ardupilot/libraries/AP_HAL_PX4/Storage.h

#pragma once

#include <AP_HAL/AP_HAL.h>
#include "AP_HAL_PX4_Namespace.h"
#include <systemlib/perf_counter.h>
#include <AP_Common/Bitmask.h>

#define PX4_STORAGE_SIZE HAL_STORAGE_SIZE
#define PX4_STORAGE_LINE_SHIFT 9
#define PX4_STORAGE_LINE_SIZE (1<<PX4_STORAGE_LINE_SHIFT)
#define PX4_STORAGE_NUM_LINES (PX4_STORAGE_SIZE/PX4_STORAGE_LINE_SIZE)

class PX4::PX4Storage : public AP_HAL::Storage {
public:
    PX4Storage();

    void init() {}
    void read_block(void *dst, uint16_t src, size_t n);
    void write_block(uint16_t dst, const void* src, size_t n);

    void _timer_tick(void);

private:
    volatile bool _initialised;
    void _storage_create(void);
    void _storage_open(void);
    void _mark_dirty(uint16_t loc, uint16_t length);
    uint8_t _buffer[PX4_STORAGE_SIZE] __attribute__((aligned(4)));
    Bitmask _dirty_mask{PX4_STORAGE_NUM_LINES};
    perf_counter_t  _perf_storage;
    perf_counter_t  _perf_errors;

    int _fd = -1;
    void _mtd_load(void);
    void _mtd_write(uint16_t line);
    
#if defined (CONFIG_ARCH_BOARD_PX4FMU_V4)
    irqstate_t irq_state;
#endif
    void bus_lock(bool lock);
};