Macro-Based Register Config Helper

Code

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

// Define macros here
#define SET(val, pos) val |= (1 << pos)
#define ENABLE(val, enable) enable ? SET(val, 0) : val
#define MODE(val, mode) {   \
    if (mode >= 3) {        \
        SET(val, 1);        \
        SET(val, 2);        \
    } else {                \
        SET(val, mode);     \
    }                       \
}                           \

#define SPEED(val, speed) { \
    switch(speed)           \
    {                       \
        case 1:             \
            SET(val, 3);    \
            break;          \
        case 2:             \
            SET(val, 4);    \
            break;          \
        case 3:             \
            SET(val, 3);    \
            SET(val, 4);    \
            break;          \
        case 4:             \
            SET(val, 5);    \
            break;          \
        case 5:             \
            SET(val, 3);    \
            SET(val, 5);    \
            break;          \
        case 6:             \
            SET(val, 4);    \
            SET(val, 5);    \
            break;          \
        case 7:             \
            SET(val, 3);    \
            SET(val, 4);    \
            SET(val, 5);    \
            break;          \
    }                       \
}                           \

uint16_t build_register(uint8_t enable, uint8_t mode, uint8_t speed) {
    // Use macros to set fields
    uint16_t val = 0;
    // Enable bit
    ENABLE(val, enable);
    MODE(val, mode);
    SPEED(val, speed);
    return val;
}

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;
}

Solving Approach