WiFi信号强度--SIGNAL_POLL

http://blog.csdn.net/myarrow/article/details/8958402

1. 信号强度算法

    WifiManager.java

 /** Anything worse than or equal to this will show 0 bars. */
 private static final int MIN_RSSI = -100;

 /** Anything better than or equal to this will show the max bars. */
 private static final int MAX_RSSI = -55;

 /**
  * Calculates the level of the signal. This should be used any time a signal
  * is being shown.
  *
  * @param rssi The power of the signal measured in RSSI.
  * @param numLevels The number of levels to consider in the calculated
  *            level.
  * @return A level of the signal, given in the range of 0 to numLevels-1
  *         (both inclusive).
  */
 public static int calculateSignalLevel(int rssi, int numLevels) {
     /* in general, numLevels is 4  */
     if (rssi <= MIN_RSSI) {
         return 0;
     } else if (rssi >= MAX_RSSI) {
         return numLevels - 1;
     } else {
         float inputRange = (MAX_RSSI - MIN_RSSI);
         float outputRange = (numLevels - 1);

         return (int)((float)(rssi - MIN_RSSI) * outputRange / inputRange);
     }
 }

 

2. WiFi Command流程

 

3. wpa_supplicant启动流程

4. WifiService启动流程

5. SIGNAL_POLL调用流程

 eloop_run->..
 wpa_supplicant_ctrl_iface_receive-> //接收并处理来自framework的command
 wpa_supplicant_ctrl_iface_process-> (SIGNAL_POLL)
 wpa_supplicant_signal_poll->
 wpa_drv_signal_poll  (struct wpa_supplicant *wpa_s,struct wpa_signal_info *si)->
 wpa_driver_signal_poll  (void *priv, struct wpa_signal_info *si)->
     wpa_driver_wext_driver_cmd(priv, RSSI_CMD, buf, sizeof(buf))或  //driver_cmd_wext.c
     wpa_driver_wext_driver_cmd(priv, LINKSPEED_CMD, buf, sizeof(buf))->

       struct iwreq iwr;
       iwr.u.data.pointer = buf;
       iwr.u.data.length = buf_len;
       ioctl(drv->ioctl_sock, SIOCSIWPRIV, &iwr);
       在Kernel中对应函数：
       cfg80211_wext_setpriv (wext-compat.c)
       RSSI_CMD:
       cfg80211_wireless_stats (获取当前已连接AP的信号强度等信息)

      对于上面的LINKSPEED_CMD,如果ioctl不成功，则调用ioctl(drv->ioctl_sock, SIOCGIWRATE, &wrq)
      在Kernel中对应函数：
      cfg80211_wext_giwrate (获取当前已连接AP的发送速度)

      //每个AP对应的信息
      struct station_info {
     u32 filled;
     u32 connected_time;
     u32 inactive_time;
     u32 rx_bytes;
     u32 tx_bytes;
     u16 llid;
     u16 plid;
     u8 plink_state;
     s8 signal;  //信号强度
     s8 signal_avg;
     struct rate_info txrate;  //发送速度
     struct rate_info rxrate;
     u32 rx_packets;
     u32 tx_packets;
     u32 tx_retries;
     u32 tx_failed;
     u32 rx_dropped_misc;
     struct sta_bss_parameters bss_param;

     int generation;
     };