9820E平台关于SSDA MODE说明

9820E是Android.4.4平台。
ssda_mode的配置是位于工程配置目录下：
device/sprd/sharkle/sp9820e_2h10_ft02/sp9820e_2h10_base.mk

persist.radio.ssda.mode=fdd-csfb

关于CSFB的解释CSFB、LTE_CSFB、FDD_CSFB等概念简介

该属性影响了手机的网络模式。
在TelephonyManager.java中有如下定义：

public static enum RadioCapbility {
    NONE, TDD_SVLTE, FDD_CSFB, TDD_CSFB, CSFB
};

获取属性

private static String PROP_SSDA_MODE = "persist.radio.ssda.mode";
// ssda mode
private static String MODE_SVLTE = "svlte";
private static String MODE_TDD_CSFB = "tdd-csfb";
private static String MODE_FDD_CSFB = "fdd-csfb";
private static String MODE_CSFB = "csfb";

public static RadioCapbility getRadioCapbility() {

    String ssdaMode = SystemProperties.get(PROP_SSDA_MODE);
    Log.d(TAG, "getRadioCapbility: ssdaMode=" + ssdaMode);
    if (ssdaMode.equals(MODE_SVLTE)) {
        return RadioCapbility.TDD_SVLTE;
    } else if (ssdaMode.equals(MODE_TDD_CSFB)) {
        return RadioCapbility.TDD_CSFB;
    } else if (ssdaMode.equals(MODE_FDD_CSFB)) {
        return RadioCapbility.FDD_CSFB;
    }else if (ssdaMode.equals(MODE_CSFB)) {
        return RadioCapbility.CSFB;
    }

    return RadioCapbility.NONE;
}

手机设置中的首先网络模式也跟它有关：
代码packages/services/Telephony/src/com/android/phone/NetworkTypeOptions.java

if (TelephonyManager.getRadioCapbility() == RadioCapbility.CSFB) {
    mButtonEnabledNetworks.setEntries(R.array.lte_preferred_networks_choices_for_common);
    mButtonEnabledNetworks.setEntryValues(R.array.lte_network_mode_choices_values_for_common);
} else if (TelephonyManager.getRadioCapbility() == RadioCapbility.FDD_CSFB) {
    mButtonEnabledNetworks.setEntries(R.array.lte_preferred_networks_for_common);
    mButtonEnabledNetworks.setEntryValues(R.array.lte_network_mode_choices_values_for_3mode);
} else {
    mButtonEnabledNetworks.setEntries(R.array.lte_preferred_networks_choices_for_3mode);
    mButtonEnabledNetworks.setEntryValues(R.array.lte_network_mode_choices_values_for_3mode);
}

其中对应的字符串和值，举例说明我当前项目配置为FDD_CSFB，则
lte_preferred_networks_for_common位于：
packages/services/Telephony/res/values-zh-rCN/strings_ex.xml

<string-array name="lte_preferred_networks_for_common">
    <item>4G/3G/2G多模式</item>
    <item>仅3G/2G模式</item>
    <item>仅2G模式</item>
</string-array>

对应的值：

<string-array name="lte_network_mode_choices_values_for_3mode" translatable="false">
    <item>"0"</item>
    <item>"1"</item>
    <item>"4"</item>
</string-array>

所以在修改网络模式时要设置对应的value值：

if ((networkMode != -1) && (SimManager.isValidPhoneId(phoneId))) {
    RadioTaskManager.getDefault().setPreferredNetworkModeForPhone(phoneId, networkMode);
}