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 //! # Examples 17 //! 18 //! ``` 19 //! use kernel::{ 20 //! page::PAGE_SIZE, 21 //! sizes::{ 22 //! SizeConstants, 23 //! SZ_1M, // 24 //! }, // 25 //! }; 26 //! 27 //! // Module-level constants continue to work without a type qualifier. 28 //! let num_pages_in_1m = SZ_1M / PAGE_SIZE; 29 //! 30 //! // Trait associated constants require a type qualifier. 31 //! let heap_size = 14 * u64::SZ_1M; 32 //! let small = u32::SZ_4K; 33 //! ``` 34 35 macro_rules! define_sizes { 36 ($($type:ty),* $(,)?) => { 37 define_sizes!(@internal [$($type),*] 38 /// `0x0000_0400`. 39 SZ_1K, 40 /// `0x0000_0800`. 41 SZ_2K, 42 /// `0x0000_1000`. 43 SZ_4K, 44 /// `0x0000_2000`. 45 SZ_8K, 46 /// `0x0000_4000`. 47 SZ_16K, 48 /// `0x0000_8000`. 49 SZ_32K, 50 /// `0x0001_0000`. 51 SZ_64K, 52 /// `0x0002_0000`. 53 SZ_128K, 54 /// `0x0004_0000`. 55 SZ_256K, 56 /// `0x0008_0000`. 57 SZ_512K, 58 /// `0x0010_0000`. 59 SZ_1M, 60 /// `0x0020_0000`. 61 SZ_2M, 62 /// `0x0040_0000`. 63 SZ_4M, 64 /// `0x0080_0000`. 65 SZ_8M, 66 /// `0x0100_0000`. 67 SZ_16M, 68 /// `0x0200_0000`. 69 SZ_32M, 70 /// `0x0400_0000`. 71 SZ_64M, 72 /// `0x0800_0000`. 73 SZ_128M, 74 /// `0x1000_0000`. 75 SZ_256M, 76 /// `0x2000_0000`. 77 SZ_512M, 78 /// `0x4000_0000`. 79 SZ_1G, 80 /// `0x8000_0000`. 81 SZ_2G, 82 ); 83 }; 84 85 (@internal [$($type:ty),*] $($names_and_metas:tt)*) => { 86 define_sizes!(@consts_and_trait $($names_and_metas)*); 87 define_sizes!(@impls [$($type),*] $($names_and_metas)*); 88 }; 89 90 (@consts_and_trait $($(#[$meta:meta])* $name:ident,)*) => { 91 $( 92 $(#[$meta])* 93 pub const $name: usize = bindings::$name as usize; 94 )* 95 96 /// Size constants for device address spaces. 97 /// 98 /// Implemented for [`u32`], [`u64`], and [`usize`] so drivers can 99 /// choose the width that matches their hardware. All `SZ_*` values fit 100 /// in a [`u32`], so all implementations are lossless. 101 /// 102 /// # Examples 103 /// 104 /// ``` 105 /// use kernel::sizes::SizeConstants; 106 /// 107 /// let gpu_heap = 14 * u64::SZ_1M; 108 /// let mmio_window = u32::SZ_16M; 109 /// ``` 110 pub trait SizeConstants { 111 $( 112 $(#[$meta])* 113 const $name: Self; 114 )* 115 } 116 }; 117 118 (@impls [] $($(#[$meta:meta])* $name:ident,)*) => {}; 119 120 (@impls [$first:ty $(, $rest:ty)*] $($(#[$meta:meta])* $name:ident,)*) => { 121 impl SizeConstants for $first { 122 $( 123 const $name: Self = { 124 assert!((self::$name as u128) <= (<$first>::MAX as u128)); 125 self::$name as $first 126 }; 127 )* 128 } 129 130 define_sizes!(@impls [$($rest),*] $($(#[$meta])* $name,)*); 131 }; 132 } 133 134 define_sizes!(u32, u64, usize); 135