Using 3T3R Atheros 802.11n PCIe card in 2T2R mode

[Adrian Chadd]

Hi!

On 14 November 2013 14:42, Christophe Prevotaux
<c.prevotaux at rural-networks.com> wrote:
>
> Hi everyone,
>
> I would like to know a few things:
>
> Is it possible to configure a 3T3R PCIe Atheros based card
> to turn it into a 2T2R equivalent ? ( ie using only 2 antennas and
> voiding the use of the 3rd one).

Yup. But you can only do it on certain combinations. I think the only
supported combination is enabling chain 0 and chain 2.

>
> If so how do you do this in FreeBSD ?

You set a kenv variable that resource_int_value() can read at bootup.

I _think_ it's:

hint.ath.X.rx_chainmask=<number>
hint.ath.X.tx_chainmask=<number>

It's in ath_attach() in if_ath.c. Look for resource_int_value().

> Which version of FreeBSD will support that  ( I guess 10 >)

Yup, > 10 and later.

> Any of you have recommendation on a known good card ?
>
> If there are multiple chipset that can do this I would
> like to know which one.

It should work for all of them.

The one thing I need to validate though is the whole "calibration"
versus "use" thing. In theory, we should be calibrating all of the
chainmasks that are present in the EEPROM but only _using_ the ones we
override for transmit and receive. I don't know if the HAL code is
doing this. It would certainly be a simple enough project for someone
to tackle.

Thanks,


-adrian