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Date: Fri, 20 Mar 2026 14:51:52 +0100
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Subject: Re: [PATCH 4/8] rust: dma: introduce dma::CoherentInit for memory
 initialization
To: Alexandre Courbot <acourbot@nvidia.com>
Cc: aliceryhl@google.com, ojeda@kernel.org, boqun@kernel.org,
 gary@garyguo.net, bjorn3_gh@protonmail.com, lossin@kernel.org,
 a.hindborg@kernel.org, tmgross@umich.edu, abdiel.janulgue@gmail.com,
 daniel.almeida@collabora.com, robin.murphy@arm.com,
 driver-core@lists.linux.dev, nouveau@lists.freedesktop.org,
 dri-devel@lists.freedesktop.org, rust-for-linux@vger.kernel.org,
 linux-kernel@vger.kernel.org
References: <20260303162314.94363-1-dakr@kernel.org>
 <20260303162314.94363-5-dakr@kernel.org>
 <DH7OO4961WUH.1MM3MW1SVWI3I@nvidia.com>
From: Danilo Krummrich <dakr@kernel.org>
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On 3/20/2026 3:35 PM, Alexandre Courbot wrote:
> On Wed Mar 4, 2026 at 1:22 AM JST, Danilo Krummrich wrote:
>> +/// # fn test(dev: &Device<Bound>) -> Result {
>> +/// let mut dmem: CoherentInit<u64> =
>> +///     CoherentInit::zeroed_with_attrs(dev, GFP_KERNEL, DMA_ATTR_NO_WARN)?;
> 
> Since this is an example, shall we use the simpler
> `CoherentInit::zeroed`?

Sure.

>> +    /// Initializes the element at `i` using the given initializer.
>> +    ///
>> +    /// Returns `EINVAL` if `i` is out of bounds.
>> +    pub fn init_at<E>(&mut self, i: usize, init: impl Init<T, E>) -> Result
> 
> Should this method be introduced in the next patch, or even in its own
> patch? It feels a bit out of place at this stage since the non-array
> `CoherentInit` doesn't have an equivalent.

The non-slice variant doesn't need it.

I don't see an advantage creating a separate patch for this.

> I was also wondering whether we could have an `init` method that
> initializes all the elements without having to zero the whole array
> first, but I guess it might be a bit difficult to implement in a
> flexible enough way.

You have this in the next patch, Coherent::init() works with arrays.