[OpenWrt-Devel] Status of ACS survey with rt2x00 driver using hostapd

Helmut Schaa helmut.schaa at googlemail.com
Thu Aug 21 16:56:21 EDT 2014

On Mon, Aug 18, 2014 at 3:27 PM, Yousong Zhou <yszhou4tech at gmail.com> wrote:
> Hi,
> I am trying to get ACS working on my available devices.
> What I have noticed is that the command `iw phy phy0 survey dump`
> returned different result between HiWiFi HC6361 which uses ath9k
> driver and a MT7620A based device using rt2x00 driver.   On HC6361,
> the command displayed statistics for all 11 channels, while only 1
> channel's statistics was fetched on the MT7620A device.
> I checked with related code of hostapd, ath9k, rt2x00, and found the
> cause in `rt2800_get_survey()`.  Is this behaviour determined by
> hardware that hostapd's current ACS implementation is not expected to
> work with rt2x00 driver?
> Hmm, how about the solution of adding a function akin to
> `ath_update_survey_stats()` for rt2x00?

Your observation is correct, rt2x00 only returns survey data for the current
channel. I also thought about doing the same approach as ath9k but duplicating
the code seems not reasonable. It might make more sense to move the
survey data buffering to mac80211 and use it from ath9k and rt2x00.

However, as a first start you could emulate ath9k's behavior in rt2x00.
Furthermore rt2x00 does not report noise floor in its survey data which
is also use by hostapd's ACS implementation. Not sure what hostapd
does if that is not present.

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