Analysis of uboot directory structure

Version number changes

2008 year 8 Month and before , Name it by version number ：u-boot-1.3.4.tar.bz2(2008 year 8 Monthly update )

2008 year 8 After the month is named by the date . The latest version ：u-boot-2011.06.tar.bz2（2011 year 6 Monthly update ）

Directory structure changes

u-boot Directory structure mainly experienced 2 Changes ,u-boot For the first time, the version came from u-boot-1.3.2 It's starting to change , Mainly increased api The content of ; The biggest change is the second time , from 2010.6 Version start .

u-boot-2010.03 And previous versions
├── api Deposit uboot Interface functions provided
├── board Customized code according to different development boards , There's a lot of code
├── common Common code , It covers all aspects , It has been processed on the command line
├── cpu Architecture related code ,uboot The play of
├── disk Disk partition related code
├── doc file , a pile README Opening file
├── drivers drive , Very rich , Each type of device driver occupies a subdirectory
├── examples The sample program
├── fs file system , Support common file system of embedded development board
├── include The header file , The general header file is the main one
├── lib_【arch】 Common library files related to architecture
├── nand_spl NAND Memory related codes
├── net Network related code , Small protocol stack
├── onenand_ipl
├── post Power on self test program
└── tools Auxiliary program , For compiling and checking uboot Target file

from u-boot-2010.06 Version begins to merge architecture related content , The original cpu And lib_arch All the contents are included in arch in , And it adds inlcude Folder ; Separate the general library file lib.

u-boot-2010.06 And later versions
├── api Deposit uboot Interface functions provided
├── arch Architecture related code ,uboot The play of
├── board Customized code according to different development boards , There's a lot of code
├── common Common code , It covers all aspects , It has been processed on the command line
├── disk Disk partition related code
├── doc file , a pile README Opening file
├── drivers drive , Very rich , Each type of device driver occupies a subdirectory
├── examples The sample program
├── fs file system , Support common file system of embedded development board
├── include The header file , The general header file is the main one
├── lib General library files
├── nand_spl NAND Memory related codes
├── net Network related code , Small protocol stack
├── onenand_ipl
├── post Power on self test program
└── tools Auxiliary program , For compiling and checking uboot Target file

The directory involved in the migration work

from uboot Code root , It can be seen that it is already very large , It's also very functional .
The most important thing for porting is to look at the corresponding processor and development board code ,2010.06 After the release, processor related code is concentrated in arch、board Catalog .( Previous versions were mainly in cpu and board Catalog )
Have a look first arch Catalog ：
arch
├── arm
├── avr32
├── blackfin
├── i386
├── m68k
├── microblaze
├── mips
├── nios2
├── powerpc
├── sh
└── sparc

arch The contents of the directory are cleaner than the previous versions , Each subdirectory represents a processor type , The subdirectory name is the type name of the processor .
We transplanted mips The processor of , So for reference arch/mips Catalog ：

arch/mips
├── cpu
├── include
└── lib

arch/mips There are three directories in the directory , It's the same structure in other processor directories ：
cpu Subdirectories correspond to different product models or series of a processor ;
include Subdirectories are header files used by the processor ;
lib Directory pairs apply to code common to processors ;

Let's see below. cpu Below ,arch/mips/cpu Contents under the directory ：

arch/mips/cpu
├── asc_serial.c
├── asc_serial.h
├── au1x00_eth.c
├── au1x00_serial.c
├── au1x00_usb_ohci.c
├── au1x00_usb_ohci.h
├── cache.S
├── config.mk
├── cpu.c
├── incaip_clock.c
├── incaip_wdt.S
├── interrupts.c
├── Makefile
└── start.S Whole uboot Code entry point

The latest version (2011.6 Version start ) in cpu Create in directory mips32 Catalog , hold incaip and au1x00 It's also classified into different categories .

u-boot.lds yes ld The program is the script file of the connector , This file describes how to connect to the target file ,ld According to the instructions of this file, the program will connect different object files together according to the requirements to generate the program for burning to the development board .
The document is placed in board In the corresponding directory .

u-boot working process

U-Boot The process of starting the kernel can be divided into two stages , The functions of the two stages are as follows ：
（1） The function of the first stage

Ø Hardware device initialization

Ø load U-Boot Phase two code to RAM Space

Ø Set up the stack

Ø Jump to the second phase code entry

（2） The function of the second stage

Ø Initialize the hardware devices used in this phase

Ø Detect system memory mapping

Ø Take the kernel from Flash Read RAM in

Ø Set the boot parameters for the kernel

Ø Call kernel

Reproduced in ：https://blog.csdn.net/ccccdddxxx/article/details/6800135
https://blog.csdn.net/AndroidBBC/article/details/50961163