From: Kevin Lo <kevlo@kevlo.org>
Subject: Re: iwx: check for MIMO peer support on MA devices
To: tech@openbsd.org
Date: Wed, 11 Mar 2026 16:04:36 +0800

On Tue, Mar 10, 2026 at 10:31:16AM +0100, Stefan Sperling wrote:
> 
> In practice, virtually all 11n/11ac APs do support MIMO. But regardless
> we should be checking whether MIMO-capable Rx rates were announced before
> sending frames using MIMO rates to the AP.
> 
> ok?

ok kevlo@, thanks.

> path + /usr/src
> commit - bcd423a398c7cef4cae8fc7ab710c0b896ee8499
> blob - a468e32fe4b545158a8fce60bdcdeed7e84349e3
> file + sys/dev/pci/if_iwx.c
> --- sys/dev/pci/if_iwx.c
> +++ sys/dev/pci/if_iwx.c
> @@ -6832,8 +6832,16 @@ iwx_mld_add_sta_cmd(struct iwx_softc *sc, struct iwx_n
>  	sta_cmd.assoc_id = htole32(IEEE80211_AID(in->in_ni.ni_associd));
>  
>  	if (in->in_ni.ni_flags & IEEE80211_NODE_HT) {
> -		if (iwx_mimo_enabled(sc))
> -			sta_cmd.mimo = htole32(1);
> +		if (iwx_mimo_enabled(sc)) {
> +			if (in->in_ni.ni_flags & IEEE80211_NODE_VHT) {
> +				uint16_t rx_mcs = (in->in_ni.ni_vht_rxmcs &
> +				    IEEE80211_VHT_MCS_FOR_SS_MASK(2)) >>
> +				    IEEE80211_VHT_MCS_FOR_SS_SHIFT(2);
> +				if (rx_mcs != IEEE80211_VHT_MCS_SS_NOT_SUPP)
> +					sta_cmd.mimo = htole32(1);
> +			} else if (in->in_ni.ni_rxmcs[1] != 0)
> +				sta_cmd.mimo = htole32(1);
> +		}
>  
>  		mpdu_dens = (in->in_ni.ni_ampdu_param &
>  		    IEEE80211_AMPDU_PARAM_SS) >> 2;
>