1. Overview[edit source]
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 OpenSTLinux BSP that includes the Linux® kernel source code[edit source]
- The OpenSTLinux BSP package is delivered through a tarball file named unknown revision for STM32MP157x-EV1
, STM32MP157x-DKx and STM32MP135x-DK 
boards.
- Download and install the STM32MP1 OpenSTLinux BSP package
| STM32MP1 Developer Package - STM32MP1-Ecosystem-v4.0.0 release | |
|---|---|
| Download |
You need to be logged on my.st.com before accessing the following link: |
| Installation |
cd <working directory path>/Developer-Package
tar xvf unknown revision
|
| Release note |
Details about the content of the OpenSTLinux BSP package are available in the associated STM32 MPU OpenSTLinux release note.
|
If you are interested in older releases, have a look into the section
3. Prepare the Linux® kernel source code[edit source]
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[edit source]
- 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[edit source]
5.1. Push the Linux® kernel onto the board[edit source]
scp arch/arm/boot/uImage root@<board ip address>:/boot
5.2. Push the devicetree into the board[edit source]
scp arch/arm/boot/dts/stm32mp1xx*.dtb root@<board ip address>:/boot
5.3. Push the kernel modules onto the board[edit source]
- Remove the link created inside the install_artifact/lib/modules/<kernel version> directory
rm install_artifact/lib/modules/5.15.24/build install_artifact/lib/modules/5.15.24/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[edit source]
reboot
6. Modify a built-in Linux® kernel device driver[edit source]
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
- Go to the Linux® kernel source directory
cd $HOME/STM32MPU_workspace/STM32MP1-Ecosystem-v4.0.0/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
