[device tree] How to decompile a compiled .dtb (device tree blog) into .dts (device tree source).

$ ./out/target/product/project_name/obj/KERNEL_OBJ/scripts/dtc/dtc -I dtb -O dts -o decompiled.dts ~/project/linux_repo/out/target/product/project_name/obj/KERNEL_OBJ/arch/arm64/boot/dts/your.dtb

也就是

scripts/dtc/dtc -I dtb -O dts -o you_want.dts your.dtb

Usage: dtc [options] <input file>

• -I, --in-format <arg>
  
  Input formats are:
  
  dts - device tree source text
  
  dtb - device tree blob
  
  fs - /proc/device-tree style directory

• -O, --out-format <arg>
  
  Output formats are:
  
  dts - device tree source text
  
  dtb - device tree blob
  
  asm - assembler source

• -o, --out <arg>
  
  Output file

注意

一個是大寫 O

一個是小寫 o

以 Qualcomm MSM8917 為例

Qualcomm code base 會 build 出許多 .dtb，

因此需先找出 project 所使用到的 .dtb

在 uart log 中會有類似以下的 log

 146 [    0.000000] Machine: Qualcomm Technologies, Inc. MSM8917-PMI8940 MTP

Machine: 後面的字串就是您所使用的 device tree file 的 model，

在 android/kernel/msm-3.18/arch/arm/boot/dts/qcom/ 目錄下 grep 此字串，

$ grep -rns "Qualcomm Technologies, Inc. MSM8917-PMI8940 MTP"
arm/boot/dts/qcom/msm8917-pmi8940-mtp.dts:20:	model = "Qualcomm Technologies, Inc. MSM8917-PMI8940 MTP";

msm8917-pmi8940-mtp 就是此 project 所使用的 dtb,

到 android/out/ 搜尋 msm8917-pmi8940-mtp.dtb，

android/out$ find -name "msm8917-pmi8940-mtp.dtb"
./target/product/msm8937_64/obj/kernel/msm-3.18/arch/arm64/boot/dts/qcom/msm8917-pmi8940-mtp.dtb

到 android/out/ 搜尋 dtc 執行檔，

$ find -name dtc
./target/product/msm8937_64/obj/kernel/msm-3.18/scripts/dtc/dtc

最後再反譯 dtb 為 dts，

android/out$ ./target/product/msm8937_64/obj/kernel/msm-3.18/scripts/dtc/dtc -I dtb -O dts -o decompiled.dts ./target/product/msm8937_64/obj/kernel/msm-3.18/arch/arm64/boot/dts/qcom/msm8917-pmi8940-mtp.dtb

decompiled.dts 就是此 project 所有被使用到的 dts 的集合。

以 MTK mt6755 為例

mtk code base 只會 build 出一個 .dtb，

所以直接到 linux_repo/out 下搜尋 *.dtb

linux_repo/out$ find -name "*.dtb"
./target/product/XXXXXXXXXX/obj/KERNEL_OBJ/arch/arm64/boot/dts/XXXXXXXXXX.dtb

到 linux_repo/out 下搜尋 dtc 執行檔

linux_repo/out$ find -name "dtc"
./target/product/XXXXXXXXXX/obj/KERNEL_OBJ/scripts/dtc/dtc

最後再反譯 dtb 為 dts，

linux_repo/out$ ./target/product/XXXXXXXXXX/obj/KERNEL_OBJ/scripts/dtc/dtc -I dtb -O dts -o decompiled.dts ./target/product/XXXXXXXXXX/obj/KERNEL_OBJ/arch/arm64/boot/dts/XXXXXXX.dtb

decompiled.dts 就是此 project 所有被使用到的 dts 的集合。