[PATCH] wpa_supplicant: support VHT capability overrides

[Johannes Berg]

On Fri, 2013-03-01 at 09:52 -0800, Ben Greear wrote:

> > +# vht_rx_mcs_nss_1/2/3/4/5/6/7/8: override the MCS set for RX NSS 1-8
> > +# vht_tx_mcs_nss_1/2/3/4/5/6/7/8: override the MCS set for TX NSS 1-8
> > +#  0: MCS 0-7
> > +#  1: MCS 0-8
> > +#  2: MCS 0-9
> > +#  3: not supported
> 
> I'm confused by this.  The MCS overrides I put in for
> HT basically allowed setting each bit in the available
> MCS rates.  Can you offer a bit more explanation on what
> these VHT MCS settings allow/do?

I think if you knew how VHT MCSes worked, it'd be obvious :)

For VHT, there are 10 MCSes (0-9), each of which has up to
configurations for the number of spatial streams (NSS). However, the VHT
capabilities only allow supporting one of 0-7, 0-8, 0-9 or none (see
also the example config file I included)

So a device could, for example, support

NSS 1: MCS 0-9
NSS 2: MCS 0-9
NSS 3-8: none

You could override this, e.g. by setting

vht_rx_mcs_nss_1=2
vht_rx_mcs_nss_2=3

and then you'd get

NSS 1: MCS 0-8
NSS 2-8: none

johannes