Android 4.2 Shutdown procedure

最新推荐文章于 2025-10-12 00:30:00 发布

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本文详细介绍了基于BSPv13.05的Linux系统中从Android层面调用到内核层面的关机过程。主要步骤包括：Android通过__reboot函数发送关机指令至Linux内核；Linux内核接收到指令后，根据指定模式执行相应操作；最终通过kernel_power_off函数完成系统关闭。文章深入剖析了关键函数及其实现路径。

The shutdown procedure within Linux (based on BSP v13.05):
        1.    Android call __reboot( LINUX_REBOOT_MAGIC1,
                                                           LINUX_REBOOT_MAGIC2,
                                                           mode,
                                                           NULL);
              /bionic/libc/unistd/reboot.c
              to pass parameters and target mode to Linux.

        2.   Linux receivs parameters and mode(cmd) in
               /kernel/kernel/sys.c
               SYSCALL_DEFINE4(reboot,
                                               int, magic1,
                                               int, magic2,
                                               unsigned int, cmd, //cmd is the mode in Android
                                               void __user *, arg)

               if the cmd is LINUX_REBOOT_CMD_POWER_OFF, call:

        3.   kernel_power_off() in /kernel/kernel/sys.c
               this function will call below functions in a row:
               a.   kernel_shutdown_prepare()   ///kernel/kernel/sys.c
                       --> device_shutdown()           ///kernel/drivers/base/core.c

               b.   machine_power_off()               ///arch/arm/kernel/process.c



        To understand the complete shutdown procedure, reference:
        http//blog.youkuaiyun.com/hufik/article/details/8964674