[Testing] some errors on iwconfig

Dan Williams dcbw at redhat.com
Mon Jul 2 15:02:43 EDT 2007


On Mon, 2007-07-02 at 11:23 -0700, Ronak Chokshi wrote:
> Dan,
> We investigated this issue.
> 
> The link quality, as reported by iwconfig, is computed by the libertas
> driver based on RSSI, NF, and tx retries.
> After a close inspection we found that minimum value of link quality is
> always set to 100, that does not sound correct.

Ah, nice.  Thanks for the find.  I'll push the fix to libertas git.

Thanks!
Dan


> Please see the below code (see the text "read this" below).
> 
> ../net/wireless/libertas/wext.c, function "wlan_get_wireless_stats"
> {
> ...
> priv->wstats.discard.misc = adapter->logmsg.ackfailure;
>  
>  /* Calculate quality */
>  priv->wstats.qual.qual = max(quality, (u32)100);    <--- read this.
>  priv->wstats.qual.updated = IW_QUAL_ALL_UPDATED | IW_QUAL_DBM;
> ...
> }
>  
> I guess the above, instead, should be 'priv->wstats.qual.qual =
> min(quality, (u32)100);'
>  
> Also, we checked the SNR (qual.level), NF (qual.noise) as reported by
> the firmware and, found that firmware reports these values properly.
> 
> Thanks
> Ronak
> 
> -----Original Message-----
> From: Dan Williams [mailto:dcbw at redhat.com] 
> Sent: Monday, July 02, 2007 4:55 AM
> To: Ronak Chokshi
> Cc: Michail Bletsas; supat at supat.eu.org; testing at laptop.org; Kim Quirk;
> testing-bounces at lists.laptop.org
> Subject: RE: [Testing] some errors on iwconfig
> 
> On Sun, 2007-07-01 at 10:11 -0700, Ronak Chokshi wrote:
> > We have talked about populating link quality field with different
> > sorts of values but we haven't gotten a consensus on that yet. I will
> > dig up the latest email threads on that topic but suggestions are
> > definitely welcome. Link quality in a mesh network usually doesn't
> > hold too much of sense because there are several links to neighbor
> > mesh nodes to start with. So, there is not one RF link that can be
> > justified as a candidate for calculating link quality.
> 
> With WEXT, link "quality" (ie, qual.qual) is a linear scale field from 0
> - 100 that may, at the option of the driver, take things like transmit
> errors, decryption failures, etc, into account.
> 
> The "level" field (ie, qual.level) is where either dBm or raw RSSI
> should go for the signal, and the "noise" field (ie, qual.noise) should
> match the level semantics, but of course with noise and not signal.
> 
> So as long as these restrictions are met, whatever gets used in
> qual.qual is probably fine by me.
> 
> Dan
> 
> >  
> > 
> > Thanks
> > 
> > Ronak
> > 
> > 
> >                                    
> > ______________________________________________________________________
> > From:testing-bounces at lists.laptop.org
> > [mailto:testing-bounces at lists.laptop.org] On Behalf Of Michail Bletsas
> > Sent: Sunday, July 01, 2007 8:36 AM
> > To: supat at supat.eu.org
> > Cc: Dan Williams; testing at laptop.org; Kim Quirk;
> > testing-bounces at lists.laptop.org
> > Subject: Re: [Testing] some errors on iwconfig
> > 
> > 
> >  
> > 
> > 
> > I assume that you are using an XO. 
> > What OS build does it run? 
> > 
> > I am not sure how link quality is calculated and I never pay too much
> > attention to it. 
> > Points 2,3 and 4 are normal 
> > 
> > M. 
> > 
> > 
> > 
> > 
> > 
> > supat at supat.eu.org 
> > 
> > 07/01/2007 10:46 AM 
> > 
> > 
> >                To
> > 
> > 
> > Michail Bletsas
> > <mbletsas at laptop.org> 
> > 
> > 
> >                cc
> > 
> > 
> > Dan Williams
> > <dcbw at redhat.com>, testing at laptop.org, Kim Quirk
> <kim.quirk at gmail.com>, "OLPC Developer's List" <devel at laptop.org>,
> testing-bounces at lists.laptop.org 
> > 
> > 
> >           Subject
> > 
> > 
> > some errors on
> > iwconfig
> > 
> > 
> > 
> >  
> > 
> >  
> > 
> > 
> >  
> > 
> > 
> > 
> > 
> > 
> > 
> > 
> > 
> > always got below errors:
> > 
> > eth0      MRVL-USB8388  ESSID:"zxc555"  Nickname:"zxc55555"
> >           Mode:Managed  Frequency:2.412 GHz  Access Point: 
> > 00:15:E9:F9:29:CA
> >           Bit Rate:11 Mb/s   Tx-Power=15 dBm
> >           Retry limit:8   RTS thr=2347 B   Fragment thr=2346 B
> >           Encryption key:off
> >           Power Management:off
> >           Link Quality=100/100  Signal level=-83 dBm  Noise level=-98
> > dBm
> >           Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid frag:22023
> >           Tx excessive retries:293  Invalid misc:648   Missed beacon:0
> > 
> > 
> > 1. link quality alway 100% which is impossible
> > 2. Rx invalid frag: always happen
> > 3.  Tx excessive retries: always high
> > 4. Invalid misc: alway increasing in numbers.
> > 
> > 
> > 
> > 
> 



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