best practice to integrate CONFIG variables in sysbuild for application only

[mathiasstorck]

Hi,

I'm starting using sysbuild to generate the mcuboot bootloader and the application at once.
For the application I behave different depending if the bootloader should be build or not.
So I have 2 options:

1. no bootloader, application only:

• west build my-application
• -> my-application/prj.conf is used only
• CONFIG_BOOTLOADER_MCUBOOT is not set
• CONFIG_MCUMGR_* should not be configured

2. bootloader + application

• west build my-application --sysbuild
• -> sysbuild/mcuboot.conf is used for additional config variables for mcuboot
• -> SB_CONFIG_BOOTLOADER_MCUBOOT is set there, CONFIG_BOOTLOADER_MCUBOOT will be set
• CONFIG_MCUMGR_* should be configured for main app only
• so I want to specify these additional config variables for the main application also now, something like sysbuild/application.conf
• these should be added to prj.conf

Which is the best practice to do so?

Thanks
Mathias

[mathiasstorck]

SB_CONFIG_BOOTLOADER_MCUBOOT is set in sysbuild.conf of course
additional config for mcuboot is set in sysbuild/mcuboot.conf

[mathiasstorck]

Just found out that I can introduce a sysbuild/app.conf (as my $APP_DIR is app) that is taken into account
Unfortunalty this is not documented, documentation should get improved there

[Sylphe88]

If anyone stumbles upon this, it is "quickly" mentioned here:
https://docs.zephyrproject.org/latest/build/sysbuild/index.html#sysbuild-file-suffix-support