WIFI on Android

Take the following blog information as a referrence:

http://blog.csdn.net/hongjiujing/archive/2010/05/07/5565431.aspx

 

 

Android WIFI state: DISABLED, DISABLING, ENABLED, ENABLING, UNKNOWN.

 

1. Porting WIFI driver on Android

    --> #create filesystem for wifi &dhcp (add this in the init.rc file)

    ++++++++++++++++++++++++++++++++++++++++

    mkdir /data/misc/wifi 0771 wifi system

    chown wifi system /data/misc/wifi

    chmod 0771 /data/misc/wifi

 

    mkdir /data/misc/wifi/sockets 0771 wifi system

    chown wifi system /data/misc/wifi/sockets

    chmod 07771 /data/misc/wifi/sockets

   

    mkdir /data/misc/dhcp 0770 dhcp dhcp

    chown dhcp dhcp /data/misc/dhcp

    chmod 0770 /data/misc/dhcp

    ++++++++++++++++++++++++++++++++++++++++

2. WPA and WPA2 implement

    --> init.rc configuration

    ++++++++++++++++++++++++++++++++++++++++

    mkdir /data/system/wpa_supplicant 0771 wifi system

    chown wifi system /data/system/wpa_supplicant

    chmod 0771 /data/eth0

   

    setprop wifi.interface mlan0   

 

    service wpa_supplicant /system/bin/wpa_supplicant -Dwext -imlan0 -c/data/misc/wifi/wpa_supplicant.conf

    user root

    group system wifi

    disabled

 

    service dhcpcd /system/bin/dhcpcd -BKL mlan0

    disabled

    one shot

    ++++++++++++++++++++++++++++++++++++++++

 

    --> useful tool: wpa_cli

    --> requirement: driver_wext.c expects the wifi kernel driver to implement the SIOCSIWPRIV ioctrl and respond to android commands like RSSI, MACADDR, LINKSPEED and etc.

    --> implement: add the upper ioctl to kernel wifi driver. (in wlan_wext.c). The following is the detail implement source code.

        Add the "BOARD_WPA_SUPPLICANT_DRIVER := WEXT" in BoardConfig.mk

 

++++++++++++++++++++++++++++++++++++++++

    /**
 *  @brief Set priv command
 *
 *  @param dev          A pointer to net_device structure
 *  @param info         A pointer to iw_request_info structure
 *  @param dwrq         A pointer to iw_point structure
 *  @param extra        A pointer to extra data buf
 *
 *  @return                     0 --success, otherwise fail
 */
static int wlan_set_priv(struct net_device *dev, struct iw_request_info *info,
                struct iw_point* dwrq, char *extra)
{
    int             ret = 0;
    wlan_private*    priv     = (wlan_private *) netdev_priv(dev);
    char *          buf = NULL;
    int len = 0;
    int  rssi = 0;
    BSSDescriptor_t* pBSSDesc = NULL;

    ENTER();
    if (!(buf = kmalloc(dwrq->length, GFP_KERNEL))) {
     ret = -ENOMEM;
        goto done;
    }
    if (copy_from_user(buf, dwrq->pointer, dwrq->length)) {
        ret = -EFAULT;
        goto done;
    }
    PRINTM(CMND,"SIOCSIWPRIV requst = %s/n",buf);
    if(strncmp(buf,"RSSI",strlen("RSSI")) == 0){
        if (priv->adapter->MediaConnectStatus == WlanMediaStateConnected){
            if(wlan_prepare_cmd(priv,
    HostCmd_CMD_RSSI_INFO,
    HostCmd_ACT_GEN_GET,HostCmd_OPTION_WAITFORRSP,
    0, NULL)) {
                ret = -EFAULT;
                goto done;
            }
            rssi = priv->adapter->BcnRSSIAvg;
            pBSSDesc = &priv->adapter->CurBssParams.BSSDescriptor;
            len = sprintf(buf,"%s rssi %d/n",pBSSDesc->Ssid.Ssid,rssi) + 1;           
        }           
    }
    else if(strncmp(buf, "LINKSPEED",strlen("LINKSPEED")) == 0) {
        if(wlan_prepare_cmd(priv, HostCmd_CMD_802_11_TX_RATE_QUERY,
   HostCmd_ACT_GEN_GET, HostCmd_OPTION_WAITFORRSP,
   0, NULL)){
            ret = -EFAULT;
            goto done;
        }
        PRINTM(CMND, "tx rate=%d/n",(int)priv->adapter->TxRate);
        len = sprintf(buf,"LinkSpeed %d/n",(int)(index_to_data_rate(priv->adapter->TxRate) * 500000 / 1000000)) + 1;
    }
    else if(strncmp(buf,"MACADDR",strlen("MACADDR")) == 0) {
        len = sprintf(buf,"Macaddr = %02X:%02X:%02X:%02X:%02X:%02X/n",priv->adapter->CurrentAddr[0],
                priv->adapter->CurrentAddr[1],priv->adapter->CurrentAddr[2],priv->adapter->CurrentAddr[3],
                priv->adapter->CurrentAddr[4],priv->adapter->CurrentAddr[5]);
    }
    else {
        len = sprintf(buf,"OK/n") + 1;
        PRINTM(WARN,"Unknow PRIVATE command: %s, ignored/n", buf);
    }
    PRINTM(CMND,"PRIV Command return: %s, length=%d/n", buf, len);
    dwrq->length = len;
    if(copy_to_user(dwrq->pointer,buf,dwrq->length)){
        ret = -EFAULT;
    }
done:
    if(buf)
        kfree(buf);
    LEAVE();
    return ret;
}

 

    (iw_handler) wlan_set_priv,          /* SIOCSIWPRIV */

++++++++++++++++++++++++++++++++++++++++

 

3. WIFI Service

    --> android/frameworks/base/services/java/com/android/server/WifiService.java

 

4. WIFI Power Management

    --> Take the following webpage for a reference

          http://www.cnmsdn.com/html/201003/1268408234ID1814.html

 

5. Problem:

   --> after successfully connect to AP with WPA2 encryption, then disconnect with this AP, and reconnect with it, then it can not connect with this AP successfully.

   workaroud: turn off the wifi and then turn on it.