wifi: mac80211: fetch and store the EML capability information

We need to teach the low level driver about the EML capability which
includes information for EMLSR / EMLMR operation.

Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Gregory Greenman <gregory.greenman@intel.com>
Link: https://lore.kernel.org/r/20230504134511.828474-11-gregory.greenman@intel.com
Signed-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_cap - returns the EML capability
+ * @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 EML capability can't be found (the type is not basic, or
+ * the EML capability presence bit is clear), 0 will be returned.
+ */
+static inline u16 ieee80211_mle_get_eml_cap(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_EML_CAPA))
+		return 0;
+
+	if (control & IEEE80211_MLC_BASIC_PRES_LINK_ID)
+		common += 1;
+	if (control & IEEE80211_MLC_BASIC_PRES_BSS_PARAM_CH_CNT)
+		common += 1;
+	if (control & IEEE80211_MLC_BASIC_PRES_MED_SYNC_DELAY)
+		common += 2;
+
+	return get_unaligned_le16(common);
+}
+
 /**
  * ieee80211_mle_size_ok - validate multi-link element size
  * @data: pointer to the element data

include/net/mac80211.h

@@ -1790,6 +1790,7 @@ enum ieee80211_offload_flags {
  * @ps: power-save mode (STA only). This flag is NOT affected by
  *	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.
  * @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
@@ -1812,6 +1813,7 @@ struct ieee80211_vif_cfg {
 	bool ibss_creator;
 	bool ps;
 	u16 aid;
+	u16 eml_cap;
 
 	__be32 arp_addr_list[IEEE80211_BSS_ARP_ADDR_LIST_LEN];
 	int arp_addr_cnt;

net/mac80211/mlme.c

@@ -4838,6 +4838,7 @@ static int ieee80211_prep_channel(struct ieee80211_sub_if_data *sdata,
 			 IEEE80211_CONN_DISABLE_EHT)) &&
 	    he_oper) {
 		const struct cfg80211_bss_ies *cbss_ies;
+		const struct element *eht_ml_elem;
 		const u8 *eht_oper_ie;
 
 		cbss_ies = rcu_dereference(cbss->ies);
@@ -4848,6 +4849,16 @@ static int ieee80211_prep_channel(struct ieee80211_sub_if_data *sdata,
 			eht_oper = (void *)(eht_oper_ie + 3);
 		else
 			eht_oper = NULL;
+
+		eht_ml_elem = cfg80211_find_ext_elem(WLAN_EID_EXT_EHT_MULTI_LINK,
+						     cbss_ies->data, cbss_ies->len);
+
+		/* 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))
+			sdata->vif.cfg.eml_cap =
+				ieee80211_mle_get_eml_cap(eht_ml_elem->data + 1);
 	}
 
 	/* Allow VHT if at least one channel on the sband supports 80 MHz */