Re: [PATCH 2/8] rust: dma: add generalized container for types other than slices

["Alexandre Courbot" <acourbot@nvidia.com>]

On Tue Mar 17, 2026 at 9:56 PM JST, Gary Guo wrote:
> On Tue Mar 17, 2026 at 6:50 AM GMT, Alice Ryhl wrote:
>> On Tue, Mar 03, 2026 at 05:22:53PM +0100, Danilo Krummrich wrote:
>>> From: Gary Guo <gary@garyguo.net>
>>> 
>>> Currently, `CoherentAllocation` is concecptually a DMA coherent container
>>> of a slice of `[T]` of runtime-checked length. Generalize it by creating
>>> `dma::Coherent<T>` which can hold any value of `T`.
>>> `Coherent::alloc_with_attrs` is implemented but not yet exposed, as I
>>> believe we should not expose the way to obtain an uninitialized coherent
>>> region.
>>> 
>>> `Coherent<[T]>` provides a `len` method instead of the previous `count()`
>>> method to be consistent with methods on slices.
>>> 
>>> The existing type is re-defined as a type alias of `Coherent<[T]>` to ease
>>> transition. Methods in use are not yet removed.
>>> 
>>> Signed-off-by: Gary Guo <gary@garyguo.net>
>>> Signed-off-by: Danilo Krummrich <dakr@kernel.org>
>>
>> I see you have both `size()` and `len()`. I think it would be clearer to
>> rename `size()` to `len_bytes()`.
>
> This is an API that already exists and I simply moved it around so it is
> implemented for all types, not just `[T]`.
>
> I also think that `size()` quite unambiguously means the size in bytes (like, in
> all allocation and I/O APIs, `size` means size of object in bytes); I don't see
> much benefit in renaming it `len_bytes`.

Agreed, furthermore `len` is used in the standard library so the pattern
of it returning a number of elements is pretty established.

Generally speaking I tend to prefer having the units mentioned in the
doccomment rather than the method name.