Subject: Re: [PATCH] improved statistics for bcm43xx-softmac

From: Michael Buesch <[email-masked]>
Date: Thu, 29 Jun 2006 17:12:21 +0200

On Thursday 29 June 2006 06:08, Larry Finger wrote:
> This patch improves the statistics returned from bcm43xx_get_wireless_stats. The signal level comes
> from smoothing the rssi value returned by the firmware. The quality value is a hack derived from the
> smoothed rssi value and an assumed rssi_max of -25. If anyone has a better value, please let me
> know. The noise value is still the one calculated from the clean-room formula. On my system, this is
> roughly -65 dBm, which seems too high. I would appreciate getting any ideas on what other 
> interface/driver combinations get for the noise value.
> 
> Signed-Off-By: Larry Finger <[email-masked]>
> 
> ==========================================================
> 
> diff --git a/drivers/net/wireless/bcm43xx/bcm43xx_main.c b/drivers/net/wireless/bcm43xx/bcm43xx_main.c
> index af97755..c80fdcd 100644
> --- a/drivers/net/wireless/bcm43xx/bcm43xx_main.c
> +++ b/drivers/net/wireless/bcm43xx/bcm43xx_main.c
> @@ -1581,17 +1581,8 @@ static void handle_irq_noise(struct bcm4
> 		else
> 			average -= 48;
> 
> -/* FIXME: This is wrong, but people want fancy stats. well... */
> -bcm->stats.noise = average;
> -		if (average > -65)
> -			bcm->stats.link_quality = 0;
> -		else if (average > -75)
> -			bcm->stats.link_quality = 1;
> -		else if (average > -85)
> -			bcm->stats.link_quality = 2;
> -		else
> -			bcm->stats.link_quality = 3;
> -//		dprintk(KERN_INFO PFX "Link Quality: %u (avg was %d)\n", bcm->stats.link_quality, average);
> +/* FIXME: This matches the formula from the clean-room, but yields a value that is probably too
> large. */
> +		bcm->stats.noise = average;
>   drop_calculation:
> 		bcm->noisecalc.calculation_running = 0;
> 		return;
> diff --git a/drivers/net/wireless/bcm43xx/bcm43xx_wx.c b/drivers/net/wireless/bcm43xx/bcm43xx_wx.c
> index 5c36e29..8224da1 100644
> --- a/drivers/net/wireless/bcm43xx/bcm43xx_wx.c
> +++ b/drivers/net/wireless/bcm43xx/bcm43xx_wx.c
> @@ -47,6 +47,8 @@ #include "bcm43xx_phy.h"
>   #define BCM43xx_WX_VERSION	18
> 
>   #define MAX_WX_STRING		80
> +/* FIXME: the next line is a guess as to what the maximum value of rssi might be */
> +#define RSSI_MAX		-25
> 
> 
>   static int bcm43xx_wx_get_name(struct net_device *net_dev,
> @@ -227,15 +229,15 @@ static int bcm43xx_wx_get_rangeparams(st
> 
> 	range->max_qual.qual = 100;
> 	/* TODO: Real max RSSI */
> -	range->max_qual.level = 3;
> -	range->max_qual.noise = 100;
> -	range->max_qual.updated = 7;
> -
> -	range->avg_qual.qual = 70;
> -	range->avg_qual.level = 2;
> -	range->avg_qual.noise = 40;
> -	range->avg_qual.updated = 7;
> -
> +	range->max_qual.level = -100;
> +	range->max_qual.noise = -100;
> +	range->max_qual.updated = IW_QUAL_ALL_UPDATED;
> +
> +	range->avg_qual.qual = 50;
> +	range->avg_qual.level = -40;
> +	range->avg_qual.noise = -65;
> +	range->avg_qual.updated = IW_QUAL_ALL_UPDATED;
> +
> 	range->min_rts = BCM43xx_MIN_RTS_THRESHOLD;
> 	range->max_rts = BCM43xx_MAX_RTS_THRESHOLD;
> 	range->min_frag = MIN_FRAG_THRESHOLD;
> @@ -827,6 +829,8 @@ static struct iw_statistics *bcm43xx_get
> 	struct bcm43xx_private *bcm = bcm43xx_priv(net_dev);
> 	struct ieee80211softmac_device *mac = ieee80211_priv(net_dev);
> 	struct iw_statistics *wstats;
> +	struct ieee80211_network *network = NULL;
> +	static int tmp_level = 0;
> 
> 	wstats = &bcm->stats.wstats;
> 	if (!mac->associated) {
> @@ -849,11 +853,19 @@ static struct iw_statistics *bcm43xx_get
> 		return wstats;
> 	}
> 	/* fill in the real statistics when iface associated */
> -	wstats->qual.qual = 100;     // TODO: get the real signal quality
> -	wstats->qual.level = 3 - bcm->stats.link_quality;
> +	list_for_each_entry(network, &mac->ieee->network_list, list) {
> +		if (!memcmp(mac->associnfo.bssid, network->bssid, ETH_ALEN)) {
> +			if (!tmp_level)		/* get initial value */
> +				tmp_level = network->stats.rssi;
> +			else			/* smooth results */
> +				tmp_level = (7 * tmp_level + network->stats.rssi)/8;
> +			break;
> +		}
> +	}

You need to lock the ieee80211 lock here. Otherwise it might race and crash,
if some workqueue modifies the list inbetween.

> +	wstats->qual.level = tmp_level;
> +	wstats->qual.qual = 100 + tmp_level - RSSI_MAX; // TODO: get the real signal quality
> 	wstats->qual.noise = bcm->stats.noise;
> -	wstats->qual.updated = IW_QUAL_QUAL_UPDATED | IW_QUAL_LEVEL_UPDATED |
> -		IW_QUAL_NOISE_UPDATED;
> +	wstats->qual.updated = IW_QUAL_ALL_UPDATED;
> 	wstats->discard.code = bcm->ieee->ieee_stats.rx_discards_undecryptable;
> 	wstats->discard.retries = bcm->ieee->ieee_stats.tx_retry_limit_exceeded;
> 	wstats->discard.nwid = bcm->ieee->ieee_stats.tx_discards_wrong_sa;

-- 
Greetings Michael.