/***************************************************************************
 *             __________               __   ___.
 *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
 *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
 *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
 *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
 *                     \/            \/     \/    \/            \/
 * $Id$
 *
 * Copyright (C) 2002 by Björn Stenberg
 *
 * All files in this archive are subject to the GNU General Public License.
 * See the file COPYING in the source tree root for full license agreement.
 *
 * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
 * KIND, either express or implied.
 *
 ****************************************************************************/
#ifndef _KERNEL_H_
#define _KERNEL_H_

/* wrap-safe macros for tick comparison */
#define TIME_AFTER(a,b)         ((long)(b) - (long)(a) < 0)
#define TIME_BEFORE(a,b)        TIME_AFTER(b,a)

#define HZ      100 /* number of ticks per second */

#define QUEUE_LENGTH 16 /* MUST be a power of 2 */
#define QUEUE_LENGTH_MASK (QUEUE_LENGTH - 1)

struct event
{
    int id;
    void *data;
};

struct event_queue
{
    struct event events[QUEUE_LENGTH];
    unsigned int read;
    unsigned int write;
};

/* global tick variable */
extern long current_tick;

/* kernel functions */
extern void kernel_init(void);
extern void yield(void);
extern void sleep(int ticks);
int set_irq_level(int level);
int tick_add_task(void (*f)(void));
int tick_remove_task(void (*f)(void));

extern void queue_init(struct event_queue *q);
extern struct event *queue_wait(struct event_queue *q);
extern void queue_post(struct event_queue *q, int id, void *data);

#endif
