Configuration

Kconfig options and compile-time macros.

Kernel limits are set at compile time. The options are declared in Kconfig at the repository root.

Options

Option	Type	Default	Range	Meaning
`CONFIG_MAX_TASKS`	int	16	2 to 256	Size of the static TCB array. The idle task uses one slot.
`CONFIG_NUM_PRIORITIES`	int	8	2 to 32	Number of priority levels. 0 is the highest. The idle task runs at the lowest.
`CONFIG_DEFAULT_STACK_SIZE`	int	1024	128 to 65536	Stack size of the idle task, in bytes.
`CONFIG_TICKLESS`	bool	y		Declared, but not read by any kernel or port source in 0.0.3.
`CONFIG_RR_TIME_SLICE_US`	int	10000	100 to 1000000	Round-robin slice for tasks of equal priority, in microseconds.
`CONFIG_ASSERT`	bool	y		Enables `br_assert()`. When off, the expression is still evaluated.
`CONFIG_ARCH_ARM_CORTEX_M`	choice	y		Target architecture. ARM Cortex-M is the only choice.
`CONFIG_SYS_CLOCK_HZ`	int	16000000		Core clock. Mapped to `BR_HAL_SYS_CLOCK_HZ`.

The Cortex-M timer derives microseconds from the core clock and fails to compile if BR_HAL_SYS_CLOCK_HZ is below 1 MHz.

Generating autoconf.h

The configuration targets use kconfig-tools. Build them once:

chorus build-tools

This runs zig build in 3rd/tools/kconfig and places the binaries in 3rd/tools/kconfig/zig-out/bin.

Target	Action
`chorus defconfig`	Applies `boards/qemu-cortex-m3/defconfig`, writes `.config` and the header.
`chorus menuconfig`	Opens the interactive editor.
`chorus configure`	Regenerates the header from the existing `.config`.

The generated header is include/generated/autoconf.h. include/bedrock/br_config.h includes it when it exists. Without it, br_config.h falls back to the defaults listed above.

menuconfig keys

Key	Action
Up, Down, `k`, `j`	Move
Enter, Space	Toggle, edit, or open a submenu or choice
Right	Open submenu
Left, Esc	Back
`S`	Mark for save
`Q`	Save and quit
`X`	Quit without saving

Without Kconfig

Every option in br_config.h is wrapped in #ifndef, so values can also be passed as -D flags. Add them to CFLAGS in chorus.build:

CFLAGS: "... -DCONFIG_MAX_TASKS=32 -DCONFIG_RR_TIME_SLICE_US=5000"

Other macros

Macro	Default	Defined in	Meaning
`BR_POOL_MAX_BLOCKS`	128	`lib/br_pool.h`	Maximum blocks per pool.
`BR_POOL_MAX_POOLS`	8	`lib/br_pool.c`	Maximum number of pools.
`BR_WARN_EXPERIMENTAL`	unset	`bedrock.h`	Marks `BR_EXPERIMENTAL` functions as deprecated, so their use produces warnings.
`BR_WARN_INTERNAL`	unset	`bedrock.h`	Same for `BR_INTERNAL` functions.
`BR_HOST_TEST`	unset	`chorus.build`	Set by the host build.