Macro-Based Register Config Helper

#include <stdio.h>
#include <stdint.h>

#define ENABLE_POS 0
#define MODE_POS   1
#define SPEED_POS  3

// Define macros here
#define SET_FIELD(reg, pos, len, val) \
            ((reg) |= (((val) & ((1U << (len)) - 1)) << (pos)))


uint16_t build_register(uint8_t enable, uint8_t mode, uint8_t speed)
{
    uint16_t reg = 0;

    SET_FIELD(reg, ENABLE_POS, 1, enable);
    SET_FIELD(reg, MODE_POS,   2, mode);
    SET_FIELD(reg, SPEED_POS,  3, speed);

    return reg;
}

int main() {
    uint8_t enable, mode, speed;
    scanf("%hhu %hhu %hhu", &enable, &mode, &speed);

    uint16_t reg = build_register(enable, mode, speed);
    printf("%u", reg);
    return 0;
}