linux-kernel - Re: [PATCH v14 06/11] rust: dma: add dma addressing capabilities

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Message-ID: <874izqjvmo.fsf@kernel.org>
Date: Tue, 18 Mar 2025 14:50:23 +0100
From: Andreas Hindborg <a.hindborg@...nel.org>
To: Abdiel Janulgue <abdiel.janulgue@...il.com>
Cc: rust-for-linux@...r.kernel.org,  daniel.almeida@...labora.com,
  dakr@...nel.org,  robin.murphy@....com,  aliceryhl@...gle.com,  Miguel
 Ojeda <ojeda@...nel.org>,  Alex Gaynor <alex.gaynor@...il.com>,  Boqun
 Feng <boqun.feng@...il.com>,  Gary Guo <gary@...yguo.net>,  Björn Roy
 Baron <bjorn3_gh@...tonmail.com>,  Benno Lossin <benno.lossin@...ton.me>,
  Trevor Gross <tmgross@...ch.edu>,  Valentin Obst
 <kernel@...entinobst.de>,  linux-kernel@...r.kernel.org (open list),
  Christoph Hellwig <hch@....de>,  Marek Szyprowski
 <m.szyprowski@...sung.com>,  airlied@...hat.com,  iommu@...ts.linux.dev
 (open list:DMA MAPPING HELPERS)
Subject: Re: [PATCH v14 06/11] rust: dma: add dma addressing capabilities

Abdiel Janulgue <abdiel.janulgue@...il.com> writes:

> From: Danilo Krummrich <dakr@...nel.org>
>
> Implement `dma_set_mask()` and `dma_set_mask_and_coherent()` in the
> `dma::Device` trait.
>
> Those methods are used to inform the kernel about the device's DMA
> addressing capabilities.
>
> Co-developed-by: Abdiel Janulgue <abdiel.janulgue@...il.com>
> Signed-off-by: Abdiel Janulgue <abdiel.janulgue@...il.com>
> Signed-off-by: Danilo Krummrich <dakr@...nel.org>

[...]

> +
> +/// Helper function to set the bit mask for DMA addressing.
> +pub const fn dma_bit_mask(n: usize) -> u64 {
> +    if n > 64 {
> +        return 0;
> +    }
> +    if n == 64 {
> +        !0
> +    } else {
> +        (1 << (n)) - 1
> +    }
> +}

I think this is dead code?


Best regards,
Andreas Hindborg