[rt2x00-users] rt2800usb and automatic channel selection

Johannes Stezenbach js at sig21.net
Mon Dec 15 22:52:28 AEDT 2014

On Mon, Dec 15, 2014 at 11:25:35AM +0100, Sven Neumann wrote:
> we are trying to use hostapd with a rt2800usb device. This works
> fine so far, but we have found that the automatic channel
> selection feature of hostapd (see
> http://wireless.kernel.org/en/users/Documentation/acs) doesn't
> work properly. This is because the survey based algorithm relies
> on the nl80211 survey API command to  query the interface for
> channel active time, channel busy time, channel  tx time and
> noise It appears that the rt2800 drivers implement the
> get_survey command, but it is are not filling in infomation
> about the noise floor. Now I wonder if there is a chance that
> this information is somehow available in the driver and whether
> the get_survey command could be changed to also provide
> information about the noise floor on a specific channel. Any
> help with that would be much appreciated.

Probably I remember it wrong because it is a long time
since I did a bit of work on rt2800usb (2011), but I
think there is no documentation available for the
baseband processor registers, thus the usual advice
is to download the vendor driver for your particular
hardware and check if it implements it, and then port
it to rt2x00. But I think the vender drivers do not implement
AP mode, so it is likely that the function you need is
not available.

Anyway, maybe you can give more details on the device you want to use.

Generally I'm not sure how well the rt2800 USB devices work for
AP mode vs. the PCI devices, IIRC the USB interface has
some limitation for getting the TX status of each
sent packets, and issues for implementing power save
(though that might not affect AP mode).  So while it may
basically work it might not be fit for production use.
I hope I'm not spreading FUD, maybe someone else from rt2x00
team can confirm or object since my knowledge is basically
from 2011.


PS: please turn off HTML

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