Some regulations (like germany, but also FCC) express their transmission
power limit in dBm/MHz or mW/MHz. To cope with that and be on the safe
side, reduce the maximum power to half (10 MHz) or quarter (5 MHz)
when operating on these reduced bandwidth channels.
Signed-off-by: Simon Wunderlich <siwu@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Mathias Kretschmer <mathias.kretschmer@xxxxxxxxxxxxxxxxxxx>
---
Changes to PATCHv3:
* consider max_reg_power, max_power might contain the hardware limit
---
include/net/cfg80211.h | 27 +++++++++++++++++++++++++++
net/mac80211/iface.c | 2 +-
net/mac80211/main.c | 2 +-
net/mac80211/mlme.c | 3 ++-
4 files changed, 31 insertions(+), 3 deletions(-)
diff --git a/include/net/cfg80211.h b/include/net/cfg80211.h
index 4ca16ab..75471ee 100644
--- a/include/net/cfg80211.h
+++ b/include/net/cfg80211.h
@@ -461,6 +461,33 @@ ieee80211_chandef_rate_flags(struct cfg80211_chan_def *chandef)
}
/**
+ * ieee80211_chandef_max_power - maximum transmission power for the chandef
+ *
+ * In some regulations, the transmit power may depend on the configured channel
+ * bandwidth which may be defined as dBm/MHz. This function returns the actual
+ * max_power for non-standard (20 MHz) channels.
+ *
+ * @chandef: channel definition for the channel
+ *
+ * Returns: maximum allowed transmission power in dBm for the chandef
+ */
+static inline int
+ieee80211_chandef_max_power(struct cfg80211_chan_def *chandef)
+{
+ switch (chandef->width) {
+ case NL80211_CHAN_WIDTH_5:
+ return min(chandef->chan->max_reg_power - 6,
+ chandef->chan->max_power);
+ case NL80211_CHAN_WIDTH_10:
+ return min(chandef->chan->max_reg_power - 3,
+ chandef->chan->max_power);
+ default:
+ break;
+ }
+ return chandef->chan->max_power;
+}
+
+/**
* enum survey_info_flags - survey information flags
*
* @SURVEY_INFO_NOISE_DBM: noise (in dBm) was filled in
diff --git a/net/mac80211/iface.c b/net/mac80211/iface.c
index a2a8250..093c34a 100644
--- a/net/mac80211/iface.c
+++ b/net/mac80211/iface.c
@@ -54,7 +54,7 @@ bool __ieee80211_recalc_txpower(struct ieee80211_sub_if_data *sdata)
return false;
}
- power = chanctx_conf->def.chan->max_power;
+ power = ieee80211_chandef_max_power(&chanctx_conf->def);
rcu_read_unlock();
if (sdata->user_power_level != IEEE80211_UNSET_POWER_LEVEL)
diff --git a/net/mac80211/main.c b/net/mac80211/main.c
index 626c83c..a1d51af 100644
--- a/net/mac80211/main.c
+++ b/net/mac80211/main.c
@@ -151,7 +151,7 @@ static u32 ieee80211_hw_conf_chan(struct ieee80211_local *local)
changed |= IEEE80211_CONF_CHANGE_SMPS;
}
- power = chandef.chan->max_power;
+ power = ieee80211_chandef_max_power(&chandef);
rcu_read_lock();
list_for_each_entry_rcu(sdata, &local->interfaces, list) {
diff --git a/net/mac80211/mlme.c b/net/mac80211/mlme.c
index f7552c2..211246b 100644
--- a/net/mac80211/mlme.c
+++ b/net/mac80211/mlme.c
@@ -747,7 +747,8 @@ static void ieee80211_send_assoc(struct ieee80211_sub_if_data *sdata)
*pos++ = WLAN_EID_PWR_CAPABILITY;
*pos++ = 2;
*pos++ = 0; /* min tx power */
- *pos++ = chan->max_power; /* max tx power */
+ /* max tx power */
+ *pos++ = ieee80211_chandef_max_power(&chanctx_conf->def);
/* 2. supported channels */
/* TODO: get this in reg domain format */
--
1.7.10.4
--
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