wifi: mac80211: provide a helper to fetch the medium synchronization delay

There are drivers which need this information.
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Gregory Greenman <gregory.greenman@intel.com>
Link: https://lore.kernel.org/r/20230604120651.b1043f3126e2.Iad3806f8bf8df07f52ef0a02cc3d0373c44a8c93@changeidSigned-off-by: Johannes Berg <johannes.berg@intel.com>

include/linux/ieee80211.h

@@ -4635,6 +4635,41 @@ static inline u8 ieee80211_mle_common_size(const u8 *data)
 	return sizeof(*mle) + common + mle->variable[0];
 }
 
+/**
+ * ieee80211_mle_get_eml_sync_delay - returns the medium sync delay
+ * @data: pointer to the multi link EHT IE
+ *
+ * The element is assumed to be big enough. This must be checked by
+ * ieee80211_mle_size_ok().
+ * If the medium synchronization can't be found (the type is not basic, or
+ * the medium sync presence bit is clear), 0 will be returned.
+ */
+static inline u16 ieee80211_mle_get_eml_med_sync_delay(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;
+
+	if (u16_get_bits(control, IEEE80211_ML_CONTROL_TYPE) !=
+	    IEEE80211_ML_CONTROL_TYPE_BASIC)
+		return 0;
+
+	/* 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_MED_SYNC_DELAY))
+		return 0;
+
+	if (control & IEEE80211_MLC_BASIC_PRES_LINK_ID)
+		common += 1;
+	if (control & IEEE80211_MLC_BASIC_PRES_BSS_PARAM_CH_CNT)
+		common += 1;
+
+	return get_unaligned_le16(common);
+}
+
 /**
  * ieee80211_mle_get_eml_cap - returns the EML capability
  * @data: pointer to the multi link EHT IE

include/net/mac80211.h

@@ -1791,6 +1791,8 @@ enum ieee80211_offload_flags {
  *	offchannel/dynamic_ps operations.
  * @aid: association ID number, valid only when @assoc is true
  * @eml_cap: EML capabilities as described in P802.11be_D2.2 Figure 9-1002k.
+ * @eml_med_sync_delay: Medium Synchronization delay as described in
+ *	P802.11be_D2.2 Figure 9-1002j.
  * @arp_addr_list: List of IPv4 addresses for hardware ARP filtering. The
  *	may filter ARP queries targeted for other addresses than listed here.
  *	The driver must allow ARP queries targeted for all address listed here
@@ -1814,6 +1816,7 @@ struct ieee80211_vif_cfg {
 	bool ps;
 	u16 aid;
 	u16 eml_cap;
+	u16 eml_med_sync_delay;
 
 	__be32 arp_addr_list[IEEE80211_BSS_ARP_ADDR_LIST_LEN];
 	int arp_addr_cnt;

net/mac80211/mlme.c

@@ -4856,9 +4856,12 @@ static int ieee80211_prep_channel(struct ieee80211_sub_if_data *sdata,
 		/* data + 1 / datalen - 1 since it's an extended element */
 		if (eht_ml_elem &&
 		    ieee80211_mle_size_ok(eht_ml_elem->data + 1,
-					  eht_ml_elem->datalen - 1))
+					  eht_ml_elem->datalen - 1)) {
 			sdata->vif.cfg.eml_cap =
 				ieee80211_mle_get_eml_cap(eht_ml_elem->data + 1);
+			sdata->vif.cfg.eml_med_sync_delay =
+				ieee80211_mle_get_eml_med_sync_delay(eht_ml_elem->data + 1);
+		}
 	}
 
 	/* Allow VHT if at least one channel on the sband supports 80 MHz */