v2.6.1 から、拡張 DI ポートに割込処理を追加しました。
select() / poll() / epoll を使用することで、DI の状態が変化するイベントを待つことができます。

#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <unistd.h>
#include <poll.h>

int main(int argc, char **argv)
{
    int fd, ret;
    char c;
    struct pollfd pfd;

    /* DI: port 0 割込極性設定 */
    fd = open("/sys/class/gpio/DI_00/edge", O_WRONLY);

    write(fd, "both", 4); /* "rising" / "falling" / "both" */
    close(fd);

    /* DI: port 0 */
    fd = open("/sys/class/gpio/DI_00/value", O_RDONLY);

    pfd.fd = fd;
    pfd.events = POLLPRI;

    while (1) {
        lseek(fd, 0, SEEK_SET);
        
        /* 割込待ち: 5000 [ms] */
        ret = poll(&pfd, 1, 5000);
        read(fd, &c, 1);

        if (ret != 0)
            /* Event */
            printf("DI: %c\n", c);
        else
            printf("timeouted...\n");
    }

    close(fd);

    return 0;
}

#! /usr/bin/env python3

import select


def setup_gpios(nums):
    gpios = {}

    GPIO_BASE = "/sys/class/gpio/DI_%02d"

    for i in range(nums):
        # setup interrupt
        open((GPIO_BASE + "/edge") % i, 'w').write("both")

        f = open((GPIO_BASE + "/value") % i, "r")
        # dummy read
        f.readline()

        gpios[f.fileno()] = (i, f)

    return gpios

def main():
    gpios = setup_gpios(8)

    epoll = select.epoll()

    for fd, info in gpios.items():
        epoll.register(fd, select.EPOLLPRI)

    for i in range(10):
        print("waiting event...")
        events = epoll.poll()

        print(" event! nums = %d" % len(events))

        for event in events:
            fd = event[0]
            info = gpios[fd]

            print("  event in GPIO%d" % info[0])
            info[1].seek(0)
            val = int(info[1].readline().strip())
            print("  value: %d" % val)


if __name__ == "__main__":
    main()

root@plum:/tmp# python3 gpio_epoll.py 
waiting event...
 event! nums = 1
  event in GPIO0
  value: 1
waiting event...
 event! nums = 1
  event in GPIO0
  value: 0
waiting event...