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These are to be used by the nova-core driver, but they are so ubiquitous that other drivers should be able to take advantage of them as well. The currently implemented operations are: - align_down() - align_up() - fls() But this trait is expected to be expanded further. `NumExt` is on unsigned types using a macro. An approach using another trait constrained by the operator traits that we need (`Add`, `Sub`, etc) was also considered, but had to be dropped as we need to use wrapping operations, which are not provided by any trait. Co-developed-by: Joel Fernandes Signed-off-by: Joel Fernandes Signed-off-by: Alexandre Courbot --- rust/kernel/lib.rs | 1 + rust/kernel/num.rs | 82 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 83 insertions(+) diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs index ab0286857061d2de1be0279cbd2cd3490e5a48c3..be75b196aa7a29cf3eed7c902ed8fb98689bbb50 100644 --- a/rust/kernel/lib.rs +++ b/rust/kernel/lib.rs @@ -67,6 +67,7 @@ pub mod miscdevice; #[cfg(CONFIG_NET)] pub mod net; +pub mod num; pub mod of; pub mod page; #[cfg(CONFIG_PCI)] diff --git a/rust/kernel/num.rs b/rust/kernel/num.rs new file mode 100644 index 0000000000000000000000000000000000000000..05d45b59313d830876c1a7b452827689a6dd5400 --- /dev/null +++ b/rust/kernel/num.rs @@ -0,0 +1,82 @@ +// SPDX-License-Identifier: GPL-2.0 + +//! Numerical and binary utilities for primitive types. + +/// Extension trait providing useful methods for the kernel on integers. +pub trait NumExt { + /// Align `self` down to `alignment`. + /// + /// `alignment` must be a power of 2 for accurate results. + /// + /// # Examples + /// + /// ``` + /// use kernel::num::NumExt; + /// + /// assert_eq!(0x4fffu32.align_down(0x1000), 0x4000); + /// assert_eq!(0x4fffu32.align_down(0x0), 0x0); + /// ``` + fn align_down(self, alignment: Self) -> Self; + + /// Align `self` up to `alignment`. + /// + /// `alignment` must be a power of 2 for accurate results. + /// + /// Wraps around to `0` if the requested alignment pushes the result above the type's limits. + /// + /// # Examples + /// + /// ``` + /// use kernel::num::NumExt; + /// + /// assert_eq!(0x4fffu32.align_up(0x1000), 0x5000); + /// assert_eq!(0x4000u32.align_up(0x1000), 0x4000); + /// assert_eq!(0x0u32.align_up(0x1000), 0x0); + /// assert_eq!(0xffffu16.align_up(0x100), 0x0); + /// assert_eq!(0x4fffu32.align_up(0x0), 0x0); + /// ``` + fn align_up(self, alignment: Self) -> Self; + + /// Find Last Set Bit: return the 1-based index of the last (i.e. most significant) set bit in + /// `self`. + /// + /// Equivalent to the C `fls` function. + /// + /// # Examples + /// + /// ``` + /// use kernel::num::NumExt; + /// + /// assert_eq!(0x0u32.fls(), 0); + /// assert_eq!(0x1u32.fls(), 1); + /// assert_eq!(0x10u32.fls(), 5); + /// assert_eq!(0xffffu32.fls(), 16); + /// assert_eq!(0x8000_0000u32.fls(), 32); + /// ``` + fn fls(self) -> u32; +} + +macro_rules! numext_impl { + ($($t:ty),+) => { + $( + impl NumExt for $t { + #[inline] + fn align_down(self, alignment: Self) -> Self { + self & !alignment.wrapping_sub(1) + } + + #[inline] + fn align_up(self, alignment: Self) -> Self { + self.wrapping_add(alignment.wrapping_sub(1)).align_down(alignment) + } + + #[inline] + fn fls(self) -> u32 { + Self::BITS - self.leading_zeros() + } + } + )+ + }; +} + +numext_impl!(usize, u8, u16, u32, u64, u128); -- 2.49.0