Test for tcdrain bug in ftdi_sio

gistfile1.txt

#include <termios.h>
#include <string.h>
#include <stdio.h>
#include <stdint.h>
#include <fcntl.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>

/* Tests if tcdrain is actually blocking until all bytes are sent over the wire.
 * This requires a hardware loopback (short RX and TX pins).
 * Tested with FT230X and Linux 3.19.0
 *
 * A successful test will receive as many bytes as written.
 * An unsuccessful test will receive fewer.
 *
 * -Enabling sleep should always be successful.
 * Compile as follows
 * gcc ftdi_tcdrain_bug.c -o ftdi_tcdrain_bug -std=gnu11
 *
 * */

int main(int argc, char **argv){
	int ret;
	int sleep = 0;

	if(argc < 2){
		fprintf(stderr, "Usage: TTY_DEV_NODE SLEEP\n");
		return 1;
	}

	if(argc > 2)
		sleep = 1;

	int fd = open(argv[1], O_RDWR);
	if(fd < 0){
		fprintf(stderr, "Unable to open port: %s\n", strerror(errno));
		return 1;
	}

	struct termios ser_options;
	ret = tcgetattr(fd, &ser_options);
	if(ret < 0){
		fprintf(stderr, "err tcgetattr: %s\n", strerror(errno));
		return 1;
	}

	unsigned baudrate = B9600;
	ret = cfsetispeed(&ser_options, baudrate);
	if(ret < 0){
		fprintf(stderr, "err cfsetispeed: %s\n", strerror(errno));
		return 1;
	}

	ret = cfsetospeed(&ser_options, baudrate);
	if(ret < 0){
		fprintf(stderr, "err cfsetospeed: %s\n", strerror(errno));
		return 1;
	}

	/* Setup for raw binary comms. */
	cfmakeraw(&ser_options);

	/* Reset options for communications. */
	ser_options.c_cflag &= ~(PARODD | PARENB | CS5 | CS6 | CS7 | CSTOPB);
	ser_options.c_cflag |= CS8;

	ret = tcsetattr(fd, TCSANOW, &ser_options);
	if(ret < 0){
		fprintf(stderr, "err tcsetattr: %s\n", strerror(errno));
		return 1;
	}

	/* Send initial break */
	tcsendbreak(fd, 1);

	const uint8_t buff[] = "ABCDEFG12345";

	ret = write(fd, buff, sizeof(buff));
	fprintf(stderr, "Wrote %i\n", ret);
	if(tcdrain(fd))
		fprintf(stderr, "tcdrain: %s\n", strerror(errno));

	/* Safety sleep because tcdrain doesn't work worth a hist. */
	if(sleep)
		usleep(sizeof(buff) * 2 * 1000);

	/* Send final break */
	tcsendbreak(fd, 1);

	char recvbuff[128];
	ret = read(fd, recvbuff, 128);
	fprintf(stderr, "Read %i\n", ret);

	return 0;
}