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Commit 1d60ab05 authored by Stefano Brivio's avatar Stefano Brivio Committed by John W. Linville
Browse files

rc80211-pid: fix rate adjustment 



Merge rate_control_pid_shift_adjust() to rate_control_pid_adjust_rate()
in order to make the learning algorithm aware of constraints on rates. Also
add some comments and rename variables.

This fixes a bug which prevented 802.11b/g non-AP STAs from working with
802.11b only AP STAs.

This patch was originally destined for 2.6.26, and is being backported
to fix a user reported problem in post-2.6.24 kernels.

Signed-off-by: default avatarStefano Brivio <stefano.brivio@polimi.it>
Signed-off-by: default avatarJohn W. Linville <linville@tuxdriver.com>
parent ec9b6add

net/mac80211/rc80211_pid_algo.c

+43 −49
Original line number Diff line number Diff line
@@ -2,7 +2,7 @@ 
 * 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>

 * Copyright 2007-2008, 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
@@ -63,72 +63,66 @@ 
 * 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;

}



/* Adjust the rate while ensuring 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 new rate is valid. */

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;

	int cur_sorted, new_sorted, probe, tmp, n_bitrates;

	int cur = sta->txrate;



	sdata = IEEE80211_DEV_TO_SUB_IF(sta->dev);



	mode = local->oper_hw_mode;

	maxrate = sdata->bss ? sdata->bss->max_ratectrl_rateidx : -1;

	n_bitrates = mode->num_rates;



	newidx = rate_control_pid_shift_adjust(rinfo, adj, sta->txrate,

					       mode->num_rates);

	/* Map passed arguments to sorted values. */

	cur_sorted = rinfo[cur].rev_index;

	new_sorted = cur_sorted + adj;



	while (newidx != sta->txrate) {

		if (rate_supported(sta, mode, newidx) &&

		    (maxrate < 0 || newidx <= maxrate)) {

			sta->txrate = newidx;

			break;

	/* Check limits. */

	if (new_sorted < 0)

		new_sorted = rinfo[0].rev_index;

	else if (new_sorted >= n_bitrates)

		new_sorted = rinfo[n_bitrates - 1].rev_index;



	tmp = new_sorted;



	if (adj < 0) {

		/* Ensure that the rate decrease isn't disadvantageous. */

		for (probe = cur_sorted; probe >= new_sorted; probe--)

			if (rinfo[probe].diff <= rinfo[cur_sorted].diff &&

			    rate_supported(sta, mode, rinfo[probe].index))

				tmp = probe;

	} else {

		/* Look for rate increase with zero (or below) cost. */

		for (probe = new_sorted + 1; probe < n_bitrates; probe++)

			if (rinfo[probe].diff <= rinfo[new_sorted].diff &&

			    rate_supported(sta, mode, rinfo[probe].index))

				tmp = probe;

	}



		newidx += back;

	/* Fit the rate found to the nearest supported rate. */

	do {

		if (rate_supported(sta, mode, rinfo[tmp].index)) {

			sta->txrate = rinfo[tmp].index;

			break;

		}

		if (adj < 0)

			tmp--;

		else

			tmp++;

	} while (tmp < n_bitrates && tmp >= 0);



#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);

		cur, mode->rates[cur].rate);

#endif

}