } else {
                mrr_ndx[0] = mi->max_tp_rate2;
        }
+
+       /* mrr setup for 3rd & 4th stage */
        mrr_ndx[1] = mi->max_prob_rate;
        mrr_ndx[2] = 0;
        for (i = 1; i < 4; i++) {
@@ -352,7 +369,7 @@ init_sample_table(struct minstrel_sta_info *mi)
        u8 rnd[8];
 
        mi->sample_column = 0;
-       mi->sample_idx = 0;
+       mi->sample_row = 0;
        memset(mi->sample_table, 0, SAMPLE_COLUMNS * mi->n_rates);
 
        for (col = 0; col < SAMPLE_COLUMNS; col++) {

diff --git a/net/mac80211/rc80211_minstrel.h b/net/mac80211/rc80211_minstrel.h
index fda4a6154c87d8315d5eb94551c1037097cd92ec..5fb5cb81d0dabc2bb7cfb7c4dcd247e70b9e80cc 100644 (file)
--- a/net/mac80211/rc80211_minstrel.h
+++ b/net/mac80211/rc80211_minstrel.h
@@ -69,7 +69,7 @@ struct minstrel_sta_info {
        unsigned int sample_count;
        int sample_deferred;
 
-       unsigned int sample_idx;
+       unsigned int sample_row;
        unsigned int sample_column;
 
        int n_rates;