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#include <sys/io.h>
#include <stdio.h>
#include <time.h>

int main(void)
{
        if (ioperm(0x61, 1, 1) || ioperm(0x40, 4, 1)) {
                perror("No privileges");
                return 1;
        }

        unsigned int i;

        outb(0x76, 0x43);
        outb(18, 0x41);
        outb(0, 0x41);

        unsigned int p;
        struct timespec ts;
        unsigned int cnt[2] = { 0 };
        unsigned int t[2] = { 0 };
        /* wait for 0/1 edge */
        for (;  (inb(0x61) & 0x10); ++i);
        for (; !(inb(0x61) & 0x10); ++i);
        clock_gettime(CLOCK_MONOTONIC, &ts);
        for (i = 0, p = 0; i < 1234567; p ^= 1) {
                /* wait for p */
                for (; (inb(0x61) >> 4 & 1) != p; ++i);

                struct timespec now;
                clock_gettime(CLOCK_MONOTONIC, &now);
                const unsigned int ns =
                        (now.tv_sec - ts.tv_sec) * 1000*1000*1000
                        + (now.tv_nsec - ts.tv_nsec);
                t[p] += ns / 1000;
                ++cnt[p];
                ts = now;
        }
        if (cnt[1])
                printf("0 avg: %u.%03uus (%u / %u)\n", t[1] / cnt[1], t[1] * 1000 / cnt[1] % 1000, t[1], cnt[1]);
        if (cnt[0])
                printf("1 avg: %u.%03uus (%u / %u)\n", t[0] / cnt[0], t[0] * 1000 / cnt[0] % 1000, t[0], cnt[0]);

        cnt[0] = 0;
        /* wait for 0/1 edge */
        for (;  (inb(0x61) & 0x10); ++i);
        for (; !(inb(0x61) & 0x10); ++i);
        clock_gettime(CLOCK_MONOTONIC, &ts);
        for (i = 0; i < 1234567; ++cnt[0]) {
                /* wait for 0/1 edge */
                for (;  (inb(0x61) & 0x10); ++i);
                for (; !(inb(0x61) & 0x10); ++i);
        }
        struct timespec now;
        clock_gettime(CLOCK_MONOTONIC, &now);
        const unsigned long long ns =
                (now.tv_sec - ts.tv_sec) * 1000000000ull
                + (now.tv_nsec - ts.tv_nsec);

        if (cnt[0])
                printf("avg: %u.%03uus (%u / %u)\n", ns / cnt[0] / 1000, ns / cnt[0] % 1000, ns / 1000, cnt[0]);

        return 0;
}