#include <stdlib.h>
#include <unistd.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <string.h>
#include <sys/ioctl.h>
#include <linux/spi/spidev.h>


#define SMALL 2
#define BIG 120
#define NB 3

const int FILL_BYTE = 0xaa;
const int RX_BYTE = 0xFF;
const unsigned int MAX_LOOPS = 50;

struct spi_ioc_transfer xfer[NB];
char rx_header[SMALL];
char rx_buffer[BIG];
char rx_footer[SMALL];
char tx_header[SMALL];
char tx_buffer[BIG];
char tx_footer[SMALL];

void dump(char *buf, unsigned int len)
{
	unsigned int i;

	for (i = 0; i < len; i++) {
		printf("%2.2x ", buf[i]);
		if (((i + 1) % 16) == 0)
			printf("\n");
	}
	printf("\n");
}

/*
 * Checks if the buffer buf is filled with val bytes
 * return 0 if it is, 1 if a byte is != val
 */
int check_buf(char *buf, unsigned int len, unsigned int val)
{
	while (len--)
		if (buf[len] != RX_BYTE)
			return 1;
	return 0;
}

void usage(const char *progname)
{
	printf("Usage: %s spidev\n", progname);
}

int main(int argc, char **argv)
{
	const char *spi_dev_name;
	int err = 0;
	int fd;
	unsigned int i;
	unsigned int loops = MAX_LOOPS;

	if (argc < 2) {
		usage(argv[0]);
		err = -1;
		goto out;
	}

	spi_dev_name = argv[1];

	fd = open(spi_dev_name, O_RDWR);
	if (fd < 0) {
		perror("open");
		err = -1;
		goto out;
	}

	xfer[0].tx_buf = (unsigned long)tx_header;
	xfer[0].rx_buf = (unsigned long)rx_header;
	xfer[0].len = SMALL;
	xfer[1].tx_buf = (unsigned long)tx_buffer;
	xfer[1].rx_buf = (unsigned long)rx_buffer;
	xfer[1].len = BIG;
	xfer[2].tx_buf = (unsigned long)tx_footer;
	xfer[2].rx_buf = (unsigned long)rx_footer;
	xfer[2].len = SMALL;

	while (loops--) {
		for (i = 0; i < NB; i++) {
			memset((void *)xfer[i].tx_buf, FILL_BYTE, xfer[i].len);
			memset((void *)xfer[i].rx_buf, FILL_BYTE, xfer[i].len);
		}

		err = ioctl(fd, SPI_IOC_MESSAGE(NB), xfer);
		if (err < 0) {
			perror("ioctl");
			break;
		}
		if (err != (sizeof(rx_buffer) + sizeof(rx_footer)
			    + sizeof(rx_header))) {
			printf("message too short: %d bytes\n", err);
			break;
		}
		for (i = 0; i < NB; i++) {
			err = check_buf((char *)(xfer[i].rx_buf), xfer[i].len, RX_BYTE);
			if (err)
				dump((char *)(xfer[i].rx_buf), xfer[i].len);
		}
	}

	(void) close(fd);
out:
	return err;
}