Re: [RFCv2 2/3] mac80211: mesh power save doze scheduling

[Marco Porsch <marco@cozybit.com>]

On 02/08/2013 10:57 PM, Johannes Berg wrote:
> On Fri, 2013-02-08 at 11:09 +0100, Marco Porsch wrote:
>
>>>> For mesh Awake Windows wakeup on SWBA (beacon_get_tim) and start
>>>> a timer which triggers a doze call on expiry.
>>>
>>> That seems questionable -- drivers are not required to request each
>>> beacon. I know you only want to make it work on ath9k, but I don't think
>>> "stretching" the API, without even documenting it, is a good idea.
>>
>> Currently, we already use ieee80211_beacon_get_tim as time reference for
>> mesh sync's adjust_tbtt. And, as far as I know, all mesh-capable drivers
>> use the call for each and every beacon.
>
> Oops, why did I miss that before? :-)
>
>> So what would you recommend: keep using beacon_get and adding
>> documentation - or - creating an exported callback for awake_window_start?
>
> I guess you could add it... However, I don't really fully understand.
> There's no guarantee that fetching the beacon is done anywhere close to
> TBTT? Or does ath9k happen to do it just after TXing a beacon? You're
> encoding quite a lot of ath9k-specific assumptions here it seems?

I think the assumption is currently correct for ath5k, ath9k, ath9k_htc, 
carl9170 and rt2800 (that's as far as I checked). All of these fetch a 
beacon on SWBA/PRETBTT interrupt (more or less) immediately before TBTT.

--Marco