mirror of https://github.com/torvalds/linux.git
135 lines
3.8 KiB
Rust
135 lines
3.8 KiB
Rust
// SPDX-License-Identifier: GPL-2.0
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//! Commonly used sizes.
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//!
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//! C headers: [`include/linux/sizes.h`](srctree/include/linux/sizes.h).
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//!
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//! The top-level `SZ_*` constants are [`usize`]-typed, for use in kernel page
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//! arithmetic and similar CPU-side work.
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//!
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//! The [`SizeConstants`] trait provides the same constants as associated constants
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//! on [`u32`], [`u64`], and [`usize`], for use in device address spaces where
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//! the address width depends on the hardware. Device drivers frequently need
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//! these constants as [`u64`] (or [`u32`]) rather than [`usize`], because
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//! device address spaces are sized independently of the CPU pointer width.
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//!
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//! # Examples
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//!
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//! ```
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//! use kernel::{
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//! page::PAGE_SIZE,
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//! sizes::{
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//! SizeConstants,
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//! SZ_1M, //
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//! }, //
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//! };
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//!
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//! // Module-level constants continue to work without a type qualifier.
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//! let num_pages_in_1m = SZ_1M / PAGE_SIZE;
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//!
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//! // Trait associated constants require a type qualifier.
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//! let heap_size = 14 * u64::SZ_1M;
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//! let small = u32::SZ_4K;
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//! ```
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macro_rules! define_sizes {
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($($type:ty),* $(,)?) => {
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define_sizes!(@internal [$($type),*]
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/// `0x0000_0400`.
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SZ_1K,
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/// `0x0000_0800`.
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SZ_2K,
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/// `0x0000_1000`.
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SZ_4K,
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/// `0x0000_2000`.
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SZ_8K,
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/// `0x0000_4000`.
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SZ_16K,
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/// `0x0000_8000`.
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SZ_32K,
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/// `0x0001_0000`.
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SZ_64K,
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/// `0x0002_0000`.
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SZ_128K,
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/// `0x0004_0000`.
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SZ_256K,
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/// `0x0008_0000`.
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SZ_512K,
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/// `0x0010_0000`.
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SZ_1M,
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/// `0x0020_0000`.
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SZ_2M,
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/// `0x0040_0000`.
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SZ_4M,
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/// `0x0080_0000`.
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SZ_8M,
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/// `0x0100_0000`.
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SZ_16M,
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/// `0x0200_0000`.
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SZ_32M,
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/// `0x0400_0000`.
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SZ_64M,
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/// `0x0800_0000`.
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SZ_128M,
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/// `0x1000_0000`.
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SZ_256M,
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/// `0x2000_0000`.
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SZ_512M,
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/// `0x4000_0000`.
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SZ_1G,
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/// `0x8000_0000`.
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SZ_2G,
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);
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};
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(@internal [$($type:ty),*] $($names_and_metas:tt)*) => {
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define_sizes!(@consts_and_trait $($names_and_metas)*);
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define_sizes!(@impls [$($type),*] $($names_and_metas)*);
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};
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(@consts_and_trait $($(#[$meta:meta])* $name:ident,)*) => {
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$(
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$(#[$meta])*
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pub const $name: usize = bindings::$name as usize;
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)*
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/// Size constants for device address spaces.
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///
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/// Implemented for [`u32`], [`u64`], and [`usize`] so drivers can
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/// choose the width that matches their hardware. All `SZ_*` values fit
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/// in a [`u32`], so all implementations are lossless.
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///
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/// # Examples
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///
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/// ```
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/// use kernel::sizes::SizeConstants;
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///
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/// let gpu_heap = 14 * u64::SZ_1M;
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/// let mmio_window = u32::SZ_16M;
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/// ```
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pub trait SizeConstants {
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$(
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$(#[$meta])*
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const $name: Self;
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)*
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}
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};
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(@impls [] $($(#[$meta:meta])* $name:ident,)*) => {};
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(@impls [$first:ty $(, $rest:ty)*] $($(#[$meta:meta])* $name:ident,)*) => {
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impl SizeConstants for $first {
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$(
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const $name: Self = {
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assert!((self::$name as u128) <= (<$first>::MAX as u128));
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self::$name as $first
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};
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)*
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}
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define_sizes!(@impls [$($rest),*] $($(#[$meta])* $name,)*);
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};
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}
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define_sizes!(u32, u64, usize);
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