#include <sys/mman.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>

int main(int argc, char *argv[])
{
    int fd[argc];
    int maxfd = 0;

    fd_set fds;
    struct timeval timeout;

    uint32_t info = 1; /* unmask */
    ssize_t nb = 0;

    FD_ZERO(&fds);

    for (int i=1; i<argc; i++) {
    	fd[i] = open(argv[i], O_RDWR);
	if (fd < 0) {
	    perror("open");
	    exit(EXIT_FAILURE);
	}
	FD_SET(fd[i], &fds);
	if (maxfd < fd[i])
	    maxfd = fd[i];

	nb = write(fd[i], &info, sizeof(info));

	if (nb != (ssize_t)sizeof(info)) {
	    perror("write");
	    exit(EXIT_FAILURE);
	}
    }

    char *dev_mem = "/dev/mem";

    int sfd = open(dev_mem, O_RDWR | O_SYNC);
    if (sfd == -1) {
	fprintf(stderr,
	    "error opening >%s<.\n%s\n",
	    dev_mem, strerror(errno));
	exit(1);
    }

    uint32_t scn_base = 0x80200000;
    uint32_t scn_size = 0x00001000;
    uint32_t scn_addr = 0x00000000;

    void *scnb = mmap((void *)scn_addr, scn_size,
	PROT_READ | PROT_WRITE, MAP_SHARED,
	sfd, scn_base);
    if (scnb == (void *)-1) {
	fprintf(stderr,
	    "error mapping 0x%08lX+0x%08lX @0x%08lX.\n%s\n",
	    (long)scn_base, (long)scn_size, (long)scn_addr,
	    strerror(errno));
	exit(2);
    } else
	scn_addr = (long unsigned)scnb;

    uint16_t *scn = scnb + 0x100;

    fprintf(stderr,
	"mapped 0x%08lX+0x%08lX to 0x%08lX.\n",
	(long unsigned)scn_base, (long unsigned)scn_size,
	(long unsigned)scn_addr);

    while (1) { /* some condition here */

	timeout.tv_sec = 5;
	timeout.tv_usec = 0;

    	fd_set rfds = fds;
	int res = select(maxfd+1, &rfds, NULL, NULL, &timeout);

	if (res == -1) {
	    perror("select");
	    exit(EXIT_FAILURE);

	} else if (res == 0) {
	    printf("timeout\n");

	} else {
	    for (int i=1; i<argc; i++) {
		if (FD_ISSET(fd[i], &rfds)) {
		    scn[39] = (i == 1) ? 0xFFF : 0x000;


		    nb = read(fd[i], &info, sizeof(info));
		    if (nb == (ssize_t)sizeof(info)) {
			printf("Interrupt #%u @%d!\n", info, i);
		    }

		    info = 1;
		    nb = write(fd[i], &info, sizeof(info));

		    if (nb != (ssize_t)sizeof(info)) {
			perror("write");
			exit(EXIT_FAILURE);
		    }
		}
	    }
	}
    }

    for (int i=1; i<argc; i++)
	close(fd[i]);
    exit(EXIT_SUCCESS);
}