Request for testing - ath channel survey support
adrian at freebsd.org
Sat Apr 28 08:38:08 UTC 2012
I've implemented a basic, ath(4) driver specific channel survey
extension using the diagnostic API. I'd like for this to eventually be
made available to net80211.
What you need:
* freebsd-head as of two minutes ago;
* an AR5416 or later NIC (I haven't ported it back to the AR5212 era
legacy NICs, and AR5210/AR5211 don't have the needed registers);
* built src/tools/tools/ath/athsurvey/
What you get:
* a per-second snapshot of the channel busy status - TX busy %, RX
busy %, channel busy %, and extension channel busy %.
* since 32 samples are kept (and they're done every 1/10th of a
second), there's enough history to get 3 seconds of data - so the
lower, average and upper values are reported.
What's currently broken/unimplemented:
* It's not that useful when a channel scan is going on. I'll
eventually extend it to be available from the normal userland, so a
single snapshot of the channel state can be recorded
* Fetching the 'off-channel' state (ie, to compare all the channels at once)
* the extension channel counters seem to get thoroughly upset
occasionally and report some garbage values. I'll track down why that
is and document it, for the mean time don't pay attention to them if
you're in a 20MHz wide channel.
But with all the above issues (and the TODO list in the commit!), it's
still a good indication of exactly how busy the channel is and how
much time you're spending RX'ing frames versus RX'ing "other stuff
that it can't decode". Those of you in noisy wireless environments
would probably benefit from these statistics. Note the difference
between how "busy" a channel can get - it can be quite bursty, so you
can see a big difference between the lower and upper values. Don't be
too frightened, that's to be expected. :)
Please report and weirdnesses and crashes that may occur.
Finally, if someone would like to port this stuff to the AR5212 HAL,
please contact me. It'll be very straight forward to do and you'll
also then get survey support for all the 11abg NICs out there.
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