Pointer to Struct with Bitfields

Code

#include <stdio.h>

struct UART_ControlRegister {
    unsigned int baudrate : 4;
    unsigned int tx_enable : 1;
    unsigned int rx_enable : 1;
    unsigned int tx_irq_en : 1;
    unsigned int rx_irq_en : 1;
    unsigned int parity_en : 1;
    unsigned int stop_bits : 1;
    unsigned int reserved : 22;
};

void configure_uart(struct UART_ControlRegister *reg) {
    // (reg -> baudrate) = 9;
    // (reg -> tx_enable) = 1;
    // (reg -> rx_enable) = 1;
    // (reg -> tx_irq_en) = 1;
    // (reg -> rx_irq_en) = 0;
    // (reg -> parity_en) = 1;
    // (reg -> stop_bits) = 0;
    ((*reg).baudrate) = 9;
    ((*reg).tx_enable) = 1;
    ((*reg).rx_enable) = 1;
    ((*reg).tx_irq_en) = 1;
    ((*reg).rx_irq_en) = 0;
    ((*reg).parity_en) = 1;
    ((*reg).stop_bits) = 0;

    
}

int main() {
    struct UART_ControlRegister reg = {0};

    configure_uart(&reg);

    printf("baudrate = %u\n", reg.baudrate);
    printf("tx_enable = %u\n", reg.tx_enable);
    printf("rx_enable = %u\n", reg.rx_enable);
    printf("tx_irq_en = %u\n", reg.tx_irq_en);
    printf("rx_irq_en = %u\n", reg.rx_irq_en);
    printf("parity_en = %u\n", reg.parity_en);
    printf("stop_bits = %u", reg.stop_bits);
    // printf("stop_bits = %u", sizeof(reg));

    return 0;
}

Solving Approach