On Wed, Nov 19, 2008 at 10:45:21PM +0300, Andrey Borzenkov wrote:
> 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@xxxxxxx>
> > >
> > > /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.
And what is your perspective regarding potential 'userland ABI'
issues of either this patch or of Pavel's suggestion?
John
--
John W. Linville Linux should be at the core
linville@xxxxxxxxxxxxx of your literate lifestyle.
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