Support transmit power

This commit introduces 'tx_power' to the virtual interface to specify
the device's transmit power level. It also adds vwifi_set_tx_power()
and vwifi_get_tx_power() to align with 'set_tx_power' and 'get_tx_power'
in cfg80211_ops, respectively. The vwifi_set_tx_power() enables the
setting of the device's transmit power, whereas vwifi_get_tx_power()
facilitates the retrieval of this information.

Users can adjust the transmit power by employing the command:
iwconfig vwN txpower
where N stands for the entry of network interface.

Author: jychen0611

scripts/verify.sh

@@ -24,6 +24,11 @@ if [ $final_ret -eq 0 ]; then
     # to avoid device or resource busy error
     sleep 0.5
 
+    # set transmit power
+    sudo iwconfig vw0 txpower 11
+    sudo iwconfig vw1 txpower 12
+    sudo iwconfig vw2 txpower 13
+
     # get phy number of each interface
     sudo iw dev > device.log
     vw0_phy=$(get_wiphy_name vw0)

vwifi.c

@@ -155,6 +155,9 @@ struct vwifi_vif {
 
     /* Packet virtio header size */
     u8 vnet_hdr_len;
+    
+    /* Transmit power */
+    s32 tx_power;
 };
 
 static int station = 2;
@@ -1840,6 +1843,28 @@ static int vwifi_delete_interface(struct vwifi_vif *vif)
     return 0;
 }
 
+/* Set transmit power for the virtual interface */
+static int vwifi_set_tx_power(struct wiphy *wiphy, struct wireless_dev *wdev,
+			enum nl80211_tx_power_setting type, int mbm)
+{
+    struct vwifi_vif *vif = wdev_get_vwifi_vif(wdev);
+    if (mutex_lock_interruptible(&vif->lock))
+        return -ERESTARTSYS;
+    /* 1 DBM = 100 MBM */
+    vif->tx_power = MBM_TO_DBM(mbm); 
+    mutex_unlock(&vif->lock);  
+	return 0;
+}
+
+/* Get transmit power from the virtual interface */
+static int vwifi_get_tx_power(struct wiphy *wiphy, struct wireless_dev *wdev,
+			int *dbm)
+{	
+    struct vwifi_vif *vif = wdev_get_vwifi_vif(wdev);    
+    *dbm = vif->tx_power;
+	return 0;
+}
+
 /* Structure of functions for FullMAC 80211 drivers. Functions implemented
  * along with fields/flags in the wiphy structure represent driver features.
  * This module can only perform "scan" and "connect". Some functions cannot
@@ -1860,6 +1885,8 @@ static struct cfg80211_ops vwifi_cfg_ops = {
     .del_key = vwifi_del_key,
     .set_default_key = vwifi_set_default_key,
     .change_station = vwifi_change_station,
+    .set_tx_power = vwifi_set_tx_power,
+    .get_tx_power = vwifi_get_tx_power,
 };
 
 /* Macro for defining 2GHZ channel array */