Macro-Based Register Config Helper

Code

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

#define ENABLE_BIT(reg, enable) (reg |= enable)
#define MODE_BITS(reg, mode) (reg |= (mode << 1))
#define SPEED_BITS(reg, speed) (reg |= (speed << 3))
#define RESERVED_BITS(reg) (reg &= ~(2 << 6))
#define REG_CONFIG(reg, enable, mode, speed) (   \
    ENABLE_BIT(reg, enable),                     \
    MODE_BITS(reg, mode),                        \
    SPEED_BITS(reg, speed),                      \
    RESERVED_BITS(reg),                          \
    (reg) )


uint16_t build_register(uint8_t enable, uint8_t mode, uint8_t speed) {
    // Use macros to set fields
    uint16_t reg = 0;
    reg |= REG_CONFIG(reg, enable, mode, 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;
}

Solving Approach