View source for Android Customizing the Linux kernel

<!-- Set release according to "release" parameter in URL and use RELEASE_N7.1.1_1.0.0_VAR-SOM-MX6 as default
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--> {{PageHeader|{{#var:HARDWARE_NAME}} - Android {{#var:ANDROID_NAME}} {{#var:ANDROID_VERSION}} - Customizing the Linux kernel}} {{DocImage|category1=Android|category2={{#var:HARDWARE_NAME}}}} __toc__

== Making changes to kernel configuration ==
 $ cd {{#var:BUILD_FOLDER}}/{{#var:BUILD_FOLDER_ANDROID}}/vendor/variscite/kernel_imx/
 $ make ARCH={{#ifeq: {{#var:HARDWARE_NAME}} |VAR-SOM-MX6|arm|arm64}} mrproper
 $ make ARCH={{#ifeq: {{#var:HARDWARE_NAME}} |VAR-SOM-MX6|arm|arm64}} {{#var:KERNEL_DEFCONFIG}}
 $ make ARCH={{#ifeq: {{#var:HARDWARE_NAME}} |VAR-SOM-MX6|arm|arm64}} menuconfig
Navigate the menu and select the desired kernel functionalities, save the new configuration and exit.<br>
Then, save the new configuration as the default configuration:<br>
 $ make ARCH={{#ifeq: {{#var:HARDWARE_NAME}} |VAR-SOM-MX6|arm|arm64}} savedefconfig
 $ cp arch/{{#ifeq: {{#var:HARDWARE_NAME}} |VAR-SOM-MX6|arm|arm64}}/configs/{{#var:KERNEL_DEFCONFIG}} arch/{{#ifeq: {{#var:HARDWARE_NAME}} |VAR-SOM-MX6|arm|arm64}}/configs/{{#var:KERNEL_DEFCONFIG}}.orig 
 $ cp defconfig arch/{{#ifeq: {{#var:HARDWARE_NAME}} |VAR-SOM-MX6|arm|arm64}}/configs/

== Making changes to the device tree ==
For example, edit the following file: {{#ifeq: {{#var:HARDWARE_NAME}}|VAR-SOM-MX6| * VAR-SOM-MX6 : {{#var:BUILD_FOLDER}}/{{#var:BUILD_FOLDER_ANDROID}}/vendor/variscite/kernel_imx/arch/arm/boot/dts/imx6qdl-var-som.dtsi <br>
*DART-MX6: {{#var:BUILD_FOLDER}}/{{#var:BUILD_FOLDER_ANDROID}}/vendor/variscite/kernel_imx/arch/arm/boot/dts/imx6qdl-var-dart.dtsi| {{#var:BUILD_FOLDER}}/{{#var:BUILD_FOLDER_ANDROID}}/vendor/variscite/kernel_imx/arch/arm64/boot/dts/{{#ifeq: {{#var:HARDWARE_NAME}} | DART-MX8M |freescale/fsl-imx8mq-var-dart-common.dtsi | freescale/fsl-imx8mm-var-dart.dts}}}} <br>
For example, if you want to make changes related to the SPI configuration you can refer to: {{#ifeq: {{#var:HARDWARE_NAME}}|VAR-SOM-MX6 |[[{{#var:HARDWARE_NAME}} SPI|SPI]]|{{Varlink|DART-MX8M SPI|{{#var:RELEASE_LINK}}|SPI}}}}

== Build a new boot.img ==
When you perform changes to the kernel, you may build boot.img solely instead of building the whole Android.
 $ cd {{#var:BUILD_FOLDER}}/{{#var:BUILD_FOLDER_ANDROID}}
 $ source build/envsetup.sh
 $ lunch {{#var:ANDROID_MACHINE_NAME}}-userdebug
 $ make bootimage
 $ make dtboimage

== Flashing the boot image to the target ==
Run the following to boot the device into fastboot mode and reflash the boot image:<br>
 $ adb reboot bootloader
 $ sudo `which fastboot` flash boot{{#ifeq: {{#var:HARDWARE_NAME}} | VAR-SOM-MX6 | out/target/product/var_mx6/boot-<setup-name>.img |_a out/target/product/out/target/product/{{#var:ANDROID_MACHINE_NAME}}/boot.img }}
 {{#ifeq: {{#var:HARDWARE_NAME}} | VAR-SOM-MX6 |

Replace setup-name as per above table.
 |
 $ sudo `which fastboot` flash dtbo_a out/target/product/{{#var:ANDROID_MACHINE_NAME}}/dtbo-<name>.img
 $ sudo `which fastboot` flash vbmeta_a out/target/product/{{#var:ANDROID_MACHINE_NAME}}/vbmeta-<name>.img
Replace <name> with the actual desired setup name according to the table in the {{Varlink|Android_NXP_Guide#Images_created_by_the_Android_build|{{#var:RELEASE_LINK}}|"images created by the Android build" section}} in the "Build Android from source code" page.
}}
 $ sudo `which fastboot` reboot
{{#ifeq: {{#var:HARDWARE_NAME}} | VAR-SOM-MX6 ||
*Note: While flashing if you encouter like below <br>
 $ sudo `which fastboot` flash boot_a out/target/product/{{#var:ANDROID_MACHINE_NAME}}/boot.img <br>
 target reported max download size of 1073741824 bytes
 Sending 'boot_a' (49152 KB)...
 OKAY [  1.740s]
 Writing 'boot_a'...
 FAILED (remote:  device is locked.)
 Finished. Total time: 1.772s
Make sure you unlock your device following<br>
{{Varlink|Fastboot Unlock|{{#var:RELEASE_LINK}}|Fastboot Unlock}} and then follow the steps above
}}