cfg80211: Add support to set tx power for a station associated

This patch adds support to set transmit power setting type and transmit
power level attributes to NL80211_CMD_SET_STATION in order to facilitate
adjusting the transmit power level of a station associated to the AP.

The added attributes allow selection of automatic and limited transmit
power level, with the level defined in dBm format.

Co-developed-by: Balaji Pothunoori <bpothuno@codeaurora.org>
Signed-off-by: Ashok Raj Nagarajan <arnagara@codeaurora.org>
Signed-off-by: Balaji Pothunoori <bpothuno@codeaurora.org>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

include/net/cfg80211.h

@@ -975,6 +975,27 @@ enum station_parameters_apply_mask {
 	STATION_PARAM_APPLY_UAPSD = BIT(0),
 	STATION_PARAM_APPLY_CAPABILITY = BIT(1),
 	STATION_PARAM_APPLY_PLINK_STATE = BIT(2),
+	STATION_PARAM_APPLY_STA_TXPOWER = BIT(3),
+};
+
+/**
+ * struct sta_txpwr - station txpower configuration
+ *
+ * Used to configure txpower for station.
+ *
+ * @power: tx power (in dBm) to be used for sending data traffic. If tx power
+ *	is not provided, the default per-interface tx power setting will be
+ *	overriding. Driver should be picking up the lowest tx power, either tx
+ *	power per-interface or per-station.
+ * @type: In particular if TPC %type is NL80211_TX_POWER_LIMITED then tx power
+ *	will be less than or equal to specified from userspace, whereas if TPC
+ *	%type is NL80211_TX_POWER_AUTOMATIC then it indicates default tx power.
+ *	NL80211_TX_POWER_FIXED is not a valid configuration option for
+ *	per peer TPC.
+ */
+struct sta_txpwr {
+	s16 power;
+	enum nl80211_tx_power_setting type;
 };
 
 /**
@@ -1049,6 +1070,7 @@ struct station_parameters {
 	const struct ieee80211_he_cap_elem *he_capa;
 	u8 he_capa_len;
 	u16 airtime_weight;
+	struct sta_txpwr txpwr;
 };
 
 /**

include/uapi/linux/nl80211.h

@@ -2315,6 +2315,15 @@ enum nl80211_commands {
  * @NL80211_ATTR_AIRTIME_WEIGHT: Station's weight when scheduled by the airtime
  *	scheduler.
  *
+ * @NL80211_ATTR_STA_TX_POWER_SETTING: Transmit power setting type (u8) for
+ *	station associated with the AP. See &enum nl80211_tx_power_setting for
+ *	possible values.
+ * @NL80211_ATTR_STA_TX_POWER: Transmit power level (s16) in dBm units. This
+ *	allows to set Tx power for a station. If this attribute is not included,
+ *	the default per-interface tx power setting will be overriding. Driver
+ *	should be picking up the lowest tx power, either tx power per-interface
+ *	or per-station.
+ *
  * @NUM_NL80211_ATTR: total number of nl80211_attrs available
  * @NL80211_ATTR_MAX: highest attribute number currently defined
  * @__NL80211_ATTR_AFTER_LAST: internal use
@@ -2765,6 +2774,8 @@ enum nl80211_attrs {
 	NL80211_ATTR_PEER_MEASUREMENTS,
 
 	NL80211_ATTR_AIRTIME_WEIGHT,
+	NL80211_ATTR_STA_TX_POWER_SETTING,
+	NL80211_ATTR_STA_TX_POWER,
 
 	/* add attributes here, update the policy in nl80211.c */
 
@@ -5391,6 +5402,9 @@ enum nl80211_feature_flags {
  * @NL80211_EXT_FEATURE_SCHED_SCAN_BAND_SPECIFIC_RSSI_THOLD: Driver supports
  *	filtering of sched scan results using band specific RSSI thresholds.
  *
+ * @NL80211_EXT_FEATURE_STA_TX_PWR: This driver supports controlling tx power
+ *	to a station.
+ *
  * @NUM_NL80211_EXT_FEATURES: number of extended features.
  * @MAX_NL80211_EXT_FEATURES: highest extended feature index.
  */
@@ -5434,6 +5448,7 @@ enum nl80211_ext_feature_index {
 	NL80211_EXT_FEATURE_AP_PMKSA_CACHING,
 	NL80211_EXT_FEATURE_SCHED_SCAN_BAND_SPECIFIC_RSSI_THOLD,
 	NL80211_EXT_FEATURE_EXT_KEY_ID,
+	NL80211_EXT_FEATURE_STA_TX_PWR,
 
 	/* add new features before the definition below */
 	NUM_NL80211_EXT_FEATURES,

net/wireless/nl80211.c

@@ -331,6 +331,11 @@ const struct nla_policy nl80211_policy[NUM_NL80211_ATTR] = {
 					       .len = NL80211_MAX_SUPP_RATES },
 	[NL80211_ATTR_STA_PLINK_ACTION] =
 		NLA_POLICY_MAX(NLA_U8, NUM_NL80211_PLINK_ACTIONS - 1),
+	[NL80211_ATTR_STA_TX_POWER_SETTING] =
+		NLA_POLICY_RANGE(NLA_U8,
+				 NL80211_TX_POWER_AUTOMATIC,
+				 NL80211_TX_POWER_FIXED),
+	[NL80211_ATTR_STA_TX_POWER] = { .type = NLA_S16 },
 	[NL80211_ATTR_STA_VLAN] = { .type = NLA_U32 },
 	[NL80211_ATTR_MNTR_FLAGS] = { /* NLA_NESTED can't be empty */ },
 	[NL80211_ATTR_MESH_ID] = { .type = NLA_BINARY,
@@ -5420,6 +5425,36 @@ static int nl80211_set_station_tdls(struct genl_info *info,
 	return nl80211_parse_sta_wme(info, params);
 }
 
+static int nl80211_parse_sta_txpower_setting(struct genl_info *info,
+					     struct station_parameters *params)
+{
+	struct cfg80211_registered_device *rdev = info->user_ptr[0];
+	int idx;
+
+	if (info->attrs[NL80211_ATTR_STA_TX_POWER_SETTING]) {
+		if (!rdev->ops->set_tx_power ||
+		    !wiphy_ext_feature_isset(&rdev->wiphy,
+					 NL80211_EXT_FEATURE_STA_TX_PWR))
+			return -EOPNOTSUPP;
+
+		idx = NL80211_ATTR_STA_TX_POWER_SETTING;
+		params->txpwr.type = nla_get_u8(info->attrs[idx]);
+
+		if (params->txpwr.type == NL80211_TX_POWER_LIMITED) {
+			idx = NL80211_ATTR_STA_TX_POWER;
+
+			if (info->attrs[idx])
+				params->txpwr.power =
+					nla_get_s16(info->attrs[idx]);
+			else
+				return -EINVAL;
+		}
+		params->sta_modify_mask |= STATION_PARAM_APPLY_STA_TXPOWER;
+	}
+
+	return 0;
+}
+
 static int nl80211_set_station(struct sk_buff *skb, struct genl_info *info)
 {
 	struct cfg80211_registered_device *rdev = info->user_ptr[0];
@@ -5513,6 +5548,10 @@ static int nl80211_set_station(struct sk_buff *skb, struct genl_info *info)
 				     NL80211_EXT_FEATURE_AIRTIME_FAIRNESS))
 		return -EOPNOTSUPP;
 
+	err = nl80211_parse_sta_txpower_setting(info, &params);
+	if (err)
+		return err;
+
 	/* Include parameters for TDLS peer (will check later) */
 	err = nl80211_set_station_tdls(info, &params);
 	if (err)
@@ -5650,6 +5689,10 @@ static int nl80211_new_station(struct sk_buff *skb, struct genl_info *info)
 				     NL80211_EXT_FEATURE_AIRTIME_FAIRNESS))
 		return -EOPNOTSUPP;
 
+	err = nl80211_parse_sta_txpower_setting(info, &params);
+	if (err)
+		return err;
+
 	err = nl80211_parse_sta_channel_info(info, &params);
 	if (err)
 		return err;