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

/* After starting the driver, make the
 * device send us interrupt by writing 1 to 0x40:
 * # sudo setpci -s 00:04.0 0x40.W=0x1
 * Spurious irqs are ok if the irq is shared.
 * Missed irqs mean there's a bug.
 * */
int main()
{
	int uiofd;
	int configfd;
	int err;
	int i;
	unsigned exp, act;
	int spurious = 0;
	unsigned char interrupt = 0x0;
	unsigned char command_high;
	uiofd = open("/dev/uio0", O_RDONLY);
	if (uiofd < 0) {
		perror("uio open:");
		return errno;
	}
	configfd = open("/sys/class/uio/uio0/device/config", O_RDWR);
	if (uiofd < 0) {
		perror("config open:");
		return errno;
	}

	/* Read and cache command value */
	err = pread(configfd, &command_high, 1, 5);
	if (err != 1) {
		perror("command config read:");
		return errno;
	}
	command_high &= ~0x4;

	for(i = 0;; ++i) {
		if (i == 0)
			fprintf(stderr, "Started uio test driver.\n");
		else
			fprintf(stderr, "Interrupts: %d\n", act);

		/* Clear interrupt on the device */
		err = pwrite(configfd, &interrupt, 1, 0x40);
		if (err != 1) {
			perror("command config read:");
			return errno;
		}

		err = pread(configfd, &exp, 4, 0x44);
		if (err != 4) {
			perror("config read:");
			break;
		}

		/* Re-enable interrupts. */
		err = pwrite(configfd, &command_high, 1, 5);
		if (err != 1) {
			perror("config write:");
			break;
		}

		/* Wait for next interrupt. */
		err = read(uiofd, &act, 4);
		if (err != 4) {
			perror("uio read:");
			break;
		}

		if (i == 0) {
			/* First time, ignore the counter so far. */
			spurious = act - exp;
		} else if (act < exp + spurious) {
			fprintf(stderr, "Missed irq: actual %d, expected %d\n",
				act, exp + spurious);
		} else if (act > exp + spurious) {
			fprintf(stderr, "Spurious irq: actual %d, expected %d\n",
				act, exp + spurious);
			spurious = act - exp;
		}
	}
	return errno;
}