linux-kernel - Re: [PATCH 2/5] rust: dma: add DMA addressing capabilities

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <2025071627-outlet-slacker-9382@gregkh>
Date: Wed, 16 Jul 2025 11:15:39 +0200
From: Greg KH <gregkh@...uxfoundation.org>
To: Danilo Krummrich <dakr@...nel.org>
Cc: abdiel.janulgue@...il.com, daniel.almeida@...labora.com,
	robin.murphy@....com, a.hindborg@...nel.org, ojeda@...nel.org,
	alex.gaynor@...il.com, boqun.feng@...il.com, gary@...yguo.net,
	bjorn3_gh@...tonmail.com, lossin@...nel.org, aliceryhl@...gle.com,
	tmgross@...ch.edu, bhelgaas@...gle.com, kwilczynski@...nel.org,
	rafael@...nel.org, rust-for-linux@...r.kernel.org,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/5] rust: dma: add DMA addressing capabilities

On Thu, Jul 10, 2025 at 09:45:44PM +0200, Danilo Krummrich wrote:
> +/// Returns a bitmask with the lowest `n` bits set to `1`.
> +///
> +/// For `n` in `0..=64`, returns a mask with the lowest `n` bits set.
> +/// For `n > 64`, returns `u64::MAX` (all bits set).
> +///
> +/// # Examples
> +///
> +/// ```
> +/// use kernel::dma::dma_bit_mask;
> +///
> +/// assert_eq!(dma_bit_mask(0), 0);
> +/// assert_eq!(dma_bit_mask(1), 0b1);
> +/// assert_eq!(dma_bit_mask(64), u64::MAX);
> +/// assert_eq!(dma_bit_mask(100), u64::MAX); // Saturates at all bits set.
> +/// ```
> +pub const fn dma_bit_mask(n: usize) -> u64 {
> +    match n {
> +        0 => 0,
> +        1..=64 => u64::MAX >> (64 - n),
> +        _ => u64::MAX,
> +    }
> +}

This is just the C macro DMA_BIT_MASK(), right?  If so, can that be said
here somewhere?  Or, how about turning DMA_BIT_MASK() into an inline
function which could then be just called by the rust code directly
instead?

Just a minor thing, but it stood out to me here.

thanks,

greg k-h