Pack Multiple Fields into a 16-bit Control Register

Code

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

#define BIT_MODE      0
#define BIT_SPEED     3
#define BIT_RESERVED  8
#define BIT_STATUS   10

#define MASK_MODE     ((1 <<  2) | (1 <<  1) | (1 <<  0))
#define MASK_SPEED    ((1 <<  7) | (1 <<  6) | (1 <<  5) | (1 <<  4) | (1 <<  3))
#define MASK_RESERVED ((1 <<  9) | (1 <<  8))
#define MASK_STATUS   ((1 << 15) | (1 << 14) | (1 << 13) | (1 << 12) | (1 << 11) | (1 << 10))

uint16_t pack_register(uint8_t mode, uint8_t speed, uint8_t status) {
    return          (mode                   & MASK_MODE)   |
                    ((speed  << BIT_SPEED)  & MASK_SPEED)  |
                    ((status << BIT_STATUS) & MASK_STATUS);
}

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

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

Solving Approach