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【转】uboot 源代码分析

前几天看了uboot,代码不多,原理也挺简单的,就是配置的东西太多,往往会模糊人的注意力,大多开源的东西都差不多是这样.大多数的人往往被配置,编译,运行这类琐碎的事情所困扰.使得自己不能从开源的代码吸取自己需要的东西.如果每次都停留在"使用"的阶段,那么开源对于国内的软件行业估计也起不了多大的作用,反正国内的盗版也猖獗的很.

   uboot是一个支持多种体系结构的bootloader.我目前使用的源代码是1.1.4版本,不过1.1.5版本也在2006-10-20号(昨天)发布了,可以去http://sourceforge.net/projects/u-boot上下载到新版本的源代码.

   uboot的源代码布局和Linux还是有点像的.按模块划分,充分考虑了体系结构跨平台的问题.其源代码树如下:

  • board          该文件夹中包含开发板相关的定义
  • common         该文件夹中定义了各种uboot命名的处理函数
  • cpu            该文件夹定义了各种体系结构及处理器系列的相关功能
  • disk           该文件定义了一些磁盘操作
  • doc            文档文件夹
  • drivers        该文件夹中包含了一些常用外设的驱动程序
  • dtt            该文件夹中包含一些温度传感器操作的驱动,主要有Analog Devices的ADM1021,Dallas  Semiconductor的DS1621, 以及LM75
  • examples       例子文件夹
  • fs             包含文件系统的支持,文件系统有cramfs,ext2,fat,fdos,jffs2,reiserfs
  • include        头文件的文件夹,包含配置头文件
  • lib_arm        arm体系相关的操作
  • lib_generic    通用的库操作定义,比如字符串的操作
  • lib_i386
  • lib_m68k
  • lib_microblaze
  • lib_mips
  • lib_nios
  • lib_nios2
  • lib_ppc
  • net             网络协议,bootp,nfs,rarp,tftp
  • post            上电自检
  • rtc             实时时钟相关的操作
  • tools           一些工具,用于生成image等

    对于bootloader来说,了解它的启动过程是很重要的,了解了启动过程可以方便程序员移植平台,虽然在board文件夹中已经定义了些常用开发板,cpu中也定义了一些常用的体系结构.不过平台移植在开发过程中也是有必要的.总的来看,目前的移植主要在于开发板的移植.所以关注开发板的移植可能更有意义一些.

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