wifi: mac80211: align ieee80211_mle_get_bss_param_ch_cnt()

Align the prototype of ieee80211_mle_get_bss_param_ch_cnt()
to also take a u8 * like the other functions, and make it
return -1 when the field isn't found, so that mac80211 can
check that instead of explicitly open-coding the check.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Miri Korenblit <miriam.rachel.korenblit@intel.com>
Link: https://msgid.link/20240216135047.583309181bc3.Ia61cb0b4fc034d5ac8fcfaf6f6fb2e115fadafe7@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

include/linux/ieee80211.h

@@ -4990,25 +4990,26 @@ static inline int ieee80211_mle_get_link_id(const u8 *data)
 
 /**
  * ieee80211_mle_get_bss_param_ch_cnt - returns the BSS parameter change count
- * @mle: the basic multi link element
+ * @data: pointer to the basic multi link element
  *
  * The element is assumed to be of the correct type (BASIC) and big enough,
  * this must be checked using ieee80211_mle_type_ok().
  *
  * If the BSS parameter change count value can't be found (the presence bit
- * for it is clear), 0 will be returned.
+ * for it is clear), -1 will be returned.
  */
-static inline u8
-ieee80211_mle_get_bss_param_ch_cnt(const struct ieee80211_multi_link_elem *mle)
+static inline int
+ieee80211_mle_get_bss_param_ch_cnt(const u8 *data)
 {
+	const struct ieee80211_multi_link_elem *mle = (const void *)data;
 	u16 control = le16_to_cpu(mle->control);
 	const u8 *common = mle->variable;
 
 	/* common points now at the beginning of ieee80211_mle_basic_common_info */
 	common += sizeof(struct ieee80211_mle_basic_common_info);
 
 	if (!(control & IEEE80211_MLC_BASIC_PRES_BSS_PARAM_CH_CNT))
-		return 0;
+		return -1;
 
 	if (control & IEEE80211_MLC_BASIC_PRES_LINK_ID)
 		common += 1;

net/mac80211/mlme.c

@@ -4202,13 +4202,14 @@ static bool ieee80211_assoc_config_link(struct ieee80211_link_data *link,
 		 */
 		assoc_data->link[link_id].status = WLAN_STATUS_SUCCESS;
 		if (elems->ml_basic) {
-			if (!(elems->ml_basic->control &
-					cpu_to_le16(IEEE80211_MLC_BASIC_PRES_BSS_PARAM_CH_CNT))) {
+			int bss_param_ch_cnt =
+				ieee80211_mle_get_bss_param_ch_cnt((const void *)elems->ml_basic);
+
+			if (bss_param_ch_cnt < 0) {
 				ret = false;
 				goto out;
 			}
-			link->u.mgd.bss_param_ch_cnt =
-				ieee80211_mle_get_bss_param_ch_cnt(elems->ml_basic);
+			link->u.mgd.bss_param_ch_cnt = bss_param_ch_cnt;
 		}
 	} else if (elems->parse_error & IEEE80211_PARSE_ERR_DUP_NEST_ML_BASIC ||
 		   !elems->prof ||