OneWo zepLinux — A New Zephyr OS with Linux API for MCU, Developed by OneWo-rtLinux Team

Implementing a Linux-compatible interface layer on Zephyr RTOS, enabling Linux applications to run on ARM Cortex-M3 and ANSILIC RISC-V 32 microcontrollers with minimal modifications.

Core Highlights

• 4 Linux-style schedulers (DL/RT/CFS/Idle) deeply integrated into the Zephyr kernel, truly driving k_thread scheduling decisions
• Currently documented 39 Linux/POSIX compatible interfaces, covering threads, processes, scheduling, signals, memory, devices, and I/O multiplexing modules
• Target platforms: rocket_pi/stm32f401xe (Arm Cortex M3), ANSILIC/as32x601 (RISC-V 32)

Directory Structure

OneWo-zepLinux/
├── README.md                       # Project overview (this file)
├── docs/                           # English documentation
│   ├── zephyr-linux-api-reference.md
│   ├── zephyr-linux-interface-definition.md
│   ├── zepLinux-interface-and-validation.md
│   ├── zephyr-linux-build-and-dev.md
│   └── test-demos/                 # Board validation, device demos, benchmarks, scheduler tests
├── docs/zh/                        # Chinese Version
│   ├── README.zh.md                # Project overview (Chinese Version)
│   ├── zephyr-linux-api-reference.zh.md
│   ├── zephyr-linux-build-and-dev.zh.md
│   ├── zephyr-linux-interface-definition.zh.md
│   ├── zepLinux-interface-and-validation.zh.md
│   └── test-demos/                 # 
├── modules/
│   └── hal/
│       ├── ansilic/                # ANSILIC RISC-V 32 HAL
│       └── stm32/                  # STM32 HAL (placeholder)
└── zephyr/                         # Built-in Zephyr source tree and kernel implementation
    ├── kernel/                     # Kernel scheduling and thread core logic
    ├── include/                    # Public header files
    ├── lib/                        # Base libraries
    ├── subsys/                     # Various subsystems
    ├── tests/                      # Zephyr built-in tests
    ├── samples/                    # Zephyr samples
    └── boards/others/              # Custom board support (rocket_pi, stm32f401_mini)

Scheduler Architecture

Enabled through the CONFIG_SCHED_LINUX Kconfig option, serving as Zephyr's 4th pluggable ready queue implementation (alongside SIMPLE/SCALABLE/MULTIQ).

┌─────────────────────────────────────────┐
│        Zephyr Kernel Scheduler          │
│  _priq_run_add / remove / best / yield  │
└──────────────┬──────────────────────────┘
               │ CONFIG_SCHED_LINUX
               ▼
┌─────────────────────────────────────────┐
│         z_priq_linux_best()             │
│  DL(EDF/CBS) → RT(FIFO/RR) → CFS → Idle│
└──────────────┬──────────────────────────┘
               │
    ┌──────────┼──────────┬───────────┐
    ▼          ▼          ▼           ▼
  DL Queue   RT Queue   CFS Queue   Idle
  Sorted by  bitmap     Sorted by   (Zephyr
  deadline   O(1)       vruntime    built-in)
  ascending  lookup     ascending

Scheduling Class Priority: DL > RT > CFS > Idle

Sched Class	Policy	Sort Criteria	Features
DL	SCHED_DEADLINE	Absolute deadline ascending	EDF + CBS throttling/replenishment
RT	SCHED_FIFO / SCHED_RR	Priority 1-99 bitmap	FIFO no timeslice, RR 10 tick round-robin
CFS	SCHED_NORMAL	vruntime ascending	nice -20..19 weight table, fair allocation
Idle	SCHED_IDLE	—	Zephyr idle thread fallback

Modified Zephyr Kernel Files

File	Modification
include/zephyr/kernel_structs.h	Added struct _priq_linux, extended _ready_q
include/zephyr/kernel/thread.h	Added scheduling class metadata fields to _thread_base
kernel/include/priority_q.h	Added CONFIG_SCHED_LINUX macro + override z_sched_prio_cmp
kernel/Kconfig	Added CONFIG_SCHED_LINUX option
kernel/thread.c	New threads default initialized to CFS class
kernel/timeslicing.c	Added z_linux_sched_tick() hook
kernel/CMakeLists.txt	Added linux_sched/ source files

Build and Test

# Build kernel integration test (real thread scheduling)
west build -b rocket_pi/stm32f401xe zephyr/tests/kernel/sched/schedule_api

Interface Category Overview

Category	Interface Count	Examples
Thread Management	7	pthread_create, pthread_join, pthread_cancel, pthread_mutex_lock, pthread_mutex_unlock, pthread_cond_wait, pthread_cond_signal
Process Management	3	fork, execve, exit
Scheduling & Priority	3	sched_yield, sched_setparam, sched_getparam
Signals & Timers	8	signal, kill, alarm, timer_create, sleep, usleep, nanosleep, timer_settime
Memory Management	3	malloc, realloc, free
Device Management	5	open, close, read, write, ioctl
IPC & Environment	3	pipe, getenv, getuid
Time & Process Control	4	clock_gettime, wait, waitpid, posix_spawn
I/O Multiplexing	3	select, poll, epoll

Documentation

English

• Interface API Reference: docs/zephyr-linux-api-reference.md
• Interface Design and Kernel Mapping: docs/zephyr-linux-interface-definition.md
• Interface and Validation Overview: docs/zepLinux-interface-and-validation.md
• Build and Development Guide: docs/zephyr-linux-build-and-dev.md
• Test Demo Documentation: docs/test-demos/

Chinese Version

• README: docs/zh/README.zh.md
• Interface API Reference: docs/zh/zephyr-linux-api-reference.zh.md
• Interface Design and Kernel Mapping: docs/zh/zephyr-linux-interface-definition.zh.md
• Interface and Validation Overview: docs/zh/zepLinux-interface-and-validation.zh.md
• Build and Development Guide: docs/zh/zephyr-linux-build-and-dev.zh.md
• Test Demo Documentation: docs/zh/test-demos/

License

Apache-2.0