Re: [PATCH v4 6/6] mac80211: add ap channel switch command/event

[Victor Goldenshtein <victorg@ti.com>]

On 14/11/2012 13:23, Johannes Berg wrote:
> On Tue, 2012-11-13 at 17:04 +0200, Victor Goldenshtein wrote:
>> This whole DFS implementation initially intended for a single channel
>> mac. I don't might to deal with the channel context stuff but not sure
>> how much available time I"ll have for it, so it might take awhile.
>> I know there are people waiting for this, so I'm thinking would you
>> consider to go first with this single channel DFS support and later to
>> extend it to work with channel context stuff ?
>
> Fair enough, but like I've been telling you, the current code doesn't
> even match the current APIs.
>
> Initially, I thought that for radar detection, you need to reserve the
> channel context (in mac80211), make sure it's the only channel context
> and prohibit other channel contexts from being added, until radar
> detection is done.
>

I thought the same, but to prohibit other channel contexts from being 
added as long as we on DFS channel (not just until the end of the CAC).

> However, then I realised that that still doesn't work -- once initial
> radar detection is done, it needs to continue while the AP is active. If
> the channel context was going to be relinquished, or even just the
> channel changed for a few seconds, it would be unsafe. So as a result,
> the radar detect operation has to somehow be coupled to the start AP
> operation and prohibit channel changes and additional channel contexts
> during the entire operation time.
>

What would be "unsafe" here if from the beginning we will allow only one 
channel context ?

> I definitely think this needs some work, because the APIs and cfg80211
> code have to be correct for multi-channel operation even if you don't
> support it.
>

Agree.

-- 
Thanks,
Victor.