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1/* SPDX-License-Identifier: GPL-2.0-or-later */
2/*
3 * Copyright (C) 2025, Collabora Ltd.
4 */
5
6#ifndef _LINUX_HW_BITFIELD_H
7#define _LINUX_HW_BITFIELD_H
8
9#include <linux/bitfield.h>
10#include <linux/build_bug.h>
11#include <linux/limits.h>
12
13/**
14 * FIELD_PREP_WM16() - prepare a bitfield element with a mask in the upper half
15 * @_mask: shifted mask defining the field's length and position
16 * @_val: value to put in the field
17 *
18 * FIELD_PREP_WM16() masks and shifts up the value, as well as bitwise ORs the
19 * result with the mask shifted up by 16.
20 *
21 * This is useful for a common design of hardware registers where the upper
22 * 16-bit half of a 32-bit register is used as a write-enable mask. In such a
23 * register, a bit in the lower half is only updated if the corresponding bit
24 * in the upper half is high.
25 */
26#define FIELD_PREP_WM16(_mask, _val) \
27 ({ \
28 typeof(_val) __val = _val; \
29 typeof(_mask) __mask = _mask; \
30 __BF_FIELD_CHECK(__mask, ((u16)0U), __val, \
31 "HWORD_UPDATE: "); \
32 (((typeof(__mask))(__val) << __bf_shf(__mask)) & (__mask)) | \
33 ((__mask) << 16); \
34 })
35
36/**
37 * FIELD_PREP_WM16_CONST() - prepare a constant bitfield element with a mask in
38 * the upper half
39 * @_mask: shifted mask defining the field's length and position
40 * @_val: value to put in the field
41 *
42 * FIELD_PREP_WM16_CONST() masks and shifts up the value, as well as bitwise ORs
43 * the result with the mask shifted up by 16.
44 *
45 * This is useful for a common design of hardware registers where the upper
46 * 16-bit half of a 32-bit register is used as a write-enable mask. In such a
47 * register, a bit in the lower half is only updated if the corresponding bit
48 * in the upper half is high.
49 *
50 * Unlike FIELD_PREP_WM16(), this is a constant expression and can therefore
51 * be used in initializers. Error checking is less comfortable for this
52 * version.
53 */
54#define FIELD_PREP_WM16_CONST(_mask, _val) \
55 ( \
56 FIELD_PREP_CONST(_mask, _val) | \
57 (BUILD_BUG_ON_ZERO(const_true((u64)(_mask) > U16_MAX)) + \
58 ((_mask) << 16)) \
59 )
60
61
62#endif /* _LINUX_HW_BITFIELD_H */