Modify, rebuild and reload the Linux® kernel

1 Overview

This stage explains how modify, rebuild and reload the Linux^® kernel.
You will first be guided to install the Linux^® kernel source code in the Developer Package directory. Then you will execute step by step procedures to modify, rebuild and reload the Linux^® kernel.

2 Download the Linux^® kernel source code

The software package is provided AS IS, and by downloading it, you agree to be bound to the terms of the software license agreement (SLA0048). The detailed content licenses can be found here.

2.1 For STM32MP13x lines 

• The STM32MP1 Linux kernel is delivered through a tarball file named unknown revision for STM32MP135x-DK boards.

• Download and install the STM32MP1 Linux kernel

The software package is provided AS IS, and by downloading it, you agree to be bound to the terms of the software license agreement (SLA0048). The detailed content licenses can be found here.

	STM32MP1 Developer Package Linux kernel - STM32MP13-Ecosystem-v3.1.0.ALPHA release
Download	If you didn't retrieve yet the file unknown revision , please follow instructions on the downloading instructions page. You will get all source files in the directory you choose when you extracted the .jar file.

• Uncompress the tarball file to get the Linux® kernel tarball, the ST patches and the ST configuration fragments

 cd $HOME/STM32MPU_workspace/STM32MP13-Ecosystem-v3.1.0/Developer-Package
 tar xvf unknown revision 

2.2 For STM32MP15x lines 

• Download the [unknown revision /unknown revision STM32MP15-Ecosystem-v3.1.0 Developer Package Sources] to the following directory:
  $HOME/STM32MPU_workspace/STM32MP15-Ecosystem-v3.1.0/Developer-Package

• Uncompress the tarball file to get the Linux^® kernel tarball, ST patches and ST configuration fragments

 cd $HOME/STM32MPU_workspace/STM32MP15-Ecosystem-v3.1.0/Developer-Package
 tar xvf unknown revision 

3 Prepare the Linux^® kernel source code

• For STM32MP13x lines :

 cd unknown revision 

Extract the Linux^® kernel source

 tar xvf unknown revision 

Apply ST patches

 cd unknown revision 
 for p in `ls -1 ../*.patch`; do patch -p1 < $p; done

• For STM32MP15x lines :

 cd unknown revision 

Extract the Linux^® kernel source

 tar xvf unknown revision 

Apply ST patches

 cd unknown revision 
 for p in `ls -1 ../*.patch`; do patch -p1 < $p; done

---

Apply fragments

 make ARCH=arm multi_v7_defconfig "fragment*.config"
 for f in `ls -1 ../fragment*.config`; do scripts/kconfig/merge_config.sh -m -r .config $f; done
 yes '' | make ARCH=arm oldconfig

4 Build the Linux^® kernel source code for the first time

Information

Building the kernel for the first time can take several minutes.

• Build kernel images (uImage and vmlinux) and device tree (dtbs)

 make ARCH=arm uImage vmlinux dtbs LOADADDR=0xC2000040

• Build kernel module

 make ARCH=arm modules

• Generate output build artifacts

 mkdir -p $PWD/install_artifact/
 make ARCH=arm INSTALL_MOD_PATH="$PWD/install_artifact" modules_install

5 Deploy the Linux^® kernel on the board

5.1 Push the Linux^® kernel onto the board

 scp arch/arm/boot/uImage root@<board ip address>:/boot

5.2 Push the devicetree into the board

 scp arch/arm/boot/dts/stm32mp1xx*.dtb root@<board ip address>:/boot

5.3 Push the kernel modules onto the board

• Remove the link created inside the install_artifact/lib/modules/<kernel version> directory

 rm install_artifact/lib/modules/5.10.61/build install_artifact/lib/modules/5.10.61/source 

• Optionally, strip kernel modules (to reduce the size of each kernel modules)

 find install_artifact/ -name "*.ko" | xargs $STRIP --strip-debug --remove-section=.comment --remove-section=.note --preserve-dates

• Copy kernel modules

 scp -r install_artifact/lib/modules/* root@<ip of board>:/lib/modules

• Using the Linux^® console, regenerate the list of module dependencies (modules.dep) and the list of symbols provided by modules (modules.symbols)

 /sbin/depmod -a

• Synchronize data on disk with memory

 sync

5.4 Reboot the board

 reboot

6 Modify a built-in Linux^® kernel device driver

This simple example adds unconditional log information when the display driver is probed.

• Using the Linux^® console, check that there is no log information when the display driver is probed

 dmesg | grep -i stm_drm_platform_probe

For STM32MP13x lines :

• Go to the Linux^® kernel source directory

 cd $HOME/STM32MPU_workspace/STM32MP13-Ecosystem-v3.1.0/Developer-Package/unknown revision /unknown revision 

For STM32MP15x lines :

• Go to the Linux^® kernel source directory

 cd $HOME/STM32MPU_workspace/STM32MP15-Ecosystem-v3.1.0/Developer-Package/unknown revision /unknown revision 

---

• Edit the ./drivers/gpu/drm/stm/drv.c source file
• Add a log information in the stm_drm_platform_probe function as follows

static int stm_drm_platform_probe(struct platform_device *pdev)
{
	struct device *dev = &pdev->dev;
	struct drm_device *ddev;
	int ret;
	[...]

	DRM_INFO("Simple example - %s\n", __func__);

	return 0;
	[...]
}

• Save the file
• Rebuild the Linux^® kernel

 make uImage LOADADDR=0xC2000040

• Update the Linux kernel image into board

 scp arch/arm/boot/uImage root@<board ip address>:/boot

• Reboot the board

 reboot

• Check that log information is now present when the display driver is probed

 dmesg | grep -i stm_drm_platform_probe
[    2.764080] [drm] Simple example - stm_drm_platform_probe

Linux^® is a registered trademark of Linus Torvalds.

Direct rendering manager (kernel module that gives direct hardware access to DRI clients, find more information on official DRI web site http://dri.freedesktop.org/wiki/DRM)

Linux^® is a registered trademark of Linus Torvalds.

Direct rendering manager (kernel module that gives direct hardware access to DRI clients, find more information on official DRI web site http://dri.freedesktop.org/wiki/DRM)

Direct rendering infrastructure (Linux^® framework for allowing direct access to graphics hardware... find more information on official DRI web site http://dri.freedesktop.org/)