DM（显示管理器）功能如下：
不增加其他额外的启动时间；
See <linux/platform_device.h> for the driver model interface to the platform bus: platform_device, and platform_driver. This pseudo-bus is used to connect devices on busses with minimal infrastructure,
like those used to integrate peripherals on many system-on-chip processors, or some "legacy" PC interconnects; as opposed to large formally specified ones like PCI or USB.
Platform devices are devices that typically appear as autonomous entities in the system. This includes legacy port-based devices and host bridges to peripheral buses, and most controllers integrated into system-on-chip platforms. What they usually have in common is direct addressing from a CPU bus. Rarely, a platform_device will be connected through a segment of some other kind of bus; but its registers will still be directly addressable.
...对于NandFlash的认识尝试不做更多理解，只需要了解非易失存储、擦除寿命有限、通常是10K级别，同时写操作需要基于Page来。没有办法按照内存的存储基本单位字节来操作,由多个Page组成一个Block 每个 Page保留 一些字节用以 做ECC （ error correcting code ）校验。
烧写工具HiTool-STB-3.1.35.zip 会在成功编译镜像后自动拷贝到out文件夹。
参考ServerInstall.sh进行初始化环境，主要是包含java 、python、依赖库、gcc安装，然而很多依赖版本过低，所以必须要添加 ubuntu12.04或者14.04源安装。
编译打包相关脚本文件。
拷贝tools/pack/chips/sun50iw1p1/bin/boot0_sdcard_sun50iw1p1.bin到out/boot0_sdcard.fex
全志 a64 linux sdk采用了android 的boot image，这里顺着该sdk系统理解android的引导镜像。
如下linux-3.10/scripts/build.sh 代码片段显示，在完成内核编译后，改脚本直接将kernel的二进制可执行文件和cpio的gzip压缩包rootfs.cpio.gz 一起合并进入boot.img。
Ramfs is a very simple FileSystem that exports Linux's disk cacheing mechanisms (the page cache and dentry cache) as a dynamically resizable ram-based filesystem.
ramfs 是一个基于linux缓存机制（page cache and dentry cache）的简易文件系统，基于ram，大小可动态调整。
...这里系统了解全志和海思的解码能力。
从Allwinner_H6_V200_User_Manual_V1.1_decrypted->Chapter 2 Overview->2.2.6. Video Engine ->2.2.6.1. Video Decoder
如上启动顺序
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