View source for Modify, rebuild and reload the Linux® kernel


==Overview==
This stage explains how modify, rebuild and reload the Linux<sup>&reg;</sup> kernel.<br>
You will first be guided to install the Linux<sup>&reg;</sup> kernel source code in the Developer Package directory. Then you will execute step by step procedures to modify, rebuild and reload the Linux<sup>&reg;</sup> kernel.

==Download the Linux<sup>&reg;</sup> kernel source code==
{{SoftwareLicenseAgreement | distribution=OpenSTLinux | chapter=Kernel partitions:}}
'''For {{EcosystemRelease | revision=3.1.0}}''':
* Download the [{{EcosystemRelease/Package | revision=3.1.0 | package=Linux kernel package | request=url}}/{{EcosystemRelease/Package | revision=3.1.0 | package=Linux kernel package | request=name}} STM32MP15-Ecosystem-v3.1.0 Developer Package Sources] into the following directory:<br> '''$HOME/STM32MPU_workspace/STM32MP15-Ecosystem-v3.1.0/Developer-Package'''
* Uncompress the tarball file to get the Linux<sup>&reg;</sup> kernel tarball, ST patches and ST configuration fragments
 {{PC$}} cd $HOME/STM32MPU_workspace/STM32MP15-Ecosystem-v3.1.0/Developer-Package
 {{PC$}} tar xvf {{EcosystemRelease/Package | revision=3.1.0 | package=Linux kernel package | request=name}}

'''For {{EcosystemRelease | revision=3.0.0}}''': <div class="mw-collapsible mw-collapsed">
* Download the [{{EcosystemRelease/Package | revision=3.0.0 | package=Linux kernel package | request=url}}/{{EcosystemRelease/Package | revision=3.0.0 | package=Linux kernel package | request=name}} STM32MP15-Ecosystem-v3.0.0 Developer Package Sources] into the following directory:<br> '''$HOME/STM32MPU_workspace/STM32MP15-Ecosystem-v3.0.0/Developer-Package'''
* Uncompress the tarball file to get the Linux<sup>&reg;</sup> kernel tarball, ST patches and ST configuration fragments
 {{PC$}} cd $HOME/STM32MPU_workspace/STM32MP15-Ecosystem-v3.0.0/Developer-Package
 {{PC$}} tar xvf {{EcosystemRelease/Package | revision=3.0.0 | package=Linux kernel package | request=name}}
</div>

==Prepare the Linux<sup>&reg;</sup> kernel source code==
* Extract the Linux<sup>&reg;</sup> kernel source

'''For {{EcosystemRelease | revision=3.1.0}}''':
 {{PC$}} cd {{EcosystemRelease/Package | revision=3.1.0 | package=Linux kernel package | request=path}}
 {{PC$}} tar xvf {{EcosystemRelease/Package | revision=3.1.0 | package=Linux kernel source | request=name}}

* Apply ST patches
 {{PC$}} cd {{EcosystemRelease/Package | revision=3.1.0 | package=Linux kernel source | request=path}}
 {{PC$}} for p in `ls -1 ../*.patch`; do patch -p1 < $p; done

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

'''For {{EcosystemRelease | revision=3.0.0}}''': <div class="mw-collapsible mw-collapsed">
 {{PC$}} cd {{EcosystemRelease/Package | revision=3.0.0 | package=Linux kernel package | request=path}}
 {{PC$}} tar xvf {{EcosystemRelease/Package | revision=3.0.0 | package=Linux kernel source | request=name}}

* Apply ST patches
 {{PC$}} cd {{EcosystemRelease/Package | revision=3.0.0 | package=Linux kernel source | request=path}}
 {{PC$}} for p in `ls -1 ../*.patch`; do patch -p1 < $p; done

* Apply fragments
 {{PC$}} make ARCH=arm multi_v7_defconfig "fragment*.config"
 {{PC$}} for f in `ls -1 ../fragment*.config`; do scripts/kconfig/merge_config.sh -m -r .config $f; done
 {{PC$}} yes <nowiki>''</nowiki> | make ARCH=arm oldconfig
</div>

==Build the Linux<sup>&reg;</sup> kernel source code for the first time==
{{Info|Building the kernel for the first time can take several minutes.}}
* Build kernel images (uImage and vmlinux) and device tree (dtbs)
 {{PC$}} make ARCH=arm uImage vmlinux dtbs LOADADDR=0xC2000040
* Build kernel module
 {{PC$}} make ARCH=arm modules
* Generate output build artifacts
 {{PC$}} mkdir -p $PWD/install_artifact/
 {{PC$}} make ARCH=arm INSTALL_MOD_PATH="$PWD/install_artifact" modules_install

==Deploy the Linux<sup>&reg;</sup> kernel on the board==
===Push the Linux<sup>&reg;</sup> kernel onto the board===
 {{PC$}} scp arch/arm/boot/uImage root@<board ip address>:/boot

===Push the device tree onto the board===
 {{PC$}} scp arch/arm/boot/dts/stm32mp157*.dtb root@<board ip address>:/boot

===Push the kernel modules onto the board===
'''For {{EcosystemRelease | revision=3.1.0}}''':
* Remove the link created inside the '''install_artifact/lib/modules/<kernel version>''' directory
 {{PC$}} 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)
 {{PC$}} find install_artifact/ -name "*.ko" | xargs $STRIP --strip-debug --remove-section=.comment --remove-section=.note --preserve-dates
* Copy kernel modules
 {{PC$}} scp -r install_artifact/lib/modules/* root@<ip of board>:/lib/modules
* Using the Linux<sup>&reg;</sup> console, regenerate the list of module dependencies (modules.dep) and the list of symbols provided by modules (modules.symbols)
 {{Board$}} /sbin/depmod -a
* Synchronize data on disk with memory
 {{Board$}} sync
'''For {{EcosystemRelease | revision=3.0.0}}''': <div class="mw-collapsible mw-collapsed">
* Remove the link created inside the '''install_artifact/lib/modules/<kernel version>''' directory
 {{PC$}} rm install_artifact/lib/modules/5.10.10/build install_artifact/lib/modules/5.10.10/source 

* Optionally, strip kernel modules (to reduce the size of each kernel modules)
 {{PC$}} find install_artifact/ -name "*.ko" | xargs $STRIP --strip-debug --remove-section=.comment --remove-section=.note --preserve-dates
* Copy kernel modules
 {{PC$}} scp -r install_artifact/lib/modules/* root@<ip of board>:/lib/modules
* Using the Linux<sup>&reg;</sup> console, regenerate the list of module dependencies (modules.dep) and the list of symbols provided by modules (modules.symbols)
 {{Board$}} /sbin/depmod -a
* Synchronize data on disk with memory
 {{Board$}} sync
</div>

===Reboot the board===
 {{Board$}} reboot

==Modify a built-in Linux<sup>&reg;</sup> kernel device driver==
This simple example adds unconditional log information when the display driver is probed.
<br><br>

* Using the Linux<sup>&reg;</sup> console, check that there is no log information when the display driver is probed
 {{Board$}} dmesg | grep -i stm_drm_platform_probe
 {{Board$}}

'''For {{EcosystemRelease | revision=3.1.0}}''':
* Go to the Linux<sup>&reg;</sup> kernel source directory

 {{PC$}} cd $HOME/STM32MPU_workspace/STM32MP15-Ecosystem-v3.1.0/Developer-Package/{{EcosystemRelease/Package | revision=3.1.0 | package=Linux kernel package | request=path}}/{{EcosystemRelease/Package | revision=3.1.0 | package=Linux kernel source | request=path}}
 

* 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;
 	[...]
 
 	{{Highlight|DRM_INFO("Simple example - %s\n", __func__);}}
 
 	return 0;
 	[...]
 }
* Save the file
* Rebuild the Linux<sup>&reg;</sup> kernel
 {{PC$}} make uImage LOADADDR=0xC2000040
* Update the Linux kernel image into board
 {{PC$}} scp arch/arm/boot/uImage root@<board ip address>:/boot
* Reboot the board
 {{Board$}} reboot
* Check that log information is now present when the display driver is probed
 {{Board$}} dmesg | grep -i stm_drm_platform_probe
 [    2.764080] [drm] Simple example - stm_drm_platform_probe

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'''For {{EcosystemRelease | revision=3.0.0}}''': <div class="mw-collapsible mw-collapsed">
* Go to the Linux<sup>&reg;</sup> kernel source directory

 {{PC$}} cd $HOME/STM32MPU_workspace/STM32MP15-Ecosystem-v3.0.0/Developer-Package/{{EcosystemRelease/Package | revision=3.0.0 | package=Linux kernel package | request=path}}/{{EcosystemRelease/Package | revision=3.0.0 | package=Linux kernel source | request=path}}
 

* 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;
 	[...]
 
 	{{Highlight|DRM_INFO("Simple example - %s\n", __func__);}}
 
 	return 0;
 	[...]
 }
* Save the file
* Rebuild the Linux<sup>&reg;</sup> kernel
 {{PC$}} make uImage LOADADDR=0xC2000040
* Update the Linux kernel image into board
 {{PC$}} scp arch/arm/boot/uImage root@<board ip address>:/boot
* Reboot the board
 {{Board$}} reboot
* Check that log information is now present when the display driver is probed
 {{Board$}} dmesg | grep -i stm_drm_platform_probe
 [    2.764080] [drm] Simple example - stm_drm_platform_probe

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__NOTOC__
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{{PublicationRequestId | 19661|2021-04-20}}
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