/*
 * DF-5083 on-path trigger attempt: issue 64KB reads from the nata-controlled
 * ATAPI device (acd0/cd0 on the PIIX3 IDE controller) through a buffer that
 * straddles 17 pages and, once userland has consumed the low 4GB, consists
 * of pages above 4GB -> the nata data tag must bounce 17 pages against a
 * 16-page pool -> bus_dmamap_load() == EINPROGRESS -> queued forever ->
 * the channel wedges ("setting up DMA failed" from then on).
 */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>

int
main(int argc, char **argv)
{
	const char *dev = argc > 1 ? argv[1] : "/dev/cd0";
	unsigned char *p;
	size_t bufsz = 64 * 1024;
	ssize_t n;
	long total = 0;
	int fd, i;

	p = malloc(bufsz + 4096);
	if (!p) { perror("malloc"); return 1; }
	p += 2048;			/* misalign: 64KB now straddles 17 pages */

	fd = open(dev, O_RDONLY);
	if (fd < 0) { perror(dev); return 1; }

	for (i = 0; i < 4096; i++) {
		n = read(fd, p, bufsz);
		if (n < 0) {
			printf("read %d failed after %ld bytes: %s\n",
			       i, total, strerror(errno));
			printf("=> if this is EIO/'Input/output error' after "
			       "a DMA-setup failure, the nata channel wedged "
			       "(DF-5083 on-path wedge)\n");
			return 2;
		}
		total += n;
		if (n == 0) break;
	}
	printf("read %ld bytes OK\n", total);
	return 0;
}