[RFC] mac80211: Fix setting txpower to zero.

[greearb@candelatech.com]

From: Ben Greear <greearb@candelatech.com>

With multiple VIFS ath10k, and probably others, tries to find the
minimum txpower for all vifs and uses that when setting txpower in
the firmware.

If a second vif is added and starts to scan, it's txpower is not initialized yet
and it set to zero.

ath10k had a patch to ignore zero values, but then it is impossible to actually set
txpower to zero.

So, instead initialize the txpower to -1 in mac80211, and let drivers know that
means the power has not been set and so should be ignored.

This should fix regression in:

commit 88407beb1b1462f706a1950a355fd086e1c450b6
Author: Ryan Hsu <ryanhsu@qca.qualcomm.com>
Date:   Tue Dec 13 14:55:19 2016 -0800

    ath10k: fix incorrect txpower set by P2P_DEVICE interface

Tested on ath10k 9984 with ath10k-ct firmware.

Signed-off-by: Ben Greear <greearb@candelatech.com>
---
 drivers/net/wireless/ath/ath10k/mac.c | 2 +-
 drivers/net/wireless/ath/ath9k/main.c | 3 +++
 drivers/net/wireless/ath/ath9k/xmit.c | 7 +++++--
 include/net/mac80211.h                | 2 +-
 net/mac80211/iface.c                  | 1 +
 net/mac80211/main.c                   | 2 ++
 6 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/drivers/net/wireless/ath/ath10k/mac.c b/drivers/net/wireless/ath/ath10k/mac.c
index 289d03da14b2..c846f232e930 100644
--- a/drivers/net/wireless/ath/ath10k/mac.c
+++ b/drivers/net/wireless/ath/ath10k/mac.c
@@ -5906,7 +5906,7 @@ static int ath10k_mac_txpower_recalc(struct ath10k *ar)
 	lockdep_assert_held(&ar->conf_mutex);
 
 	list_for_each_entry(arvif, &ar->arvifs, list) {
-		if (arvif->txpower <= 0)
+		if (arvif->txpower < 0) /* txpower not initialized yet? */
 			continue;
 
 		if (txpower == -1)
diff --git a/drivers/net/wireless/ath/ath9k/main.c b/drivers/net/wireless/ath/ath9k/main.c
index 14f253199909..2edf70cf7e7e 100644
--- a/drivers/net/wireless/ath/ath9k/main.c
+++ b/drivers/net/wireless/ath/ath9k/main.c
@@ -1196,6 +1196,9 @@ static void ath9k_tpc_vif_iter(void *data, u8 *mac, struct ieee80211_vif *vif)
 {
 	int *power = data;
 
+	if (vif->bss_conf.txpower < 0)
+		return;
+
 	if (*power < vif->bss_conf.txpower)
 		*power = vif->bss_conf.txpower;
 }
diff --git a/drivers/net/wireless/ath/ath9k/xmit.c b/drivers/net/wireless/ath/ath9k/xmit.c
index 751d0d0550b5..82c592ca2cd2 100644
--- a/drivers/net/wireless/ath/ath9k/xmit.c
+++ b/drivers/net/wireless/ath/ath9k/xmit.c
@@ -2114,10 +2114,13 @@ static void setup_frame_info(struct ieee80211_hw *hw,
 
 	if (tx_info->control.vif) {
 		struct ieee80211_vif *vif = tx_info->control.vif;
-
+		if (vif->bss_conf.txpower < 0)
+			goto nonvifpower;
 		txpower = 2 * vif->bss_conf.txpower;
 	} else {
-		struct ath_softc *sc = hw->priv;
+		struct ath_softc *sc;
+	nonvifpower:
+		sc = hw->priv;
 
 		txpower = sc->cur_chan->cur_txpower;
 	}
diff --git a/include/net/mac80211.h b/include/net/mac80211.h
index 2b70b9268f76..db66520c5389 100644
--- a/include/net/mac80211.h
+++ b/include/net/mac80211.h
@@ -569,7 +569,7 @@ struct ieee80211_ftm_responder_params {
  * @ssid: The SSID of the current vif. Valid in AP and IBSS mode.
  * @ssid_len: Length of SSID given in @ssid.
  * @hidden_ssid: The SSID of the current vif is hidden. Only valid in AP-mode.
- * @txpower: TX power in dBm
+ * @txpower: TX power in dBm.  -1 means not configured.
  * @txpower_type: TX power adjustment used to control per packet Transmit
  *	Power Control (TPC) in lower driver for the current vif. In particular
  *	TPC is enabled if value passed in %txpower_type is
diff --git a/net/mac80211/iface.c b/net/mac80211/iface.c
index b0c2df6e22c5..49fcf9d80f85 100644
--- a/net/mac80211/iface.c
+++ b/net/mac80211/iface.c
@@ -1459,6 +1459,7 @@ static void ieee80211_setup_sdata(struct ieee80211_sub_if_data *sdata,
 	sdata->control_port_no_encrypt = false;
 	sdata->encrypt_headroom = IEEE80211_ENCRYPT_HEADROOM;
 	sdata->vif.bss_conf.idle = true;
+	sdata->vif.bss_conf.txpower = -1; /* unset */
 
 	sdata->noack_map = 0;
 
diff --git a/net/mac80211/main.c b/net/mac80211/main.c
index a148509a88bc..2f53188851ee 100644
--- a/net/mac80211/main.c
+++ b/net/mac80211/main.c
@@ -145,6 +145,8 @@ static u32 ieee80211_hw_conf_chan(struct ieee80211_local *local)
 			continue;
 		if (sdata->vif.type == NL80211_IFTYPE_AP_VLAN)
 			continue;
+		if (sdata->vif.bss_conf.txpower < 0)
+			continue;
 		power = min(power, sdata->vif.bss_conf.txpower);
 	}
 	rcu_read_unlock();
-- 
2.20.1