Re: [PATCH] wireless: sysfs was displaying different values for level and noise than procfs

[Andrey Borzenkov <arvidjaar@mail.ru>]

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On Wednesday 19 November 2008, Pavel Roskin wrote:
> On Sat, 2008-11-15 at 18:31 +0300, Andrey Borzenkov wrote:
> > Subject: [PATCH] wireless: sysfs was displaying different values for level and noise than procfs
> > From: Andrey Borzenkov <arvidjaar@mail.ru>
> > 
> > /proc/net/wireless asjusts display of signal and noise level depending on
> > whether units are percentage or dBm. Use the same format in sysfs. This
> > makes it easy to know unit - below zero is dBm, above zero is percent.
> 
> I've seen received power up to 3 dBm.  The AP was using an amplifier
> (it's specialized hardware), and it's possible that the card on the
> station side was exaggerating the signal.  However, the data we report
> should not need any guesswork to be interpreted.  It may be parsed by
> userspace software.
> 

But positive dBm is not even possible to represnt right now. It is u8 and
is displayed as ((s32)level - 256); so it is *always* negative.

> Receiving 1 mW out of 200 mW is not impossible in some antenna
> configurations even with consumer devices.
> 
> > Before:
> > {pts/1}% cat /sys/class/net/eth1/wireless/level
> > 203
> > {pts/1}% cat /sys/class/net/eth1/wireless/noise
> > 166
> 
> > +	return sprintf(buf, format_string, (__s32)iw->field -		\
> > +			((iw->qual.updated & IW_QUAL_DBM) ? 0x100 : 0)); \
> 
> I think non-dBm data should be shown in a special format: "203/255"
> where 255 is the maximal value, and the dBm data should be shown as
> numbers: "-48".  This way, we encourage use of dBm data by making it
> easier to parse.
> 

Well, I do not have any strong opinion regarding this; I just noticed
discrepancy between procfs and sysfs for what effectively is the same raw
value.

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