off charging mode flow

/system/core/init/init.cpp

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int main(int argc, char** argv) {
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    // Don't mount filesystems or start core system services in charger mode.
    std::string bootmode = GetProperty("ro.bootmode", "");
    if (bootmode == "charger") {
        am.QueueEventTrigger("charger");
    } else {
        am.QueueEventTrigger("late-init");
    }
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/system/core/rootdir/init.rc

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on charger
    class_start charger
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/system/core/healthd/Android.mk

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LOCAL_SRC_FILES := \
    charger.cpp \

LOCAL_MODULE := charger
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/system/core/healthd/charger.cpp

int healthd_charger_main(int argc, char** argv) {
    int ch;

    healthd_mode_ops = &charger_ops;

    while ((ch = getopt(argc, argv, "cr")) != -1) {
        switch (ch) {
            case 'c':
                // -c is now a noop
                break;
            case 'r':
                // force nops for recovery
                healthd_mode_ops = &healthd_nops;
                break;
            case '?':
            default:
                KLOG_ERROR(LOG_TAG, "Unrecognized charger option: %c\n",
                        optopt);
                exit(1);
        }
    }

    return healthd_main();
}

int main(int argc, char** argv) {
    return healthd_charger_main(argc, argv);
}

[To Be Continued]