#include <err.h>
#include <errno.h>
#include <unistd.h>
#include <stdio.h>
#include <fcntl.h>
#include <sys/param.h>
#include <sys/mman.h>

uint16_t *mmcr;
static int dir;

static void
usage()
{
    fprintf(stderr, "usage: env4526 [-i seconds]\n");
    exit(2);
}

static void
W(int a, unsigned d)
{
	mmcr[a / 2] = d;
}

static unsigned
R(int a)
{
	return (mmcr[a/2]);
}

static void
BO(int i)
{
	u_int u;

	if (i)
		W(0xc34, 0x0080);
	else
		W(0xc38, 0x0080);
	if (dir == 0) {
		u = R(0xc2a);
		W(0xc2a, u | 0x0080);
		dir = 1;
	}
	W(0xc34, 0x0100);
	W(0xc34, 0x0100);
	W(0xc34, 0x0100);
	W(0xc34, 0x0100);
	W(0xc38, 0x0100);
	W(0xc38, 0x0100);
	W(0xc38, 0x0100);
	W(0xc38, 0x0100);
}

static int
BI(void)
{
	u_int u;

	if (dir == 1) {
		u = R(0xc2a);
		W(0xc2a, u & ~0x0080);
		dir = 0;
	}
	W(0xc34, 0x0100);
	W(0xc34, 0x0100);
	W(0xc34, 0x0100);
	W(0xc34, 0x0100);
	u = R(0xc30) & 0x0080;
	W(0xc38, 0x0100);
	W(0xc38, 0x0100);
	W(0xc38, 0x0100);
	W(0xc38, 0x0100);
	return (u ? 1 : 0);
}

static void
START(void)
{
	u_int u;

	W(0xc34, 0x0180);
	if (dir == 0) {
		u = R(0xc2a);
		W(0xc2a, u | 0x0080);
		dir = 1;
	}
	W(0xc38, 0x0080);
	W(0xc38, 0x0100);
	W(0xc38, 0x0100);
}

static void
STOP(void)
{
	u_int u;

	W(0xc38, 0x0080);
	if (dir == 0) {
		u = R(0xc2a);
		W(0xc2a, u | 0x0080);
		dir = 1;
	}
	W(0xc34, 0x0100);
	W(0xc34, 0x0100);
	W(0xc34, 0x0100);
	W(0xc34, 0x0100);
	W(0xc34, 0x0080);
}

static void
read_temp()
{
	int i;
	u_int j, u;
	char buf1[20];
	char buf2[20];

	u = R(0xc2a);
	W(0xc2a, u | 0x0180);
	W(0xc34, 0x0180);

	u = 0;
	START();
	BO(1);
	BO(0);
	BO(0);
	BO(1);
	BO(u & 4);
	BO(u & 2);
	BO(u & 1);
	BO(0);
	BI();
	for (i = 0; i < 6; i++)
		BO(0);
	BO(0);
	BO(0);
	BI();
	STOP();

	START();
	BO(1);
	BO(0);
	BO(0);
	BO(1);
	BO(u & 4);
	BO(u & 2);
	BO(u & 1);
	BO(1);
	for (i = 0; i < 9; i++)
		buf1[i] = BI();
	BO(0);
	for (i = 0; i < 8; i++)
		buf2[i] = BI();
	BO(1);
	STOP();

	j = 0;
	for (i = 1; i < 9; i++) {
		j |= buf1[i];
		j += j;
	}
	for (i = 0; i < 8; i++) {
		j |= buf2[i];
		j += j;
	}

    printf("lm75: %.2fC\n", j / 512.0);
}

int
main(int argc, char **argv)
{
    int seconds = 0;
    char *t;
    FILE *f;
    int ch;
	int fd;

    while ((ch = getopt (argc, argv, "i:")) != -1) {
        switch(ch) {
        case 'i':
            seconds = strtol (optarg, &t, 10);
            if (*t || seconds < 0)
                usage ();
            break;
        default:
            usage ();
            break;
        }
    }

    argc -= optind;
    argv += optind;

    if (argc != 0)
        usage ();

	fd = open ("/dev/elan-mmcr", O_RDWR);
	if (fd < 0)
		err (1, "couldn't open: /dev/elan-mmcr");
	mmcr = mmap (NULL, 4096, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);

    for (;;) {
        read_temp ();
        fflush (stdout);
        if (!seconds)
            break;
        sleep (seconds);
    }

    return 0;
}