Yocto Development

If you have completed the Get Started with IoT Yocto section, you should now have built a image for your Genio device. This section aims to provide help and advice to enable you to continue your development journey.

Partial Build

During development, you might want to build a single package instead of the entire image. To do so, use the following commands:

$ bitbake <recipe-name>

The <recipe-name> is the name of the BitBake recipe of the package you want to build. For example, the Linux kernel is defined in these recipe .bb files:

  • meta-mediatek-bsp/recipes-kernel/linux/linux-mtk/recipes-kernel/linux/linux-mtk_5.4.bb

  • meta-mediatek-bsp/recipes-kernel/linux/linux-mtk/recipes-kernel/linux/linux-mtk_5.10.bb

  • meta-mediatek-bsp/recipes-kernel/linux/linux-mtk/recipes-kernel/linux/linux-mtk_5.15.bb

The name of the package is therefore linux_mtk. To only rebuild the kernel instead of the entire rity-demo-image, use the following command:

$ bitbake linux-mtk

Please note that this only rebuilds the kernel image (fitImage), but not the image of the entire system (*.wic.img). To update the kernel image, use Yocto virtual provider:

$ bitbake virtual/kernel

Similarly, if you only want to rebuild bootloader BL2 image (bl2.img), you can use:

$ bitbake trusted-firmware-a

Similarly, if you only want to rebuild bootloader U-Boot (BL33) image, you can use the commands below and repackage the bootloader BL31/BL32/BL33 image fip.bin:

$ bitbake virtual/bootloader
$ bitbake trusted-firmware-a

Build for Other Boards

Warning

The boards listed below contains 3rd party boards and boards under development. There is no guarantee that these combinations will work out-of-box.

You can use the MACHINE variable to assign the board you would like to build:

DISTRO=rity-demo MACHINE=<machine> bitbake rity-demo-image

The available values for <machine> can be found in the $BUILD_DIR/conf/local.conf configuration file. A snip of the file is shown below:

# uncomment the line related to the target
    #MACHINE ??= "genio-1200-evk"
    #MACHINE ??= "genio-350-evk"
    #MACHINE ??= "genio-510-evk"
    MACHINE ??= "genio-700-evk"

You can also locate all the reference IoT board recipes in:

src/meta-mediatek-bsp/conf/machine/

For example, if the .conf files in the directory are:

genio-1200-evk.conf -> mt8395-evk.conf
genio-1200-evk-p1v1.conf -> mt8395-evk-p1v1.conf
genio-1200-evk-ufs.conf -> mt8395-evk-ufs.conf
genio-350-evk.conf -> mt8365-evk.conf
genio-510-evk.conf -> mt8370-evk.conf
genio-700-evk.conf -> mt8390-evk.conf
mt8183-evb.conf
mt8183-pumpkin.conf
mt8365-evk.conf
mt8365-pumpkin.conf
mt8365-sb35.conf
mt8370-evk.conf
mt8390-evk.conf
mt8395-evb-ufs.conf
mt8395-evk.conf
mt8395-evk-p1v1.conf
mt8395-evk-ufs.conf
mt8516-pumpkin.conf

Note that genio-1200-evk.conf is an alias to mt8395-evk.conf. In this case, the following <machine> names are available:

  • genio-1200-evk

  • mt8395-evk

For details, please refer to the BSP documentation.

Build Other Images

The Get Started guide made use of the rity-demo-image image recipe. There are other recipes in IoT Yocto that supports different development boards and also different software packages. The IoT Yocto bring up image (rity-bringup-image) is mostly used for BSP development and board bring up. This image contains the some tools necessary to validate software and hardware.

rity-bringup-image is designed to be built with the DISTRO variable set to the following:

DISTRO=rity-bringup

You can use the following command to build the rity-bringup-image:

DISTRO=rity-bringup MACHINE=<machine> bitbake rity-bringup-image

The resulting image is located in

$BUILD_DIR/tmp/deploy/images/<machine>

Please note that the same image directory may contain multiple distro images.

For example, if you build both rity-demo-image and rity-bringup-image for g350-EVK:

DISTRO=rity-demo MACHINE=g350-evk bitbake rity-demo-image
DISTRO=rity-bringup MACHINE=g350-evk bitbake rity-bringup-image

The image directory $BUILD_DIR/tmp/deploy/images/g350-evk contains both images. You can use genio-flash-tool -i <image-name> to select the image you want to flash. For example, to flash rity-bring-image, use:

genio-flash -i rity-bringup-image

For more details, please refer to Genio Tools page.

BSP Source Code Modification

Kernel

Please note that modifying source code directly under the build/tmp/work directory causes a lot of problems. To modify the source code of kernel, please refer to Kernel Development and use devtool to modify package source code.

Trusted-Firmware-A (BL2/BL31)

For BL2/BL31 source modification, the BL2/BL31 is implemented and based on Trusted-firmware-A (TF-A). If you would like to modify the source code of TF-A, please use devtool tool and modify the source under build/workspace folder.

  1. Run devtool modify trusted-firmware-a. This will fetch the sources for the recipe and unpack them to a workspace/sources/trusted-firmware-a/ directory and initialize it as a git repository if it isn’t already one.

$ devtool modify trusted-firmware-a

  1. Make the changes you want to make to the source.

  2. Run a build to test your changes - you can partial build trusted-firmware-a.

$ bitbake trusted-firmware-a

U-Boot (BL33)

For BL33 source modification, the BL33 is implemented and based on U-Boot. If you would like to modify the source code of U-Boot, please use devtool tool and modify the source under build/workspace folder.

  1. Run devtool modify u-boot. This will fetch the sources for the recipe and unpack them to a workspace/sources/u-boot/ directory and initialize it as a git repository if it isn’t already one.

$ devtool modify u-boot

  1. Make the changes you want to make to the source.

  2. Run a build to test your changes - you can partial build U-Boot.

$ bitbake u-boot

Clean Output and Intermediate Files

The Bitbake system used by Yocto project manages various caches and intermediate files when building recipes.

In some cases, you might want to remove the intermediate files and rebuild images or packages from scratch. To remove the output of a package recipe, use the command:

$ bitbake -c clean <recipe-name>

For example, to remove kernel output and intermediate files,

$ bitbake -c clean virtual/kernel

If you suspect there are corrupted recipe task states, you can clean the sstate cache by:

$ bitbake -c cleansstate virtual/kernel

To learn more about various clean tasks, refer to Yocto manual.