zephyr-kconfig

name

zephyr-kconfig

description

Comprehensive Zephyr Kconfig expertise for build-time configuration. Use this skill when you need to: (1) Create or edit Kconfig files to define new configuration symbols, (2) Configure applications via prj.conf, boards/*.conf, or overlay configs, (3) Debug 'unmet dependencies', 'symbol not visible', or 'unknown symbol' errors, (4) Use menuconfig/guiconfig interactively, (5) Integrate Kconfig with external modules or out-of-tree drivers, (6) Use Kconfig functions with devicetree (dt_chosen_enabled, etc.), (7) Understand symbol visibility, hidden configs, or select/imply behavior.

Zephyr Kconfig Skill

Expert guidance on Zephyr's Kconfig system for build-time configuration, symbol definition, and dependency management.

Table of Contents

1. Core Concepts
2. Common Workflows
3. Configuration Files
4. Advanced Topics
5. Troubleshooting

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Core Concepts

Define vs. Configure (CRITICAL)

Action	File	Syntax
Define symbol	Kconfig	config MY_FEAT (NO prefix)
Configure value	prj.conf	CONFIG_MY_FEAT=y (WITH prefix)

Symbol Types

• bool: y or n
• int: Integer value
• hex: Hexadecimal value
• string: Quoted text

Key Files After Build

• build/zephyr/.config — Final resolved configuration
• build/zephyr/kconfig/Kconfig.modules — Auto-generated module Kconfigs

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Common Workflows

1. Defining Symbols in Kconfig

Create new configuration options for drivers, modules, or apps.

• Syntax (types, menus, choices, conditionals): See syntax.md
• Best practices (naming, placement, dependencies): See best_practices.md

Quick Example:

config MY_DRIVER_ENABLE
    bool "Enable My Driver"
    depends on I2C
    help
      Enable support for My Driver over I2C.

2. Configuring Applications

Set values in prj.conf or board-specific overlays.

Type	Example
Boolean	CONFIG_LOG=y
Integer	CONFIG_MAIN_STACK_SIZE=2048
String	CONFIG_BT_DEVICE_NAME="MyDevice"
Hex	CONFIG_FLASH_BASE_ADDRESS=0x08000000

3. Using Menuconfig

Interactive configuration exploration and modification.

• Launch and navigate menuconfig: See menuconfig.md

west build -t menuconfig

4. Writing Module Kconfig

Integrate external modules with Zephyr's build system.

• Module integration details: See best_practices.md

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Configuration Files

Application Level

File	Purpose
prj.conf	Main app configuration
boards/<board>.conf	Board-specific overrides
app.overlay	Devicetree + Kconfig overlay

Module/Driver Level

File	Purpose
Kconfig	Symbol definitions
zephyr/module.yml	Module metadata pointing to Kconfig

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Advanced Topics

Kconfig Functions

Integrate Kconfig with devicetree at build time.

• Functions reference (dt_chosen_enabled, dt_nodelabel_enabled, etc.): See functions.md

Practical Examples

Complete Kconfig patterns for common scenarios.

• Driver, subsystem, choice examples: See examples.md

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Troubleshooting

For common errors and debugging techniques:

• See debugging.md

Quick Reference

Error	Likely Cause	Fix
"X" has unmet dependencies	Missing depends on	Enable required dependency first
Symbol not visible	depends on condition false	Check what it depends on
Unknown symbol "X"	Typo or Kconfig not sourced	Verify spelling, check module.yml
warning: Y selected by X but not visible	select bypassing depends on	Use imply or fix dependencies

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References

• syntax.md — Types, menus, choices, conditionals, sourcing
• best_practices.md — Naming, organization, modules, dependency safety
• menuconfig.md — Interactive configuration workflow
• functions.md — Kconfig functions for devicetree integration
• examples.md — Complete Kconfig patterns
• debugging.md — Error resolution and debugging techniques