On Wed May 21, 2025 at 8:44 AM CEST, Alexandre Courbot wrote: > Introduce the `num` module, featuring the `NumExt` extension trait > that expands unsigned integers with useful operations for the kernel. > > 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 <joelagn...@nvidia.com> > Signed-off-by: Joel Fernandes <joelagn...@nvidia.com> > Signed-off-by: Alexandre Courbot <acour...@nvidia.com> > --- > rust/kernel/lib.rs | 1 + > rust/kernel/num.rs | 82 > ++++++++++++++++++++++++++++++++++++++++++++++++++++++ > 2 files changed, 83 insertions(+)
Have you proposed `align_down` to upstream rust? Not saying that we shouldn't do it here, but if we haven't tried yet, it might be a good idea to just get them upstreamed. (if you do, it should probably be named `prev_multiple_of`) > + /// 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; Isn't this `next_multiple_of` [1] (it also allows non power of 2 inputs). [1]: https://doc.rust-lang.org/std/primitive.u32.html#method.next_multiple_of > + > + /// 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; Isn't this just `trailing_zeros` [2]? [2]: https://doc.rust-lang.org/std/primitive.u32.html#method.trailing_zeros --- Cheers, Benno
