blob: ec4815c8e05179508c00cce24655acd7382ba62e [file] [log] [blame]
Darwin Rambo989ce042014-02-11 11:06:34 -08001/*
2 * Copyright 2013 Broadcom Corporation.
3 *
4 * SPDX-License-Identifier: GPL-2.0+
5 */
6
7/*
8 * Bitfield operations
9 *
10 * These are generic bitfield operations which allow manipulation of variable
11 * width bitfields within a word. One use of this would be to use data tables
12 * to determine how to reprogram fields within R/W hardware registers.
13 *
14 * Example:
15 *
16 * old_reg_val
17 * +--------+----+---+--+-----+----------+
18 * | | | | | old | |
19 * +--------+----+---+--+-----+----------+
20 *
21 * new_reg_val
22 * +--------+----+---+--+-----+----------+
23 * | | | | | new | |
24 * +--------+----+---+--+-----+----------+
25 *
26 * mask = bitfield_mask(10, 5);
27 * old = bitfield_extract(old_reg_val, 10, 5);
28 * new_reg_val = bitfield_replace(old_reg_val, 10, 5, new);
29 *
30 * The numbers 10 and 5 could for example come from data
31 * tables which describe all bitfields in all registers.
32 */
33
34#include <linux/types.h>
35
36/* Produces a mask of set bits covering a range of a uint value */
37static inline uint bitfield_mask(uint shift, uint width)
38{
39 return ((1 << width) - 1) << shift;
40}
41
42/* Extract the value of a bitfield found within a given register value */
43static inline uint bitfield_extract(uint reg_val, uint shift, uint width)
44{
45 return (reg_val & bitfield_mask(shift, width)) >> shift;
46}
47
48/*
49 * Replace the value of a bitfield found within a given register value
50 * Returns the newly modified uint value with the replaced field.
51 */
52static inline uint bitfield_replace(uint reg_val, uint shift, uint width,
53 uint bitfield_val)
54{
55 uint mask = bitfield_mask(shift, width);
56
57 return (reg_val & ~mask) | (bitfield_val << shift);
58}