Re: [PATCH v4 1/2] rust: add `Alignment` type

[Danilo Krummrich <dakr@kernel.org>]

On 8/21/25 2:42 PM, Alexandre Courbot wrote:
> +    /// Validates that `align` is a power of two at build-time, and returns an [`Alignment`] of the
> +    /// same value.
> +    ///
> +    /// A build error is triggered if `align` cannot be asserted to be a power of two.
> +    ///
> +    /// # Examples
> +    ///
> +    /// ```
> +    /// use kernel::ptr::Alignment;
> +    ///
> +    /// let v = Alignment::new(16);
> +    /// assert_eq!(v.as_usize(), 16);
> +    /// ```
> +    #[inline(always)]
> +    pub const fn new(align: usize) -> Self {
> +        build_assert!(align.is_power_of_two());
> +
> +        // INVARIANT: `align` is a power of two.
> +        // SAFETY: `align` is a power of two, and thus non-zero.
> +        Self(unsafe { NonZero::new_unchecked(align) })
> +    }

For DmaMask::new() we used a const generic instead, which makes it more obvious
to the caller that the argument must be known at compile time. So, I'd prefer
this here as well.

Either way,

Reviewed-by: Danilo Krummrich <dakr@kernel.org>