kernel/
sizes.rs

1// SPDX-License-Identifier: GPL-2.0
2
3//! Commonly used sizes.
4//!
5//! C headers: [`include/linux/sizes.h`](srctree/include/linux/sizes.h).
6//!
7//! The top-level `SZ_*` constants are [`usize`]-typed, for use in kernel page
8//! arithmetic and similar CPU-side work.
9//!
10//! The [`SizeConstants`] trait provides the same constants as associated constants
11//! on [`u32`], [`u64`], and [`usize`], for use in device address spaces where
12//! the address width depends on the hardware. Device drivers frequently need
13//! these constants as [`u64`] (or [`u32`]) rather than [`usize`], because
14//! device address spaces are sized independently of the CPU pointer width.
15//!
16//! The trait is also implemented for [`Alignment`], providing each size as a
17//! compile-time validated alignment.
18//!
19//! [`Alignment`]: crate::ptr::Alignment
20//!
21//! # Examples
22//!
23//! ```
24//! use kernel::{
25//!     page::PAGE_SIZE,
26//!     sizes::{
27//!         SizeConstants,
28//!         SZ_1M, //
29//!     }, //
30//! };
31//!
32//! // Module-level constants continue to work without a type qualifier.
33//! let num_pages_in_1m = SZ_1M / PAGE_SIZE;
34//!
35//! // Trait associated constants require a type qualifier.
36//! let heap_size = 14 * u64::SZ_1M;
37//! let small = u32::SZ_4K;
38//! ```
39
40macro_rules! define_sizes {
41    ($($type:ty),* $(,)?) => {
42        define_sizes!(@internal [$($type),*]
43            /// `0x0000_0001`.
44            SZ_1,
45            /// `0x0000_0002`.
46            SZ_2,
47            /// `0x0000_0004`.
48            SZ_4,
49            /// `0x0000_0008`.
50            SZ_8,
51            /// `0x0000_0010`.
52            SZ_16,
53            /// `0x0000_0020`.
54            SZ_32,
55            /// `0x0000_0040`.
56            SZ_64,
57            /// `0x0000_0080`.
58            SZ_128,
59            /// `0x0000_0100`.
60            SZ_256,
61            /// `0x0000_0200`.
62            SZ_512,
63            /// `0x0000_0400`.
64            SZ_1K,
65            /// `0x0000_0800`.
66            SZ_2K,
67            /// `0x0000_1000`.
68            SZ_4K,
69            /// `0x0000_2000`.
70            SZ_8K,
71            /// `0x0000_4000`.
72            SZ_16K,
73            /// `0x0000_8000`.
74            SZ_32K,
75            /// `0x0001_0000`.
76            SZ_64K,
77            /// `0x0002_0000`.
78            SZ_128K,
79            /// `0x0004_0000`.
80            SZ_256K,
81            /// `0x0008_0000`.
82            SZ_512K,
83            /// `0x0010_0000`.
84            SZ_1M,
85            /// `0x0020_0000`.
86            SZ_2M,
87            /// `0x0040_0000`.
88            SZ_4M,
89            /// `0x0080_0000`.
90            SZ_8M,
91            /// `0x0100_0000`.
92            SZ_16M,
93            /// `0x0200_0000`.
94            SZ_32M,
95            /// `0x0400_0000`.
96            SZ_64M,
97            /// `0x0800_0000`.
98            SZ_128M,
99            /// `0x1000_0000`.
100            SZ_256M,
101            /// `0x2000_0000`.
102            SZ_512M,
103            /// `0x4000_0000`.
104            SZ_1G,
105            /// `0x8000_0000`.
106            SZ_2G,
107        );
108    };
109
110    (@internal [$($type:ty),*] $($names_and_metas:tt)*) => {
111        define_sizes!(@consts_and_trait $($names_and_metas)*);
112        define_sizes!(@impls [$($type),*] $($names_and_metas)*);
113        define_sizes!(@impl_alignment $($names_and_metas)*);
114    };
115
116    (@consts_and_trait $($(#[$meta:meta])* $name:ident,)*) => {
117        $(
118            $(#[$meta])*
119            pub const $name: usize = bindings::$name as usize;
120        )*
121
122        /// Size constants for device address spaces.
123        ///
124        /// Implemented for [`u32`], [`u64`], and [`usize`] so drivers can
125        /// choose the width that matches their hardware. All `SZ_*` values fit
126        /// in a [`u32`], so all implementations are lossless.
127        ///
128        /// Also implemented for [`Alignment`], providing each size as a
129        /// compile-time validated alignment.
130        ///
131        /// [`Alignment`]: crate::ptr::Alignment
132        ///
133        /// # Examples
134        ///
135        /// ```
136        /// use kernel::{
137        ///     ptr::Alignment,
138        ///     sizes::SizeConstants, //
139        /// };
140        ///
141        /// let gpu_heap = 14 * u64::SZ_1M;
142        /// let mmio_window = u32::SZ_16M;
143        /// let page_align = Alignment::SZ_4K;
144        /// ```
145        pub trait SizeConstants {
146            $(
147                $(#[$meta])*
148                const $name: Self;
149            )*
150        }
151    };
152
153    (@impls [] $($(#[$meta:meta])* $name:ident,)*) => {};
154
155    (@impl_alignment $($(#[$meta:meta])* $name:ident,)*) => {
156        impl SizeConstants for crate::ptr::Alignment {
157            $(
158                $(#[$meta])*
159                // A non-power-of-two constant will fail the build here if used.
160                const $name: Self = crate::ptr::Alignment::new::<{ self::$name }>();
161            )*
162        }
163    };
164
165    (@impls [$first:ty $(, $rest:ty)*] $($(#[$meta:meta])* $name:ident,)*) => {
166        impl SizeConstants for $first {
167            $(
168                const $name: Self = {
169                    assert!((self::$name as u128) <= (<$first>::MAX as u128));
170                    self::$name as $first
171                };
172            )*
173        }
174
175        define_sizes!(@impls [$($rest),*] $($(#[$meta])* $name,)*);
176    };
177}
178
179define_sizes!(u32, u64, usize);
kernel/sizes.rs

kernel/
sizes.rs
