Re: [PATCH v5 15/20] rust: io: implement a view type for `Coherent`

[Gary Guo]

On Fri Jul 3, 2026 at 3:39 PM BST, Alexandre Courbot wrote:
> On Fri Jul 3, 2026 at 10:50 PM JST, Gary Guo wrote:
>> On Fri Jul 3, 2026 at 2:14 PM BST, Alexandre Courbot wrote:
>>> On Fri Jun 26, 2026 at 11:45 PM JST, Gary Guo wrote:
>>>> Implement a `CoherentView` type which is a view of `Coherent`. To be able
>>>> to give out DMA handles, the view type contains both CPU and DMA pointers,
>>>> and the projection method projects both at once.
>>>>
>>>> Delegate most of the `Io` implementation to `SysMemBackend`. Provide a
>>>> method to erase the DMA handle and give out a `SysMem` view, if the user
>>>> does not need the `dma_handle`.
>>>>
>>>> Signed-off-by: Gary Guo <gary@xxxxxxxxxxx>
>>>
>>> Of the Sashiko comments, the second one (adding exclusivity requirement
>>> to the safety comment) looks actionable; with that:
>>
>> Most of the text is taken from existing `as_mut` method on the full `Coherent`.
>> I think these can be addressed, but I'd prefer to leave it to a further patch
>> (perhaps as a good first issue).
>
> For this an acceptable fix would be to add a sentence to the safety
> comment of `as_mut` saying that the caller is responsible for ensuring
> there is no concurrent access - I suspect you are talking about
> something different for a good first issue.

I was referring to the existing `Coherent::as_mut`.
https://rust.docs.kernel.org/next/kernel/dma/struct.Coherent.html#method.as_mut

Best,
Gary