Simpler way to do weird baud rate setting in C(++) on (whatever has asm/termbits.h - most likely just Linux) than the (non-working) method recommended by Stuck Overflow

test_custom_baudrate.cpp

/*  
lifted from python's serial.serialposix.set_special_baudrate and made to look like C 
compile with `g++ -o test_custom_baudrate test_custom_baudrate.cpp`
using 250000 to test because 3D printing people seem to love it
*/

#include <stdio.h>
#include <unistd.h>

#include <fcntl.h>
#include <sys/ioctl.h>
#include <asm/termbits.h>

int main(void) {
    struct termios2 options;

    int rate = 250000;

    int fd = open("/dev/ttyUSB0", O_RDWR | O_NOCTTY);

    if (ioctl(fd, TCGETS2, &options) < 0) {
        printf("failed to get options\n");
        return -1;
    }

    options.c_cflag &= ~CBAUD;
    options.c_cflag |= BOTHER;

    options.c_ispeed = rate;
    options.c_ospeed = rate;
    
    if (ioctl(fd, TCSETS2, &options) < 0) {
        printf("unable to set baudrate %d\n", rate);
        return -1;
    }

    printf("Success! (?)\n");

    // attach a scope, see if the shortest pulse is ~ 4 us
    for(int i=0; i<10; i++) {
        sleep(1);
        write(fd, "moo", 3);
    }
    close(fd);
}