Pack Multiple Fields into a 16-bit Control Register

Code

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

typedef struct{
    union{
        uint16_t value; 
        struct{
            uint16_t mode: 3;
            uint16_t speed: 5; 
            uint16_t reserved : 2; 
            uint16_t status : 6; 
        }bits; 
    };
}ControlRegister_t; 

uint16_t pack_register(uint8_t mode, uint8_t speed, uint8_t status) {
    ControlRegister_t reg; 
    reg.bits.mode = mode; 
    reg.bits.speed = speed; 
    reg.bits.reserved = 0; 
    reg.bits.status = status; 

    return reg.value; 
}

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