How to change Linux Kernel configuration file in Yocto Project metalayer

Document created by Daiane Angolini Employee on Apr 1, 2020Last modified by Daiane Angolini Employee on Apr 1, 2020
Version 3Show Document
  • View in full screen mode


How to change Linux Kernel configuration file in Yocto Project metalayer

 

It is common that the metalayer providing a Linux Kernel recipe includes a default configuration file for the Linux Kernel source code (the defconfig file).

There are several approaches to customize the Linux Kernel source code and defconfig file. This article presents the option to patch the defconfig from the Linux Kernel source code and is a good approach to be used with meta-fsl-bsp-release or meta-imx.

 

Preparing the requirements

The list of requirements:

  • the target metalayer (in this example, it's meta-imx:imx-5.4.3-2.0.0)
  • the same Linux Kernel source code, but git cloned

Download the metalayer

 

For example, take BSP release imx-5.4.3-2.0.0 for meta-imx

$ mkdir <BSP_DIR>
$ cd <BSP_DIR>
$ repo init -u https://source.codeaurora.org/external/imx/imx-manifest -b imx-linux-zeus -m imx-5.4.3-2.0.0.xml
$ repo sync
$ MACHINE=imx8mnevk DISTRO=fsl-imx-xwayland source ./imx-setup-release.sh -b bld-xwayland


Git clone the Linux Kernel source code

Use the very same Linux Kernel source code from the metalayer. In this example, open the file sources/meta-imx/meta-bsp/recipes-kernel/linux/linux-imx_5.4.bb to get the git repository, and git commit.

 

$ cd ~
$ git clone git://source.codeaurora.org/external/imx/linux-imx.git
$ cd linux-imx
$ git checkout fd263a3edd95dfe812397fabf1059b5f99bba2ab -b change_defconfig


Customize the configuration

Using the default defconfig as a base, configure the Linux Kernel, and then use make menuconfig to change the configuration as desired.

After the customization, generate a new defconfig file and replace the default one.

The step by step with all the commands can be see in next snippet:

$ export ARCH=arm64
$ export CROSS_COMPILE=aarch64-linux-gnu-
$ make defconfig
$ make menuconfig
$ make savedefconfig
$ cp defconfig arch/arm64/configs/defconfig

 

The customization can be highlighted by git, in this example the result is show in next log:

$ git status
On branch change_defconfig
Changes not staged for commit:
(use "git add <file>..." to update what will be committed)
(use "git checkout -- <file>..." to discard changes in working directory)

modified: arch/arm64/configs/defconfig

Untracked files:
(use "git add <file>..." to include in what will be committed)

defconfig

no changes added to commit (use "git add" and/or "git commit -a")

 

Review the change and create a commit, with that commit, create a patch.

TIP: The defconfig file can also be directly changed. The make menuconfig can be skipped in that case.

$ git add arch/arm64/configs/defconfig
$ git commit -s -m "defconfig: Customize defconfig"
$ git format-patch -1
0001-defconfig-Customize-defconfig.patch


Copy the configuration to the metalayer

Now that the Linux Kernel configuration is customized, and a patch to the kernel is created, copy over that patch to the metalayer, and install it to the Linux Kernel recipe file.

$ mkdir <BSP_DIR>/sources/meta-imx/meta-bsp/recipes-kernel/linux/linux-imx/
$ cp 0001-defconfig-Customize-defconfig.patch <BSP_DIR>/sources/meta-imx/meta-bsp/recipes-kernel/linux/linux-imx/


Install the patch in the Linux Kernel recipe

The Linux Kernel recipe for this example is linux-imx_5.4.bb. Edit the file to install the patch.

$ gedit <BSP_DIR>/sources/meta-imx/meta-bsp/recipes-kernel/linux/linux-imx_5.4.bb

Add the following line:

SRC_URI += "file://0001-defconfig-Customize-defconfig.patch "

The resultant change is show above:

$ cd <BSP_DIR>/sources/meta-imx/
$ git diff
diff --git a/meta-bsp/recipes-kernel/linux/linux-imx_5.4.bb b/meta-bsp/recipes-kernel/linux/linux-imx_5.4.bb
index 214647abb..3f926314c 100644
--- a/meta-bsp/recipes-kernel/linux/linux-imx_5.4.bb
+++ b/meta-bsp/recipes-kernel/linux/linux-imx_5.4.bb
@@ -16,6 +16,7 @@ KERNEL_BRANCH ?= "imx_5.4.3_2.0.0"
LOCALVERSION = "-2.0.0"
KERNEL_SRC ?= "git://source.codeaurora.org/external/imx/linux-imx.git;protocol=https"
SRC_URI = "${KERNEL_SRC};branch=${KERNEL_BRANCH}"
+SRC_URI += "file://0001-defconfig-Customize-defconfig.patch "

SRCREV = "fd263a3edd95dfe812397fabf1059b5f99bba2ab"


Build the new image with the different Linux Kernel configuration

Remember to change the current directory to the metalayer.

Build the image again. The new image binary reflects the changes in Linux Kernel, and in case the change removes some kernel module, the rootfs also reflects the change.

$ cd <BSP_DIR>/bld-xwayland
$ bitbake <image-name>

Attachments

    Outcomes