Reduce Channel Scanning Time in wpa_supplicant

Dan Williams dcbw
Fri Feb 24 11:37:31 PST 2012

On Thu, 2012-02-23 at 00:48 -0500, Nithyananthan Poosamani wrote:
> Hi,
> I am working with wpa_supplicant 0.6.x provided along with the Android
> source git. I am working on supplicant for NexusOne phone.
> In driver_wext.c file and in the method
> "wpa_driver_wext_set_cscan_params", there is the code to do passive
> channel scanning.
> So by default of 250 ms dwell time, if my understanding is right,
> Android takes close to 3.5 sec to do one full-channel scan and return
> the results.
> My question is, how can I do scanning for only one specified channel ?
> So basically I would do scanning for 250 ms only and then return
> results.

That depends largely on the wifi driver, and how much control that
driver exposes to userspace for the scanning process.  Most drivers
don't expose much control at all, though nl80211-based drivers are
starting to get there.


> Also the previous scan results are cached somewhere, so whenever the
> phone screen is turned on, we check the cached results first to
> speed-up association else do new scanning.
> How are the cache results changed, how periodically ?
> I would be happy if any of you can help me understand these
> phenomenon's.
> Thanks for your time !
> Sincerely,
> Nithy
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