问使用termios -无法将奇偶校验设置为even，出现EINVAL错误

EN

// C library headers
#include <stdio.h>
#include <string.h>

// Linux headers
#include <errno.h>  // Error integer and strerror() function
#include <fcntl.h>  // Contains file controls like O_RDWR
#include <stdlib.h>
#include <sys/types.h>
#include <termios.h>  // Contains POSIX terminal control definitions
#include <unistd.h>   // write(), read(), close()

#define SERIAL_DEVICE "/dev/ttyS0"

int main() {
    struct termios serial_port_settings;
    int fd;
    int retval;
    char buf[] = "hello world \n bye\n";
    char ch;
    int i;

    //SERAIL_DEVICE is "/dev/ttyS0"
    fd = open(SERIAL_DEVICE, O_RDWR);
    if (fd < 0) {
        perror("Failed to open SERIAL_DEVICE");
        exit(1);
    }

    retval = tcgetattr(fd, &serial_port_settings);
    if (retval < 0) {
        perror("Failed to get termios structure");
        exit(2);
    }

    //setting baud rate to B115200
    retval = cfsetospeed(&serial_port_settings, B115200);
    if (retval < 0) {
        perror("Failed to set 115200 output baud rate");
        exit(3);
    }
    retval = cfsetispeed(&serial_port_settings, B115200);
    if (retval < 0) {
        perror("Failed to set 115200 input baud rate");
        exit(4);
    }

    //parity and bytes, grabbed from documentation
    serial_port_settings.c_cflag |= PARENB;   //enable parity
    serial_port_settings.c_cflag &= ~PARODD;  //disable odd parity, therefore-> even parity
    serial_port_settings.c_cflag &= ~CSTOPB; //disable 2 stop bits, therefore-> 1 stop bit
    serial_port_settings.c_cflag &= ~CSIZE;  //remove size
    serial_port_settings.c_cflag |= CS8;     //8 data bits
    serial_port_settings.c_cflag |= CLOCAL | CREAD;  //ignore modem control lines, enable reciever
    serial_port_settings.c_lflag |= ICANON; // enable canonical mode

    
    retval = tcsetattr(fd, TCSANOW, &serial_port_settings);
    /*************** ERROR HAPPENS HERE ********************/
    /* errno is set to EINVAL here */
    
    if (retval < 0) {
        perror("Failed to set serial attributes");
        exit(5);
    }
    printf("Successfully set the baud rate\n");

    retval = write(fd, buf, 18);
    if (retval < 0) {
        perror("write on SERIAL_DEVICE failed");
        exit(6);
    }

    retval = tcdrain(fd);
    if (retval < 0) {
        perror("write on SERIAL_DEVICE failed");
        exit(6);
    }

    close(fd);
    return 0;
}