/*
 * SPI testing utility (using spidev driver)
 *
 * Copyright (c) 2007  MontaVista Software, Inc.
 * Copyright (c) 2007  Anton Vorontsov <avorontsov@ru.mvista.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License.
 *
 * Cross-compile with cross-gcc -I/path/to/cross-kernel/include
 */

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

#include <sys/time.h> /* gettimeofday, timeval (for timestamp in microsecond) */
#include <sys/timeb.h> /* ftime, timeb (for timestamp in millisecond) */
#include <time.h> /* time_t, time (for timestamp in second) */
#include <pthread.h>
#include <stdbool.h>

#define SPI_LOOP_INTERVAL_US 5000

#define ARRAY_SIZE(a) (sizeof(a) / sizeof((a)[0]))
#define PACKET_LENGTH 8

#define REQ_MAG_X "\x00\x04\x00\x00\x00\x00\xc0\xf1"
#define REQ_MAG_Y "\x00\x08\x00\x00\x00\x00\xc1\xe1"
#define REQ_MAG_Z "\x00\x0c\x00\x00\x00\x00\x01\x10"
#define REQ_PING "\x00\x00\x0a\x4d\x52\x58\x55\xaf"

#define CRC16 0x8005
#define CRC_LENGTH 2

enum {
    SPI_RX,
    SPI_TX,
    SPI_NUM
};

static const char* device = "/dev/spidev1.1";
static uint32_t mode;
static uint8_t bits = 8;
static char* input_file;
static char* output_file;
static uint32_t speed = 500000;
static uint16_t delay;
static int verbose;

char* input_tx;
int test_case;

static void pabort(const char* s);
static int unescape(char* _dst, char* _src, size_t len);
static void print_usage(const char* prog);
static void set_spi_mode();
static void transfer_file(int fd, char* filename);
static void transfer_escaped_string(char* str);
static void parse_opts(int argc, char* argv[]);
static void transferN(struct spi_ioc_transfer *buf, size_t len);
static void TransferWithOpenedFile(int fd, uint8_t const* tx, uint8_t const* rx, size_t len);
static long long int GetMicroSeconds();

static void TransferAdisTestLong();
static void TransferNAdisTestLong();
static void TransferNAdisTestLong2();
static void TransferAdisTestShort();

static void SetPthreadPriority(int priority);

void *main_thread()
{
    SetPthreadPriority(99);
    set_spi_mode(mode);

    if (input_tx) {
        transfer_escaped_string(input_tx);
    } else if (input_file) {
        // int fd;
        // transfer_file(fd, input_file);
    } else if (test_case == 1) {
    } else if (test_case == 20) {
        TransferAdisTestLong();
    } else if (test_case == 21) {
        TransferAdisTestShort();
    } else if (test_case == 22) {
        TransferNAdisTestLong();
    } else if (test_case == 23) {
        TransferNAdisTestLong2();
    } else {
        printf("Something is wrong!!\n");
    }
}

int main(int argc, char* argv[])
{
    pthread_t mthread;
    parse_opts(argc, argv);

    pthread_create(&mthread, NULL, main_thread, NULL);
    pthread_join(mthread, NULL);
    return 0;
}

static void hex_dump(const void* src, size_t length, size_t line_size,
    char* prefix)
{
    const unsigned char* address = src;
    long long int timestamp_usec; /* timestamp in microsecond */

    timestamp_usec = GetMicroSeconds();
    printf("%.6lf ", timestamp_usec / 1000000.0);

    printf("%s | ", prefix);

    while (length-- > 0) {
        printf("%02X ", *address++);
    }
    printf("\n");
}

static void transfer(uint8_t const* tx, uint8_t const* rx, size_t len)
{
    int fd;

    fd = open(device, O_RDWR);
    if (fd < 0)
        pabort("can't open device");

    TransferWithOpenedFile(fd, tx, rx, len);

    close(fd);
}

static void transferN(struct spi_ioc_transfer *buf, size_t len)
{
    int ret;

    int fd;

    fd = open(device, O_RDWR);
    if (fd < 0)
        pabort("can't open device");

    ret = ioctl(fd, SPI_IOC_MESSAGE(len), buf);
    if (ret < 1)
    {
        printf("error code %d\n", ret);
        pabort("can't send spi message");
    }

    close(fd);
}

static void TransferWithOpenedFile(int fd, uint8_t const* tx, uint8_t const* rx, size_t len)
{
    int ret;
    struct spi_ioc_transfer tr = {
        .tx_buf = (unsigned long long)tx,
        .rx_buf = (unsigned long long)rx,
        .len = len,
        .delay_usecs = delay,
        .speed_hz = speed,
        .bits_per_word = bits,
    };

    if (mode & SPI_TX_QUAD)
        tr.tx_nbits = 4;
    else if (mode & SPI_TX_DUAL)
        tr.tx_nbits = 2;
    if (mode & SPI_RX_QUAD)
        tr.rx_nbits = 4;
    else if (mode & SPI_RX_DUAL)
        tr.rx_nbits = 2;
    if (!(mode & SPI_LOOP)) {
        if (mode & (SPI_TX_QUAD | SPI_TX_DUAL))
            tr.rx_buf = 0;
        else if (mode & (SPI_RX_QUAD | SPI_RX_DUAL))
            tr.tx_buf = 0;
    }

    uint32_t start_time = GetMicroSeconds();
    ret = ioctl(fd, SPI_IOC_MESSAGE(1), &tr);
    uint32_t end_time = GetMicroSeconds();
    // printf("%.6f: diff2=%d us\n", end_time/1000000.0, end_time-start_time);
    if (ret < 1)
        pabort("can't send spi message");

    if (verbose)
        hex_dump(tx, len, 32, "TX");

    if (output_file) {
        int out_fd;
        out_fd = open(output_file, O_WRONLY | O_CREAT | O_TRUNC, 0666);
        if (out_fd < 0)
            pabort("could not open output file");

        ret = write(out_fd, rx, len);
        if (ret != len)
            pabort("not all bytes written to output file");

        close(out_fd);
    }

    if (verbose)
        hex_dump(rx, len, 32, "RX");
}

static void TransferAdisTestLong()
{
    size_t size = 86;
    uint8_t rx[86];
    uint8_t tx[86] = { 0x7E, 0x0, 0x0E, 0x0, 0x10, 0x0, 0x12, 0x0, 0x14, 0x0, 0x16, 0x0, 0x18, 0x0, 0x1A, 0x0, 0x1C, 0x0, 0x1E, 0x0, 0x20,
        0x0, 0x22, 0x0, 0x24, 0x0, 0x26, 0x0, 0x28, 0x0, 0x2A, 0x0, 0x2C, 0x0, 0x2E, 0x0, 0x30, 0x0, 0x40, 0x0, 0x42, 0x0, 0x44,
        0x0, 0x46, 0x0, 0x48, 0x0, 0x4A, 0x00, 0x4C, 0x00, 0x4E, 0x00, 0x50, 0x0, 0x52, 0x0, 0x54, 0x0, 0x56, 0x0, 0x7E, 0x00,
        0x8, 0x0, 0x7e, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0 };

    // transfer(tx, rx, 2);
    // printf("prod id 0x%02X%02X\n", rx[0], rx[1]);

    while (1)
    {
        bool no_error = true;
        uint32_t start_time = GetMicroSeconds();
        transfer(tx, rx, size);
        uint32_t end_time = GetMicroSeconds();

        no_error &= (rx[4] == 0x40);
        no_error &= (rx[66] == 0x40);
        no_error &= (rx[70] == 0x40);
        no_error &= (rx[5] == 0x60);
        no_error &= (rx[67] == 0x60);
        no_error &= (rx[71] == 0x60);
        no_error &= (rx[69] == 0);
        no_error &= ((rx[68] & ~0x3) == 0);
        if (no_error == false)
        {
            printf("s prod id 0x%02X%02X\n", rx[4], rx[5]);
            printf("e prod id 0x%02X%02X\n", rx[66], rx[67]);
            printf("sys_e_flag 0x%02X%02X\n", rx[68], rx[69]);
            printf("e prod id 0x%02X%02X\n", rx[70], rx[71]);
            printf("%.6f: diff=%d us\n", end_time/1000000.0, end_time-start_time);
            hex_dump(rx, 86, 32, "RX");
        }
        uint32_t end_time2 = GetMicroSeconds();
        // every 5ms
        usleep(5000-(end_time2-start_time)); 
    }
}

// This doesn't work with Jetson NX because spi-tegra114.c doesn't support SPI_IOC_MESSAGE(N)
/*
[when the size is 6]
root@cerberus:~# ./spidev_test_ioc_message_n -D /dev/spidev0.0 -s 1000000 -b 8 -H -O -t 22 -v
priority: 99, ret: 0, policy: 1
start time: 1600662898.918802 s
spi mode: 0x3
bits per word: 8
max speed: 1000000 Hz (1000 KHz)
1600662898.919029 TX | 7E 00 
1600662898.919080 RX | 00 00 
1600662898.919236 TX | 7E 00 
1600662898.919277 RX | 40 60 
prod id 0x4060
1602.144436: diff=307 us
1600662898.919623 TX | 7E 00 0E 00 10 00 
1600662898.919641 RX | 40 60 40 60 09 3C 
[when the size is 8]
root@cerberus:~# ./spidev_test_ioc_message_n -D /dev/spidev0.0 -s 1000000 -b 8 -H -O -t 22 -v
priority: 99, ret: 0, policy: 1
start time: 1600662952.318174 s
spi mode: 0x3
bits per word: 8
max speed: 1000000 Hz (1000 KHz)
1600662952.318415 TX | 7E 00 
1600662952.318440 RX | 00 00 
1600662952.318617 TX | 7E 00 
1600662952.318634 RX | 40 60 
prod id 0x4060
error code -1
can't send spi message: Input/output error
Aborted
*/
static void TransferNAdisTestLong()
{
    size_t size = 8;
    uint8_t rx[66];
    uint8_t tx[66] = { 0x7E, 0x0, 0x0E, 0x0, 0x10, 0x0, 0x12, 0x0, 0x14, 0x0, 0x16, 0x0, 0x18, 0x0, 0x1A, 0x0, 0x1C, 0x0, 0x1E, 0x0, 0x20,
        0x0, 0x22, 0x0, 0x24, 0x0, 0x26, 0x0, 0x28, 0x0, 0x2A, 0x0, 0x2C, 0x0, 0x2E, 0x0, 0x30, 0x0, 0x40, 0x0, 0x42, 0x0, 0x44,
        0x0, 0x46, 0x0, 0x48, 0x0, 0x4A, 0x00, 0x4C, 0x00, 0x4E, 0x00, 0x50, 0x0, 0x52, 0x0, 0x54, 0x0, 0x56, 0x0, 0x7E, 0x00,
        0, 0};
    struct spi_ioc_transfer tr_buf[size/2];
    int i;

    transfer(tx, rx, 2);
    transfer(tx, rx, 2);
    printf("prod id 0x%02X%02X\n", rx[0], rx[1]);

    for (i=0; i<size/2; i++)
    {
        memset(&tr_buf[i], 0, sizeof(struct spi_ioc_transfer));
        tr_buf[i].tx_buf = (unsigned long long) (tx + i*2);
        tr_buf[i].rx_buf = (unsigned long long) (rx + i*2);
        tr_buf[i].len = 2;
        tr_buf[i].delay_usecs = 0;
        tr_buf[i].speed_hz = speed;
        tr_buf[i].bits_per_word = bits;
    }

    tr_buf[0].rx_buf = 0;
    tr_buf[size/2 - 1].tx_buf = 0;

    uint32_t start_time = GetMicroSeconds(); 
    transferN(tr_buf, size/2);
    uint32_t end_time = GetMicroSeconds();
    
    printf("%.6f: diff=%d us\n", end_time/1000000.0, end_time-start_time);
    if (verbose)
    {
        hex_dump(tx, size, 32, "TX");
        hex_dump(rx, size, 32, "RX");
    }
}

static void TransferNAdisTestLong2()
{
    size_t size = 4;
    uint8_t rx[66];
    uint8_t tx[66] = { 0x7E, 0x0, 0x0E, 0x0, 0x10, 0x0, 0x12, 0x0, 0x14, 0x0, 0x16, 0x0, 0x18, 0x0, 0x1A, 0x0, 0x1C, 0x0, 0x1E, 0x0, 0x20,
        0x0, 0x22, 0x0, 0x24, 0x0, 0x26, 0x0, 0x28, 0x0, 0x2A, 0x0, 0x2C, 0x0, 0x2E, 0x0, 0x30, 0x0, 0x40, 0x0, 0x42, 0x0, 0x44,
        0x0, 0x46, 0x0, 0x48, 0x0, 0x4A, 0x00, 0x4C, 0x00, 0x4E, 0x00, 0x50, 0x0, 0x52, 0x0, 0x54, 0x0, 0x56, 0x0, 0x7E, 0x00,
        0, 0};
    struct spi_ioc_transfer tr_buf[size];

    memset(tr_buf, 0, sizeof(tr_buf));
    memset(rx, 0, sizeof(rx));
    tr_buf[0].tx_buf = (unsigned long long) (tx+2);
    tr_buf[0].len = 2;
    tr_buf[0].speed_hz = speed;
    tr_buf[0].bits_per_word = bits;

    tr_buf[1].tx_buf = (unsigned long long) (tx+4);
    tr_buf[1].rx_buf = (unsigned long long) (rx);
    tr_buf[1].len = 2;
    tr_buf[1].speed_hz = speed;
    tr_buf[1].bits_per_word = bits;

    tr_buf[2].tx_buf = (unsigned long long) (tx+6);
    tr_buf[2].rx_buf = (unsigned long long) (rx+2);
    tr_buf[2].len = 2;
    tr_buf[2].speed_hz = speed;
    tr_buf[2].bits_per_word = bits;

    tr_buf[3].rx_buf = (unsigned long long) (rx+4);
    tr_buf[3].len = 2;
    tr_buf[3].speed_hz = speed;
    tr_buf[3].bits_per_word = bits;


    uint32_t start_time = GetMicroSeconds(); 
    transferN(tr_buf, size);
    uint32_t end_time = GetMicroSeconds();
    
    size = 36;
    printf("%.6f: diff=%d us\n", end_time/1000000.0, end_time-start_time);
    if (verbose)
    {
        hex_dump(tx, size, 32, "TX");
        hex_dump(rx, size, 32, "RX");
    }
}

static void TransferAdisTestShort()
{
    size_t cnt = 0;
    uint8_t rx[2];
    uint8_t tx[2] = { 0x7E, 0x0 };

    transfer(tx, rx, 2);
    transfer(tx, rx, 2);
    printf("prod id 0x%02X%02X\n", rx[0], rx[1]);
    uint32_t start_time = GetMicroSeconds();

    int fd = open(device, O_RDWR);
    if (fd < 0)
        pabort("can't open device");
    cnt += 1; TransferWithOpenedFile(fd, tx, rx, 2);
    cnt += 1; tx[0] = 0x10; TransferWithOpenedFile(fd, tx, rx, 2);
    cnt += 1; tx[0] = 0x12; TransferWithOpenedFile(fd, tx, rx, 2);
    cnt += 1; tx[0] = 0x14; TransferWithOpenedFile(fd, tx, rx, 2);
    cnt += 1; tx[0] = 0x16; TransferWithOpenedFile(fd, tx, rx, 2);
    cnt += 1; tx[0] = 0x18; TransferWithOpenedFile(fd, tx, rx, 2);
    cnt += 1; tx[0] = 0x1A; TransferWithOpenedFile(fd, tx, rx, 2);
    cnt += 1; tx[0] = 0x1C; TransferWithOpenedFile(fd, tx, rx, 2);
    cnt += 1; tx[0] = 0x1E; TransferWithOpenedFile(fd, tx, rx, 2);
    cnt += 1; tx[0] = 0x20; TransferWithOpenedFile(fd, tx, rx, 2);
    cnt += 1; tx[0] = 0x22; TransferWithOpenedFile(fd, tx, rx, 2);
    cnt += 1; tx[0] = 0x24; TransferWithOpenedFile(fd, tx, rx, 2);
    cnt += 1; tx[0] = 0x26; TransferWithOpenedFile(fd, tx, rx, 2);
    cnt += 1; tx[0] = 0x28; TransferWithOpenedFile(fd, tx, rx, 2);
    cnt += 1; tx[0] = 0x2A; TransferWithOpenedFile(fd, tx, rx, 2);
    cnt += 1; tx[0] = 0x2C; TransferWithOpenedFile(fd, tx, rx, 2);
    cnt += 1; tx[0] = 0x2E; TransferWithOpenedFile(fd, tx, rx, 2);
    cnt += 1; tx[0] = 0x30; TransferWithOpenedFile(fd, tx, rx, 2);
    cnt += 1; tx[0] = 0x40; TransferWithOpenedFile(fd, tx, rx, 2);
    cnt += 1; tx[0] = 0x42; TransferWithOpenedFile(fd, tx, rx, 2);
    cnt += 1; tx[0] = 0x44; TransferWithOpenedFile(fd, tx, rx, 2);
    cnt += 1; tx[0] = 0x46; TransferWithOpenedFile(fd, tx, rx, 2);
    cnt += 1; tx[0] = 0x48; TransferWithOpenedFile(fd, tx, rx, 2);
    cnt += 1; tx[0] = 0x48; TransferWithOpenedFile(fd, tx, rx, 2);
    cnt += 1; tx[0] = 0x4A; TransferWithOpenedFile(fd, tx, rx, 2);
    cnt += 1; tx[0] = 0x4E; TransferWithOpenedFile(fd, tx, rx, 2);
    cnt += 1; tx[0] = 0x50; TransferWithOpenedFile(fd, tx, rx, 2);
    cnt += 1; tx[0] = 0x52; TransferWithOpenedFile(fd, tx, rx, 2);
    cnt += 1; tx[0] = 0x54; TransferWithOpenedFile(fd, tx, rx, 2);
    cnt += 1; tx[0] = 0x56; TransferWithOpenedFile(fd, tx, rx, 2);
    cnt += 1; tx[0] = 0x7E; TransferWithOpenedFile(fd, tx, rx, 2);
    close(fd);
    uint32_t end_time = GetMicroSeconds();
    printf("%.6f: diff=%d us\n", end_time/1000000.0, end_time-start_time);
    printf("Number of regisers: %lu (bytes: %lu)\n", cnt, cnt*2);
}

static void transfer_escaped_string(char* str)
{
    size_t size = strlen(str);
    uint8_t* tx;
    uint8_t* rx;

    tx = malloc(size);
    if (!tx)
        pabort("can't allocate tx buffer");

    rx = malloc(size);
    if (!rx)
        pabort("can't allocate rx buffer");

    size = unescape((char*)tx, str, size);
    transfer(tx, rx, size);
    free(rx);
    free(tx);
}

static void transfer_file(int fd, char* filename)
{
    ssize_t bytes;
    struct stat sb;
    int tx_fd;
    uint8_t* tx;
    uint8_t* rx;

    if (stat(filename, &sb) == -1)
        pabort("can't stat input file");

    tx_fd = open(filename, O_RDONLY);
    if (fd < 0)
        pabort("can't open input file");

    tx = malloc(sb.st_size);
    if (!tx)
        pabort("can't allocate tx buffer");

    rx = malloc(sb.st_size);
    if (!rx)
        pabort("can't allocate rx buffer");

    bytes = read(tx_fd, tx, sb.st_size);
    if (bytes != sb.st_size)
        pabort("failed to read input file");

    transfer(tx, rx, sb.st_size);
    free(rx);
    free(tx);
    close(tx_fd);
}

static void set_spi_mode()
{
    int fd = open(device, O_RDWR);
    int ret;
    if (fd < 0)
        pabort("can't open device");

    ret = ioctl(fd, SPI_IOC_WR_MODE, &mode);
    if (ret == -1)
        pabort("can't set spi mode");

    ret = ioctl(fd, SPI_IOC_WR_MODE, &mode);
    if (ret == -1)
        pabort("can't set spi mode");

    ret = ioctl(fd, SPI_IOC_RD_MODE, &mode);
    if (ret == -1)
        pabort("can't get spi mode");

    /*
     * bits per word
     */
    ret = ioctl(fd, SPI_IOC_WR_BITS_PER_WORD, &bits);
    if (ret == -1)
        pabort("can't set bits per word");

    ret = ioctl(fd, SPI_IOC_RD_BITS_PER_WORD, &bits);
    if (ret == -1)
        pabort("can't get bits per word");

    /*
     * max speed hz
     */
    ret = ioctl(fd, SPI_IOC_WR_MAX_SPEED_HZ, &speed);
    if (ret == -1)
        pabort("can't set max speed hz");

    ret = ioctl(fd, SPI_IOC_RD_MAX_SPEED_HZ, &speed);
    if (ret == -1)
        pabort("can't get max speed hz");

    printf("start time: %.6lf s\n", GetMicroSeconds()/1000000.0);
    printf("spi mode: 0x%x\n", mode);
    printf("bits per word: %d\n", bits);
    printf("max speed: %u Hz (%u KHz)\n", speed, speed / 1000);
    if (input_tx && input_file)
        pabort("only one of -p and --input may be selected");
    close(fd);
}

static long long int GetMicroSeconds()
{
    struct timeval timer_usec;
    long long int timestamp_usec; /* timestamp in microsecond */
    if (!gettimeofday(&timer_usec, NULL)) {
        timestamp_usec = ((long long int)timer_usec.tv_sec) * 1000000ll + (long long int)timer_usec.tv_usec;
    } else {
        timestamp_usec = -1;
    }
    return timestamp_usec;
}

static void parse_opts(int argc, char* argv[])
{
    while (1) {
        static const struct option lopts[] = {
            { "device", 1, 0, 'D' },
            { "speed", 1, 0, 's' },
            { "delay", 1, 0, 'd' },
            { "bpw", 1, 0, 'b' },
            { "input", 1, 0, 'i' },
            { "output", 1, 0, 'o' },
            { "loop", 0, 0, 'l' },
            { "cpha", 0, 0, 'H' },
            { "cpol", 0, 0, 'O' },
            { "lsb", 0, 0, 'L' },
            { "cs-high", 0, 0, 'C' },
            { "3wire", 0, 0, '3' },
            { "no-cs", 0, 0, 'N' },
            { "ready", 0, 0, 'R' },
            { "dual", 0, 0, '2' },
            { "verbose", 0, 0, 'v' },
            { "quad", 0, 0, '4' },
            { NULL, 0, 0, 0 },
        };
        int c;

        c = getopt_long(argc, argv, "D:s:d:b:i:o:lHOLC3NR24p:t:v",
            lopts, NULL);

        if (c == -1)
            break;

        switch (c) {
        case 'D':
            device = optarg;
            break;
        case 's':
            speed = atoi(optarg);
            break;
        case 'd':
            delay = atoi(optarg);
            break;
        case 'b':
            bits = atoi(optarg);
            break;
        case 'i':
            input_file = optarg;
            break;
        case 'o':
            output_file = optarg;
            break;
        case 'l':
            mode |= SPI_LOOP;
            break;
        case 'H':
            mode |= SPI_CPHA;
            break;
        case 'O':
            mode |= SPI_CPOL;
            break;
        case 'L':
            mode |= SPI_LSB_FIRST;
            break;
        case 'C':
            mode |= SPI_CS_HIGH;
            break;
        case '3':
            mode |= SPI_3WIRE;
            break;
        case 'N':
            mode |= SPI_NO_CS;
            break;
        case 'v':
            verbose = 1;
            break;
        case 'R':
            mode |= SPI_READY;
            break;
        case 'p':
            input_tx = optarg;
            break;
        case 't':
            test_case = atoi(optarg);
            break;
        case '2':
            mode |= SPI_TX_DUAL;
            break;
        case '4':
            mode |= SPI_TX_QUAD;
            break;
        default:
            print_usage(argv[0]);
            break;
        }
    }
    if (mode & SPI_LOOP) {
        if (mode & SPI_TX_DUAL)
            mode |= SPI_RX_DUAL;
        if (mode & SPI_TX_QUAD)
            mode |= SPI_RX_QUAD;
    }
}

static void pabort(const char* s)
{
    perror(s);
    abort();
}

/*
 *  Unescape - process hexadecimal escape character
 *      converts shell input "\x23" -> 0x23
 */
static int unescape(char* _dst, char* _src, size_t len)
{
    int ret = 0;
    int match;
    char* src = _src;
    char* dst = _dst;
    unsigned int ch;

    while (*src) {
        if (*src == '\\' && *(src + 1) == 'x') {
            match = sscanf(src + 2, "%2x", &ch);
            if (!match)
                pabort("malformed input string");

            src += 4;
            *dst++ = (unsigned char)ch;
        } else {
            *dst++ = *src++;
        }
        ret++;
    }
    return ret;
}

static void print_usage(const char* prog)
{
    printf("Usage: %s [-DsbdlHOLC3]\n", prog);
    puts("  -D --device   device to use (default /dev/spidev1.1)\n"
         "  -s --speed    max speed (Hz)\n"
         "  -t --test     test messages: 1: mag once, 2: mag loop\n"
         "  -d --delay    delay (usec)\n"
         "  -b --bpw      bits per word\n"
         "  -i --input    input data from a file (e.g. \"test.bin\")\n"
         "  -o --output   output data to a file (e.g. \"results.bin\")\n"
         "  -l --loop     loopback\n"
         "  -H --cpha     clock phase\n"
         "  -O --cpol     clock polarity\n"
         "  -L --lsb      least significant bit first\n"
         "  -C --cs-high  chip select active high\n"
         "  -3 --3wire    SI/SO signals shared\n"
         "  -v --verbose  Verbose (show tx buffer)\n"
         "  -p            Send data (e.g. \"1234\\xde\\xad\")\n"
         "  -N --no-cs    no chip select\n"
         "  -R --ready    slave pulls low to pause\n"
         "  -2 --dual     dual transfer\n"
         "  -4 --quad     quad transfer\n");
    exit(1);
}

static void SetPthreadPriority(int priority)
{
    struct sched_param param;
    int policy;
    int ret;

    param.sched_priority = priority;
    ret = pthread_setschedparam(pthread_self(), SCHED_FIFO, &param);
    if (0 != ret) {
        printf("Unsuccessful in setting thread realtime prio, RET %d\n", ret);
    }
    ret = pthread_getschedparam(pthread_self(), &policy, &param);
    priority = param.sched_priority;

    printf("priority: %d, ret: %d, policy: %d\n", priority, ret, policy);
}