wifi: cfg80211: separate NPCA validity from chandef validity

When considering both NPCA and DBE, it can appear that the
NPCA configuration is invalid, e.g. for an 80 MHz BSS channel
with DBE to 160 MHz:

     | primary channel
     |       NPCA primary channel
     |       |
     V       V
   | p |   | n |   |   |   |   |   |
   | BSS channel   |
   | DBE channel                   |

Now the NPCA primary channel is in the same half as the primary
channel, and the NPCA puncturing bitmap could be completely
invalid as a puncturing bitmap when considering the overall
channel.

Split out the validity checks from cfg80211_chandef_valid() to
a new cfg80211_chandef_npca_valid() function that just checks
the NPCA configuration against the BSS chandef.

Link: https://patch.msgid.link/20260428112708.1225df131557.If3a6afadcce05d215b72fd82175f72373a0f6d24@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

include/net/cfg80211.h

@@ -849,6 +849,10 @@ struct key_params {
  * struct cfg80211_chan_def - channel definition
  * @chan: the (control) channel
  * @npca_chan: the NPCA primary channel
+ *	Note that if DBE is in use, this channel may appear to be
+ *	inside the primary half of the chandef. Implementations
+ *	can use the position of this channel to understand how
+ *	NPCA is used.
  * @width: channel width
  * @center_freq1: center frequency of first segment
  * @center_freq2: center frequency of second segment
@@ -864,6 +868,8 @@ struct key_params {
  * @npca_punctured: NPCA puncturing bitmap, like @punctured but for
  *	NPCA transmissions. If NPCA is used (@npca_chan is not %NULL)
  *	this will be a superset of the @punctured bimap.
+ *	Note that if DBE is used, this bitmap is also shifted to be in
+ *	accordance with the overall chandef bandwidth.
  * @s1g_primary_2mhz: Indicates if the control channel pointed to
  *	by 'chan' exists as a 1MHz primary subchannel within an
  *	S1G 2MHz primary channel.
@@ -1154,6 +1160,23 @@ int cfg80211_chandef_primary(const struct cfg80211_chan_def *chandef,
 			     enum nl80211_chan_width primary_chan_width,
 			     u16 *punctured);
 
+/**
+ * cfg80211_chandef_npca_valid - check that NPCA information is valid
+ * @wiphy: the wiphy to check for, for channel pointer lookup
+ * @chandef: the BSS channel chandef to check against
+ * @npca: NPCA information, can be %NULL in which case this
+ *	always returns %true
+ *
+ * Note that DBE must not have been configured into the chandef yet
+ * before checking NPCA, i.e. @chandef must represent the BSS channel.
+ *
+ * Returns: %true if the NPCA channel and puncturing bitmap are valid
+ *	according to the chandef, %false otherwise
+ */
+bool cfg80211_chandef_npca_valid(struct wiphy *wiphy,
+				 const struct cfg80211_chan_def *chandef,
+				 const struct ieee80211_uhr_npca_info *npca);
+
 /**
  * cfg80211_chandef_add_npca - parse and add NPCA information to chandef
  * @wiphy: the wiphy this will be used for, for channel pointer lookup

net/mac80211/mlme.c

@@ -406,7 +406,10 @@ ieee80211_determine_ap_chan(struct ieee80211_sub_if_data *sdata,
 
 		npca = ieee80211_uhr_npca_info(uhr_oper);
 
-		if (cfg80211_chandef_add_npca(sdata->local->hw.wiphy,
+		/* DBE is not considered yet, so this works */
+		if (!cfg80211_chandef_npca_valid(sdata->local->hw.wiphy,
+						 &npca_chandef, npca) ||
+		    cfg80211_chandef_add_npca(sdata->local->hw.wiphy,
 					      &npca_chandef, npca)) {
 			sdata_info(sdata,
 				   "AP UHR NPCA settings invalid, disabling UHR\n");

net/wireless/chan.c

@@ -460,9 +460,6 @@ bool cfg80211_chandef_valid(const struct cfg80211_chan_def *chandef)
 		return false;
 
 	if (chandef->npca_chan) {
-		bool pri_upper, npca_upper;
-		u32 cf1;
-
 		switch (chandef->width) {
 		case NL80211_CHAN_WIDTH_80:
 		case NL80211_CHAN_WIDTH_160:
@@ -471,24 +468,6 @@ bool cfg80211_chandef_valid(const struct cfg80211_chan_def *chandef)
 		default:
 			return false;
 		}
-
-		if (!cfg80211_chandef_valid_control_freq(chandef,
-							 chandef->npca_chan->center_freq))
-			return false;
-
-		cf1 = chandef->center_freq1;
-		pri_upper = chandef->chan->center_freq > cf1;
-		npca_upper = chandef->npca_chan->center_freq > cf1;
-
-		if (pri_upper == npca_upper)
-			return false;
-
-		if (!valid_puncturing_bitmap(chandef,
-					     chandef->npca_chan->center_freq,
-					     chandef->npca_punctured) ||
-		    (chandef->punctured & chandef->npca_punctured) !=
-		    chandef->punctured)
-			return false;
 	} else if (chandef->npca_punctured) {
 		return false;
 	}
@@ -556,6 +535,44 @@ int cfg80211_chandef_primary(const struct cfg80211_chan_def *c,
 }
 EXPORT_SYMBOL(cfg80211_chandef_primary);
 
+bool cfg80211_chandef_npca_valid(struct wiphy *wiphy,
+				 const struct cfg80211_chan_def *chandef,
+				 const struct ieee80211_uhr_npca_info *npca)
+{
+	struct cfg80211_chan_def tmp = *chandef;
+	bool pri_upper, npca_upper;
+	u32 cf1;
+
+	if (chandef->npca_chan || chandef->npca_punctured)
+		return false;
+
+	if (!npca)
+		return true;
+
+	if (cfg80211_chandef_add_npca(wiphy, &tmp, npca))
+		return false;
+
+	if (!cfg80211_chandef_valid_control_freq(&tmp,
+						 tmp.npca_chan->center_freq))
+		return false;
+
+	cf1 = tmp.center_freq1;
+	pri_upper = tmp.chan->center_freq > cf1;
+	npca_upper = tmp.npca_chan->center_freq > cf1;
+
+	if (pri_upper == npca_upper)
+		return false;
+
+	if (!valid_puncturing_bitmap(&tmp,
+				     tmp.npca_chan->center_freq,
+				     tmp.npca_punctured) ||
+	    (tmp.punctured & tmp.npca_punctured) != tmp.punctured)
+		return false;
+
+	return true;
+}
+EXPORT_SYMBOL(cfg80211_chandef_npca_valid);
+
 int cfg80211_chandef_add_npca(struct wiphy *wiphy,
 			      struct cfg80211_chan_def *chandef,
 			      const struct ieee80211_uhr_npca_info *npca)