net/mac80211/rc80211_pid_algo.c - kernel/msm - Gitiles

 /*
  * Copyright 2002-2005, Instant802 Networks, Inc.
  * Copyright 2005, Devicescape Software, Inc.
  * Copyright 2007, Mattias Nissler <mattias.nissler@gmx.de>
  * Copyright 2007, Stefano Brivio <stefano.brivio@polimi.it>
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 2 as
  * published by the Free Software Foundation.
  */

 #include <linux/netdevice.h>
 #include <linux/types.h>
 #include <linux/skbuff.h>
 #include <linux/debugfs.h>
 #include <net/mac80211.h>
 #include "ieee80211_rate.h"

 #include "rc80211_pid.h"


 /* This is an implementation of a TX rate control algorithm that uses a PID
  * controller. Given a target failed frames rate, the controller decides about
  * TX rate changes to meet the target failed frames rate.
  *
  * The controller basically computes the following:
  *
  * adj = CP * err + CI * err_avg + CD * (err - last_err) * (1 + sharpening)
  *
  * where
  * 	adj	adjustment value that is used to switch TX rate (see below)
  * 	err	current error: target vs. current failed frames percentage
  * 	last_err	last error
  * 	err_avg	average (i.e. poor man's integral) of recent errors
  *	sharpening	non-zero when fast response is needed (i.e. right after
  *			association or no frames sent for a long time), heading
  * 			to zero over time
  * 	CP	Proportional coefficient
  * 	CI	Integral coefficient
  * 	CD	Derivative coefficient
  *
  * CP, CI, CD are subject to careful tuning.
  *
  * The integral component uses a exponential moving average approach instead of
  * an actual sliding window. The advantage is that we don't need to keep an
  * array of the last N error values and computation is easier.
  *
  * Once we have the adj value, we map it to a rate by means of a learning
  * algorithm. This algorithm keeps the state of the percentual failed frames
  * difference between rates. The behaviour of the lowest available rate is kept
  * as a reference value, and every time we switch between two rates, we compute
  * the difference between the failed frames each rate exhibited. By doing so,
  * we compare behaviours which different rates exhibited in adjacent timeslices,
  * thus the comparison is minimally affected by external conditions. This
  * difference gets propagated to the whole set of measurements, so that the
  * reference is always the same. Periodically, we normalize this set so that
  * recent events weigh the most. By comparing the adj value with this set, we
  * avoid pejorative switches to lower rates and allow for switches to higher
  * rates if they behaved well.
  *
  * Note that for the computations we use a fixed-point representation to avoid
  * floating point arithmetic. Hence, all values are shifted left by
  * RC_PID_ARITH_SHIFT.
  */


 /* Shift the adjustment so that we won't switch to a lower rate if it exhibited
  * a worse failed frames behaviour and we'll choose the highest rate whose
  * failed frames behaviour is not worse than the one of the original rate
  * target. While at it, check that the adjustment is within the ranges. Then,
  * provide the new rate index. */
 static int rate_control_pid_shift_adjust(struct rc_pid_rateinfo *r,
 					 int adj, int cur, int l)
 {
 	int i, j, k, tmp;

 	j = r[cur].rev_index;
 	i = j + adj;

 	if (i < 0)
 		return r[0].index;
 	if (i >= l - 1)
 		return r[l - 1].index;

 	tmp = i;

 	if (adj < 0) {
 		for (k = j; k >= i; k--)
 			if (r[k].diff <= r[j].diff)
 				tmp = k;
 	} else {
 		for (k = i + 1; k + i < l; k++)
 			if (r[k].diff <= r[i].diff)
 				tmp = k;
 	}

 	return r[tmp].index;
 }

 static void rate_control_pid_adjust_rate(struct ieee80211_local *local,
 					 struct sta_info *sta, int adj,
 					 struct rc_pid_rateinfo *rinfo)
 {
 	struct ieee80211_sub_if_data *sdata;
 	struct ieee80211_hw_mode *mode;
 	int newidx;
 	int maxrate;
 	int back = (adj > 0) ? 1 : -1;

 	sdata = IEEE80211_DEV_TO_SUB_IF(sta->dev);

 	mode = local->oper_hw_mode;
 	maxrate = sdata->bss ? sdata->bss->max_ratectrl_rateidx : -1;

 	newidx = rate_control_pid_shift_adjust(rinfo, adj, sta->txrate,
 					       mode->num_rates);

 	while (newidx != sta->txrate) {
 		if (rate_supported(sta, mode, newidx) &&
 		    (maxrate < 0 || newidx <= maxrate)) {
 			sta->txrate = newidx;
 			break;
 		}

 		newidx += back;
 	}

 #ifdef CONFIG_MAC80211_DEBUGFS
 	rate_control_pid_event_rate_change(
 		&((struct rc_pid_sta_info *)sta->rate_ctrl_priv)->events,
 		newidx, mode->rates[newidx].rate);
 #endif
 }

 /* Normalize the failed frames per-rate differences. */
 static void rate_control_pid_normalize(struct rc_pid_info *pinfo, int l)
 {
 	int i, norm_offset = pinfo->norm_offset;
 	struct rc_pid_rateinfo *r = pinfo->rinfo;

 	if (r[0].diff > norm_offset)
 		r[0].diff -= norm_offset;
 	else if (r[0].diff < -norm_offset)
 		r[0].diff += norm_offset;
 	for (i = 0; i < l - 1; i++)
 		if (r[i + 1].diff > r[i].diff + norm_offset)
 			r[i + 1].diff -= norm_offset;
 		else if (r[i + 1].diff <= r[i].diff)
 			r[i + 1].diff += norm_offset;
 }

 static void rate_control_pid_sample(struct rc_pid_info *pinfo,
 				    struct ieee80211_local *local,
 				    struct sta_info *sta)
 {
 	struct rc_pid_sta_info *spinfo = sta->rate_ctrl_priv;
 	struct rc_pid_rateinfo *rinfo = pinfo->rinfo;
 	struct ieee80211_hw_mode *mode;
 	u32 pf;
 	s32 err_avg;
 	u32 err_prop;
 	u32 err_int;
 	u32 err_der;
 	int adj, i, j, tmp;
 	unsigned long period;

 	mode = local->oper_hw_mode;
 	spinfo = sta->rate_ctrl_priv;

 	/* In case nothing happened during the previous control interval, turn
 	 * the sharpening factor on. */
 	period = (HZ * pinfo->sampling_period + 500) / 1000;
 	if (!period)
 		period = 1;
 	if (jiffies - spinfo->last_sample > 2 * period)
 		spinfo->sharp_cnt = pinfo->sharpen_duration;

 	spinfo->last_sample = jiffies;

 	/* This should never happen, but in case, we assume the old sample is
 	 * still a good measurement and copy it. */
 	if (unlikely(spinfo->tx_num_xmit == 0))
 		pf = spinfo->last_pf;
 	else {
 		pf = spinfo->tx_num_failed * 100 / spinfo->tx_num_xmit;
 		pf <<= RC_PID_ARITH_SHIFT;
 	}

 	spinfo->tx_num_xmit = 0;
 	spinfo->tx_num_failed = 0;

 	/* If we just switched rate, update the rate behaviour info. */
 	if (pinfo->oldrate != sta->txrate) {

 		i = rinfo[pinfo->oldrate].rev_index;
 		j = rinfo[sta->txrate].rev_index;

 		tmp = (pf - spinfo->last_pf);
 		tmp = RC_PID_DO_ARITH_RIGHT_SHIFT(tmp, RC_PID_ARITH_SHIFT);

 		rinfo[j].diff = rinfo[i].diff + tmp;
 		pinfo->oldrate = sta->txrate;
 	}
 	rate_control_pid_normalize(pinfo, mode->num_rates);

 	/* Compute the proportional, integral and derivative errors. */
 	err_prop = (pinfo->target << RC_PID_ARITH_SHIFT) - pf;

 	err_avg = spinfo->err_avg_sc >> pinfo->smoothing_shift;
 	spinfo->err_avg_sc = spinfo->err_avg_sc - err_avg + err_prop;
 	err_int = spinfo->err_avg_sc >> pinfo->smoothing_shift;

 	err_der = (pf - spinfo->last_pf) *
 		  (1 + pinfo->sharpen_factor * spinfo->sharp_cnt);
 	spinfo->last_pf = pf;
 	if (spinfo->sharp_cnt)
 			spinfo->sharp_cnt--;

 #ifdef CONFIG_MAC80211_DEBUGFS
 	rate_control_pid_event_pf_sample(&spinfo->events, pf, err_prop, err_int,
 					 err_der);
 #endif

 	/* Compute the controller output. */
 	adj = (err_prop * pinfo->coeff_p + err_int * pinfo->coeff_i
 	      + err_der * pinfo->coeff_d);
 	adj = RC_PID_DO_ARITH_RIGHT_SHIFT(adj, 2 * RC_PID_ARITH_SHIFT);

 	/* Change rate. */
 	if (adj)
 		rate_control_pid_adjust_rate(local, sta, adj, rinfo);
 }

 static void rate_control_pid_tx_status(void *priv, struct net_device *dev,
 				       struct sk_buff *skb,
 				       struct ieee80211_tx_status *status)
 {
 	struct ieee80211_local *local = wdev_priv(dev->ieee80211_ptr);
 	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
 	struct ieee80211_sub_if_data *sdata;
 	struct rc_pid_info *pinfo = priv;
 	struct sta_info *sta;
 	struct rc_pid_sta_info *spinfo;
 	unsigned long period;

 	sta = sta_info_get(local, hdr->addr1);

 	if (!sta)
 		return;

 	/* Don't update the state if we're not controlling the rate. */
 	sdata = IEEE80211_DEV_TO_SUB_IF(sta->dev);
 	if (sdata->bss && sdata->bss->force_unicast_rateidx > -1) {
 		sta->txrate = sdata->bss->max_ratectrl_rateidx;
 		return;
 	}

 	/* Ignore all frames that were sent with a different rate than the rate
 	 * we currently advise mac80211 to use. */
 	if (status->control.rate != &local->oper_hw_mode->rates[sta->txrate])
 		goto ignore;

 	spinfo = sta->rate_ctrl_priv;
 	spinfo->tx_num_xmit++;

 #ifdef CONFIG_MAC80211_DEBUGFS
 	rate_control_pid_event_tx_status(&spinfo->events, status);
 #endif

 	/* We count frames that totally failed to be transmitted as two bad
 	 * frames, those that made it out but had some retries as one good and
 	 * one bad frame. */
 	if (status->excessive_retries) {
 		spinfo->tx_num_failed += 2;
 		spinfo->tx_num_xmit++;
 	} else if (status->retry_count) {
 		spinfo->tx_num_failed++;
 		spinfo->tx_num_xmit++;
 	}

 	if (status->excessive_retries) {
 		sta->tx_retry_failed++;
 		sta->tx_num_consecutive_failures++;
 		sta->tx_num_mpdu_fail++;
 	} else {
 		sta->last_ack_rssi[0] = sta->last_ack_rssi[1];
 		sta->last_ack_rssi[1] = sta->last_ack_rssi[2];
 		sta->last_ack_rssi[2] = status->ack_signal;
 		sta->tx_num_consecutive_failures = 0;
 		sta->tx_num_mpdu_ok++;
 	}
 	sta->tx_retry_count += status->retry_count;
 	sta->tx_num_mpdu_fail += status->retry_count;

 	/* Update PID controller state. */
 	period = (HZ * pinfo->sampling_period + 500) / 1000;
 	if (!period)
 		period = 1;
 	if (time_after(jiffies, spinfo->last_sample + period))
 		rate_control_pid_sample(pinfo, local, sta);

 ignore:
 	sta_info_put(sta);
 }

 static void rate_control_pid_get_rate(void *priv, struct net_device *dev,
 				      struct ieee80211_hw_mode *mode,
 				      struct sk_buff *skb,
 				      struct rate_selection *sel)
 {
 	struct ieee80211_local *local = wdev_priv(dev->ieee80211_ptr);
 	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
 	struct sta_info *sta;
 	int rateidx;

 	sta = sta_info_get(local, hdr->addr1);

 	if (!sta) {
 		sel->rate = rate_lowest(local, mode, NULL);
 		sta_info_put(sta);
 		return;
 	}

 	rateidx = sta->txrate;

 	if (rateidx >= mode->num_rates)
 		rateidx = mode->num_rates - 1;

 	sta_info_put(sta);

 	sel->rate = &mode->rates[rateidx];

 #ifdef CONFIG_MAC80211_DEBUGFS
 	rate_control_pid_event_tx_rate(
 		&((struct rc_pid_sta_info *) sta->rate_ctrl_priv)->events,
 		rateidx, mode->rates[rateidx].rate);
 #endif
 }

 static void rate_control_pid_rate_init(void *priv, void *priv_sta,
 					  struct ieee80211_local *local,
 					  struct sta_info *sta)
 {
 	/* TODO: This routine should consider using RSSI from previous packets
 	 * as we need to have IEEE 802.1X auth succeed immediately after assoc..
 	 * Until that method is implemented, we will use the lowest supported
 	 * rate as a workaround. */
 	sta->txrate = rate_lowest_index(local, local->oper_hw_mode, sta);
 }

 static void *rate_control_pid_alloc(struct ieee80211_local *local)
 {
 	struct rc_pid_info *pinfo;
 	struct rc_pid_rateinfo *rinfo;
 	struct ieee80211_hw_mode *mode;
 	int i, j, tmp;
 	bool s;
 #ifdef CONFIG_MAC80211_DEBUGFS
 	struct rc_pid_debugfs_entries *de;
 #endif

 	pinfo = kmalloc(sizeof(*pinfo), GFP_ATOMIC);
 	if (!pinfo)
 		return NULL;

 	/* We can safely assume that oper_hw_mode won't change unless we get
 	 * reinitialized. */
 	mode = local->oper_hw_mode;
 	rinfo = kmalloc(sizeof(*rinfo) * mode->num_rates, GFP_ATOMIC);
 	if (!rinfo) {
 		kfree(pinfo);
 		return NULL;
 	}

 	/* Sort the rates. This is optimized for the most common case (i.e.
 	 * almost-sorted CCK+OFDM rates). Kind of bubble-sort with reversed
 	 * mapping too. */
 	for (i = 0; i < mode->num_rates; i++) {
 		rinfo[i].index = i;
 		rinfo[i].rev_index = i;
 		if (pinfo->fast_start)
 			rinfo[i].diff = 0;
 		else
 			rinfo[i].diff = i * pinfo->norm_offset;
 	}
 	for (i = 1; i < mode->num_rates; i++) {
 		s = 0;
 		for (j = 0; j < mode->num_rates - i; j++)
 			if (unlikely(mode->rates[rinfo[j].index].rate >
 				     mode->rates[rinfo[j + 1].index].rate)) {
 				tmp = rinfo[j].index;
 				rinfo[j].index = rinfo[j + 1].index;
 				rinfo[j + 1].index = tmp;
 				rinfo[rinfo[j].index].rev_index = j;
 				rinfo[rinfo[j + 1].index].rev_index = j + 1;
 				s = 1;
 			}
 		if (!s)
 			break;
 	}

 	pinfo->target = RC_PID_TARGET_PF;
 	pinfo->sampling_period = RC_PID_INTERVAL;
 	pinfo->coeff_p = RC_PID_COEFF_P;
 	pinfo->coeff_i = RC_PID_COEFF_I;
 	pinfo->coeff_d = RC_PID_COEFF_D;
 	pinfo->smoothing_shift = RC_PID_SMOOTHING_SHIFT;
 	pinfo->sharpen_factor = RC_PID_SHARPENING_FACTOR;
 	pinfo->sharpen_duration = RC_PID_SHARPENING_DURATION;
 	pinfo->norm_offset = RC_PID_NORM_OFFSET;
 	pinfo->fast_start = RC_PID_FAST_START;
 	pinfo->rinfo = rinfo;
 	pinfo->oldrate = 0;

 #ifdef CONFIG_MAC80211_DEBUGFS
 	de = &pinfo->dentries;
 	de->dir = debugfs_create_dir("rc80211_pid",
 				     local->hw.wiphy->debugfsdir);
 	de->target = debugfs_create_u32("target_pf", S_IRUSR | S_IWUSR,
 					de->dir, &pinfo->target);
 	de->sampling_period = debugfs_create_u32("sampling_period",
 						 S_IRUSR | S_IWUSR, de->dir,
 						 &pinfo->sampling_period);
 	de->coeff_p = debugfs_create_u32("coeff_p", S_IRUSR | S_IWUSR,
 					 de->dir, &pinfo->coeff_p);
 	de->coeff_i = debugfs_create_u32("coeff_i", S_IRUSR | S_IWUSR,
 					 de->dir, &pinfo->coeff_i);
 	de->coeff_d = debugfs_create_u32("coeff_d", S_IRUSR | S_IWUSR,
 					 de->dir, &pinfo->coeff_d);
 	de->smoothing_shift = debugfs_create_u32("smoothing_shift",
 						 S_IRUSR | S_IWUSR, de->dir,
 						 &pinfo->smoothing_shift);
 	de->sharpen_factor = debugfs_create_u32("sharpen_factor",
 					       S_IRUSR | S_IWUSR, de->dir,
 					       &pinfo->sharpen_factor);
 	de->sharpen_duration = debugfs_create_u32("sharpen_duration",
 						  S_IRUSR | S_IWUSR, de->dir,
 						  &pinfo->sharpen_duration);
 	de->norm_offset = debugfs_create_u32("norm_offset",
 					     S_IRUSR | S_IWUSR, de->dir,
 					     &pinfo->norm_offset);
 	de->fast_start = debugfs_create_bool("fast_start",
 					     S_IRUSR | S_IWUSR, de->dir,
 					     &pinfo->fast_start);
 #endif

 	return pinfo;
 }

 static void rate_control_pid_free(void *priv)
 {
 	struct rc_pid_info *pinfo = priv;
 #ifdef CONFIG_MAC80211_DEBUGFS
 	struct rc_pid_debugfs_entries *de = &pinfo->dentries;

 	debugfs_remove(de->fast_start);
 	debugfs_remove(de->norm_offset);
 	debugfs_remove(de->sharpen_duration);
 	debugfs_remove(de->sharpen_factor);
 	debugfs_remove(de->smoothing_shift);
 	debugfs_remove(de->coeff_d);
 	debugfs_remove(de->coeff_i);
 	debugfs_remove(de->coeff_p);
 	debugfs_remove(de->sampling_period);
 	debugfs_remove(de->target);
 	debugfs_remove(de->dir);
 #endif

 	kfree(pinfo->rinfo);
 	kfree(pinfo);
 }

 static void rate_control_pid_clear(void *priv)
 {
 }

 static void *rate_control_pid_alloc_sta(void *priv, gfp_t gfp)
 {
 	struct rc_pid_sta_info *spinfo;

 	spinfo = kzalloc(sizeof(*spinfo), gfp);
 	if (spinfo == NULL)
 		return NULL;

 #ifdef CONFIG_MAC80211_DEBUGFS
 	spin_lock_init(&spinfo->events.lock);
 	init_waitqueue_head(&spinfo->events.waitqueue);
 #endif

 	return spinfo;
 }

 static void rate_control_pid_free_sta(void *priv, void *priv_sta)
 {
 	struct rc_pid_sta_info *spinfo = priv_sta;
 	kfree(spinfo);
 }

 static struct rate_control_ops mac80211_rcpid = {
 	.name = "pid",
 	.tx_status = rate_control_pid_tx_status,
 	.get_rate = rate_control_pid_get_rate,
 	.rate_init = rate_control_pid_rate_init,
 	.clear = rate_control_pid_clear,
 	.alloc = rate_control_pid_alloc,
 	.free = rate_control_pid_free,
 	.alloc_sta = rate_control_pid_alloc_sta,
 	.free_sta = rate_control_pid_free_sta,
 #ifdef CONFIG_MAC80211_DEBUGFS
 	.add_sta_debugfs = rate_control_pid_add_sta_debugfs,
 	.remove_sta_debugfs = rate_control_pid_remove_sta_debugfs,
 #endif
 };

 MODULE_DESCRIPTION("PID controller based rate control algorithm");
 MODULE_AUTHOR("Stefano Brivio");
 MODULE_AUTHOR("Mattias Nissler");
 MODULE_LICENSE("GPL");

 int __init rc80211_pid_init(void)
 {
 	return ieee80211_rate_control_register(&mac80211_rcpid);
 }

 void __exit rc80211_pid_exit(void)
 {
 	ieee80211_rate_control_unregister(&mac80211_rcpid);
 }

 #ifdef CONFIG_MAC80211_RC_PID_MODULE
 module_init(rc80211_pid_init);
 module_exit(rc80211_pid_exit);
 #endif
	/*
	* Copyright 2002-2005, Instant802 Networks, Inc.
	* Copyright 2005, Devicescape Software, Inc.
	* Copyright 2007, Mattias Nissler <mattias.nissler@gmx.de>
	* Copyright 2007, Stefano Brivio <stefano.brivio@polimi.it>
	*
	* This program is free software; you can redistribute it and/or modify
	* it under the terms of the GNU General Public License version 2 as
	* published by the Free Software Foundation.
	*/

	#include <linux/netdevice.h>
	#include <linux/types.h>
	#include <linux/skbuff.h>
	#include <linux/debugfs.h>
	#include <net/mac80211.h>
	#include "ieee80211_rate.h"

	#include "rc80211_pid.h"


	/* This is an implementation of a TX rate control algorithm that uses a PID
	* controller. Given a target failed frames rate, the controller decides about
	* TX rate changes to meet the target failed frames rate.
	*
	* The controller basically computes the following:
	*
	* adj = CP * err + CI * err_avg + CD * (err - last_err) * (1 + sharpening)
	*
	* where
	* adj adjustment value that is used to switch TX rate (see below)
	* err current error: target vs. current failed frames percentage
	* last_err last error
	* err_avg average (i.e. poor man's integral) of recent errors
	* sharpening non-zero when fast response is needed (i.e. right after
	* association or no frames sent for a long time), heading
	* to zero over time
	* CP Proportional coefficient
	* CI Integral coefficient
	* CD Derivative coefficient
	*
	* CP, CI, CD are subject to careful tuning.
	*
	* The integral component uses a exponential moving average approach instead of
	* an actual sliding window. The advantage is that we don't need to keep an
	* array of the last N error values and computation is easier.
	*
	* Once we have the adj value, we map it to a rate by means of a learning
	* algorithm. This algorithm keeps the state of the percentual failed frames
	* difference between rates. The behaviour of the lowest available rate is kept
	* as a reference value, and every time we switch between two rates, we compute
	* the difference between the failed frames each rate exhibited. By doing so,
	* we compare behaviours which different rates exhibited in adjacent timeslices,
	* thus the comparison is minimally affected by external conditions. This
	* difference gets propagated to the whole set of measurements, so that the
	* reference is always the same. Periodically, we normalize this set so that
	* recent events weigh the most. By comparing the adj value with this set, we
	* avoid pejorative switches to lower rates and allow for switches to higher
	* rates if they behaved well.
	*
	* Note that for the computations we use a fixed-point representation to avoid
	* floating point arithmetic. Hence, all values are shifted left by
	* RC_PID_ARITH_SHIFT.
	*/


	/* Shift the adjustment so that we won't switch to a lower rate if it exhibited
	* a worse failed frames behaviour and we'll choose the highest rate whose
	* failed frames behaviour is not worse than the one of the original rate
	* target. While at it, check that the adjustment is within the ranges. Then,
	* provide the new rate index. */
	static int rate_control_pid_shift_adjust(struct rc_pid_rateinfo *r,
	int adj, int cur, int l)
	{
	int i, j, k, tmp;

	j = r[cur].rev_index;
	i = j + adj;

	if (i < 0)
	return r[0].index;
	if (i >= l - 1)
	return r[l - 1].index;

	tmp = i;

	if (adj < 0) {
	for (k = j; k >= i; k--)
	if (r[k].diff <= r[j].diff)
	tmp = k;
	} else {
	for (k = i + 1; k + i < l; k++)
	if (r[k].diff <= r[i].diff)
	tmp = k;
	}

	return r[tmp].index;
	}

	static void rate_control_pid_adjust_rate(struct ieee80211_local *local,
	struct sta_info *sta, int adj,
	struct rc_pid_rateinfo *rinfo)
	{
	struct ieee80211_sub_if_data *sdata;
	struct ieee80211_hw_mode *mode;
	int newidx;
	int maxrate;
	int back = (adj > 0) ? 1 : -1;

	sdata = IEEE80211_DEV_TO_SUB_IF(sta->dev);

	mode = local->oper_hw_mode;
	maxrate = sdata->bss ? sdata->bss->max_ratectrl_rateidx : -1;

	newidx = rate_control_pid_shift_adjust(rinfo, adj, sta->txrate,
	mode->num_rates);

	while (newidx != sta->txrate) {
	if (rate_supported(sta, mode, newidx) &&
	(maxrate < 0 \|\| newidx <= maxrate)) {
	sta->txrate = newidx;
	break;
	}

	newidx += back;
	}

	#ifdef CONFIG_MAC80211_DEBUGFS
	rate_control_pid_event_rate_change(
	&((struct rc_pid_sta_info *)sta->rate_ctrl_priv)->events,
	newidx, mode->rates[newidx].rate);
	#endif
	}

	/* Normalize the failed frames per-rate differences. */
	static void rate_control_pid_normalize(struct rc_pid_info *pinfo, int l)
	{
	int i, norm_offset = pinfo->norm_offset;
	struct rc_pid_rateinfo *r = pinfo->rinfo;

	if (r[0].diff > norm_offset)
	r[0].diff -= norm_offset;
	else if (r[0].diff < -norm_offset)
	r[0].diff += norm_offset;
	for (i = 0; i < l - 1; i++)
	if (r[i + 1].diff > r[i].diff + norm_offset)
	r[i + 1].diff -= norm_offset;
	else if (r[i + 1].diff <= r[i].diff)
	r[i + 1].diff += norm_offset;
	}

	static void rate_control_pid_sample(struct rc_pid_info *pinfo,
	struct ieee80211_local *local,
	struct sta_info *sta)
	{
	struct rc_pid_sta_info *spinfo = sta->rate_ctrl_priv;
	struct rc_pid_rateinfo *rinfo = pinfo->rinfo;
	struct ieee80211_hw_mode *mode;
	u32 pf;
	s32 err_avg;
	u32 err_prop;
	u32 err_int;
	u32 err_der;
	int adj, i, j, tmp;
	unsigned long period;

	mode = local->oper_hw_mode;
	spinfo = sta->rate_ctrl_priv;

	/* In case nothing happened during the previous control interval, turn
	* the sharpening factor on. */
	period = (HZ * pinfo->sampling_period + 500) / 1000;
	if (!period)
	period = 1;
	if (jiffies - spinfo->last_sample > 2 * period)
	spinfo->sharp_cnt = pinfo->sharpen_duration;

	spinfo->last_sample = jiffies;

	/* This should never happen, but in case, we assume the old sample is
	* still a good measurement and copy it. */
	if (unlikely(spinfo->tx_num_xmit == 0))
	pf = spinfo->last_pf;
	else {
	pf = spinfo->tx_num_failed * 100 / spinfo->tx_num_xmit;
	pf <<= RC_PID_ARITH_SHIFT;
	}

	spinfo->tx_num_xmit = 0;
	spinfo->tx_num_failed = 0;

	/* If we just switched rate, update the rate behaviour info. */
	if (pinfo->oldrate != sta->txrate) {

	i = rinfo[pinfo->oldrate].rev_index;
	j = rinfo[sta->txrate].rev_index;

	tmp = (pf - spinfo->last_pf);
	tmp = RC_PID_DO_ARITH_RIGHT_SHIFT(tmp, RC_PID_ARITH_SHIFT);

	rinfo[j].diff = rinfo[i].diff + tmp;
	pinfo->oldrate = sta->txrate;
	}
	rate_control_pid_normalize(pinfo, mode->num_rates);

	/* Compute the proportional, integral and derivative errors. */
	err_prop = (pinfo->target << RC_PID_ARITH_SHIFT) - pf;

	err_avg = spinfo->err_avg_sc >> pinfo->smoothing_shift;
	spinfo->err_avg_sc = spinfo->err_avg_sc - err_avg + err_prop;
	err_int = spinfo->err_avg_sc >> pinfo->smoothing_shift;

	err_der = (pf - spinfo->last_pf) *
	(1 + pinfo->sharpen_factor * spinfo->sharp_cnt);
	spinfo->last_pf = pf;
	if (spinfo->sharp_cnt)
	spinfo->sharp_cnt--;

	#ifdef CONFIG_MAC80211_DEBUGFS
	rate_control_pid_event_pf_sample(&spinfo->events, pf, err_prop, err_int,
	err_der);
	#endif

	/* Compute the controller output. */
	adj = (err_prop * pinfo->coeff_p + err_int * pinfo->coeff_i
	+ err_der * pinfo->coeff_d);
	adj = RC_PID_DO_ARITH_RIGHT_SHIFT(adj, 2 * RC_PID_ARITH_SHIFT);

	/* Change rate. */
	if (adj)
	rate_control_pid_adjust_rate(local, sta, adj, rinfo);
	}

	static void rate_control_pid_tx_status(void priv, struct net_device dev,
	struct sk_buff *skb,
	struct ieee80211_tx_status *status)
	{
	struct ieee80211_local *local = wdev_priv(dev->ieee80211_ptr);
	struct ieee80211_hdr hdr = (struct ieee80211_hdr ) skb->data;
	struct ieee80211_sub_if_data *sdata;
	struct rc_pid_info *pinfo = priv;
	struct sta_info *sta;
	struct rc_pid_sta_info *spinfo;
	unsigned long period;

	sta = sta_info_get(local, hdr->addr1);

	if (!sta)
	return;

	/* Don't update the state if we're not controlling the rate. */
	sdata = IEEE80211_DEV_TO_SUB_IF(sta->dev);
	if (sdata->bss && sdata->bss->force_unicast_rateidx > -1) {
	sta->txrate = sdata->bss->max_ratectrl_rateidx;
	return;
	}

	/* Ignore all frames that were sent with a different rate than the rate
	* we currently advise mac80211 to use. */
	if (status->control.rate != &local->oper_hw_mode->rates[sta->txrate])
	goto ignore;

	spinfo = sta->rate_ctrl_priv;
	spinfo->tx_num_xmit++;

	#ifdef CONFIG_MAC80211_DEBUGFS
	rate_control_pid_event_tx_status(&spinfo->events, status);
	#endif

	/* We count frames that totally failed to be transmitted as two bad
	* frames, those that made it out but had some retries as one good and
	* one bad frame. */
	if (status->excessive_retries) {
	spinfo->tx_num_failed += 2;
	spinfo->tx_num_xmit++;
	} else if (status->retry_count) {
	spinfo->tx_num_failed++;
	spinfo->tx_num_xmit++;
	}

	if (status->excessive_retries) {
	sta->tx_retry_failed++;
	sta->tx_num_consecutive_failures++;
	sta->tx_num_mpdu_fail++;
	} else {
	sta->last_ack_rssi[0] = sta->last_ack_rssi[1];
	sta->last_ack_rssi[1] = sta->last_ack_rssi[2];
	sta->last_ack_rssi[2] = status->ack_signal;
	sta->tx_num_consecutive_failures = 0;
	sta->tx_num_mpdu_ok++;
	}
	sta->tx_retry_count += status->retry_count;
	sta->tx_num_mpdu_fail += status->retry_count;

	/* Update PID controller state. */
	period = (HZ * pinfo->sampling_period + 500) / 1000;
	if (!period)
	period = 1;
	if (time_after(jiffies, spinfo->last_sample + period))
	rate_control_pid_sample(pinfo, local, sta);

	ignore:
	sta_info_put(sta);
	}

	static void rate_control_pid_get_rate(void priv, struct net_device dev,
	struct ieee80211_hw_mode *mode,
	struct sk_buff *skb,
	struct rate_selection *sel)
	{
	struct ieee80211_local *local = wdev_priv(dev->ieee80211_ptr);
	struct ieee80211_hdr hdr = (struct ieee80211_hdr ) skb->data;
	struct sta_info *sta;
	int rateidx;

	sta = sta_info_get(local, hdr->addr1);

	if (!sta) {
	sel->rate = rate_lowest(local, mode, NULL);
	sta_info_put(sta);
	return;
	}

	rateidx = sta->txrate;

	if (rateidx >= mode->num_rates)
	rateidx = mode->num_rates - 1;

	sta_info_put(sta);

	sel->rate = &mode->rates[rateidx];

	#ifdef CONFIG_MAC80211_DEBUGFS
	rate_control_pid_event_tx_rate(
	&((struct rc_pid_sta_info *) sta->rate_ctrl_priv)->events,
	rateidx, mode->rates[rateidx].rate);
	#endif
	}

	static void rate_control_pid_rate_init(void priv, void priv_sta,
	struct ieee80211_local *local,
	struct sta_info *sta)
	{
	/* TODO: This routine should consider using RSSI from previous packets
	* as we need to have IEEE 802.1X auth succeed immediately after assoc..
	* Until that method is implemented, we will use the lowest supported
	* rate as a workaround. */
	sta->txrate = rate_lowest_index(local, local->oper_hw_mode, sta);
	}

	static void rate_control_pid_alloc(struct ieee80211_local local)
	{
	struct rc_pid_info *pinfo;
	struct rc_pid_rateinfo *rinfo;
	struct ieee80211_hw_mode *mode;
	int i, j, tmp;
	bool s;
	#ifdef CONFIG_MAC80211_DEBUGFS
	struct rc_pid_debugfs_entries *de;
	#endif

	pinfo = kmalloc(sizeof(*pinfo), GFP_ATOMIC);
	if (!pinfo)
	return NULL;

	/* We can safely assume that oper_hw_mode won't change unless we get
	* reinitialized. */
	mode = local->oper_hw_mode;
	rinfo = kmalloc(sizeof(rinfo) mode->num_rates, GFP_ATOMIC);
	if (!rinfo) {
	kfree(pinfo);
	return NULL;
	}

	/* Sort the rates. This is optimized for the most common case (i.e.
	* almost-sorted CCK+OFDM rates). Kind of bubble-sort with reversed
	* mapping too. */
	for (i = 0; i < mode->num_rates; i++) {
	rinfo[i].index = i;
	rinfo[i].rev_index = i;
	if (pinfo->fast_start)
	rinfo[i].diff = 0;
	else
	rinfo[i].diff = i * pinfo->norm_offset;
	}
	for (i = 1; i < mode->num_rates; i++) {
	s = 0;
	for (j = 0; j < mode->num_rates - i; j++)
	if (unlikely(mode->rates[rinfo[j].index].rate >
	mode->rates[rinfo[j + 1].index].rate)) {
	tmp = rinfo[j].index;
	rinfo[j].index = rinfo[j + 1].index;
	rinfo[j + 1].index = tmp;
	rinfo[rinfo[j].index].rev_index = j;
	rinfo[rinfo[j + 1].index].rev_index = j + 1;
	s = 1;
	}
	if (!s)
	break;
	}

	pinfo->target = RC_PID_TARGET_PF;
	pinfo->sampling_period = RC_PID_INTERVAL;
	pinfo->coeff_p = RC_PID_COEFF_P;
	pinfo->coeff_i = RC_PID_COEFF_I;
	pinfo->coeff_d = RC_PID_COEFF_D;
	pinfo->smoothing_shift = RC_PID_SMOOTHING_SHIFT;
	pinfo->sharpen_factor = RC_PID_SHARPENING_FACTOR;
	pinfo->sharpen_duration = RC_PID_SHARPENING_DURATION;
	pinfo->norm_offset = RC_PID_NORM_OFFSET;
	pinfo->fast_start = RC_PID_FAST_START;
	pinfo->rinfo = rinfo;
	pinfo->oldrate = 0;

	#ifdef CONFIG_MAC80211_DEBUGFS
	de = &pinfo->dentries;
	de->dir = debugfs_create_dir("rc80211_pid",
	local->hw.wiphy->debugfsdir);
	de->target = debugfs_create_u32("target_pf", S_IRUSR \| S_IWUSR,
	de->dir, &pinfo->target);
	de->sampling_period = debugfs_create_u32("sampling_period",
	S_IRUSR \| S_IWUSR, de->dir,
	&pinfo->sampling_period);
	de->coeff_p = debugfs_create_u32("coeff_p", S_IRUSR \| S_IWUSR,
	de->dir, &pinfo->coeff_p);
	de->coeff_i = debugfs_create_u32("coeff_i", S_IRUSR \| S_IWUSR,
	de->dir, &pinfo->coeff_i);
	de->coeff_d = debugfs_create_u32("coeff_d", S_IRUSR \| S_IWUSR,
	de->dir, &pinfo->coeff_d);
	de->smoothing_shift = debugfs_create_u32("smoothing_shift",
	S_IRUSR \| S_IWUSR, de->dir,
	&pinfo->smoothing_shift);
	de->sharpen_factor = debugfs_create_u32("sharpen_factor",
	S_IRUSR \| S_IWUSR, de->dir,
	&pinfo->sharpen_factor);
	de->sharpen_duration = debugfs_create_u32("sharpen_duration",
	S_IRUSR \| S_IWUSR, de->dir,
	&pinfo->sharpen_duration);
	de->norm_offset = debugfs_create_u32("norm_offset",
	S_IRUSR \| S_IWUSR, de->dir,
	&pinfo->norm_offset);
	de->fast_start = debugfs_create_bool("fast_start",
	S_IRUSR \| S_IWUSR, de->dir,
	&pinfo->fast_start);
	#endif

	return pinfo;
	}

	static void rate_control_pid_free(void *priv)
	{
	struct rc_pid_info *pinfo = priv;
	#ifdef CONFIG_MAC80211_DEBUGFS
	struct rc_pid_debugfs_entries *de = &pinfo->dentries;

	debugfs_remove(de->fast_start);
	debugfs_remove(de->norm_offset);
	debugfs_remove(de->sharpen_duration);
	debugfs_remove(de->sharpen_factor);
	debugfs_remove(de->smoothing_shift);
	debugfs_remove(de->coeff_d);
	debugfs_remove(de->coeff_i);
	debugfs_remove(de->coeff_p);
	debugfs_remove(de->sampling_period);
	debugfs_remove(de->target);
	debugfs_remove(de->dir);
	#endif

	kfree(pinfo->rinfo);
	kfree(pinfo);
	}

	static void rate_control_pid_clear(void *priv)
	{
	}

	static void rate_control_pid_alloc_sta(void priv, gfp_t gfp)
	{
	struct rc_pid_sta_info *spinfo;

	spinfo = kzalloc(sizeof(*spinfo), gfp);
	if (spinfo == NULL)
	return NULL;

	#ifdef CONFIG_MAC80211_DEBUGFS
	spin_lock_init(&spinfo->events.lock);
	init_waitqueue_head(&spinfo->events.waitqueue);
	#endif

	return spinfo;
	}

	static void rate_control_pid_free_sta(void priv, void priv_sta)
	{
	struct rc_pid_sta_info *spinfo = priv_sta;
	kfree(spinfo);
	}

	static struct rate_control_ops mac80211_rcpid = {
	.name = "pid",
	.tx_status = rate_control_pid_tx_status,
	.get_rate = rate_control_pid_get_rate,
	.rate_init = rate_control_pid_rate_init,
	.clear = rate_control_pid_clear,
	.alloc = rate_control_pid_alloc,
	.free = rate_control_pid_free,
	.alloc_sta = rate_control_pid_alloc_sta,
	.free_sta = rate_control_pid_free_sta,
	#ifdef CONFIG_MAC80211_DEBUGFS
	.add_sta_debugfs = rate_control_pid_add_sta_debugfs,
	.remove_sta_debugfs = rate_control_pid_remove_sta_debugfs,
	#endif
	};

	MODULE_DESCRIPTION("PID controller based rate control algorithm");
	MODULE_AUTHOR("Stefano Brivio");
	MODULE_AUTHOR("Mattias Nissler");
	MODULE_LICENSE("GPL");

	int __init rc80211_pid_init(void)
	{
	return ieee80211_rate_control_register(&mac80211_rcpid);
	}

	void __exit rc80211_pid_exit(void)
	{
	ieee80211_rate_control_unregister(&mac80211_rcpid);
	}

	#ifdef CONFIG_MAC80211_RC_PID_MODULE
	module_init(rc80211_pid_init);
	module_exit(rc80211_pid_exit);
	#endif