1/*	$NetBSD: average.h,v 1.2 2021/12/19 10:38:38 riastradh Exp $	*/
2
3/*-
4 * Copyright (c) 2020 The NetBSD Foundation, Inc.
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 *    notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 *    notice, this list of conditions and the following disclaimer in the
14 *    documentation and/or other materials provided with the distribution.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
17 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
18 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
19 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
20 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
21 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
22 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
23 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
24 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
25 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
26 * POSSIBILITY OF SUCH DAMAGE.
27 */
28
29#ifndef	_LINUX_AVERAGE_H_
30#define	_LINUX_AVERAGE_H_
31
32#define	DECLARE_EWMA(NAME, PREC, RATE)					      \
33struct ewma_##NAME {							      \
34	unsigned long ewma_state;					      \
35};									      \
36									      \
37static inline void							      \
38ewma_##NAME##_init(struct ewma_##NAME *ewma)				      \
39{									      \
40	ewma->ewma_state = 0;						      \
41}									      \
42									      \
43static inline unsigned long						      \
44ewma_##NAME##_read(struct ewma_##NAME *ewma)				      \
45{									      \
46	return ewma->ewma_state >> (PREC);				      \
47}									      \
48									      \
49static inline void							      \
50ewma_##NAME##_add(struct ewma_##NAME *ewma, unsigned long sample)	      \
51{									      \
52	const unsigned long shift = ilog2(RATE);			      \
53	const unsigned long state = ewma->ewma_state;			      \
54									      \
55	sample <<= (PREC);						      \
56	if (state == 0) {						      \
57		ewma->ewma_state = sample;				      \
58		return;							      \
59	}								      \
60	ewma->ewma_state = (((state << shift) - state) + sample) >> shift;    \
61}
62
63#endif	/* _LINUX_AVERAGE_H_ */
64