Re: [PATCH-v2 1/2] mac80211: Take bitrates into account when building IEs.

[Ben Greear <greearb@candelatech.com>]

On 03/15/2016 07:15 AM, Johannes Berg wrote:
> On Thu, 2016-03-10 at 09:56 -0800, Ben Greear wrote:
>
>> First, are you proposing that I make a copy of the entire  local-
>>> hw.wiphy->bands array and store it locally in sdata?
>
> No, I think it should be pointers there, say
>
> sdata->bands[X] pointing to the same thing as local->hw.wiphy->bands[X]
> is pointing to.
>
> So the first patch would introduce that, and replace each and every use
> of local->hw.wiphy->bands[] with sdata->bands[], if necessary
> annotating the remaining ones with why they're OK and should stay.
>
>> And then, I would provide some API to modify the bands[i]->bitrates
>> and other variables to properly select the advertised features?
>
> Kinda. You'd provide some kind of helper function or API to take the
> local->hw.wiphy->bands[X] and duplicate it into a newly allocated
> buffer, modifying it along the way, before assigning it to the per-
> sdata stuff in sdata->bands[X].
>
>> I am a bit concerned about making copies (and then changing) the
>> driver's bitrates array.  Likely it will work with ath10k, but it
>> seems fragile at best.
>
> That's an interesting point, we currently use the rate *index* a lot,
> so we have to find some way of preserving that. Perhaps we need to
> introduce a flag indicating a given rate is disabled?

The logic I wrote is basically exactly this.  It uses the configured rates to
specify which of the hardware's rates are allowed and disabled.

I will look more at providing some accessor functions or otherwise abstracting
it without making copies of the driver's ratesets.

Thanks,
Ben

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