kernel.hpp

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// tinykernel: minimal preemptive task scheduler for RP2350 (Pico 2, Cortex-M33)
#pragma once
 
#include <stdint.h>
#include <stddef.h>
 
#include "pico/runtime.h"  // PICO_RUNTIME_INIT_FUNC (static task registration)

#ifndef TK_TICKS_PER_SEC
#define TK_TICKS_PER_SEC 1000u
#endif

#ifndef TK_TIME_SLICE_MS
#define TK_TIME_SLICE_MS 10u
#endif

#ifndef TK_MAX_TASKS
#define TK_MAX_TASKS 32u
#endif

#ifndef TK_DEFAULT_STACK_SIZE
#define TK_DEFAULT_STACK_SIZE (4 * 1024)
#endif
 
namespace tk {

using TaskFn = void (*)(void* arg);

enum Prio : uint32_t {
    PRIO_REALTIME = 1,   
    PRIO_HIGH     = 5,   
    PRIO_NORMAL   = 9,   
    PRIO_LOW      = 13,  
};

struct TaskHandle {
    uint8_t slot{0xFF};  

    bool is_valid() const { return slot != 0xFF; }
};

TaskHandle create(TaskFn fn, void* arg = nullptr, uint32_t prio = PRIO_NORMAL);

void start();

void yield();

void sleep_ms(uint32_t ms);

void exit(int code = 0);

uint64_t now_ms();

bool lock();

void unlock(bool was_enabled);

void preempt_disable();

void preempt_enable();

class PreemptGuard {
public:
    PreemptGuard() { preempt_disable(); }
    ~PreemptGuard() { preempt_enable(); }
 
    PreemptGuard(const PreemptGuard&) = delete;
    PreemptGuard& operator=(const PreemptGuard&) = delete;
};
 
using task_mask_t = uint32_t;
 
namespace detail {
void static_register(const char* name, TaskFn fn, uint32_t prio);
uint32_t sched_lock();
void sched_unlock(uint32_t save);
void block_current_task_locked();
void wake_task_locked(TaskHandle handle);
uint8_t current_task_slot();
uint8_t find_highest_prio_waiter(task_mask_t wait_mask);
}  // namespace detail
 
}  // namespace tk

#define TK_TASK(fn, prio)                                              \
    static void tk_register_##fn(void) {                              \
        ::tk::detail::static_register(#fn, fn, (prio));               \
    }                                                                 \
    PICO_RUNTIME_INIT_FUNC(tk_register_##fn, "ZZ900");