From: Peter Hessler <phessler@theapt.org>
Subject: Re: iwx: check for MIMO peer support on MA devices
To: tech@openbsd.org
Date: Tue, 10 Mar 2026 11:23:18 +0100

On 2026 Mar 10 (Tue) at 10:31:16 +0100 (+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?
:

tested on AX211, OK


: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;
:

-- 
Once, adv.:
	Enough.
		-- Ambrose Bierce, "The Devil's Dictionary"