Re: [PATCH 4/8] rust: dma: introduce dma::CoherentInit for memory initialization

[Danilo Krummrich]

On Tue Mar 17, 2026 at 7:52 AM CET, Alice Ryhl wrote:
> On Tue, Mar 03, 2026 at 05:22:55PM +0100, Danilo Krummrich wrote:
>> Currently, dma::Coherent cannot safely provide (mutable) access to its
>> underlying memory because the memory might be concurrently accessed by a
>> DMA device. This makes it difficult to safely initialize the memory
>> before handing it over to the hardware.
>> 
>> Introduce dma::CoherentInit, a type that encapsulates a dma::Coherent
>> before its DMA address is exposed to the device. dma::CoherentInit can
>> guarantee exclusive access to the inner dma::Coherent and implement
>> Deref and DerefMut.
>> 
>> Once the memory is properly initialized, dma::CoherentInit can be
>> converted into a regular dma::Coherent.
>> 
>> Signed-off-by: Danilo Krummrich <dakr@xxxxxxxxxx>
>
> overall LGTM
>
> Reviewed-by: Alice Ryhl <aliceryhl@xxxxxxxxxx>

Gary and me concluded that dma::CoherentBox would probably be a better name for
what this structure represents. I.e. you can carry it around and use it similar
to a "real" Box until it is converted to dma::Coherent in order to make it
available to the device.

Is your RB still valid with this rename?

>> +        let ptr = core::ptr::from_mut(&mut self[i]);
>
> &raw mut self[i].
>
> Alice