nl80211: Report max TX power in NL80211_BAND_ATTR_FREQS

This is useful information to provide for userspace (e.g., hostapd needs
this to generate Country IE).
Signed-off-by: Jouni Malinen <jouni.malinen@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

include/linux/nl80211.h

@@ -508,6 +508,7 @@ enum nl80211_band_attr {
  *	on this channel in current regulatory domain.
  * @NL80211_FREQUENCY_ATTR_RADAR: Radar detection is mandatory
  *	on this channel in current regulatory domain.
+ * @NL80211_FREQUENCY_ATTR_MAX_TX_POWER: Maximum transmission power in dBm.
  */
 enum nl80211_frequency_attr {
 	__NL80211_FREQUENCY_ATTR_INVALID,
@@ -516,12 +517,15 @@ enum nl80211_frequency_attr {
 	NL80211_FREQUENCY_ATTR_PASSIVE_SCAN,
 	NL80211_FREQUENCY_ATTR_NO_IBSS,
 	NL80211_FREQUENCY_ATTR_RADAR,
+	NL80211_FREQUENCY_ATTR_MAX_TX_POWER,
 
 	/* keep last */
 	__NL80211_FREQUENCY_ATTR_AFTER_LAST,
 	NL80211_FREQUENCY_ATTR_MAX = __NL80211_FREQUENCY_ATTR_AFTER_LAST - 1
 };
 
+#define NL80211_FREQUENCY_ATTR_MAX_TX_POWER NL80211_FREQUENCY_ATTR_MAX_TX_POWER
+
 /**
  * enum nl80211_bitrate_attr - bitrate attributes
  * @NL80211_BITRATE_ATTR_RATE: Bitrate in units of 100 kbps

net/wireless/nl80211.c

@@ -198,6 +198,9 @@ static int nl80211_send_wiphy(struct sk_buff *msg, u32 pid, u32 seq, int flags,
 			if (chan->flags & IEEE80211_CHAN_RADAR)
 				NLA_PUT_FLAG(msg, NL80211_FREQUENCY_ATTR_RADAR);
 
+			NLA_PUT_U8(msg, NL80211_FREQUENCY_ATTR_MAX_TX_POWER,
+				   chan->max_power);
+
 			nla_nest_end(msg, nl_freq);
 		}