USB Control Message to flush a FTDI device without detaching the ftdi_sio kernel driver Raw

usb.c

// gcc -I/usr/include/libftdi1 -I/usr/include/libusb-1.0 usb.c 

#include <fcntl.h>
#include <sys/ioctl.h>
#include <linux/usbdevice_fs.h>
#include <asm/byteorder.h>
#include <errno.h>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <libusb.h>
#include <ftdi.h>

void usb_control_message(int fd, struct usbdevfs_ctrltransfer* urb) {
  int rc = ioctl(fd, USBDEVFS_CONTROL, &urb);
  if (rc < 0) {
    perror(NULL);
    exit(-1);
  }
}

int main(void)
{
  int fd = open("/dev/bus/usb/002/040", O_RDWR);
  if (fd == -1) {
    perror(NULL);
    return -1;
  }

  struct usbdevfs_ctrltransfer urb;
  memset(&urb, 0, sizeof (urb));

  // Flush RX
  urb.bRequestType = FTDI_DEVICE_OUT_REQTYPE;
  urb.bRequest = SIO_RESET_REQUEST;
  urb.wValue = SIO_RESET_PURGE_RX;
  urb.wIndex = 1;
  urb.data = NULL;
  urb.wLength = 0;
  urb.timeout = 5000; /* in milliseconds */
  usb_control_message(fd, &urb);

  // Flush TX
  urb.wValue = SIO_RESET_PURGE_TX;
  usb_control_message(fd, &urb);
}