[PATCH] hostapd: take configured antenna set into consideration

[Felix Fietkau]

On 2016-01-22 15:57, Ben Greear wrote:
> 
> 
> On 01/22/2016 03:13 AM, Felix Fietkau wrote:
>> On 2015-12-09 21:20, greearb at candelatech.com wrote:
>>> From: Ben Greear <greearb at candelatech.com>
>>>
>>> If user has configured TX antennas to be less than what
>>> hardware advertises, the MCS reported by hardware will
>>> be too large.  So, remove MCS sets accordingly.
>>>
>>> Signed-off-by: Ben Greear <greearb at candelatech.com>
>> Why is it necessary to do this in user space? Shouldn't the driver
>> recalculate its MCS capabilities and let hostapd use the updated
>> information.
>> IIRC that's what ath9k is doing at the moment.
> 
> 
> I guess that could work too, but long term, I think hostapd should have
> a lot more control over this anyway:  Maybe one vAP would like to be 1x1
> and another 3x3 on the same radio (different vdevs) for instance.  I'd
> use this feature for testing, but perhaps others could take advantage
> of it in other ways.
I don't think that makes sense, and it doesn't really match up with
hardware capabilities either. You can't just enable/disable antennas per
VAP. And if you just want to advertise different MCS capabilities for
testing, then antenna configuration is a pretty bad and hackish way to
achieve that goal.

> I haven't tested ath9k in this scenario...have you been able to confirm
> that the beacons show proper MCS values with stock hostapd when you lower
> the NSS?
Yes, I just tested it with the current code and the MCS information is
correct. Running iw phy0 info will also show reduced HT capabilities.

- Felix