wifi: mac80211: allow sharing identical chanctx for S1G interfaces

Introduce support for sharing identical channel contexts for S1G
interfaces. Additionally, do not downgrade channel requests for
S1G interfaces.

Signed-off-by: Lachlan Hodges <lachlan.hodges@morsemicro.com>
Link: https://patch.msgid.link/20251126015758.149034-1-lachlan.hodges@morsemicro.com
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

Author: donnaskiez

net/mac80211/chan.c

@@ -654,8 +654,19 @@ static void _ieee80211_change_chanctx(struct ieee80211_local *local,
 	};
 	u32 changed = 0;
 
-	/* expected to handle only 20/40/80/160/320 channel widths */
+	/* 5/10 MHz not handled here */
 	switch (chandef->width) {
+	case NL80211_CHAN_WIDTH_1:
+	case NL80211_CHAN_WIDTH_2:
+	case NL80211_CHAN_WIDTH_4:
+	case NL80211_CHAN_WIDTH_8:
+	case NL80211_CHAN_WIDTH_16:
+		/*
+		 * mac80211 currently only supports sharing identical
+		 * chanctx's for S1G interfaces.
+		 */
+		WARN_ON(!ieee80211_chanreq_identical(&ctx_req, chanreq));
+		return;
 	case NL80211_CHAN_WIDTH_20_NOHT:
 	case NL80211_CHAN_WIDTH_20:
 	case NL80211_CHAN_WIDTH_40:

net/mac80211/mlme.c

@@ -6108,9 +6108,10 @@ static int ieee80211_prep_channel(struct ieee80211_sub_if_data *sdata,
 	ret = ieee80211_link_use_channel(link, &chanreq,
 					 IEEE80211_CHANCTX_SHARED);
 
-	/* don't downgrade for 5 and 10 MHz channels, though. */
+	/* don't downgrade for 5/10/S1G MHz channels, though. */
 	if (chanreq.oper.width == NL80211_CHAN_WIDTH_5 ||
-	    chanreq.oper.width == NL80211_CHAN_WIDTH_10)
+	    chanreq.oper.width == NL80211_CHAN_WIDTH_10 ||
+	    cfg80211_chandef_is_s1g(&chanreq.oper))
 		return ret;
 
 	while (ret && chanreq.oper.width != NL80211_CHAN_WIDTH_20_NOHT) {