android dts的作用,DTS相关知识

一、DTS 学习

1. kernel/arch/arm/boot/dts 目录下包含所有的dts.

a. board , msm8226.dtsi

b. pmic, msm-pm8226.dtsi

2. kernel/Androidkernel.mk;  Android makefile to build kernel as a part of Android Build

3. kernel/arch/arm/configs 目录下保存对应的config定义， CONFIG_XXXXXX

4. 可参考 jb-mr1-rhine/kernel/arch/arm/boot/dts/msm8974-rhine_togari_row.dtsi

十、device tree source(DTS)

0. http://devicetree.org/Main_Page

1. *.dts/dtsi 文件一般位于　kernel/arch/arm/boot/dts，比如msm8226-cn3ii.dts  msm8226-cn3ii.dtsi

２. 如何决定用那个*.dts文件？

@kernel/arch/arm/mach-msm/Makefile.boot

# MSM8226

zreladdr-$(CONFIG_ARCH_MSM8226)  := 0x00008000 //是啥地址？

dtb-$(CONFIG_MACH_SONY_CN3II) += msm8226-cn3ii.dtb

@kernel/arch/arm/configs/cn3ii_defconfig

CONFIG_ARCH_MSM8226=y

CONFIG_MACH_SONY_CN3II=y

3. 编译dts为dtb的工具为DTC,位于kernel/scripts/dtc

hostprogs-y := dtc　//@Makefile中，该行表示用hostprogs编译生成dtc

最后生成的dtc可执行文件位于out/target/product/cn3ii/obj/KERNEL_OBJ/scripts/dtc/dtc

4.用dtc编译*.dts生成的*.dtb文件位于

out/target/product/cn3ii/obj/KERNEL_OBJ/arch/arm/boot/msm8226-cn3ii.dtb

存放在手机什么地方？

bootloader如何读取？如何传递给kernel?

head-common.S@kernel\arch\arm\kernel中有

.long    __atags_pointer　@ r6　//表示保存dtb的地址通过r6传递给kernel

5. kernel中解析DTS

setup_machine_fdt@kernel/arch/arm/kernel/devtree.c

struct boot_param_header *devtree = phys_to_virt(dt_phys); //注意boot_param_header结构

setup_machine_fdt将分析dtb最后所有devices生成树，如何和以前的版本结果就一样了

6. kernel中各个device和driver谁先加载？