/*	$OpenBSD: owmem_subr.c,v 1.1 2008/04/07 22:55:57 miod Exp $	*/

/*
 * Copyright (c) 2008 Miodrag Vallat.
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

/*
 * Common routines to owmac and owserial drivers.
 */

#include <sys/param.h>

#include <sgi/dev/owmem_subr.h>

int
owmem_redirect(uint8_t *redir, u_int npages, u_int page)
{
	int skips = 0;

	/*
	 * Follow the redirecting table until we end up in our final
	 * position. We have to be careful not to loop if the table
	 * is wrong.
	 */
	while (redir[page] != 0xff) {
		if (++skips >= npages)
			return -1;
		page = 0xff ^ redir[page];
		if (page >= npages)
			return -1;
	}

	return page;
}