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Internal details

Minimal configurations

In this section, we describe step by step the minimal Buildroot configuration st_stm32mp157f_dk2_defconfig which targets the STM32MP157F Discovery Kit 2 platform. The other Buildroot configurations for the other platforms are very similar.

BR2_arm=y
BR2_cortex_a7=y

Obviously, this tells Buildroot to build a system for the ARM architecture, and more precisely for a Cortex-A7 based processor. This will ensure the cross-compilation toolchain targets the correct CPU architecture and specific CPU core.

BR2_TOOLCHAIN_EXTERNAL=y
BR2_TOOLCHAIN_EXTERNAL_BOOTLIN=y
BR2_TOOLCHAIN_EXTERNAL_BOOTLIN_ARMV7_EABIHF_GLIBC_STABLE=y

We decide to use external toolchain. This choice has been made to reduce the build time of the overall system, and use a well-known toolchain provided by Bootlin. We use Bootlin stable toolchain instead of ARM toolchain because ST components are a bit too old in version to bnuild the latest version of ARM toolchain.

BR2_GLOBAL_PATCH_DIR="$(BR2_EXTERNAL_ST_PATH)/board/stmicroelectronics/common/patches/"

We need to apply one patch to the Linux kernel, which is located in board/stmicroelectronics/common/patches/. This configuration option tells Buildroot where to find the patches to apply.

BR2_ROOTFS_DEVICE_CREATION_DYNAMIC_MDEV=y

This option enables mdev (a minimal re-implementation of udev which is part of BusyBox) which takes care of automatically loading kernel modules, adjusting /dev nodes permissions, and more.

BR2_ROOTFS_OVERLAY="$(BR2_EXTERNAL_ST_PATH)/board/stmicroelectronics/stm32mp1/overlay/"

This tells Buildroot to copy the contents of board/stmicroelectronics/stm32mp1/overlay into the root filesystem. The important file that this copies to the root filesystem is /boot/extlinux.conf, which tells the U-Boot bootloader how to boot the Linux system (which Linux kernel image to load, which Device Tree to use, which kernel arguments to pass). It also adds the Wifi firmware and the sound configuration files but these are only used in the demo configurations, not the minimal ones.

BR2_ROOTFS_POST_BUILD_SCRIPT="$(BR2_EXTERNAL_ST_PATH)/board/stmicroelectronics/common/post-build.sh"

This tells Buildroot to run board/stmicroelectronics/common/post-build.sh at the end of the rootfs generation. This script update the extlinux.conf of the overlay to use the correct Device Tree file at boot.

BR2_ROOTFS_POST_IMAGE_SCRIPT="$(BR2_EXTERNAL_ST_PATH)/board/stmicroelectronics/common/post-image.sh"

This tells Buildroot to run board/stmicroelectronics/common/post-image.sh at the end of the build. This script produces the final sdcard.img file using a tool called genimage and deploys the flash.tsv file to flash the board with STM32 Cube Programmer.

BR2_ROOTFS_POST_SCRIPT_ARGS="$(BR2_EXTERNAL_ST_PATH)/board/stmicroelectronics/stm32mp1/genimage.cfg"

This is an argument passed to the scripts. It is used by post-image.sh to know which genimage config to use.

BR2_LINUX_KERNEL=y
BR2_LINUX_KERNEL_CUSTOM_TARBALL=y
BR2_LINUX_KERNEL_CUSTOM_TARBALL_LOCATION="$(call github,STMicroelectronics,linux)v6.1-stm32mp-r2.tar.gz"
BR2_LINUX_KERNEL_DEFCONFIG="multi_v7"
BR2_LINUX_KERNEL_CONFIG_FRAGMENT_FILES="$(LINUX_DIR)/arch/arm/configs/fragment-01-multiv7_cleanup.config $(LINUX_DIR)/arch/arm/configs/fragment-02-multiv7_addons.config $(BR2_EXTERNAL_ST_PATH)/board/stmicroelectronics/common/linux-disable-etnaviv.config"
BR2_LINUX_KERNEL_DTS_SUPPORT=y
BR2_LINUX_KERNEL_INTREE_DTS_NAME="stm32mp157f-dk2"
BR2_LINUX_KERNEL_INSTALL_TARGET=y
BR2_LINUX_KERNEL_NEEDS_HOST_OPENSSL=y

This set of options tells Buildroot to build a Linux kernel, with the source code fetched using Git from the repository at https://github.com/STMicroelectronics/linux. The Git tag v6.1-stm32mp-r2 will be used as the kernel version. The kernel will be configured using the configuration file multi_v7_defconfig extended with three configuration fragments:

  1. fragment-01-multiv7_cleanup.config, which comes from the ST kernel tree, and that disables a number of kernel drivers/features that are not needed on STM32MP1

  2. fragment-02-multiv7_addons.config, which comes from the ST kernel tree, and which enables a few additional kernel drivers/features taht are relevant on STM32MP1

  3. linux-disable-etnaviv.config, which comes from this BR2_EXTERNAL, and is in charge of disabling the Etnaviv GPU kernel driver, as we use the proprietary GPU driver provided by ST instead.

The option BR2_LINUX_KERNEL_INTREE_DTS_NAME indicates that the stm32mp157f-dk2.dtb Device Tree file will be produced and should be used. Finally BR2_LINUX_KERNEL_INSTALL_TARGET=y tells that the kernel image should be installed to the target root filesystem, in /boot.

BR2_TARGET_ROOTFS_EXT2=y
BR2_TARGET_ROOTFS_EXT2_4=y
BR2_TARGET_ROOTFS_EXT2_SIZE="120M"
# BR2_TARGET_ROOTFS_TAR is not set

This set of options tell Buildroot to generate an ext4 filesystem image for the root filesystem, and to not build the default filesystem image, which is a tarball (.tar).

BR2_TARGET_ARM_TRUSTED_FIRMWARE=y
BR2_TARGET_ARM_TRUSTED_FIRMWARE_CUSTOM_TARBALL=y
BR2_TARGET_ARM_TRUSTED_FIRMWARE_CUSTOM_TARBALL_LOCATION="$(call github,STMicroelectronics,arm-trusted-firmware)v2.8-stm32mp-r2.tar.gz"
BR2_TARGET_ARM_TRUSTED_FIRMWARE_PLATFORM="stm32mp1"
BR2_TARGET_ARM_TRUSTED_FIRMWARE_FIP=y
BR2_TARGET_ARM_TRUSTED_FIRMWARE_BL32_OPTEE=y
BR2_TARGET_ARM_TRUSTED_FIRMWARE_UBOOT_AS_BL33=y
BR2_TARGET_ARM_TRUSTED_FIRMWARE_UBOOT_BL33_IMAGE="u-boot-nodtb.bin"
BR2_TARGET_ARM_TRUSTED_FIRMWARE_ADDITIONAL_VARIABLES="STM32MP_SDMMC=1 AARCH32_SP=optee DTB_FILE_NAME=stm32mp157f-dk2.dtb BL33_CFG=$(BINARIES_DIR)/u-boot.dtb STM32MP1_OPTEE_IN_SYSRAM=1 OPENSSL_DIR=$(BR2_HOST_DIR)"
BR2_TARGET_ARM_TRUSTED_FIRMWARE_IMAGES="*.stm32 fip.bin"
BR2_TARGET_ARM_TRUSTED_FIRMWARE_NEEDS_DTC=y

These options tell Buildroot how to build TF-A, the Trusted Firmware. It is retrieved from the Git repository at https://github.com/STMicroelectronics/arm-trusted-firmware, using version v2.8-stm32mp-r2. TF-A is configured for the stm32mp1 platform with OP-TEE as BL32, and we use the mechanism of FIP images. The Device Tree file being used in TF-A comes from the TF-A source code, and is named stm32mp157f-dk2.dtb.

BR2_PACKAGE_OPTEE_CLIENT=y
BR2_PACKAGE_OPTEE_CLIENT_CUSTOM_TARBALL=y
BR2_PACKAGE_OPTEE_CLIENT_CUSTOM_TARBALL_LOCATION="$(call github,OP-TEE,optee_client)3.19.0.tar.gz"
...
BR2_TARGET_OPTEE_OS=y
BR2_TARGET_OPTEE_OS_CUSTOM_TARBALL=y
BR2_TARGET_OPTEE_OS_CUSTOM_TARBALL_LOCATION="$(call github,STMicroelectronics,optee_os)3.19.0-stm32mp-r2.tar.gz"
BR2_TARGET_OPTEE_OS_NEEDS_DTC=y
BR2_TARGET_OPTEE_OS_NEEDS_PYTHON_CRYPTOGRAPHY=y
BR2_TARGET_OPTEE_OS_PLATFORM="stm32mp1"
BR2_TARGET_OPTEE_OS_PLATFORM_FLAVOR="157F_DK2"
BR2_TARGET_OPTEE_OS_ADDITIONAL_VARIABLES="CFG_STM32MP1_OPTEE_IN_SYSRAM=y"

These options configure the build of OP-TEE as a trusted execution environment, as well as the user-space OP-TEE client programs. It is fetched from the Git repository https://github.com/STMicroelectronics/optee_os, in version 3.19.0-stm32mp-r2. The platform is stm32mp1 and its flavor is 157F_DK2

BR2_TARGET_UBOOT=y
BR2_TARGET_UBOOT_BUILD_SYSTEM_KCONFIG=y
BR2_TARGET_UBOOT_CUSTOM_TARBALL=y
BR2_TARGET_UBOOT_CUSTOM_TARBALL_LOCATION="$(call github,STMicroelectronics,u-boot)v2022.10-stm32mp-r2.tar.gz"
BR2_TARGET_UBOOT_BOARD_DEFCONFIG="stm32mp15"
BR2_TARGET_UBOOT_NEEDS_PYLIBFDT=y
# BR2_TARGET_UBOOT_FORMAT_BIN is not set
BR2_TARGET_UBOOT_FORMAT_CUSTOM=y
BR2_TARGET_UBOOT_FORMAT_CUSTOM_NAME="u-boot-nodtb.bin u-boot.dtb"
BR2_TARGET_UBOOT_CUSTOM_MAKEOPTS="DEVICE_TREE=stm32mp157f-dk2"

These options tell Buildroot how to build U-Boot: it is fetched from the Git repository at https://github.com/STMicroelectronics/u-boot, in version v2022.10-stm32mp-r2. The configuration used is stm32mp15, and we install both the u-boot-nodtb.bin and u-boot.dtb images as both are used for the TF-A build. The Device Tree file used comes from the U-Boot source code, and is named stm32mp157f-dk2.

BR2_PACKAGE_HOST_BMAP_TOOLS=y

This option tells Buildroot to build the bmap utility for the host. This is used to produce block map files alongside the image.

BR2_PACKAGE_HOST_GENIMAGE=y

This last option tells Buildroot to build the genimage utility for the host, as it is used to produce the SD card image.

What is not visible in this configuration are all the defaults that Buildroot has: it will by default integrate Busybox in the root filesystem image, and use a number of sane defaults to build a basic embedded Linux system.

Demo configurations

In this section, we describe the demo configuration st_stm32mp157f_dk2_demo_defconfig for the STM32MP157F Discovery Kit 2. Here as well, all other demo configurations for the other platforms are very similar.

BR2_ROOTFS_DEVICE_CREATION_DYNAMIC_EUDEV=y

This option enables eudev instead of mdev selected by the basic configuration. It manages devices node and handles all user space actions when adding or removing devices.

BR2_ROOTFS_POST_BUILD_SCRIPT="$(BR2_EXTERNAL_ST_PATH)/board/stmicroelectronics/common/post-build.sh $(BR2_EXTERNAL_ST_PATH)/board/stmicroelectronics/stm32mp1/post-build-demo.sh"
BR2_ROOTFS_POST_IMAGE_SCRIPT="$(BR2_EXTERNAL_ST_PATH)/board/stmicroelectronics/common/post-image.sh $(BR2_EXTERNAL_ST_PATH)/board/stmicroelectronics/common/generate-rauc-bundle.sh"
BR2_ROOTFS_POST_SCRIPT_ARGS="$(BR2_EXTERNAL_ST_PATH)/board/stmicroelectronics/stm32mp1/genimage-demo.cfg"

Add demo post-build and post-image scripts in addition of basic scripts alongside with genimage-demo args to tell which partition configuration to use.

BR2_LINUX_KERNEL_CONFIG_FRAGMENT_FILES="$(LINUX_DIR)/arch/arm/configs/fragment-01-multiv7_cleanup.config $(LINUX_DIR)/arch/arm/configs/fragment-02-multiv7_addons.config $(BR2_EXTERNAL_ST_PATH)/board/stmicroelectronics/common/linux-disable-etnaviv.config $(BR2_EXTERNAL_ST_PATH)/board/stmicroelectronics/common/linux-enable-rauc.config"

Add linux-enable-rauc.config Linux fragment configuration to enable RAUC requirements.

BR2_TARGET_GENERIC_ROOT_PASSWD="root"

This option sets the root password to root. The root password has to be set to a non-empty value to connect to the board through SSH.

BR2_LINUX_KERNEL_INTREE_DTS_NAME="stm32mp157f-dk2-mx"
BR2_LINUX_KERNEL_CUSTOM_DTS_PATH="$(BR2_EXTERNAL_ST_PATH)/board/stmicroelectronics/stm32mp1/linux-dts/*"
BR2_LINUX_KERNEL_DTB_OVERLAY_SUPPORT=y

The demo configurations use a Linux kernel Device Tree file produced by STM32 Cube MX. These two options tell Buildroot where to find these Device Tree files, and which one to use. The last option enables the -@ Device Tree compiler build option, which produces Device Tree files with slightly more information, making it possible for the U-Boot bootloader to automatically tweak the Device Tree files passed to the Linux kernel when booting.

BR2_PACKAGE_OPTEE_EXAMPLES=y
BR2_PACKAGE_OPTEE_EXAMPLES_CUSTOM_TARBALL=y
BR2_PACKAGE_OPTEE_EXAMPLES_CUSTOM_TARBALL_LOCATION="$(call github,linaro-swg,optee_examples)3.19.0.tar.gz"
BR2_PACKAGE_OPTEE_TEST=y
BR2_PACKAGE_OPTEE_TEST_CUSTOM_TARBALL=y
BR2_PACKAGE_OPTEE_TEST_CUSTOM_TARBALL_LOCATION="$(call github,OP-TEE,optee_test)3.19.0.tar.gz"

These options enable OP-TEE tests and examples using the same version as OP-TEE OS from ST.

BR2_PACKAGE_ALSA_UTILS=y
BR2_PACKAGE_ALSA_UTILS_AMIXER=y
BR2_PACKAGE_ALSA_UTILS_APLAY=y
BR2_PACKAGE_ALSA_UTILS_SPEAKER_TEST=y

These options enable alsa-utils and examples.

BR2_PACKAGE_DEJAVU=y
BR2_PACKAGE_QT5=y
BR2_PACKAGE_QT5BASE_EXAMPLES=y
BR2_PACKAGE_QT5BASE_GUI=y
BR2_PACKAGE_QT5BASE_OPENGL_LIB=y
BR2_PACKAGE_QT5BASE_EGLFS=y
BR2_PACKAGE_QT5BASE_FONTCONFIG=y

These options enable a font (DejaVu) and the QT5 graphical toolkit.

BR2_PACKAGE_DROPBEAR=y

This option enables the dropbear SSH server.

BR2_PACKAGE_LINUX_FIRMWARE=y
BR2_PACKAGE_LINUX_FIRMWARE_BRCM_BCM43XXX=y
BR2_PACKAGE_MURATA_CYW_FW=y
BR2_PACKAGE_MURATA_CYW_FW_CYW43430=y

These options enable the installation of the firmware file needed for the WiFi and Bluetooth chips.

BR2_PACKAGE_GCNANO_BINARIES=y

This option enables the installation of the closed-source user-space library that provide OpenGL support.

BR2_PACKAGE_LIBUBOOTENV=y

This option enable tools to read and write the U-boot environment from Linux. These are required to have the OTA working properly.

BR2_PACKAGE_LIBDRM_INSTALL_TESTS=y

This option, which implies BR2_PACKAGE_LIBDRM=y installs the modetest utility that we use for display testing.

BR2_PACKAGE_BLUEZ_TOOLS=y
BR2_PACKAGE_BLUEZ5_UTILS=y
BR2_PACKAGE_BLUEZ5_UTILS_CLIENT=y

These options install the user-space utilities to manage and configure Bluetooth.

BR2_PACKAGE_IW=y
BR2_PACKAGE_WIRELESS_REGDB=y
BR2_PACKAGE_WPA_SUPPLICANT=y
BR2_PACKAGE_WPA_SUPPLICANT_AP_SUPPORT=y
BR2_PACKAGE_WPA_SUPPLICANT_WIFI_DISPLAY=y
BR2_PACKAGE_WPA_SUPPLICANT_AUTOSCAN=y
BR2_PACKAGE_WPA_SUPPLICANT_EAP=y
BR2_PACKAGE_WPA_SUPPLICANT_CLI=y
BR2_PACKAGE_WPA_SUPPLICANT_PASSPHRASE=y

These options install the user-space utilities to manage and configure WiFi, as well as the wireless regulatory database.

BR2_PACKAGE_RAUC=y
BR2_PACKAGE_RAUC_DBUS=y
BR2_PACKAGE_RAUC_GPT=y
BR2_PACKAGE_RAUC_NETWORK=y
BR2_PACKAGE_RAUC_STREAMING=y
BR2_PACKAGE_RAUC_JSON=y

These options install the rauc tool for OTA.

BR2_TARGET_ROOTFS_SQUASHFS=y

This option tells Buildroot to generate a squashfs read-only filesystem image for the root filesystem.

BR2_TARGET_ARM_TRUSTED_FIRMWARE_CUSTOM_DTS_PATH="$(BR2_EXTERNAL_ST_PATH)/board/stmicroelectronics/stm32mp1/tfa-dts/*"
BR2_TARGET_ARM_TRUSTED_FIRMWARE_ADDITIONAL_VARIABLES="STM32MP_SDMMC=1 AARCH32_SP=optee DTB_FILE_NAME=stm32mp157f-dk2-mx.dtb BL33_CFG=$(BINARIES_DIR)/u-boot.dtb STM32MP1_OPTEE_IN_SYSRAM=1 OPENSSL_DIR=$(BR2_HOST_DIR)"

These options customize the build of TF-A to use a Device Tree file produced by STM32Cube MX, called stm32mp157f-dk2-mx.dtb.

BR2_TARGET_OPTEE_OS_CUSTOM_DTS_PATH="$(BR2_EXTERNAL_ST_PATH)/board/stmicroelectronics/stm32mp1/optee-dts/*"
BR2_TARGET_OPTEE_OS_ADDITIONAL_VARIABLES="CFG_EMBED_DTB_SOURCE_FILE=stm32mp157f-dk2-mx.dts CFG_STM32MP15=y CFG_DRAM_SIZE=0x20000000 CFG_STM32MP1_OPTEE_IN_SYSRAM=y"

These options customize the build of OPTEE-OS to use a Device Tree file produced by STM32 Cube MX, called stm32mp157f-dk2-mx. The option CFG_EMBED_DTB_SOURCE_FILE=stm32mp157f-dk2-mx.dts CFG_STM32MP15=y has been added to OPTEE-OS make options, to build the external devicetree.

BR2_TARGET_UBOOT_CUSTOM_DTS_PATH="$(BR2_EXTERNAL_ST_PATH)/board/stmicroelectronics/stm32mp1/uboot-dts/*"
BR2_TARGET_UBOOT_CUSTOM_MAKEOPTS="dtb-y=stm32mp157f-dk2-mx.dtb DEVICE_TREE=stm32mp157f-dk2-mx"

These options customize the build of U-Boot to use a Device Tree file produced by STM32 Cube MX, called stm32mp157f-dk2-mx. The option dtb-y=stm32mp157f-dk2-mx.dtb has been added to U-boot make options, to build the external devicetree.

BR2_PACKAGE_HOST_GENEXT2FS=y

This option enables genext2fs tool, to be able to generate ext4 partition with genimage.

BR2_PACKAGE_HOST_RAUC=y

This option enables rauc tool for the host to generate a RAUC update bundle.

BR2_PACKAGE_M4PROJECTS=y

This option enables the installation of the Firmware examples for the Cortex M4 from STM32CubeMP1.

BR2_PACKAGE_HOST_UBOOT_TOOLS=y
BR2_PACKAGE_HOST_UBOOT_TOOLS_ENVIMAGE=y
BR2_PACKAGE_HOST_UBOOT_TOOLS_ENVIMAGE_SOURCE="$(BR2_EXTERNAL_ST_PATH)/board/stmicroelectronics/stm32mp1/uEnv.txt"
BR2_PACKAGE_HOST_UBOOT_TOOLS_ENVIMAGE_SIZE="0x2000"
BR2_PACKAGE_HOST_UBOOT_TOOLS_ENVIMAGE_REDUNDANT=y

These options generate an image of the U-Boot environment, ready to be flashed, based on the environment defined as a text file in board/stmicroelectronics/stm32mp1/uEnv.txt.

Organization of the BR2_EXTERNAL tree

  • board/
    • stmicroelectronics/
      • common/
        • ca.key.pem, a private CA key used to generate signed RAUC bundle.
        • generate-rauc-bundle.sh, the script executed by Buildroot for demo configuration at the end of the rootfs generation. It generates the rauc bundle using the manifest.raucm.
        • linux-disable-etnaviv.config, a Linux kernel configuration file fragment that disables the Etnaviv GPU driver.
        • linux-enable-rauc.config, a Linux kernel configuration file fragment that enables the requisite kernel driver to use RAUC.
        • manifest.raucm, RAUC manifest to describe the bundle content and the purpose of each included image.
        • patches, which contains one patch for the Linux kernel, fixing a module loading issue for the audio codec driver.
        • post-build.sh, the script executed by Buildroot at the end of the rootfs generation to produce update the extlinux.conf with the right devicetree name.
        • post-image.sh, the script executed by Buildroot at the end of the build to produce the SD card image and deploy the flash.tsv file.
        • uboot-enable-squashfs.config, a U-boot configuration file fragment that enables the SquashFS support.
      • stm32mp1/
        • tfa-dts/, Device Tree files produced by STM32 Cube MX for TF-A. Only used by the demo configurations.
        • overlay/, the boot filesytem overlay for the basic configurations. It contributes /boot/extlinux.conf to the root filesystem to select the right devicetree name.
        • overlay-demo/, the boot filesytem overlay for the demo configurations. It contributes /boot/extlinux.conf to the root filesystem to select the right devicetree name. It also adds the Wifi firmware, the sound configuration files and RAUC configuration files.
        • linux-dts/, Device Tree files produced by STM32 Cube MX for Linux. Only used by the demo configurations.
        • uboot-dts/, Device Tree files produced by STM32 Cube MX for U-Boot. Only used by the demo configurations.
        • optee-dts/, Device Tree files produced by STM32 Cube MX for OPTEE-OS. Only used by the demo configurations.
        • flash.tsv, configuration file for the STM32 Cube Programmer. Only valid for SD card flashing.
        • genimage.cfg, configuration file for the genimage utility, which produces the final sdcard.img SD card image. It describes the partition layout of the SD card. Only used by basic configurations.
        • genimage-demo.cfg, configuration file for the genimage utility, which produces the final sdcard.img SD card image. It describes the partition layout of the SD card. Only used by demo configurations.
        • linux-enable-fbdev-emul.config, a Linux kernel configuration file fragment that enables the fbdev emulation of the DRM subsystem, which is needed on the STM32MP135 platform to be able to use the linuxfb backend of Qt5, in the absence of GPU/OpenGL
        • post-build-demo.sh, the script executed by Buildroot at the end of the rootfs generation for the demo configuration.
        • uEnv.txt, the U-boot environment which contains definitions needed to properly support OTA.
        • fip-stm32mp135_usb.bin, pre-compiled FIP image built with st_stm32mp135_flash_defconfig in order to be able to flash the SD card. It build TF-A with STM32MP_USB_PROGRAMMER=1 in order to be able to flash the SD card (we unfortunately cannot build a single FIP image that can be used for flashing and on storage, due to memory size limitations)
        • fip-stm32mp157_usb.bin, pre-compiled FIP image built with st_stm32mp257_flash_defconfig in order to be able to flash the SD card. It build TF-A with STM32MP_USB_PROGRAMMER=1 option in order to be able to flash the SD card (we unfortunately cannot build a single FIP image that can be used for flashing and on storage, due to memory size limitations)
        • tf-a-stm32mp135_usb.stm32, precompiled TF-A image generated with st_stm32mp257_flash_defconfig in order to be able to flash the SD card. It build TF-A with STM32MP_USB_PROGRAMMER=1 option in order to be able to flash the SD card (we unfortunately cannot build a single FIP image that can be used for flashing and on storage, due to memory size limitations)
        • tf-a-stm32mp157_usb.stm32, precompiled TF-A image generated with st_stm32mp157_flash_defconfig in order to be able to flash the SD card. It build TF-A with STM32MP_USB_PROGRAMMER=1 option in order to be able to flash the SD card (we unfortunately cannot build a single FIP image that can be used for flashing and on storage, due to memory size limitations)
        • fip-stm32mp135_usb.stm32, precompiled TF-A image generated with st_stm32mp135_flash_defconfig in order to be able to flash the SD card. It build TF-A with STM32MP_USB_PROGRAMMER=1 option in order to be able to flash the SD card (we unfortunately cannot build a single FIP image that can be used for flashing and on storage, due to memory size limitations)
        • fip-stm32mp157_usb.stm32, precompiled TF-A image generated with st_stm32mp157_flash_defconfig in order to be able to flash the SD card. It build TF-A with STM32MP_USB_PROGRAMMER=1 option in order to be able to flash the SD card (we unfortunately cannot build a single FIP image that can be used for flashing and on storage, due to memory size limitations)
      • stm32mp2/
        • fip-ddr_usb.bin, pre-compiled DDR FIP image built with st_stm32mp135_flash_defconfig. It build TF-A with STM32MP_USB_PROGRAMMER=1 option in order to be able to flash the SD card (we unfortunately cannot build a single FIP image that can be used for flashing and on storage, due to memory size limitations)
        • fip_usb.bin, pre-compiled FIP image built with st_stm32mp257_flash_defconfig in order to be able to flash the SD card It build TF-A with STM32MP_USB_PROGRAMMER=1 option in order to be able to flash the SD card (we unfortunately cannot build a single FIP image that can be used for flashing and on storage, due to memory size limitations)
        • flash.tsv, configuration file for the STM32 Cube Programmer. Only valid for SD card flashing.
        • genimage.cfg, configuration file for the genimage utility, which produces the final sdcard.img SD card image. It describes the partition layout of the SD card. Only used by basic configurations.
        • genimage-demo.cfg, configuration file for the genimage utility, which produces the final sdcard.img SD card image. It describes the partition layout of the SD card. Only used by demo configurations.
        • linux-dts/, Device Tree files imported from STM32CubeMX.
        • optee-dts/, Device Tree files imported from STM32CubeMX.
        • overlay/, the boot filesytem overlay for the basic configurations. It contributes /boot/extlinux.conf to the root filesystem to select the right devicetree name.
        • overlay-demo/, the boot filesytem overlay for the demo configurations. It contributes /boot/extlinux.conf to the root filesystem to select the right devicetree name. It also adds the Wifi firmware, the sound configuration files and RAUC configuration files.
        • post-build-demo.sh, the script executed by Buildroot at the end of the rootfs generation for the demo configuration.
        • tfa-dts/, Device Device Tree files imported from STM32CubeMX. Tree files produced by STM32 Cube MX for TF-A. Only used by the demo configurations.
        • tf-a-stm32mp257f-ev1_usb.stm32, precompiled TF-A image generated with st_stm32mp257_flash_defconfig in order to be able to flash the SD card.
        • uboot-dts/, Device Tree files imported from STM32CubeMX.
        • uEnv.txt, the U-boot environment which contains definitions needed to properly support OTA.
  • package/m4projects, a Buildroot package that builds and installs all the Cortex-M4 examples of the STM32CubeMP1 sources. It uses a python script as a wrapper to transform the .project and .cproject files readable by the dedicated Makefile.
  • package/m33projects, a Buildroot package that builds and installs all the Cortex-M33 examples of the STM32CubeMP2 sources. It uses a shell script to sign the firmware before installing it.
  • configs/
  • docs, documentation
  • Config.in, top-level Config.in file mandatory in all BR2_EXTERNAL trees. Indicate the location of the Config.in file from our m4projects and m33projects packages.
  • README.md
  • external.desc, mandatory in all BR2_EXTERNAL trees, gives a name and description for the BR2_EXTERNAL tree
  • external.mk, mandatory in all BR2_EXTERNAL trees, indicate the location of *.mk file from new packages.

Changes compared to upstream Buildroot

The st/2024.02.3 branch of this BR2_EXTERNAL is designed to work with Buildroot 2024.02.3. However, we needed a few changes compared to upstream Buildroot 2024.02.10, which can be seen at https://github.com/bootlin/buildroot/commits/st/2024.02.3. We have just 11 changes on top of Buildroot 2024.02.3, and they can easily be rebased on top of the latest Buildroot 2024.02.x to continue to benefit from the security fixes provided by the Buildroot community.

Here are the 11 changes:

  • Update the gcnano-binaries package to a newer version and to support arm64. This package contains the closed-source OpenGL user-space libraries, which need to be in sync with the kernel side. This patch has been submitted to upstream Buildroot.

  • Add support for host python-intelhex package in preparation of the support for Trusted-Firmware-M. This patch has been submitted to upstream Buildroot.

  • Add support for host python-click package in preparation of the support for Trusted-Firmware-M. This patch has been submitted to upstream Buildroot.

  • Add support for host python-cbor2 package in preparation of the support for Trusted-Firmware-M. This patch has been submitted to upstream Buildroot.

  • Add support for TrustedFirmware-M which is implementing the Secure Processing Environment (SPE) for Armv8-M, Armv8.1-M architectures. This patch has been submitted to upstream Buildroot.

  • Add support for custom tarball source in optee-client to be able to match the OPTEE-OS custom tarball version. This patch has been submitted to upstream Buildroot.

  • Add support for custom tarball source in optee-test to be able to match the OPTEE-OS custom tarball version. This patch has been submitted to upstream Buildroot.

  • Add support for custom tarball source in optee-examples to be able to match the OPTEE-OS custom tarball version. This patch has been submitted to upstream Buildroot.

  • Add support to build OP-TEE OS with host-cmake as the new version of OP-TEE OS from ST need cmake to build its scmi firmware. This patch has been submitted to upstream Buildroot.

  • Update linux to manage vendor name subfolder directory for BR2_LINUX_KERNEL_CUSTOM_DTS_PATH. It adds support to build devicetree files which are organize under vendor subdirectories like for arm and arm64 architectures, such as arch//boot/dts//. This patch has been submitted to upstream Buildroot.

  • Bump arm-gnu-toolchain package to 13.2.rel1 release version. This patch is already in upstream Buildroot.