android 关机充电流程

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0.主要流程

usb插入通过传递cmdline给init解析从而启动充电进程

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1. LK

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lkappabootaboot.c

update_cmdline


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       if (boot_into_ffbm)  // 工厂测试模式
        {
                cmdline_len += strlen(androidboot_mode);
                cmdline_len += strlen(ffbm_mode_string);
                /* reduce kernel console messages to speed-up boot */
                cmdline_len += strlen(loglevel);
        }
        else if (target_pause_for_battery_charge())   // 判断是否关机充电
        {
                pause_at_bootup = 1;                    // charger flag
                cmdline_len += strlen(battchg_pause);   //更新 cmd line 长度
        }
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        else if (pause_at_bootup)                    // charger flag
                {
                        src = battchg_pause;         // static const char *battchg_pause = " androidboot.mode=charger";
                        if (have_cmdline) --dst;
                        while ((*dst++ = *src++));
                }
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2.init

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#init.c
if (!is_ffbm)
    is_charger = !strcmp(bootmode, "charger");



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if (is_charger)
   action_for_each_trigger("charger", action_add_queue_tail);


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# init.rc
on charger
    class_start charger


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# init.qcom.rc
service charger /charger
    class charger


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#system/core/healthd/Android.mk 

LOCAL_MODULE := healthd
...
# Symlink /charger to /sbin/healthd
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