Re: RFC: mac80211/ath9k: allow scanning single channel if other VIF is associated.

[Ben Greear <greearb@candelatech.com>]

On 09/15/2010 03:16 AM, Johannes Berg wrote:
> On Tue, 2010-09-14 at 22:30 -0700, Ben Greear wrote:
>
>>> If I understood the change correctly, it would prevent running full
>>> scans when in associated state. That does not sound reasonable behavior
>>> and scanning should not cause an association to be lost. Did I miss
>>> something or what exactly is this trying to do?
>>
>> That's pretty much what I'm trying to do.  We had similar code in
>> our 2.6.31 kernel with ath5k. Imagine getting 50 virtual stations
>> started with WPA and all of them trying to scan all channels at once!
>
> They can't ... cfg80211 limits it to one scan at a time per hardware ...

Right, but as soon as one finished, the next would start, and at least in .31,
that caused the first to un-associate, giving never-ending loop of interfaces
scanning and trying to associate.

>> I think for the multi-VIF scenario, it should scan the single associated
>> channel by default, but it would be nice to allow full scans on demand.
>
> Go change your userspace then to request only the single channel scan.
>
>> (I would very much like to work with standard wpa_supplicant, but if hacking it
>> is the only way, then I can attempt that.)
>
> Yes, I don't see how we can reasonably work around this in the kernel.

Ok, I'll see if I can add a 'scan-one-if-associated' flag for wpa-supplicant to
use.

Thanks,
Ben


-- 
Ben Greear <greearb@candelatech.com>
Candela Technologies Inc  http://www.candelatech.com